Preoperative assessment and risk stratification

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Why this is examined / one-line answer

Preoperative assessment is the intellectual backbone of safe anaesthesia. Examiners want structure (not a rambling history), exact ASA-PS wording, MET thresholds, the six RCRI predictors, a rule for when tests change care, and the courage to cancel or escalate when risk is uncontrolled. One-liner: I triage urgency, exclude active cardiac conditions, estimate METs and RCRI, optimise what is modifiable, order only decision-changing tests, and agree a plan including critical care and what would stop us tomorrow morning. [1]

Purpose of the preoperative visit

1. Identify disease, airway risk, medications, allergies, prior anaesthetic events.
2. Stratify cardiac, respiratory, and overall risk proportionate to surgery.
3. Optimise anaemia, diabetes, smoking, heart failure, infection, nutrition.
4. Plan technique, monitoring, blood, ICU, analgesia, VTE, PONV.
5. Consent with individualised risk discussion and alternatives (including non-operative care).
6. Document and communicate to the day-of team. [1]

Proportionate assessment: minor low-risk procedures in fit patients need focused evaluation, not a CPET. [1]

Urgency first (ESC/ESA spirit)

Never delay catastrophic bleeding for an echocardiogram that will not change immediate management.[2]

ASA Physical Status — exact classes (say them cleanly)

ASA is not a cardiac risk score alone and is subjective — use it with METs/RCRI, not instead of them. [1]

Functional capacity — METs

1 MET ≈ resting oxygen consumption (~3.5 mL O2/kg/min). [1]

Poor functional capacity: <4 METs (cannot climb a flight of stairs without stopping) — higher perioperative risk; for intermediate/high-risk surgery consider further evaluation (echo, stress test, CPET, cardiology) depending on urgency and whether results change care.[2]

Good capacity (≥4 METs) without active cardiac conditions often allows major surgery without further non-invasive testing. [1]

Use the Duke Activity Status Index (DASI) where available — more reproducible than a single question. [1]

Revised Cardiac Risk Index (Lee) — six predictors

Independent predictors of major cardiac complications after major noncardiac surgery:[1]

1. High-risk surgery — intraperitoneal, intrathoracic, or suprainguinal vascular
2. Ischaemic heart disease — history of MI, positive exercise test, current angina, nitrate use, Q waves
3. History of congestive heart failure
4. History of cerebrovascular disease — stroke or TIA
5. Diabetes mellitus treated with insulin
6. Preoperative creatinine >177 µmol/L (2.0 mg/dL) [1]

RCRI underestimates some modern populations and does not replace clinical judgement, but it is the bedside score examiners expect by name.[1]

Structured cardiac pathway (decision forks)

1. Emergency? → proceed.
2. Active cardiac condition? → evaluate/postpone elective (unstable coronary syndromes, decompensated HF, significant arrhythmia, severe symptomatic valvular disease).[2]
3. Low-risk surgery? → proceed without further testing in most cases.
4. METs ≥4 and no active conditions? → generally proceed; continue beta-blockers/statins as indicated.
5. METs <4 or unknown + elevated RCRI / high-risk surgery? → consider non-invasive testing only if it will change management (revascularisation rarely indicated solely to “get through surgery”; may change monitoring, technique, ICU plan, or decision to operate).
6. Shared decision with patient and surgeon when residual risk is high.

When to order tests

CPET numbers (high yield)

• Anaerobic threshold (AT) <11 mL/kg/min — high-risk cohort for major surgery.
• Peak VO2 <15 mL/kg/min — elevated risk.
• Use to plan critical care, prehabilitation, and shared decisions — not as a single go/no-go robot.[3]

Airway, aspiration, and medication review

• Airway: Mallampati, mouth opening, thyromental distance, neck movement, dentition, prior difficult airway letter, OSA.
• Aspiration risk: reflux, pregnancy, obstruction, delayed gastric emptying — RSI/antacid plan.
• Fasting: typically 2 h clears, 6 h solids (unit protocols; paediatric milk rules differ).
• Medications:
  • Continue most beta-blockers, statins, anticonvulsants, antiparkinson drugs, immunosuppressants as advised.
  • ACEI/ARB: many units hold morning of major surgery (hypotension risk) — follow local ERAS protocol.
  • Anticoagulants/antiplatelets: procedure-specific bleeding vs thrombosis risk; ASRA timing if neuraxial.
  • SGLT2 inhibitors: hold per local guidance (euglycaemic DKA risk).
  • GLP-1 agonists: aspiration risk discussion — evolving guidance.
  • Herbal medicines: often stop 1–2 weeks pre-op when elective. [1]

