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Acute painmanagement:scientific evidence

Endorsed November1998

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Commonwealth of Australia 1999

ISBN 1864960426

This work is copyright. Apart from any use as permitted under theCopyri ght A ct1968, no part may be reproduced by any process without permission from AusInfo.Requests and enquiries concerning reproduction and rights should be addressed to theManager, Legislative Services, AusInfo, GPO Box 1920, Canberra, ACT 2601.

The strategic intent of the National Health and Medical Research Council (NHMRC)is to work with others for the health of all Australians, by promoting informed debateon ethics and policy, providing knowledge-based advice, fostering a high quality andinternationally recognised research base, and applying research rigour to healthissues.

This document is sold through AusInfo at a price which covers the cost of printing anddistribution only. For publication purchases, please contact AusInfo on their toll-freenumber 13 24 47 or through their internet address: http://www.ausinfo.gov.au.

NHMRC documents are prepared by panels of experts drawn from appropriateAustralian academic, professional, community and government organisations.NHMRC is grateful to these people for the excellent work they do on an honorary

basis and in addition to their usual work commitments.

Produced by ampersand edi torial & design, Canberra

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3

ContentsPreface .....................................................................................................................7

Executive summary .................................................................................................9

Summary of scientific evidence and key management points...........................11

Introduction............................................................................................................21

1 The clinical picture ...........................................................................................251.1 Acute pain: mechanisms and clinical applications ....................................25

1.2 Adverse physiological and psychological effects of pain ............................29

2 Acute painservices..........................................................................................31

3 Principlesofacute painassessmentandmanagement................................35

3.1 Assessment of pain and pain history .........................................................35

3.2 Diagnosing neuropathic pain.....................................................................39

3.3 Agents used to manage acute pain.............................................................40

3.4 Education about pain management ...........................................................42

4 Acute postoperative painmanagementinadults.........................................45

4.1 Agents used in postoperative analgesia.....................................................45

4.2 Pain management plans ............................................................................81

4.3 Special postoperative patients optimising pain relief ............................83

5 Obstetric analgesia ..........................................................................................87

6 Paininchildren .................................................................................................93

6.1 Assessment of pain in children..................................................................94

6.2 Procedures and pain...................................................................................95

6.3 Management of pain associated with paediatric surgery ..........................98

6.4 Managing postoperative pain in neonates and infants............................106

6.5 Pain in children with cancer ....................................................................107

7 Burnsandtrauma pain...................................................................................109

7.1 Emergency phase.....................................................................................109

7.2 The healing phase....................................................................................110

7.3 The rehabil itation phase..........................................................................111

8 Acute painassociated withmedical conditions..........................................115

8.1 Cardiac pain.............................................................................................115

8.2 Acute herpes zoster infection (shingles)...................................................116

8.3 Acute abdominal pain ..............................................................................117

8.4 Acute headache........................................................................................120

8.5 Acute pain in haemophilia/haemarthrosis...............................................125

8.6 Acute dental and orofacial pain ...............................................................126

8.7 Acute musculoskeletal pain .....................................................................126

8.8 Sporting injuries ......................................................................................137

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4

9 Acute pain inpatientswithcancerorHIV/AIDS...........................................139

9.1 Acute pain in patients with cancer ..........................................................139

9.2 Acute pain in patients with HIV and AIDS .............................................148

10Adjuvantagentsandthe treatmentofacute neuropathic pain................151

10.1Adjuvant agents in the treatment of acute pain.....................................151

10.2Treatment of acute neuropathic pain.......................................................152

11Patientswithspecialneeds............................................................................157

11.1Non-Englishspeaking patients...............................................................157

11.2Aboriginal and Torres Strait I sland peoples............................................157

11.3Other ethnic groups.................................................................................158

11.4Patients with psychiatric illnesses...........................................................158

11.5Elderly patients........................................................................................159

11.6Management of acute pain in opioid-dependent patients........................163

12Emergency departmentand intensive care guidelines...............................167

12.1 Acute pain in the emergency department................................................ 167

12.2 Issues in intensive care and other critical care settings..........................169

Appendixes

A: Membership and terms of reference of the Working Party......................175

B: Process report...........................................................................................177

Acronyms and abbreviations.............................................................................181

Glossary................................................................................................................183

Bibliography.........................................................................................................187

Index.....................................................................................................................221

This document is a general guide to appropriate practice, to be followed only subject to

the clinicians judgement in each individual case.

The report is designed to provide information to assist decision making and is basedon the best information available at the date of publication.

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5

ListoftablesTable 1.1 Metabolic and endocrine responses to surgery ...................................30

Table 2.1 Organisational aspects of a postoperative pain program...................32

Table 3.1 Taking a pain history..........................................................................37

Table 3.2 Features that suggest neuropathic pain.............................................39

Table 4.1 Summary of pharmacological interventions.......................................45

Table 4.2 Suggested starting doses for IM/SC morphine and IM pethidinein adults ..............................................................................................47

Table 4.3 Equi-analgesic doses of opioid.............................................................48

Table 4.4 Sedation score.....................................................................................51

Table 4.5 Comparison of representative agents from anti-emetic drug classes.54

Table 4.6 Important elements of intravenous PCA preprinted orders...............61

Table 4.7 Commonly prescribed initial values for intravenous PCA variables..62

Table 4.8 NSAID dosages and pharmacokinetic data ........................................75

Table 6.1 Opioid doses in children....................................................................101

Table 7.1 Management of burn and trauma pain.............................................112

Table 8.1 Causes of abdominal pain.................................................................118

Table 8.2 Causes of headache...........................................................................120

Table 8.3 Red flags for potentially serious spinal conditions ...........................127

Table 8.4 Pointers to serious sporting injury ...................................................138

Table 9.1 Acute pain associated with direct tumor involvement......................143

Table 9.2 Acute pain associated with cancer therapy ......................................144

Table 9.3 Common painful syndromes in HI V/AIDS........................................149

Table 10.1 Table of adjuvant agents...................................................................151

Table 10.2 Proposed mechanisms of action of certain adjuvant agents.............152

Table 10.3 Efficacy of anticonvulsants for neuropathic pain .............................153

Table 12.1 Red flags against the use of nitrous oxide.......................................168

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Preface

One of the acknowledged tasks of medicine and other healing sciences through theages has been to seek to relieve pain. While acknowledging with sensitivity thediffering philosophical approaches to pain, and the genuine pursuit by some of deepand spiritual meaning in suffering and pain, medicine has sought out ways whereby

effective relief can be given to patients when desired.This report is concerned with the scientific basis of pain relief how relief can bebest achieved for pain that occurs suddenly and which may be attributable to differentcauses. I t enunciates principles for the relief of acute pain based on the best scientificevidence currently available. It does not concern pain that is chronic or long lastingand which requires management of a different style and order.

The disabling impact of acute pain as experienced by individuals can also be locatedwithin a social context. In Australian society, rough estimates suggest that thefinancial costs associated with severe unrelieved pain may be as high as $10 billion ayear. Acute pain thus must rank with the more serious causes of contemporarymorbidity in our society, and be one of the most expensive.

The intention of the National Health and Medical Research Council in publishing thisreport is to make accessible to health care professionals, patients and their carers andfriends, scientific evidence which might be used in finding the best pathway to relief.I thank the authors for their diligence and attention to critically important detail, andall those who contributed through consultation to its final form. On behalf of theNational Health and Medical Research Council, I commend this document to its wide,intended audience.

Richard Larkins

Chairman

National Health and Medical Research Council

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9

Executive summary

Despite numerous advances in the field of medicine, the management of acute painfails to be given appropriate priority and acute pain is not properly treated in avariety of clinical situations.

One survey found that 77 per cent of adults believed that postoperative pain is to be

expected, with almost 60 per cent regarding this as their primary fear before surgery(level I II ; Warfield & Kahn1995). Unfortunately, these fears are justified, given that thetraditional and common practice of administering as needed intramuscular opioids inthe past has led to unrelieved pain in more than half of postoperative patients (levelII I; Austin et al 1980, Oden 1989).

A National Health and Medical Research Council (NHMRC) report on the manage-ment of severe pain (1988, p vii) found that

changes ar e call ed for i n t ra in in g, knowledge, atti tu des and pr actice of medi cal,nu r sin g and al li ed pr ofessionals, al ong wi th gr eater pu bli c awar eness andexpectati ons in th e tr eatm ent of pain .

