Anaesthesia protocol development: Insights from National societies

regarding new antiplatelets, new anticoagulants and haemostatic

agentsG Ogweno

Dept Of Medical PhysiologyKenyatta University

Factors contributing to protocol based healthcare

• Cost pressures• Technological advances• Increase in management-led decision making• Consumer awareness• Value for money movement• Availability of information• Non-clinicians with the authority to question

effectiveness• International consensus• Professional accountability• Changing demographic profile

Why protocols in anaesthesia?

• To ‘standadize’ medical care, increase quality , effectiveness, specificity, sensitivity, resoluteness and patient outcomes=clinical pathways

• ‘Experts’ best faith efforts to offer reasonable pathways for patient management

• To enhance best evidence based practice

What are protocols?

• Special set of rules defining relationship=communication

• Based on current evidence• Identify most important questions related to

clinical practice, possible options and outcomes=decision points and course of action

• Identify, summarise, evaluate highest quality evidence, risk vs benefit and cost effectiveness

Forms of protocols

• Summarized consensus statements on best practice

• Guidelines: diagnosis, treatment by national associations

• Clinical pathways• Trials: clinical, research

Levels of Evidence

Hierachies of evidence• Clinical trials I-well designed randomised controlled trials II-1a: well –designed controlled trials with pseudo-

randomisation II-1b: well-designed controlled trials with no

randomisation• Cohort studies II-2a: well designed cohort (prospective) with

concurrent controls II-2b: well designed cohort(prospective) with

historical controls II-2c: well designed cohort (retrospective) with

concurrent controls II-3: well designed case –controlled (retrospective) III- large differences from comparisons between

times and/or places with or without intervention Iv-opinions of respected authorities based on

clinical experience, descriptive studies and reports from expert committees

Forms of evidence

Classes of recommendations and levels of evidence

• Classes of recommendations Class I Evidence and/or general agreement that a given treatment or procedure is

beneficial Class II Conflicting evidence and/or divergence of opinion about the

usefulness/efficacy of the treatment or procedure Class IIa Weight of evidence/opinion in favour of usefulness/efficacy Class IIb Usefulness/efficacy is less well established by evidence/opinion Class III Evidence or general agreement that the treatment or procedure is not

useful or effective and in some cases may be harmful• Level of evidence Level A Data derived from multiple randomised clinical trials or meta-analyses Level B Data derived from a single randomised clinical trial or large non-

randomised studies Level C Consensus of opinion of the experts and/or small studies, retrospective

studies, registries

Perioperative Anticoagulation

Indications • Patients on Anticoagulation undergoing

surgery Pitfalls • Over Anticoagulation or premature use results

in significantly increased bleeding complications

• Bleeding complications result in transfusions and stopping Anticoagulation which risks clots

Points ↘of action of anticoagulants

Laboratory testing

Common• Blood counts, including

platelets• Routine Kinetic: PT,aPTT,

TT, ACT, INR• Bleeding time• Not predictive of bleeding

Research• Kinetic: ECT• Factor assays: anti-Xa• Capacitative:

Thrombelastography, Thrombogram

• Platelets: optical aggregometry, plateletworks,multiplate

• Promising though not readily available

Perioperative anticoagulation Protocols: sources of information

• Analysis of published studies with LMWHs and the type of anaesthesia is reported

• Case reports in the literature• Calculations from cases reported to

manufacturers• Questionnaires to anaesthesiology societies

Risk stratification

Bleeding• High risk procedures:

– Neurosurgery– Abdominal or pelvic procedures– Orthopedic joint procedures– Major ENT or oral surgery– Endoscopy with biopsy– Epidural Anesthesia – Prolonged general anesthesia with

intubation• Very Low Risk Procedures:– Procedures

• Dental procedures• Cataract Surgery• Dermatologic procedures• Pacemaker and IACD placement• Endoscopy without biopsy

Thromboembolism• High:

• Deep Vein Thrombosis within last 3 months• Pulmonary Embolism within last 3 months• Cardiac thromboembolism (any cause) within 1 month• Recurrent Venous Thromboembolism• Strong Thrombophilia

