Perioperative Medicine in Internal Medicine
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Direct answer
Six variables make up the Revised Cardiac Risk Index that anchors preoperative cardiac risk: high-risk surgery (intraperitoneal, intrathoracic, vascular), ischaemic heart disease, heart failure, cerebrovascular disease, insulin-dependent diabetes, and creatinine above 2 mg/dL — each one point, and three or more points define the highest-risk group in whom cardiac testing and beta-blockade decisions concentrate. Functional capacity follows (independence in daily living equating to about 4 METs), and then medication rules: continue statins and chronic beta-blockers, never start a beta-blocker on the morning of surgery (POISE — metoprolol started perioperatively increased stroke and death), hold DOACs 24-72 hours by bleeding and renal risk, bridge warfarin only for high-thrombotic-risk mechanical valves with LMWH, continue aspirin in secondary prevention for most non-cardiac surgery, and stop SGLT2 inhibitors 3-4 days pre-operatively to prevent euglycaemic ketoacidosis. Post-operatively, the medicine continues: VTE prophylaxis by risk, glucose 140-180 mg/dL, early mobilisation, and delirium prevention.
What you must remember
- RCRI (Lee index): high-risk surgery, ischaemic heart disease, congestive heart failure, cerebrovascular disease, insulin-dependent diabetes mellitus, serum creatinine over 2 mg/dL — 0 points roughly 0.4-1 per cent cardiac event risk, 3 or more around 9-11 per cent.
- Functional capacity: able to climb two flights or live independently equals about 4 METs — adequate capacity without symptoms needs no further cardiac testing in most non-cardiac surgery.
- POISE trial lesson: metoprolol begun immediately pre-operatively reduced myocardial infarction but increased stroke and total mortality — start beta-blockers, if at all, days to weeks ahead in selected high-risk patients, titrated, and always continue chronic therapy.
- Aspirin (POISE-2): do not start aspirin for primary prevention peri-operatively; continue it in patients with established coronary disease or stents for most surgery unless bleeding risk is prohibitive — and coordinate drug-eluting stent surgery timing with cardiology.
- Anticoagulation rules: bridge only high-risk mechanical mitral valves, recent stroke, or CHA2DS2-VASc-driven high thrombotic risk (therapeutic LMWH stopped 24 hours pre-op); DOACs stopped 24 hours (low bleeding risk) to 48-72 hours (high risk or renal impairment), restarted 24-72 hours post-operatively once haemostasis is secure.
- Endocrine and metabolic: hold SGLT2 inhibitors 3-4 days before surgery (euglycaemic ketoacidosis); metformin omitted day of surgery and restarted with renal confirmation; continue basal insulin at 75-80 per cent in insulin-dependent patients; stress-dose hydrocortisone for glucocorticoid-dependent patients (etomidate-era teaching: prednisolone over about 7.5-20 mg for over 3 weeks needs coverage).
- VTE prophylaxis: risk-stratified (Caprini or similar) — pharmacologic LMWH for most abdominal and cancer surgery, mechanical alone when bleeding risk dominates; combine both in the highest risk.
- Post-operative medicine that earns marks: early mobilisation and chewing-gum ileus reduction, glucose 140-180 mg/dL, avoid routine nasogastric tubes, delirium prevention with orientation, sleep, vision and hearing aids, and monitoring for post-operative acute kidney injury with attention to nephrotoxins.
A pre-operative clinic hour
A 72-year-old man with prior stenting, heart failure, and creatinine 1.9 mg/dL is booked for open colectomy for cancer. His RCRI is 3 — high-risk territory — so the clinic sequences: functional capacity (he walks 30 minutes daily, over 4 METs, so no stress test is indicated; testing would not change the plan anyway, since cancer surgery cannot be deferred), medications (atenolol continued unchanged, atorvastatin continued, aspirin continued because this is secondary prevention, DOAC for atrial fibrillation — CHA2DS2-VASc 5 — stopped 48 hours ahead with LMWH bridging given the added thrombotic surgery setting), metabolic (metformin held, morning glargine cut to 80 per cent, none of his new empagliflozin within four days of surgery), and prophylaxis (therapeutic-dose LMWH post-operative evening once haemostasis allows, stockings, early ambulation). Post-op day one finds him confused at night: delirium bundle — glasses and hearing aids on, sleep protected, sedatives avoided, and a search for the cause lands on urinary retention. Every step in that paragraph is a known exam question, and the candidate who can narrate it in order has internalised peri-operative medicine.
Where students slip
The POISE reversal is the century's most-tested peri-operative fact: "start beta-blocker on the morning of surgery for high-risk patient" is now the wrong answer, whatever older MCQ banks say. The second slip is bridging everyone on warfarin — most atrial fibrillation patients need no bridge; mechanical mitral valves and recent thromboembolism do. Third, SGLT2 inhibitor timing: the drug's plasma half-life is irrelevant to its ketosis risk, which persists days — hence the 3-4 day hold, not 24 hours.
Frequently asked questions
What are the six Revised Cardiac Risk Index variables?
High-risk surgery, ischaemic heart disease, heart failure, cerebrovascular disease, insulin-dependent diabetes, and creatinine above 2 mg/dL — three or more points indicate major peri-operative cardiac risk.
What did the POISE trial change about peri-operative beta-blockers?
Starting metoprolol immediately before surgery increased stroke and death despite fewer infarcts, so beta-blockers are continued if chronic, and if newly started, begun well ahead and titrated — never on the day of surgery.
Which anticoagulated patients need bridging around surgery?
High thrombotic risk — mechanical mitral valves, recent stroke or thromboembolism, high CHA2DS2-VASc atrial fibrillation with additional risk factors — bridged with therapeutic LMWH stopped 24 hours pre-operatively; most others simply stop and restart.
Why are SGLT2 inhibitors stopped days before surgery?
Because surgery's fasting and stress plus persisting SGLT2 effect cause euglycaemic ketoacidosis; withholding 3-4 days pre-operatively is the accepted precaution.
What is the target blood glucose after major surgery?
140-180 mg/dL for most ward and intensive-care patients — moderate control that avoids both wound-healing hyperglycaemia and the greater danger of hypoglycaemia.