Reasonsforineffectiveanalgesia The common idea that pain is merely a symptom and not harmful in itself.

The mistaken impression that analgesia makes accurate diagnosis difficult orimpossible (level I I; Attard et al 1992).

Fear of the potential for addiction to opioids.

Concerns about respiratory depression and other opioid-related side effects such asnausea and vomiting.

Lack of understanding of the pharmacokinetics of various agents.

Lack of appreciation of variability in analgesic response to opioids.

Prescriptions for opioids which include the use of inappropriate doses and/or dose

intervals. Misinterpretation of doctors orders by nursing staff, including use of lower ranges

of opioid doses and delaying opioid administration.

The mistaken belief that patient weight is the best predictor of opioid requirement.

The mistaken belief that opioids must not be given more often than four hourly.

Patients difficulties in communicating their need for analgesia.

(level IV; Cousins & Phillips 1986, Macintyre & Ready 1996)

In the literature, there are a number of references on the topic of ethics in themanagement of pain. I n this material there is a clear directive that clinicians have amoral obligation to treat pain effectively as one of a patients basic rights. A survey

over time of nursing attitudes to ethical issues frequently encountered in clinicalpractice found that pain relief and its management rated the highest (level III; Omeryet al 1995). Most evidence for inadequate relief of pain concerns postoperative pain.Postoperative pain should not be thought inevitable, harmless or merely a discomfortto be tolerated. Although the evidence is less well documented, it appears that thetreatment of pain is also inadequate for acute trauma, burns, childbirth and inchildren and the elderly.

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Acute painmanagement: scientific evidence

10

The American Pain Society has identified a number of key strategies to improve acutepain management including:

recognition and prompt treatment of pain;

making information about analgesics readily available;

defining policies for use of advanced analgesic technologies; and

examining the process and outcomes of pain management with the goal of

continuous improvement (American Pain Society 1995).The widespread inadequacy of acute pain management has prompted recent efforts bymultiple health care disciplines, including surgery (Royal College of Surgeons & College ofAnaesthetists 1990), anaesthesia (Phillips & Cousins 1986, Ready et al 1988, Macintyre &Ready 1996); nursing (American Nurses Association 1991), and national and internationalbodies (NHMRC 1988, American Pain Society 1990, Ready & Edwards 1992).

This NHMRC report attempts to update earlier reports and present statements formanagement based on recent evidence, in an Australian context.

Principlesofpainmanagement

Principlesofpostoperativepainmanagement

(applicable inallareasofacute painmanagement). Adverse physiological and psychological effects result from unrelieved severe pain.

Proper assessment and control of pain require patient involvement, frequentassessment and re-assessment of pain intensity and charting of analgesia.

Effective pain relief requires flexibility and tailoring of treatment to an individualrather than rigid application of formulae and prescriptions.

Pain is best treated early because established, severe pain is more difficult to treat(Bach et al 1988, Katz et al 1996).

While it is not possible or always desirable to completely alleviate all pain in thepostoperative period, it should be possible to reduce pain to a tolerable orcomfortable level.

Postoperative analgesia should be planned pre-operatively, with considerationgiven to the type of surgery, medical condition of the patient, peri-operative use ofanalgesics and regional anaesthetic techniques.

Postoperative physical therapy requirements for early mobilisation should bediscussed with the patient and the timing of appropriate and adequate analgesiaand early physical therapy requirements considered.

Ultimate responsibil ity for pain management should be assigned to those mostexperienced in its administration and not to the most junior staff members.

Safe and effective analgesia depends on: adequate education of all involved in painmanagement, including the patient; formal programs, protocols and guidelinescovering acute pain management relevant to the institution; and formal quality

assurance programs to regularly evaluate the effectiveness of pain management.(adapted from AHCPR 1992)

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Executive summary

11

Summary of scientific evidence and key

management points

Statements of evidence (for which there is level I, I I or I I I evidence as defined onpage23) are presented in each section of the report. They are also presented in this

summary section, for quick reference. Readers should turn to the appropriate sectionsto understand the context of this evidence (relevant page numbers are indicated foreach statement of evidence). The key points are observations about managementwhich are rated level IV (the opinions of respected authorities based on clinicalexperience, descriptive studies or reports of expert committees).

Acute painservices

Key points

A multidisciplinary approach to the management of acute pain, particularly in aformal acute pain service, leads to improved pain relief and better patientoutcomes.

Effective pain management is fundamental to the quality of care. The key to

successful pain management is education and training of all staff.

Assessmentofpain

Key points

Careful assessment of pain should occur initially and then regularly throughouttreatment, using self-reporting techniques. As pain varies so markedly betweenindividuals, patient involvement in the initial and continuing assessment of theirpain is essential.

Pain should be assessed both at rest and during activity and pain relief assessed asto its adequacy to allow appropriate function.

Unexpected levels of pain or pain that suddenly increases, especially whenassociated with changes in other vital signs, may signal the development of a newsurgical or medical diagnosis (eg postoperative complication, neuropathic pain).

Although not specific, an important indicator of neuropathic pain is the inability torelieve pain with opioids, or no apparent relief of pain with a rapidly increasingopioid dose. Other indicators can be obtained from the history and physicalexamination, as shown in Table 3.2 on page 39.

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Acute postoperative painmanagementinadults

General

Statementsofevidence Levelofevidence

1

p 52

As significant background and/or intermittenthypoxaemia may occur for a number of days

postoperatively, supplemental oxygen isrecommended for at least the first 48 to 72 hoursfollowing major surgery and in elderly or high-riskpatients, regardless of the analgesic method used.

I I I

Reeder et al 1992a

2

p 76

Multimodal analgesia (ie the combined use ofdifferent classes of analgesics) improves theeffectiveness of pain relief after surgery. There mayalso be an associated reduction of the dose of eachanalgesic drug and the intensity of any side effects.

I I

Kehlet & Dahl 1993a,

1993b, Power et al 1994,

Schulze et al 1988,

Brodner et al 1998

3

p 77

Studies to date suggest that more aggressive, andpossibly pre-emptive, approaches to themanagement of early postoperative pain may reduce

the transition to chronic postoperative pain.

I I

Katz et al 1996;

Bach et al 1988

Opioid analgesia


4

p 60

Patient-controlled analgesia (PCA) managed by anacute pain service (APS) or by non-pain specialisthealth professionals is associated with similar painscores; however the incidence of side effects is lowerin patients whose PCA is managed by an APS.Further well designed studies are needed to evaluatehow supervision of PCA by an APS affects cost,quality of care and patient satisfaction.

I I I

Stacey et al 1997

5

p 60

PCA has been shown to provide greater patientsatisfaction and improved ventilation compared toconventional routes of administration.

I I

McArdle 1987

Key points

Respiratory depression and hypoxia are often feared consequences of opioidadministration but can generally be avoided with careful titration andindividualisation of dose.

A decrease in respiratory rate has been found to be a late and unreliable clinicalindicator of respiratory depression. Sedation is a better indicator and all patients

on opioids should be monitored using a sedation score.

To attain therapeutic effects with minimal adverse effects, it is necessary toindividualise and titrate doses of opioids. This relies on using age as the initialguide for dosage range (in adults), and the use of dose intervals appropriate tothe route of administration, monitoring of pain and sedation scores, respiratoryrate and other side effects.

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Executive summary

13

Key points(cont)

The aim of analgesia should be patient comfort with minimal sedation andimpairment of respiratory function (eg sedation score of less than 2 and respiratoryrate greater than 8/minute).

A true allergy to opioids is very uncommon. As with any drug, the term allergy isoften mistakenly applied to an intolerance to the drug, a common side effect, or adose-related effect.

There is no evidence that the use of opioids for treatment of severe pain leads toopioid dependence or addiction.

Traditional methods of opioid administration include oral, intramuscular,subcutaneous, intravenous and continuous intravenous routes. These methodseach have advantages and disadvantages in different groups of patients, but aremore likely to be effective when the dosage regimen is tailored to the individual.The patients need for pain relief should be seen as more important than strictadherence to a dose interval.

Patient-controlled analgesia (PCA) allows patients to adjust the degree of painrelief to their own desired level of comfort and tolerance of side effects.

Adequate knowledge of patient-controlled analgesia (PCA) is essential to avoid

documented serious outcomes.

