Procedural sedationDave Mcilroy

What is it ? The American College of Emergency Physicians (ACEP) defines procedural

sedation as "a technique of administering sedatives or dissociative agents with or without analgesics to induce a state that allows the patient to tolerate unpleasant procedures while maintaining cardiorespiratory function. Procedural sedation and analgesia (PSA) is intended to result in a depressed level of consciousness that allows the patient to maintain oxygenation and airway control independently.

Minimal sedation Response to verbal stimulation is normal.

Cognitive function and coordination may be impaired.

Ventilatory and cardiovascular functions are unaffected.

Moderate (formerly conscious) sedation Depression of consciousness is drug-induced.

Patient responds purposefully to verbal commands.

Airway is patent, and spontaneous ventilation is adequate.

Cardiovascular function is usually unaffected.

Deep sedation Depression of consciousness is drug-induced.

Patient is not easily aroused but responds purposefully following repeated or painful stimulation.

Independent maintenance of ventilatory function may be impaired.

Patient may require assistance in maintaining a patent airway.

Spontaneous ventilation may be inadequate.

Cardiovascular function is usually maintained.

General anaesthesia Loss of consciousness is drug-induced, where the patient is not able to be

aroused, even by painful stimulation.

Patient's ability to maintain ventilatory function independently is impaired.

Patient requires assistance to maintain patent airway, and positive pressure ventilation may be required because of depressed spontaneous ventilation or drug-induced depression of neuromuscular function.

Cardiovascular function may be impaired.

A light anaesthetic ? Guedel in 1937, first widely accepted guide to depth of anaesthesia (I – IV)

Artusio later divided stage 1 into 3 planes, first plane no analgesia no amnesia, second amnesia no analgesia and 3rd both analgesia and amnesia

Entropy and Bis , (around 60 – 80 )

When is it used?Fracture reduction

Joint relocation

Painful procedures, esp children

Radiological procedures, eg CT , MRI

Cardioversion

Foreign body removal

Suturing , and other procedures

Other options GA in theatre with Image intensifier and anaesthetic support

Bier’s block

Haematoma block

Regional techniques

Just don’t do it

Assessment Your own level ability and experience, and that of your assistants

The state of the department, resource hungry procedure

Availability of appropriate area and equipment

Plan for it all to go wrong, don’t just have a plan A

Patient factors

Patient factors ASA grade (3+), co-morbidities

Fasted ?

Airway assessment

Obesity or pregnancy

Intoxicated

Allergies , previous anaesthetic

Am I happy to RSI this patient?

Patient selection Short painful procedure (<20 mins )

Age

ASA 1 and 2

Airway assessment

PMHx

fasting

fasting How important is it?

Several studies studies , with several different agents , maybe not as important as we once thought 1,2,3

urgency Emergency

Urgent

Semi-urgent

elective

Other considerations Carers / parents

Informed consent

Documentation, what was given, how much when and by whom and any problems

Post sedation observation

Instructions on driving and alcohol

Staffing Minimum 3 trained staff

Practitioner administering sedation must be familiar with the agent, experience and able to monitor and detect problems

Airway competent

Anaesthetist ?

ALS competent

Equipment (ACEM minimum) Adequate room and appropriate lighting

Tiltable table, preferable but not mandatory

Suction

Oxygen

Means to inflate the lungs, readily available airway equipment

Appropriate drugs

continued Pulse oximeter

BP measurement

Ready access to ECG and defib

Means to summon assistance

ET CO2 monitoring

Choice of agent Midazolam, diazepam

Morphine, fentanyl, remifentanyl

Propofol

Ketamine

Etomidate

Promethazine ( twice now )

Choices, choices Use what you are familiar with and know how to use

Titrate dose, it is easier to put more in than take some out

ketamine Safe

IV / IM

Laryngospasm

Role of atropine / glycopyrolate

Emergence phenomenon

Dissociative agent, powerful analgesic

Ketamine 2 Effect on ICP

Co administration of anxiolytics eg midazolam or propofol

Dose 0.5 – 2 mg /kg iv

2 – 4 mg / kg IM

10 mg / kg IM via syringe dart ( dangerous animal gun )

Propofol Rapid

Short acting

Easily titrated

Respiratory depression 50% +

Hypotension

0.5 – 2 mg /kg iv

Amnesic

midazolam Amnesic, but no analgesia

Fairly rapid and predictable

Slower recovery than propofol

Reversable (big advantage for some operators )

fentanyl Fast acting

Powerful analgesic

Duration of action 20 – 40 minutes (at low doses)

Reversible

IV or IN popular, but all routes

What could possibly go wrong ? Loss of airway reflexes

Depression of respiration

CV depression

Drug interactions, adverse reactions and anaphylaxis

Variations in expected response to drugs used

Possible deeper sedation than expected

Risks from the procedure

Preoxygenation Good idea or not

How is it best achieved?