– Active cancer– Antiphospholipid Antibody Syndrome

(uncommon)– Antithrombin III deficiency (rare)– Protein C Deficiency – Protein S Deficiency

• Mechanical heart valves– Mitral valve replacement– Ball-Cage or other older cardiac valve– Higher risks

» Comorbidity (e.g. Congestive Heart Failure)

» Atrial Fibrillation with mechanical valve• Intermediate:

• Atrial Fibrillation with CHADS-2 Score 4 or higher• Very Low Risk:

• No DVT for 3 months• Chronic Atrial Fibrillation without stroke• New bileaflet aortic valves (St. Jude or Medtronic)

Central neural blockade (CNB) in anticoagulated patients: Risks

• Symptomatic spinal/epidural haematoma• greatest risk appears effective during insertion or

removal of spinal or epidural needles or catheters

• SSEH do NOT necessarily progress to permanent neurological damage

• Risk of SSEH appears higher for epidural than spinal-especially traumatic or difficult access

• Not all vascular traumatic damage recognizable

LMWH and spinal Haematoma In US

• Enoxaparin introduced US in 1992=dose 30mg bd• More than 40 cases of spinal haematomas for 1st

5 years of use• 1997: FDA issued warning, manufacturers to

adjust insert• ASRA tasked to provide guidelines• Horlocker et al analysed case reports/ series of

complications introduction of enoxaparin• ASRA consesus conferences in 1998, 2002, 2007

and 2007

Highlights of US Guidelines• Anticoagulation is not an absolute

contraindication for regional anesthesia• Regional anesthesia may be safely performed

provided risk stratification is done• No added risk at prophylactic doses• Complications may be independent of drug

action: patient related, procedure specific• Cases to be judged on individual basis and

exercise caution= continous vigilance• Recognizes data insufficiency

European perspectives

• LMWH-enoxaparin many years experience@40mg od

• Moen et al 2004 review of severe neurological complications between 1990-1999

1,260, 000 spinal blocks450, 000 epidurals including 200,000 labor

epidurals

Results of Moen et al

Findings• 127 complications Spinal haematomas=33 Cauda equina syndrome=32 Meningitis=29 Epidural abscess=13 Miscellanous=20• Permanent neurological

damage in 85 patients

Severe neurological complications

• 1: 20-30,000 in all groups• 1:25,000 after obstetric

epidurals• 1:3,600 in all others• Rates less in obstetrics• Epidurals higher than spinal• Osteoporosis risk factor

Haemostatic agents

• Whole blood and plasma products as haemostatic agents limited efficacy and associated with complications

• Available systemic alternatives:Fibrinogen concentrateProthrombin complex concentrate (PCC)Recombinant factor vii

Recombinant factor vii

• Efficacy demonstrated in haemophilia-level 1a• Trials ongoing in trauma= level iii• Case reports of post administration

thrombophilia• Most guidelines indicated only in bleeding

haemophilia• Other uses experimental=must warn of grave

consequences

European perspectives on haemostatic agents

• Efforts to eradicate use of FFP• Use of capacitative tests strongly

recommended, if available• Strong recommendation on identification and

replacement of individual factors• Austrian OGARI: use of fibrinogen and PCC as

opposed to FFP in trauma

Anesthetic management of patients receiving antiplatelet medications

• Exert diverse effects on platelet function• Impossible to extrapolate between groups• No wholly accepted test to guide therapy• Appear to represent no added risk for CNB

complications-actual risk unknown• Bleeding risk may be increased by concurrent use

of other antithrombotic medications• Cyclooxygenase-2 inhibitors minimal effect on

platelets, could be considered as alternatives

Limitations of Guidelines

• Desired level of evidence does not exist• Subject to major flaws• Failure to account for multiple comorbidities• Tend to produce an average result• Unintended consequences• Poorly understood factors• Too complicated• Misuse of guidelines

Conclusions

• Perioperative management of haemostatic agents pose significant challenge

• Guidelines may help minimize risks• Risks vs benefit should be carefully weighed in

any protocol development• Good protocols should be simple to follow

and based on facts• Unfortunately, NO such data exist for

perioperative antithrombotic agents