Regional techniques

Key point

Regional methods of pain relief using local anaesthetic, either alone or incombination with systemic analgesia, can be effective after a number of localisedprocedures.

Epidural analgesia


6p 65

Postoperative epidural analgesia can significantlyreduce the incidence of pulmonary morbidity.

IBallantyne et al 1998

7

p 65

Large audits of closely supervised epidural analgesiashow the safety of the technique to be equivalent tothat of traditional analgesic methods whencoordinated by an acute pain service with appropriatepatient observations and monitoring.

I I I

Ready et al 1991, Schug

& Torrie 1993, Scott et

al 1995, Tanaka et al

1993, Breivik 1996;

Rawal & Allvin 1996

8

p 65

Epidural opioids are more effective when used incombination with local anaesthetic to produce asynergistic analgesic action and reduce the requireddose and side effects associated with either the localanaesthetic or opioid alone.

I

Wiebalck et al 1997

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Nonsteroidal anti-inflammatory drugs(NSAIDs)


9

p 72

While the currently available NSAIDs do not relievesevere pain when used alone, their efficacy ascomponents of multimodal analgesia has beenconfirmed by clinical trials.

I

McQuay & Moore 1998,

Royal College of

Anaesthetists 1998

IIPower et al 1990, 1994,Cepeda et al 1995, Pavy

1995, Liu et al 1995a

10

p 72

The adverse effects of NSAIDs are potentiallyserious and it is imperative that contraindicationsare respected.

II, IIIPower et al 1992,Strom et al 1996;

Gillis & Brogden 1997;Feldman et al 1997;

Merry & Power 1995:J aquenod et al 1998

Non-pharmacological methods

Statementof evidence Level of evidence11

p 80

In 15 of 17 randomised controlled trials of transcut-aneous electrical nerve stimulation (TENS) in post-operative pain, there was no benefit compared withplacebo. In excluded non-randomised studies therewas an overestimation of treatment effects of TENS.

I

Carroll et al 1996

Key point

Although evidence for the efficacy of non-pharmacological modalities such asphysical therapeutic agents and modalities such as spinal manual therapy,mobilisation, application of superficial heat or cold, massage, exercise, trans-

cutaneous electrical nerve stimulation (TENS) therapy and acupuncture in acutepain management is largely at the expert opinion level, certain patients derivebenefit from these techniques.

Special postoperative patients

Day surgicalpatients

Statements of evidence Level of evidence

12

p 76

A recent meta-analysis confirmed that paracetamol isan effective postoperative analgesic, and that codeine 60mg added to paracetamol produces worthwhileadditional pain relief even in single oral doses.

I

Moore & Collins 1997

13

p 81

Pain following discharge from day surgery influences thetime taken to return to normal activity and may lead tofurther, unplanned hospitalisation. I t is recommendedthat adequate plans are made for post-dischargeanalgesia.

I I I

Fancourt-Smith et al

1990,

Gold et al 1989

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Executive summary

15

Key points

The ability to perform increasingly complex surgery on a day-case basis highlightsthe need for appropriate screening, selection, pre-operative preparation, treatmentand discharge planning for these patients.

Pharmacological options for day-case postoperative analgesia include oral opioids,non-steroidal anti-inflammatory drugs (NSAIDs) and local anaesthetics, or

combinations of these treatments. Simple oral analgesics such as aspirin andparacetamol are more effective than placebo and should not be overlooked,particularly in cases of mild to moderate pain.

Neurosurgical patients

Key point

Pain management in neurosurgical patients employs conventional analgesic agentsplus adjuvant agents where appropriate. Extremely careful monitoring is required,including assessment for abnormal neurological signs and symptoms during thepostoperative period. Pain and sedation scoring systems should be an integral partof this monitoring.

Obstetric analgesia


14

p 88

Lumbar epidural analgesia is the most effectiveform of pain relief during childbirth. Using low-doselocal anaesthetic/opioid mixtures can significantlyreduce the severity of side effects.

IHowell & Chalmers

1992

15

p 89

Recent studies appear to indicate that there is

no increase in caesarean delivery rate

associated with epidural analgesia.

I I

Sharma et al 1997,Bofill et al 1997

Key points

All options for pain relief, and their efficacy, should be discussed with theparturient so that she can make an informed decision. Pain relief planned duringthe antenatal period and implemented during labour should be monitored andappropriately modified during the course of the labour. The wishes of the womanand the well-being of the baby are paramount.

Maternal-foetal factors and obstetric management, not epidural analgesia, are themain determinants of caesarean section rates.

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Paininchildren

Key points

Regular assessment of pain and monitoring of treatment in children presentparticular challenges to health carers. Close observation of non-verbal cues andbehaviour is important. The use of pain rating scales suitable for the age anddevelopmental stage of the child is essential for the accurate treatment of pain.

The child should be respected as an authority on their own pain. Procedural pain in children should be managed systematically, using a combina-

tion of analgesia and non-drug strategies and avoiding painful routes of admini-stration where possible. General anaesthesia may be required, especially forfrequent painful interventions where other strategies have failed.

Drug therapy is the mainstay of postoperative analgesia in children, but non-drugmodalities may also be useful.

Analgesia should be given by the least painful route where possible.

Regular re-evaluation of analgesic efficacy is required.

There is no evidence that the use of opioids for treatment of severe pain in childrenleads to opioid dependence or addiction.

PCA provides safe and effective analgesia in children as young as five to six yearsand offers superior analgesia to intermittent intramuscular injections in children.

Regular assessment of vital signs and level of consciousness is necessary whenparenteral opioids are used for managing postoperative pain.

Regional techniques are almost always employed as an adjunct to generalanaesthesia in children, while in adults they are frequently used as a primarytechnique.

Burnsand trauma pain

Key points

Patients with burn or trauma pain need a range of strategies which may differduring the emergency, healing and rehabilitation phases.

A combination of nociceptive and neuropathic pain is common and psychological/environmental factors usually play an important role (eg anxiety, fear ofpermanent disability or death).

Severe pain may persist in the healing and rehabilitation phases; pain treatmentis an essential ingredient of an active rehabilitation plan.

The use of long-acting oral opioids is appropriate while there is obvious evidence oftrauma-associated persisting nociception.

Treatment of neuropathy may need to continue well after the healing phase.

Unexpectedly prolonged requirement for opioids should prompt referral formultidisciplinary pain unit assessment.

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Executive summary

17

Acute herpeszosterinfection


16

p 116

Antiviral agents used early for the treatment ofacute herpes zoster infection have been shown toaccelerate lesion healing and result in fasterresolution of pain.

I

Kost & Straus 1996

17

p 116

Antidepressants and anticonvulsants are effectivein the treatment of neuropathic pain such as post-herpetic neuralgia.

I

McQuay et al 1996,

1995a

Acute headache


18

p 121

A stepwise approach to the use of pharmacologicalagents in the treatment of migraine is effective.Moderate to severe migraine may require the use ofspecific antimigraine medications such as

ergotamine or sumatriptan, unless contraindicated.

I I I

Raskin 1986,

Callahan & Raskin 1986

19

p 121

The combination of aspirin (900 mg) and meta-clopramide is as effective as sumatriptan in thetreatment of migraine, is better tolerated and isalso considerably cheaper.

I I

Tfelt-Hansen et al 1995

20

p 121

Pethidine has been found to be no more effectivethan dihydroergotamine, chlorpromazine orNSAIDs in the treatment of migraine.

I I

Lane et al 1989,

Stiell et al 1991, Davis

1995, Scherl 1995,

Nicolodi 1996

Key point

There are very few situations in which pethidine is useful in acute migraine,although it may be considered during pregnancy when the use of ergotaminepreparations, triptans and dihydroergotamine is contraindicated.

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Acute musculoskeletal pain


21

p 131

Treatment for acute lower back pain based on bedrest and immobilisation is ineffective.

I

Koes & van den

Hoogen 1994

22

p 131

A return to a normal range of activities as soon as

possible leads to more rapid recovery from acutelower back pain than do either bed rest or back-mobilising exercises.

I I

Malmivaara et al1995, Hadler et al

1987

23

p 132

Spinal manual therapy is used for the treatmentof acute lower back pain in the first six weeksfollowing onset of pain. The scientific evidence forits efficacy has yet to be established.