Nasal prongs, hudson, non-rebreather mask, self inflating bag with reservoir, CPAP mask ?

Preoxygenation or denitrogenation Lungs can hold much more oxygen than blood (about 20 times)

Lungs full of air equals about 0.4 l available oxygen (FiO2 0.21 x 2l)

Lungs full of oxygen equal 2 l (FRC x FiO2)

Body oxygen consumption about 250 ml under normal conditions

All the oxygen reserve is provided by preoxygenation

Rate of preoxygenation is a predictor of rate of deoxygenation, as represents the relationship between alveolar minute volume FRC

Technique big breaths v TV x longer time

Really should measure FeO2 (>90%)

Prolonging DAWD, apnoiec oxygenation General aspects

Preoxygenation, position, technique, and method of O2 delivery

Apnoeic oxygenation

Duration of apnoea without desaturation DAWD = time from onset of apnoea to saturation <90%

DAWD depends on

Initial oxygen reserve

Rate of O2 consumption

Ongoing apnoeic oxygen delivery or not

DAWD <1 minute – 8 minutes without apnoeic oxygenation depending on various

factors

Obesity

Pregnancy

Increase rate of consumption, fever, tachycardia

Inadequate preoxygenation

Study Endpoint

Tidal VolumeBreaths

4 (in 30 sec)Deep Breaths

8 (in 60 sec)Deep Breaths

Gambee DAWD 8.9 (1.0) min

6.8 (1.8) -----

Nimmagadda

FeO2 % 88 (5) % 80 (5) 87 (3)

Pandit FeO2 % 92 (1) % 83 (2) 91 (4)

Gagnon FeO2 % 89 (3) % 76 (7) -----Gambee et al Preoxygenation techniques: comparison of three minutes and four breaths. Anesth Analg 1987; 66: 468–70.

Nimmagadda et al. Preoxygenation with tidal volume and deep breathing techniques: the impact of duration of breathing and fresh gas flow. Anesth Analg 2001; 92: 1337–41.

Pandit etal Total oxygen uptake with two maximal breathing techniques and the tidal volume breathing technique: a physiologic study of preoxygenation. Anesthesiology 2003; 99: 841-6

Gagnon et al When a leak is unavoidable, preoxygenation is equally ineffective with vital capacity or tidal volume breathing. Can J Anesth 2006; 53: 86–91.

High flow nasal vs high flow mask oxygen delivery: tracheal gas concentrations through a head extension airway model 2002 Open Forum Abstracts, Am Assoc Resp Care

High flow nasal cannula delivery > non-rebreather mask

at equivalent flows

Apnoeic oxygenation 250 ml oxygen leaving lung per minute

10 – 20 ml CO2 entering lung

Results in slightly subatmospheric alveolar pressure

Net gas flow 240 ml / minute

Techniques of O2 delivery Nasal cannula

10 Fc catheter into nasopharynx (distance of mouth angle to ear tragus) @5l/min O2

Paediatic south facing Rae tube to angle of the mouth

“apneic diffusion oxygenation, diffusion respiration, and mass flow ventilation”

Hypotension under anaesthesia, sedation Usually temporary

? Best agent or way to resolve ?

Elevate legs, fluid bolus,. Metaraminol ?

laryngospasm PEEP

Deepen

Sux low dose

Sux full dose

Iv lignocaine

documentation consent

Make sure its clear

What was given, when, how much, problems encountered

How long to stay monitored

How long until fit to discharge

Driving, avoidance of alcohol

1 Treston G. Prolonged pre –procedure fasting time is unnecessary when using titrated intravenous ketamine for paediatric procedural sedation. Emergency medicine Australasia 2004; 16(2): 145-150

2 Agrawal D, Manzi SF, Gupta R et al. Preprocedural fasting state and adverse events in children undergoing procedural sedation and analgesia in a paediatric emergency department. Annals of emergency medicine 2003: 42(5) 636-646

3 Roback MG, Bajaj L, Wanthan JE, et al. Preprocedural fasting and adverse events in procedural sedation and analgesia in a paediatric emergency department are they related? Annals of Emergency Medicine 2004; 44(5): 454 - 459