Key Facts

Preoperative assessment is a systematic evaluation performed before planned surgery to identify patient risk factors, optimise comorbidities, plan anaesthetic technique, and arrange appropriate post-operative care. It improves surgical outcomes and reduces cancellations.

Epidemiology

Approximately 10 million surgical procedures are performed annually in England. Same-day cancellation rates are approximately 6-8%, with medical reasons being a significant contributor. Effective preoperative assessment reduces cancellation rates by up to 50%.

Aetiology

Preoperative assessment addresses:

• Patient factors: Comorbidities, medications, allergies, functional capacity, nutritional status
• Surgical factors: Procedure complexity, estimated blood loss, position, duration
• Anaesthetic factors: Airway assessment, anaesthetic technique, post-operative care level

Pathophysiology

Surgery induces a stress response (sympathetic activation, cortisol release, catabolic state) that places demands on cardiovascular, respiratory, and metabolic systems. Patients with limited physiological reserve are at higher risk of post-operative complications. Preoperative assessment aims to identify those at risk and implement strategies to improve reserve.

Key Components of Assessment

• History: Comorbidities, previous anaesthetics (problems?), family history (MH?), functional capacity, medications, allergies, smoking/alcohol
• Examination: Airway (Mallampati, mouth opening, neck extension), cardiovascular, respiratory, BMI
• Risk stratification: ASA grade, procedure severity, estimated blood loss

Specific Conditions Requiring Attention

• Cardiovascular: Ischaemic heart disease, heart failure, valvular disease, arrhythmias, hypertension
• Respiratory: COPD, asthma, OSA, recent URTI
• Endocrine: Diabetes (HbA1c, insulin management), thyroid disease, adrenal insufficiency
• Haematological: Anticoagulants, bleeding disorders, sickle cell disease
• Renal: eGFR, electrolytes, fluid balance

Red Flags Requiring Further Investigation

• Unstable angina or recent MI (<30 days) - defer elective surgery
• Decompensated heart failure - optimise before proceeding
• Severe aortic stenosis - high-risk; cardiology input
• HbA1c >69 mmol/mol (8.5%) - optimise diabetic control
• Active respiratory infection - defer elective surgery 2-4 weeks

Bedside

• Airway assessment: Mallampati, thyromental distance, mouth opening, neck extension
• Observations: BP, HR, SpO2, BMI, NEWS2
• ECG: If cardiovascular disease, age >65 with comorbidities, ASA ≥III
• Urinalysis: Diabetes screening if indicated

Bloods

• As per NICE NG45 - targeted, not routine:
• FBC: If anaemia suspected, expected blood loss, renal/liver disease
• U&Es: If renal disease, diuretics, ACEi/ARBs, diabetes
• Coagulation: If on anticoagulants, liver disease, bleeding history
• HbA1c: Diabetic patients (target <69 mmol/mol for elective surgery)
• Group and save: If blood loss >500mL anticipated
• Sickle cell screen: At-risk populations

Imaging

• CXR: Not routine - only if acute respiratory symptoms, known cardiorespiratory disease with change in symptoms
• Echocardiography: If valvular disease, unexplained murmur, heart failure assessment
• Pulmonary function tests: Severe respiratory disease, lung resection surgery

Special Tests

• CPET: High-risk patients before major surgery (AT <11 mL/kg/min = high risk; VO2 peak <15 mL/kg/min = very high risk)
• Dobutamine stress echo or myocardial perfusion: If cardiac risk factors and poor functional capacity
• Sleep study: If suspected OSA (STOP-BANG ≥5)

Non-pharmacological

• Prehabilitation: 4-6 weeks structured exercise + nutritional optimisation + psychological preparation
• Smoking cessation: Ideally ≥8 weeks pre-operatively (reduces respiratory complications by 50%)
• Alcohol cessation: ≥4 weeks reduces post-operative complications
• Nutritional optimisation: Correct anaemia (iron supplementation), protein supplementation if malnourished
• Patient education: Explain anaesthetic plan, expected post-operative course, pain management

Pharmacological

Medication management:

• Continue: Beta-blockers, statins, anti-epileptics, Parkinson's drugs, thyroid medication, inhalers, long-term steroids (may need supplementation)
• Stop day of surgery: ACEi/ARBs (reduce intraoperative hypotension), short-acting sulfonylureas
• Stop before surgery: Warfarin (5 days, bridge with LMWH if high risk), DOACs (48-72h), clopidogrel (7 days), metformin (day of surgery for major - variable practice)
• Diabetic management: Follow JBDS perioperative guidelines - VRIII if fasting >1 meal or HbA1c poorly controlled

Surgical/Interventional

• Pre-operative anaemia correction: IV iron (ferric carboxymaltose 1g) if Hb <130 g/L and surgery in 2-6 weeks
• Blood conservation: Cell salvage, tranexamic acid, restrictive transfusion targets

Referral Criteria

• Unstable cardiac disease - cardiology optimisation before elective surgery
• Severe respiratory disease - respiratory physician input
• Complex diabetes - diabetic team involvement
• Suspected difficult airway - senior anaesthetist planning
• Morbid obesity - bariatric anaesthesia planning

• Well-assessed patients: Lower cancellation rates, shorter hospital stays, fewer complications
• Prehabilitation: Reduces post-operative complications by 20-40% (meta-analyses)
• Smoking cessation: Reduces respiratory complications by 50% if ≥8 weeks pre-operatively
• Anaemia correction: Pre-operative IV iron reduces transfusion rates by 30-60%
• CPET-directed care: Allows risk stratification and appropriate post-operative care planning (HDU/ICU vs ward)

NICE NG45 - Preoperative Tests Summary

ASA Classification Summary

Medication Management Summary