I

Koes et al 1996

24

p 132

The little evidence available about the use ofspinal manual therapy for acute neck painsuggests some benefit in mechanical neck pain,although subgroups of patients need to be better

identified.

I

Gross et al 1998, Shekelle

& Coulter 1997, Aker et

al 1996.

25

p 132

Although rare, serious complications have beenassociated with neck manipulation and suchprocedures should therefore be performed only byappropriately trained personnel.

I I I

Hurwitz et al 1996,

Rivett & Reid 1998,

Rivett & Milburn

1997,

Rivett & Milburn

1996

26

p 137

Corticosteroids are effective anti-inflammatoryagents, but are not suitable treatment for acutesporting injuries for up to six weeks after theincident. Experimental studies have shown that

corticosteroids may adversely affect normal tissuehealing and repair.

I I I

Wrenn et al 1964,

Kapetanos 1982,

Wesley et al 1991

Key points

The key to managing acute lower back pain is to clearly distinguish seriouspathology from benign musculoskeletal causes.

The treatment of serious spinal pathology requires urgent referral to specialistservices.

Non-specific backache is best managed using a simple multimodal approach aimedat pain relief, active rehabilitation and return to normal activity.

While they do have a role in the treatment of myositis ossificans followingintramuscular haematoma, and in the management of chronic sporting injuries,non-steroidal anti-inflammatory drugs (NSAIDs) have not been shown to beeffective in the treatment of ligament sprains.

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Executive summary

19

Acute pain inpatientswithcancer


27

p 144

Oral analgesics are the mainstay of pain relief inpatients with cancer. Strong opioids are safe andeffective for moderate to severe pain.

I

AHPCR 1994b

28

p 146

Radiotherapy plays a major role in themanagement of acute pain due to cancer.

I

McQuay 1997

29

p 147

Bisphosphonates have a general role in thetreatment of bone pain related to breast cancer andmyeloma (and possibly prostate cancer).

I I

Purohit et al 1994

II I

Coleman et al 1997

30

p 147

Epidural, intrathecal and intracerebroventricularopioids are often effective in treating acute pain inpatients with cancer that is not controlled withconventional treatment.

IBallantyne et al

1996

Key points Not all acute pain in patients with cancer is due to the cancer progressing.

Optimal communication between oncological, surgical, anaesthetic, and palliativecare teams is essential.

Even when the cancer is progressing, it is important to consider the anatomicaetiology, as this may be amenable to disease-specific therapy (radiotherapy,chemotherapy, surgery etc).

While waiting for specific anti-cancer therapy to work, adequate analgesia must beprovided. Invasive procedures (spinal opioids, nerve blocks etc) are occasionallyrequired.

Acute pain in cancer patients often takes place against a background of chronic

pain and therefore existing analgesic use. An integral part of management is therecognition and treatment of procedural pain and breakthrough pain.

The barriers to management of pain in cancer patients must be recognised andovercome if possible.

Acute paininpatientswithHIV/AIDS

Key points

Acute pain in HIV/AIDS patients often has more than one cause and location andtends to increase in severity with disease progression. Intervention requires amultidisciplinary approach.

A careful history and physical examination commonly identifies treatable painsyndromes seen in HIV/AIDS. Determination of the level of immunosuppression inpatients presenting with pain is a critical diagnostic manoeuvre, as immuno-competent patients are more likely to have benign conditions than infections ormalignancies.

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Adjuvantagentsand the treatmentofneuropathic pain

Statementofevidence Levelofevidence

31

p 152

Anticonvulsants and antidepressants have beenshown by meta-analysis to be effective in thetreatment of neuropathic pain.

I

McQuay et al

1996, 1995a

Key point

The effectiveness of anticonvulsants and antidepressants in the treatment of painneeds to be balanced against their potential adverse effects.

Painin the elderly

Statementofevidence Levelofevidence

32

p 161

Non-steroidal anti-inflammatory drugs (NSAIDs)should only be used with extreme caution in elderlypeople. For non-inflammatory complaints,paracetamol and/or low-dose opioids are

recommended. Low-dose corticosteroids may beappropriate in inflammatory conditions.

I I I

Roth 1989

Key point

Effective pain management in elderly people needs to consider a number of factorswhich may complicate management, including co-existent pathologies, multiplemedications, altered pain response and cognitive impairment.

Emergency departmentandcritical care


33

p 168

Early administration of opioids in patients with anacute abdomen does not reduce the detection rateof serious pathology, but may actually facilitate it.

I IAttard et al 1992,Zoltie & Cust 1986

34

p 169

Non-steroidals have been shown to be more effectivethan opioids in relieving the pain of renal colic. Acomparative study of an intramuscular NSAID andintramuscular opioid has verified the efficacy ofNSAIDs in this indication. Comparison of twoNSAIDs, diclofenac and ketoprofen, in anotherstudy found them to be equally effective in relievingthe pain of acute ureteral colic.

I I

Hetherington &

Philp 1986

Walden et al 1993

Key points

In most acute care situations in the emergency department, the intravenous routeof opioid delivery is by far the most efficacious and is therefore preferable.

All of the techniques and drugs used to treat acute postoperative pain, includingnon-drug techniques, are potentially applicable in intensive care units.

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Clinical practice guidelines on acute pain management published by the Agency forHealth Care Policy and Research (AHCPR) of the United States Department ofHealth and Human Services. The same agency has prepared guidelines on cancerpain management (AHCPR 1994a) and on acute lower back pain (AHCPR 1994b), andthese also served as helpful source documents in the preparation of this report.

The assistance of Dr D Carr is acknowledged.

In addition, a number of professional organisations and official bodies provided

material which is acknowledged at appropriate places in the report.

Scope

This report presents statements to assist clinical decision making, based on thesynthesis of available evidence. I t is not intended to replace clinical judgement butprovides a consensus from a wide body of documented knowledge.

The report is intended for health care practitioners engaged in the care of patients

experiencing acute pain. I t is likely that all medical and allied health professionals

will be involved in the management of patients with acute pain at some point in their

practice.

This report cannot provide complete coverage of all recent developments in thetreatment of acute pain. Nor can it cover in detail all of the treatment modalitiesused in the many specialised situations in which acute pain is managed. However, anattempt has been made to highlight the major aspects of new knowledge and toprovide key references that will allow a deeper perusal of this material.

A deliberate effort has been made to identify the main treatment options that may beapplicable across the broad range of acute pain problems. It is hoped that this willstimulate a re-evaluation of methods and approaches that are currently not uti lisedin some patients and in some situations of acute pain management. I t has nowbecome clear that the provision of appropriate pain relief does not impair thediagnosis of acute conditions, nor does it mask the appearance of complications.Health care professionals and patients should be aware that patients have a right to

effective treatment of acute pain, limited only by availability of methods that can besafely applied in their particular situation.

There is substantial, and quite deliberate, overlap in the report concerning thetreatment of pain in cancer patients and chronic non-cancer pain, mainly withrespect to acute exacerbations of pain. However, reference is also made to thepotential preventativerole of early intervention in persistent acute pain, as a methodof preventing chronic pain. TheWorkingParty has taken care not toencroachotherwiseon the important subjects of cancer pain and chronic non-cancerpain; it is strongly recommended thatseparate reportsbewritten on boththeseareasofpain management.This is a high priority in view of the enormousindividual, family and community suffering and the financial costs of severeunrelieved pain, currently amounting to more than $10 billion annually in Australia.

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Introduction

23

Levelsofclinical evidence

This report has been written in a way that enables readers to judge the strength ofthe evidence on which statements of evidence are based. In relation to issues ofeffectiveness of health care, the report uses the four-point rating system given belowto identify the evidence base for key decision points. The rating system has beenadapted from the system developed by the United States Preventive Services Task

Force and is recommended by the NHMRC (1995).

Levelsofevidence ratings

LevelI Evidence obtained from systematic review of relevant randomisedcontrolled trials (with meta-analysis where possible).

Level II Evidence obtained from one or more well-designed randomised controlledtrials.

Level III Evidence obtained from well-designed non-randomised controlled trials; ORfrom well-designed cohort or case-control analytical studies, preferablymulticentre or conducted at different times.

Level IV The opinions of respected authorities based on clinical experience,descriptive studies or reports of expert committees.

While level I evidence represents the desired standard on which to base clinicaldecision making, treatment based on other levels of evidence can be used inappropriate circumstances.

