Perioperative Care

🏥 Perioperative Care

Risk Assessment · ERAS · Bowel Preparation · Surgical Nutrition — MRCS high-yield notes

Surgical Risk Assessment

Accurately predicting surgical risk is fundamental for informed consent, preoperative optimisation, and benchmarking outcomes. Each tool has different strengths and appropriate use cases.

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ASA Grade

American Society of Anesthesiologists

Scale6-point (ASA 1–6)

TypeSimple, subjective, universally used

VariablesClinical judgement of patient’s systemic health

TimingPre- AND intraoperative; incorporated into complex scoring tools

LimitationSubjective; does not account for operative complexity

StrengthStrongly correlates with perioperative mortality despite simplicity

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POSSUM

Physiological & Operative Severity Score

Variables12 physiological + 6 operative variables

PredictsMortality AND morbidity

Key limitRequires intraoperative data — cannot be used preoperatively for consent

P-POSSUMModification correcting overestimation of mortality in low-risk patients

CR-POSSUMColorectal-specific version

UseAudit, benchmarking, outcome research

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SORT

Surgical Outcome Risk Tool

Variables6 preoperative variables only

Predicts30-day postoperative mortality

6 VariablesASA grade, urgency, procedure complexity, age, surgical specialty, malignancy

AdvantageNewer, simpler, fully preoperative — ideal for consent

UsePreoperative 30-day mortality estimation; patient counselling

vs POSSUMSORT usable before the operation; POSSUM requires intraoperative data

ASA Classification in Detail

ASA 1

Normal Healthy Patient

No organic, physiological, biochemical, or psychiatric disturbance. Non-smoker, minimal alcohol.

~0.05% mortality

ASA 2

Mild Systemic Disease

e.g., Well-controlled DM/HTN, mild obesity (BMI 30–40), current smoker, pregnancy, mild lung disease.

~0.4% mortality

ASA 3

Severe Systemic Disease

e.g., Poorly controlled DM/HTN, COPD, morbid obesity (BMI >40), alcohol dependence, history of MI/CVA >3 months, ESRD on dialysis.

~1.8% mortality

ASA 4

Severe Systemic Disease — Constant Threat to Life

e.g., Recent MI/CVA <3 months, severe valve disease, sepsis, DIC. The disease itself is an ongoing life threat independent of surgery.

~7.8% mortality

ASA 5

Moribund Patient

Not expected to survive without surgery. e.g., Ruptured AAA, massive PE, intracranial bleed with raised ICP. Surgery is a last resort.

~9.4% mortality

ASA 6

Brain-Dead Organ Donor

Declared brain-dead; surgery for organ procurement only.

N/A

POSSUM Cannot Be Used for Consent — The Classic Exam Trap

A classic MRCS question asks which scoring tool can be used before the operation to inform patient consent. The answer is SORT, not POSSUM. POSSUM requires intraoperative findings — specifically the volume of intraoperative blood loss and whether peritoneal soiling was present — which are only known during or after surgery. SORT was specifically designed to fill this gap.

Comparison Table

Feature	ASA	POSSUM / P-POSSUM	SORT
When usable	Pre- and intraoperative	Intraoperative / postoperative only	Preoperative
Variables	1 (clinical judgement)	18 (12 physio + 6 operative)	6 (all preoperative)
Predicts	General perioperative risk	Mortality AND morbidity	30-day mortality
Primary use	Universal classification	Audit and benchmarking	Preoperative consent
Key limitation	Doesn’t account for operative complexity	Cannot inform preoperative consent	Newer — less historical validation
Subspecialty versions	None	CR-POSSUM, V-POSSUM, O-POSSUM	None currently

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