Optimisation targets (modifiable risk)

• Anaemia: investigate iron deficiency; IV/oral iron weeks before elective major surgery (PBM).
• Diabetes: elective targets often HbA1c <69 mmol/mol (8.5%) in many UK/ANZ pathways — balance against cancer delay.
• Smoking: cessation ≥4 weeks ideal for wound/respiratory benefit.
• Heart failure / CAD: optimise volume status, ischaemia work-up if active symptoms.
• OSA: CPAP compliance, opioid-sparing plan, overnight monitoring if inpatient.
• Frailty: Comprehensive Geriatric Assessment; shared decision on benefit vs burden.
• Nutrition / prehabilitation: protein, exercise programmes before major elective. [1]

Shared decision-making for high-risk surgery

High-risk = poor METs + high RCRI + major surgery, AT <11, ASA IV, frailty, or limited life expectancy. [1]

Discuss explicitly:

• Absolute risks in plain language (cardiac event, death, prolonged ventilation, dialysis, dependence).
• Alternatives: less invasive surgery, embolisation, medical management, palliative pathways.
• What “success” means to the patient (time at home, cognition, independence).
• Ceiling of treatment / ICU willingness.
• Document MDT discussion when relevant (high-risk anaesthetic clinic). [1]

Day-of-surgery cancel / postpone thresholds

Strong reasons to postpone elective surgery:

• Acute coronary syndrome, decompensated heart failure, uncontrolled tachyarrhythmia.
• Acute severe respiratory infection with systemic features (context-dependent for minor cases).
• Uncontrolled hyperglycaemia with ketosis / hyperosmolar state.
• New neurological deficit needing work-up.
• Inadequate fasting for GA without urgent indication.
• Anticoagulation not managed for high-bleed or neuraxial procedures.
• Missing critical information (e.g. unknown severe aortic stenosis murmur + poor capacity + major case).
• No escort for planned day-case GA pathway. [1]

Usually not cancel alone: mild isolated hypertension if no end-organ crisis; anxiety; late arrival without clinical risk (process issue). Severe asymptomatic hypertension management is unit-specific — treat and proceed vs delay for very high readings with end-organ concern. [1]

Communicate early with surgeon and patient; convert to inpatient or alternative technique when that is safer than cancel. [1]

SAQ scaffold

1. List six RCRI predictors and risks at 0 vs ≥3 (4)
2. Define METs and 4-MET threshold activities (2)
3. ASA III vs IV with examples (2)
4. When to order echo/CPET (3)
5. Day-of cancel criteria (3) [1]

Viva stems

“Patient cannot climb stairs before colectomy.” — <4 METs; review RCRI; consider echo/CPET; ICU plan; shared decision.
“What is RCRI?” — six predictors, % risks.
“Does everyone need bloods?” — no; proportionate.
“HbA1c 10% for elective knee.” — optimise if pure elective; balance.
“New murmur, breathless, AAA repair.” — active valve/HF work-up before elective. [1]

Common traps

• Ordering a battery of tests that never get reviewed.
• Using ASA as the only risk tool.
• Forgetting insulin-treated diabetes and creatinine in RCRI.
• Cancelling for mild issues while missing true active cardiac disease.
• No airway plan documented.
• Consent as a signature, not a conversation. [1]

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Red flags

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References

1. [1]Lee TH, Marcantonio ER, Mangione CM, et al. Derivation and prospective validation of a simple index for prediction of cardiac risk of major noncardiac surgery Circulation, 1999.PMID 10477528
2. [2]Kristensen SD, Knuuti J, Saraste A, et al. 2014 ESC/ESA guidelines on noncardiac surgery: Cardiovascular assessment and management : Are the differences clinically relevant? The European perspective J Nucl Cardiol, 2017.PMID 27538569
3. [3]Older PO, Levett DZH. Cardiopulmonary Exercise Testing and Surgery Ann Am Thorac Soc, 2017.PMID 28511024