Level I evidence was not available for many areas in the report. I t is hoped that, in afuture revision of the report, it will be possible to commission further meta-analysesfor major areas in the document that currently lack such evidence. In discussion withthe Oxford group, many such areas have been identified, however major meta-analysis can take up to 12 months, at significant cost. I t is hoped that their work willact as a focus to stimulate the formation of subgroups in a number of countries, to

carry out meta-analyses in a cooperative manner. This will ensure that the field ofacute pain management is based upon a comprehensive evidence-based approach.

Information forconsumers

In addition to this report, the NHMRC wil l also publish a consumers guide on acutepain management which is intended to inform patients, their families and carers, andmembers of the general community about the current status of acute pain manage-ment, the options available to consumers, and the best ways for them to communicatewith health care professionals in order to obtain effective and safe pain relief.

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Implicationsforgeneral practice

The general practitioner (GP) is in the front line for a wide range of the presentationsof acute pain described in this report. I t is estimated that back pain accounts for aboutone third of the total costs of chronic pain and associated disability. This emphasisesthe total size of the problem of back pain, which mostly falls into the area of generalpractice. Early and appropriate interventions by the GP can have a major impact in

improving assessment and treatment of acute back pain.

Other opportunities exist for improved assessment and treatment strategies that canbe implemented in general practice. Examples include acute herpes zoster infection,acute abdominal pain, acute headache, acute exacerbations of pain in cancer patients,acute pain in haemophil ia/haemarthrosis, acute pain in HIV/AIDS, acute orofacialpain, acute musculoskeletal pain and severe dysmenorrhoea. The GP is alsocommonly called upon to deal with patients with special needs and some who needemergency care.

In some settings, particularly rural and remote areas, GPs may be involved in acutepain management in association with adult post-surgical patients, obstetric patients,paediatric patients and burns and trauma. In these more demanding areas of acutepain management, GPs will need to make an assessment of their own expertise and

the local facilities and support staff, in deciding which treatments are appropriate inthe particular setting of their own practice. Obviously, some of the highly specialisedmethods of pain relief may not be feasible or safe in some general practiceenvironments.

A particular challenge for GPs in managing forms of acute pain such as back pain andheadache, is to practice a coordinated care approach, strongly anchored in evidence-based medicine. Thus GPs should use the evidence presented in this report to considerthe options for their patients, choosing only those options where there is soundevidence, and continue to play a role in coordinating each aspect of the patients careand the duration of such care. An excellent example of this approach is themanagement of acute musculoskeletal pain (see Section 8.7 on page 126 andassociated figures/tables).

A Qu i ck Refer ence Gu ide for GPswill be derived from this report, to provide quickaccess to the major management points of relevance to GPs.

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1 The clinical picture

1.1 Acute pain: mechanismsand clinicalapplications

Definitionofacute pain

According to the International Association for the Study of Pain (IASP), pain is asensory and emoti onal exper i ence associ ated w i th actua l or potent i al ti ssue damage, ordescri bed i n t erms of such damage(level IV; Merskey 1979). This definition applies toacute pain, cancer pain and chronic non-cancer pain.

The IASP defines acute pain as:

pain of r ecent onset and probable lim it ed du rat ion. It usuall y has an id enti f iabl etemporal and causal relat ionshi p to inj ur y or d isease. Thi s is in di st i nction tochr oni c pain w hi ch i s defin ed as pain lasting for l ong peri ods of ti me. Chroni cpai n commonl y per sists beyond t he ti me of heal in g of an i nj ur y and fr equent ly

th er e may not be any clear ly id ent i fi able cause.(Ready & Edwards 1992)

While there is no absolute distinction between acute pain and chronic pain, thisdefinition is still useful because there are many areas of difference in theirmanagement.

Evidence from experimental models is revising concepts of pain mechanisms. This hasimplications for clinical practice, as it enables treatments to be based on scientificprinciples rather than on traditions. In areas in which pain mechanisms are stillpoorly understood (eg neuropathic pain) there is a lack of effective treatment options(Siddall & Cousins 1995a).

Painperceptionandpainpathways

Pain perception involves multiple interacting central and peripheral mechanisms. Inaddition, pain is multifactorial and involves physical, psychological and environ-mental aspects in every individual.

Acute pain begins when algogens (pain-causing substances) are released at the site ofinjury. They stimulate the nerve endings of small fibres (nociceptors) which transmitthe signal into the dorsal horn of the spinal cord (nociception). The signal is thenprojected into specific areas of the brain. At all points of this pain pathway, there areresponses which can increase or decrease the duration and nature of the painperceived. For example, nociceptors may be activated by simple direct pressure,chemical or heat stimuli. These may be exaggerated by sensitisation from multipleinflammatory mediators including substance P, serotonin, bradykinin and theproducts of arachidonic acid metabolism (Campbell et al 1989).

These mediators create a sensitising soup which is responsible for primary hyper-algesia (increased pain in response to painful stimuli in the injured area) and whichcontains components modifiable by non-steroidal anti-inflammatory drugs (NSAIDs)(Vane 1971). While opioids have been considered to exert their action in centralpathways, receptors for opioids at peripheral sites may exist following tissue damage(Bentley et al 1981, Stein 1995). Unmyelinated primary afferent neurons that respondactively only in the presence of chemical sensitisation have been identified (Schaible &

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Schmidt 1988). These silent nociceptors require further study to determine their exactrole in pain transmission but highlight the important role that peripheralmechanisms have in pain perception.

In practice, pain is characterised by both peripheral sensitisation as described above(see Figure 1.2) and central sensitisation, which occurs by means of a change in theexcitability of neurons in the spinal cord. This brings about a number of changesincluding an increased area of the periphery provoking a response in dorsal horn

neurons, an increased duration of response and a decrease in the threshold toactivation (see Figure 1.1). These progressive changes in the response of spinal cordneurons have been termed wind-up. The results of this combined sensitisation areallodynia (pain in response to stimuli not normally associated with pain) andsecondary hyperalgesia (increased pain in response to painful stimuli in areas awayfrom the injured area).

Primary afferentfibres, the dorsal hornand descendingmodulation

Following activation of primary afferent neurons, release of substances from thesefibres at their termination in the dorsal horn activates spinothalamic, spinoreticularand other ascending pain pathways(see Figure 1.1). Section of these primary afferentfibres (eg during an operation) can result in a variety of anatomical, physiological and

biochemical changes arising from aberrant activity at the periphery, at dorsal rootganglia and at dorsal horn neurons. Changes in the dorsal horn mediate centralsensitisation, resulting in secondary hyperalgesia in areas remote from the site ofinitial injury, and allodynia as described above. Descend i ng modul ati onfrom highercentres provides a powerful inhibitory system to modify these enhanced neuronalresponses (see Figure 1.3).

Figure 1.1Under physiological cond iti ons, low i ntensity stim ul i activate low th reshold receptors

to generat e non-painfu l sensations and hi gh i ntensity stim ul i activat e hi gh th reshold nociceptorswh ich m ay lead to pain tr ansmission. I n cl i ni cal practice, centr al and peri pheral changes leadto abnormal excit abil i ty i n t he nervous system. Th is means that low i ntensity stim ul i ar e able toproduce pain (figure adapted fr om Woolf & Chong 1993).

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Theclinical picture

27

*5-HT = 5-hydroxytryptamineFigure 1.2Th e sensit ivi ty of high t hr eshold nociceptors can be modi fi ed i n th e peri phery by acombi nat ion of chemical s that act as a sensit isin g soup. Th ese chemi cals are produ ced bydamaged t issue, as part of th e in flammat ory reaction, and by sympath etic termi nal s (from Woolf& Chong 1993).

Peripheral Sensitisation

Tissue damage Inflammation Sympathetic terminals

Sensitising soupHydrogen ions Histamine Purines Leucotrienes

Noradrenaline Potassium ions Cytokines Nerve growth factor

Bradykinin Prostaglandins 5-HT Neuropeptides

High threshold nociceptor

Transduction sensitivity

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Figure 1.3Sim pl if ied schema of afferent sensory pathways (left) and descend in g modul atorypathw ays (ri ght). Stim ul ation of nociceptors in the ski n sur face leads to impu lse generat ion i nthe pri mar y afferent. Concomitan t w ith thi s imp ul se generat ion, in creased levels of vari ousend ogenous algesic agent s (substan ce P, prostaglan di ns, histam in e, ser otonin , brad yki ni n) ar e

detected near t he ar ea of sti mu lat ion i n t he per iph ery. Pr im ar y afferent nociceptors relay toprojection n eur ons in the dorsal h orn, wh ich ascend in the anterolateral f uni cul us to term in atein the thal amu s. En route, collaterals of the projecttion n eur ons activat e mu lt ipl e hi gher centers,in clu di ng in the nucleus reticul ari s gigantocell ul ari s (NRG). Neur ons from t he NRG pr oject tothe thal amu s and al so activat e the nucleus raph e magnu s (NRM ) and peri -aqueductal grey(PAG) of th e mi dbrai n. Descendi ng fi bres from the PAG project to th e NRM and reticul arformati on adjacent to the NRM . Th ese neur ons activate descend in g in hi bitory n eur ons wh ich ar elocated in these regions and tr avel via the dorsolateral fun iculu s to term in ate in t he dorsal hornof the spina l cord . Descend in g projecti ons also ari se fr om a number of brai nstem sit es in clud in gthe locus cer ul eus. A num ber of neurotr ansm it ters are released by afferent fi br es, descend in gterm in ati ons, or l ocal i nter neurons in th e dorsal horn and modul ate peri pheral nocicepti vein put. Th ese include substance P, gamma-amin obutyr ic acid (GABA), serotonin, noradr enal in e,enk epha li n, neurotensin, acetyl cholin e, dynorph in , cholecystoki ni n, vasoactive in testi nal pepti de,calcitoni n-gene-relat ed peptid e, somatostati n, adenosine, neuropepti de Y, glu tam ate, ni tr ic oxide,

bombesin an d pr ostagl and in s. I nh ibi tors of enzymes such as enk epha li nase, acetyl cholin estera seand ni tr ic oxid e synt hase may act to modi fy the action of these neurotr ansmi tters (fr om Cousin s& Br idenbaugh 1998).

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Theclinical picture

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1.2 Adverse physiological and psychological

effectsofpain

Acute pain is a symptom which signals tissue damage or impending tissue damage(Ready & Edwards 1992). While there are clear ethical reasons for reducing pain, therequirement for analgesia in order to modify the injury response is less apparent.

Generally, the intensity of the injury response is proportional to the degree of tissuetrauma (Chernow 1987), but is influenced by a variety of other factors (see Figure 1.4).Substances released from injured tissue evoke str ess hormoneresponses in addition toactivation of cytokines, adhesion molecules and coagulation factors (Fong et al 1994).The end result of these responses consists of numerous physiological changespromoting catabolism, sympathetic activation, hypercoagulability, immuno-suppression and other adverse states. Adverse cardiovascular effects includinghypertension, tachycardia and increased cardiac work may result from unrelievedpain and may compromise at-risk cardiac patients. Respiratory effects of unrelievedpain can also result in substantial reductions in respiratory parameters and theability to cough. The psychological effects of pain may be less readily observed but areno less harmful and interact with physical alterations, often as part of a vicious cycle(see Figure 1.5) (Cousins & Phillips 1986, Dinarello 1984).

Figure 1.4Note that pain is only one of th e factors, includi ng psychological an d envir onmentalfactors, th at tr igger compl ex in termedia tes (neur al, hum oral etc) leadi ng to the inj ur y response.Th us, acute pai n and th e in ju r y response ar e in evit ably i nt er-r elat ed. Th e end r esult i s physicaland mental deacti vati on. It is therefore appr opri ate to regard a n acute pai n serv ice as one ofpai n management and acute r ehabi li tat ion (see Cousins 1989).

Physi ological changesbrought about by pain are produced by activation of both theperipheral and central nervous systems (Woolf 1989, Kehlet 1997). Changes that reflectthe stress response include alterations in all major organ systems with a predominant

input from the neuroendocrine system (see Table 1.1). It should be noted that effectiveanalgesia is capable of modifying many of these responses, thereby assisting recovery.Patients at great risk of adverse outcomes from unrelieved pain include those withconcomitant medical illness, those undergoing major surgery (eg repair of abdominalaortic aneurysm) and the very young or very old.

INJURY

RESPONSE

including:

Postoperative pain Acute phase cytokines(eg Interleukin 1,6) Inflammation

Surgical traumaNeural Hyperalgesia

Psychological,environmental factors Humoral Catabolism

Other factors (eg drugs) Metabolic Other systemic

adaptationsImmune

Physical, mentaldeactivation

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Figure 1.5Vi cious cycl e of pai n, an xi ety an d sl eepl essness.

Psychol ogical factorshave been closely linked to the exacerbation or, when favourable,the diminution of pain. Psychological determinants that may positively or negativelyinfluence the experience of pain include:

fear and anxiety;

depression;

the degree of control felt by the patient over their pain and disease;

learned responses to pain;

the meaning of pain to the patient; and

the personal consequences of both the pain and its cause.

The endocrine and metabolic responses to surgery are summarised in Table 1.1.

Table 1.1 Metabolic and endocrine responsesto surgery

Endocrine Catabolic hormones ACTH, cortisol, ADH, growthhormone, catecholaminesangiotensin I I, aldosterone,glucagon, IL-1, TNF, IL-6

Anabolic hormones insulin, testosterone

MetabolicCar bohyd r at e Hyperglycaemia, glucose

intolerance, insulin resistancehepatic glycogenolysis,gluconeogenesis (cortisol, glucagon,growth hormone, adrenaline, freefatty acids)insulin secretion/action

Pr otei n Muscle protein catabolism,synthesis of acute phase proteins

cortisol, adrenaline, glucagon, IL-1,IL-6, TNF

Fa t Increased lipolysis and oxidation catecholamines, cortisol, glucagon,growth hormone

Waterand

electrolyte flux

Retention of water and sodium,excretion of potassium andfunctional ECF with shifts toICF

catecholamines, aldosterone, ADH,cortisol, angiotensin I I ,prostaglandins and other factors

ACTH=adrenocorticotropic hormone; ADH=antidiuretic hormone; IL=interleukin;TNF=tumour necrosis factor; ECF=extracellular fluid; ICF=intracellular fluid

Anxiety

Pain Sleeplessness

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2 Acute painservices

Sophisticated methods of pain relief, such as epidural analgesia and patient-controlled analgesia (PCA), have been used for the management of postoperative painsince the early 1980s. However, their widespread use, particularly in general wards,was not common until the introduction of a more organised approach to acute pain

management and the establishment of acute pain services. Acute pain servicesgenerally include at least members of the medical and nursing staff. In institutionswhere such teams cannot be recruited, responsibility is usually given to particularmembers of staff. Anaesthetists have been identified as being particularly qualified todevelop and manage acute pain teams because the knowledge and techniquesemployed are extensions of those used in anaesthesia (level IV; Ready et al 1988).

The first acute pain service (APS) was established in 1986 at the University ofWashington, Seattle (Ready et al 1988). Services began to develop worldwide in the late1980s (Macintyre et al 1990, Wheatley et al 1991). Around that time, a report of the RoyalCollege of Surgeons of England and College of Anaesthetists (Royal College of Surgeonsof England & College of Anaesthetists 1990) recommended that acute pain teams beestablished in all major hospitals. Similarly, the US Department of Health and

Human Services recommended a formal, team approach to the management of acutepain with clear lines of responsibility (AHCPR 1992).

A formal acute pain service can offer:

education about acute pain management in general as well as more specialisedanalgesic techniques;

the introduction of newer and more specialised methods of pain relief and guidanceto improve more traditional methods;

the provision and standardisation of orders, procedures and methods of painassessment for all methods of pain relief, as well as ongoing improvement to thesebased on the results of audit activity;

daily supervision and 24-hour cover for patients under the care of the acute pain

service, as well as for patients with any other acute pain management problems;and

audit and clinical research activity.

Details of these aspects are given in Chapter 4.

In order to fulfi l these roles effectively, a coordinated team approach is essential. TheAmerican Society of Anesthesiologists (ASA) guidelines summarise suggestedorganisational aspects of an acute pain service (see Table 2.1).

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Table 2.1 Organisational aspectsofa postoperative painprogram

1 Education(initial,updates):

Anaesthetists

Surgeons

Nurses

Pharmacists

Patients and families

Hospital administrators

Health insurance carriers

2 Areasofregularadministrative activity:

Maintenance of clear l ines of communication

Workforce24-hour availability of pain service personnel

Evaluation (including safety) of equipment (eg pumps)

Secretarial support

Economic issues

Continuous quality improvement

Resident medical teaching (if applicable)

Pain management-related research

3 Collaboration with nursing services:

J ob description of pain service nurse (if applicable)

Nursing policies and procedures

Nurses in-service and continuing education

Definition of roles in patient care

Institutional administrative activities

Continuous quality improvement

Research activities (if applicable)

4 Elements of documentation

Preprinted ordersProcedures

Protocols

Bedside pain management flow sheets

Daily consultation notes

Educational packages

Modified from Ready et al 1995.

As part of this multidisciplinary approach, all medical and paramedical staff have arole to play in pain management, whether there is a formalised team such as an acutepain service or in routine practice.

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Acute painservices

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Where an anaesthesia-based service is not possible, the desired improvement in acutepain management may be achieved by:

institutional commitment to the relief of pain and suffering;

multidisciplinary, regular education programs on pain management;

responsibility of care to be assigned to those most knowledgeable, experienced andavailable to deal with patients needs in a timely fashion; and

regular quality review of outcome.Effective pain management by all members of the multidisciplinary team can only beachieved by sound educational strategies instigated at an institutional level (seeSection 3.3 on page 40).

Sample case: earlypainservice interventionandacute rehabilitation

A 23-year-old m ale suffers mu lt ipl e in ju ri es, requir in g laparotomy for i ntr a-abdomin altr aum a, and i nt er nal fi xati on of left lower l im b fractu res. By seven da ys post-opera ti vely he is maki ng a good gener al recovery, except th at he is now r equi r in gescala ti ng doses of opioid via PCA an d comp lai ni ng of sever e bur ni ng pai n i n t he leftleg and foot below hi s limb fr actur e site. As a result he cann ot toler ate the cont in uous

passiv e movement tr eatm ent for h is l eft lower l imb and has been un able to even sit outof bed. Th e pati ent , his fami l y, the orth opaedi c sur geon and n ur sing staff arefru str ated an d a view is form in g that he is a diff i cul t pati ent w ho is not cooperati ngwi th r ehabi li tat ion. Sur gical assessment r eveals no surgi cal ly tr eatabl e compl icati ons.Th e pai n ser vice in thi s hospi tal is an i nt egrat ed acute, chr onic and cancer pai nser vi ce. When consul ted, immedi at e di agnosis of neur opath i c pai n, second ar y to l eftlat er al popli teal n erv e tr aum a, is made and a subcutan eous l ign ocai ne in fusionreli eves th e pai n, perm it ti ng w it hd r awa l of opi oids. Th e pati ent i s able to cooper ateful ly w it h r ehabi li tati on and i s subsequent ly foll owed by the pai n servi ce and tr eatedwi th a low d ose of sodi um valpr oate (200 mg bd) and am it r i ptyl i ne (25 mg) at ni ght.(Th e tr eatm ent of neur opath i c pai n i s di scussed i n Section 10.2 on page 152.)

Key points

A multidisciplinary approach to the management of acute pain, particularly in aformal acute pain service, leads to improved pain relief and better patientoutcomes.

Effective pain management is fundamental to the quality of care. The key tosuccessful pain management is education and training of all staff.

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3 Principlesofacute painassessment

and management

3.1 Assessmentofpainand painhistory

Painrating methods

Because pain is an individual experience influenced by many factors includingprevious experiences, culture, prognosis, coping strategies and fear and anxiety,there is a poor correlation between patient and staff assessments of pain severity.Self reports are among the most reliable indicators of pain severity, with a number ofsimple self-reporting tools commonly used for adults.

The approach commonly used for postoperative patients is to use verbal painscoring methods such as the categorical ratingscale. Different descriptors can

be used to rate the patients pain, eg no pain, mild pain, moderate pain, severe

pain, worst possible pain.

The visual analoguescale (VAS) employs a 10 cm line rated from no pain at theleft to worst pain possible on the right and requires the patient to mark their painon this continuum. The VAS score is the distance from the no pain point to thepatients estimate.

no pain worst possiblepain

The verbal numerical rating scale (VNRS) also asks the patient to rate theirpain from no pain (0) to worst pain possible (10). Numbers are avoided on thisscale in order to prevent the patient receiving cues.

There is good correlation from pooled data between the VAS and the VNRS of painscoring (level III; Murphy et al 1988). However, for an individual, once an appropriatescale has been selected it should continue to be used for monitoring pain.

While it is not always possible to relieve pain entirely, the aim should be to achievecomfort. Patients should be assessed during movement and activity as well as at rest,and incident pain (pain during movement) reduced as much as possible.

Patientswithspecialneeds

Patients who have difficulty communicating their pain (eg children, hearing andcognitively impaired patients) require special attention. There are a number of painrating scales designed for use in children (see page 94). The needs of patients whoseeducational or cultural background differs significantly from that of their health care

team should be taken into account, with scales modified to suit the individual needs ofpatients. Patients who do not speak English should be given the opportunity tocommunicate in their chosen language through an interpreter.

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Continuing assessment

A patients pain and response to treatment should be assessed regularly, at leastevery two hours for the first 24 to 48 hours following major surgery. It is important tomonitor pain and response to therapy, and to tailor the frequency of monitoring to theindividual patients needs. If pain is poorly controlled or therapy is being altered,assessment may need to be more frequent. Pain assessment should be recorded in areadily available and visible form, such as on the bedside chart with other vital

observations.

It should be remembered that an unexpected increase in pain, especially whenassociated with changes in other vital signs, may signal the development of a newdiagnosis or postoperative complication (eg peritonitis, compartment syndrome orneuropathic pain) (level IV; AHCPR 1992).

Patients should be actively involved in the continuing assessment of their pain. Anyfactors which reduce the efficacy of the treatment wil l alter their confidence in thepain management plan. Patients may also experience a change in the character andseverity of pain in association with a complication. A careful history and examinationof the patient is essential when pain severity increases unexpectedly.

Key points

Careful assessment of pain should occur initially and then regularly throughouttreatment, using self-reporting techniques. As pain varies so markedly betweenindividuals, patient involvement in the initial and continuing assessment of theirpain is essential.

Pain should be assessed both at rest and during activity and pain relief assessed asto its adequacy, to allow appropriate function.

Unexpected levels of pain or pain that suddenly increases, especially whenassociated with changes in other vital signs, may signal the development of a new

surgical or medical diagnosis (eg postoperative complication, neuropathic pain).

Painhistory

In addition to a thorough general medical history and physical examination, patientswith any form of pain should be evaluated with a specific pain history as follows inTable 3.1. A useful method for assessing the extent of pain is for patients to chart theprimary area of pain and areas of radiation on a pain diagram (a sample chart isgiven in Figure 3.1).

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Principlesofacute painassessmentandmanagement

37

Table3.1 Taking a painhistory

Circumstances associated with pain onset

Primary site of pain (see Figure 3.1)

Radiation of pain (see Figure 3.1)

Character of pain (using McGill Melzack multidimensional pain inventoryeg is pain throbbing, sharp, aching etc)

Intensity of pain (eg on visual analogue scale)at rest

on movement

at present

during last week

highest level

Factors altering pain

what makes it worse?

what makes it better?

Associated symptoms (eg nausea)

Temporal factors

is pain present continuously or otherwise?

Effect of pain on activities

Effect of pain on sleep

Medications taken for pain

Other treatments used for pain

Health professionals consulted for pain treatment

Pai n h i s tor y in for ma t i on of sign i f i can ce for symp tom at ic t r eat m ent of pa i n

Expectations of outcome of pain treatment

Patients belief concerning the causes of pain

Reduction in pain required to resume reasonable activities

Patients typical coping response for stress or pain, including presence of anxiety orpsychiatric disorders (eg depression or psychosis)

Family expectations and beliefs about pain, stress and postoperative course

Ways the patient describes or shows pain

Patients knowledge, expectations and preferences for pain management

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Figure 3.1Pain diagram

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3.2 Diagnosing neuropathic pain

Neuropathic pain is underdiagnosed in patients with acute pain in many differentsettings eg postoperative, post-trauma and acute pain in patients with cancer. Auseful definition is pai n associ ated w it h i nj ur y, disease or surgi cal section of theper i pher al or cent r al n er vous system. A wide range of neuropathic pain syndromes is

described in the IASP taxonomy of chronic pain syndromes (IASP Task Force onTaxonomy 1994). As described in Section 1.1 on pain mechanisms (see page 25),neuropathic pain frequently involves both peripheral and central sensitisation. Thetreatment of neuropathic pain is discussed in Section 10.2 on page 152.

Diagnosis of neuropathic pain can usually be made on the basis of history andphysical examination. There is often a history of an event which may have resulted innerve damage associated with the onset of neuralgia, or complex regional pain syn-drome after surgery. There may be considerable delay between the event and theonset of pain. Pain is often described as paroxysmal, burning, stabbing, pulsing,electric shock-like or dysaesthesic. Hyperalgesia may be present in the area of injury(primary) or in the surrounding area (secondary) which is indicative of central sensiti-sation. Allodynia (pain in response to a non-painful stimulus such as a light touch)

also indicates central sensitisation. Hyperpathia may be present, where there is anincreased pain threshold and repetitive stimulation results in summation of pain.

Early diagnosis and treatment of neuropathic pain are preferable as chronicneuropathic pain is extremely difficult to treat. Complex regional pain syndromes(CRPS) are discussed on page 154.

Key point

Although not specific, an important indicator of neuropathic pain is the inability torelieve pain with opioids, or no apparent relief of pain with a rapidly increasingopioid dose. Other indicators can be obtained from the history and physicalexamination, as shown in Table 3.2.

Table 3.2 Featuresthatsuggestneuropathic pain

Pain in the absence of ongoing tissue damage

Pain in an area of sensory loss Paroxysmal or spontaneous pain Allodynia (pain in response to non-painful stimuli) Hyperalgesia (increased pain in response to painful stimuli) Dysaesthesias (unpleasant abnormal sensations; ants crawling on the skin etc) Characteristic of pain different from nociception: burning, pulsing, stabbing pain Sometimes a delay in onset of pain after nerve injury (NB some neuropathic pain has

immediate onset)

Hyperpathia: increasing pain with repetitive stimulation; after response (continuedexacerbation of pain after stimulation); radiation of pain to adjacent areas after stimulation

Tapping of neuromas (spontaneously firing growth buds from damaged peripheral nerves)produces a radiating electric shock sensation in the distribution of the nerve (Tinels sign)

Poor response (not unresponsiveness) to opioids Presence of a major neurological deficit (eg brachial plexus avulsion, spinal cord injury etc)

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3.3 Agentsused to manage acute pain

In this section there is a brief description of the major agents used in the managementof acute pain. More detail about dosing, routes of administration, optimal usage andside effects can be found in the chapters on managing specific types of pain, especiallyin the chapter on postoperative pain.

Pharmacological interventionsOpioids

Opioid analgesics are the cornerstone of the management of moderate to severe pain.They produce analgesia by binding to opioid receptors both within and outside thecentral nervous system. Opioid analgesics are classified as full agonists, partialagonists or mixed agonist-antagonists, depending on the way in which they interactwith opioid receptors. Full agonists produce a maximal response within the cells towhich they bind; partial agonists produce a lesser response, regardless of theirconcentration; and mixed agonist-antagonists activate one type of opioid receptorwhile simultaneously blocking another type. The most important receptor type forclinical analgesia is named mu because of its affinity for morphine. Examples ofother commonly used mu opioid agonists include codeine, pethidine, oxycodone,methadone and fentanyl. Tramadol, a recently introduced mu opioid agonist, also hasimportant non-opioid spinal and central nervous system effects.

These opioids all have the potential to cause important side effects, which arediscussed on page 50.

Titratio n

The key to effective titration of opioids is the use of incremental doses and carefulobservation of side effects and relief of pain.

Routes of administration

Traditional methods of opioid administration are via oral, rectal, intravenous, sub-cutaneous, or intramuscular routes. Newer methods, using the epidural or intrathecalroutes and PCA, have been shown to be effective and safe but need to be administeredby highly skilled staff.

Non-steroidal anti-inflammatory drugs

NSAIDs can be very useful for managing mild to moderate pain. They act by decreas-ing levels of inflammatory mediators generated at the site of tissue injury. WhenNSAIDs alone cannot control pain, they have a significant opioid dose-sparing effectand can be useful in reducing opioid side effects. The concurrent use of opioids andNSAIDs often provides more effective analgesia than either of the drug classes alone.Most NSAIDs are available in both oral and rectal forms. Certain NSAIDs can also begiven intravenously or intramuscularly. NSAI Ds have important side effects andcannot be used in all patients. Potential risks are discussed on page 73.

Paracetamol

Paracetamol is an important option in the treatment of mild to moderate pain and anadjunct to opioids in more severe pain. It has analgesic and antipyretic effects, but isnot considered to be anti-inflammatory. There is controversy about the mechanism ofaction, but paracetamol seems to have a significant central action. I t is available inboth oral and rectal forms. Proparacetamol, an intravenous preparation, is availablein some European countries and appears to be more effective than paracetamol.

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Local anaesthetics

Local anaesthetics interrupt pain pathways by blocking axonal conduction. Localanaesthetics for acute pain relief have various indications, including infiltration andnerve and plexus block, and are often used with opioids in continuous epiduraladministration.

Adjuvantagents

A number of adjuvant agents have been shown to be effective in the treatment ofcertain pain syndromes. These include antidepressants, anticonvulsants andcorticosteroids (see Section 10.1 on page 151).

Multimodal analgesia

There is evidence that patients benefit from the use of multimodal analgesia (ie use ofdifferent classes of analgesics) after surgery. NSAIDs, local anaesthetics, paracetamol,other non-opioid analgesics and opioids are used in combination to improve pain reliefand to reduce the dose of each analgesic drug and the intensity of side effects.

Future agents

Recently, the roles of the N-methyl-D-aspartate (NMDA) receptor and nitric oxide inthe production of wind-up and morphine tolerance have been investigated (Ren 1994,

level I II; Mao et al 1995). Ketamine, an NMDA antagonist, has been shown to markedlyreduce opioid requirements when given pre-operatively (level III; Royblat et al 1993).When combined with morphine, ketamine has been shown to provide superior post-operative pain relief at a lower dosage and with fewer side effects than morphinealone (level II; J avery et al 1996). Ketamine may be used by low-dose infusion wherepain relief by opioids proves to be difficult, such as for acute neuropathic pain,although it may cause unpleasant psychomimetic side effects. S-K etamine has beenreported to have a lower incidence of side effects in clinical studies but is not yetapproved for use in Australia.

It appears that the pain mechanisms involving nitric oxide work through the NMDAreceptor. Further therapeutic manoeuvres based on the manipulation of nitric oxideare anticipated, probably initially by investigation of the long-used component of

cough mixtures, dextromethorphan. This has an excellent safety record and is aproven NMDA receptor blocker. Current clinical trials of dextromethorphan plusmorphine in postoperative pain are evaluating whether dextromethorphan reducesthe doses of morphine required for pain relief. At present, dextromethorphan or othernovel analgesics acting on NMDA or nitric oxide mechanisms are not approved forpostoperative pain management.

Non-pharmacological interventions

These interventions are appropriate for patients who wish to use them, who maybenefit from reducing drug therapy, or who are likely to experience a prolongedinterval of pain.

Cognitive-behavioural approaches include preparatory information, simple relaxation,

imagery, hypnosis and biofeedback. Physical therapeutic agents and modalitiesinclude spinal manual therapy, mobilisation, application of superficial heat or cold,massage, exercise, electro-analgesia such as transcutaneous electrical nervestimulation (TENS) therapy and acupuncture.

These techniques are discussed further on pages 78, 87, 95 and 131.

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3.4 Educationaboutpainmanagement

Given the importance of good pain management and the changes in clinical practice inthis field, continuing education of GPs, medical specialists, junior medical staff,nurses and allied health professionals is essential.

Medical andalliedhealthworkers

Professional colleges now recognise the importance of appropriate training for painmanagement. The Australian and New Zealand College of Anaesthetists (ANZCA)includes pain management as a major area of experience for all specialty trainees. In1996, the ANZCA initiated a Certificate in Pain Management, based upon a post-qualification year of experience in an ANZCA approved

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