Perioperative Medicine — Viva

Long Case Viva Defence

Candidate's opening statement (model answer)

"Mr Henare is a 74-year-old retired farmer referred two weeks before an elective anterior resection for a stage II rectal adenocarcinoma. He has atrial fibrillation on apixaban 5 milligrams twice daily; type 2 diabetes for 20 years on insulin glargine 30 units nocte and rapid-acting 12 units with meals, plus empagliflozin 10 milligrams; COPD with an FEV1 of 55 per cent predicted on tiotropium and budesonide-formoterol; ischaemic heart disease with a drug-eluting stent inserted eight months ago, on aspirin and clopidogrel; hypertension on perindopril and bisoprolol; and stage 3 chronic kidney disease with an eGFR of 45. He smokes ten cigarettes a day. His HbA1c is 64. He can walk on the flat but stops after one flight of stairs with breathlessness." [1]

"His main problems are:

1. High perioperative cardiac risk — a Revised Cardiac Risk Index of at least three, with poor functional capacity, and a recent coronary stent.
2. Perioperative diabetes needing an SGLT2 inhibitor hold and an insulin infusion plan.
3. A complex anticoagulation and antiplatelet strategy — apixaban for AF, dual antiplatelet therapy with a recent stent, all needing to be reconciled around major cancer surgery.
4. COPD optimisation and smoking cessation.
5. Very high VTE risk requiring pharmacological and mechanical prophylaxis. [1]

"My immediate priorities are to risk-stratify his heart and decide on functional testing, to make a written perioperative medication and anticoagulation plan, to optimise his COPD, and to enrol him in an enhanced recovery pathway." [1]

Examiner probing questions and model answers

Examiner: "His RCRI is high and his functional capacity is poor. What is the role of a dobutamine stress echo here?" [1]

"By the guideline rule, non-invasive cardiac testing is reserved for a patient with elevated clinical risk AND poor or unknown functional capacity in whom the result will change management. He meets both — his RCRI is at least three and he cannot climb a flight of stairs. So a dobutamine stress echocardiogram is appropriate, because if it shows significant inducible ischaemia I would involve cardiology to consider whether he has a flow-limiting lesion that needs intervention for an independent cardiac indication. What I would not do is revascularise him purely to clear him for surgery — the CARP trial showed that prophylactic revascularisation before vascular surgery did not improve survival or reduce cardiac events in stable disease. I would also not initiate a beta-blocker acutely — the POISE trial showed that starting metoprolol just before surgery increased mortality and stroke, driven by hypotension and bradycardia. He should continue his bisoprolol, and I would make sure he is on a statin." [1]

Examiner: "How will you manage his apixaban around the surgery?" [1]

"Apixaban does not need bridging because it reaches full effect within hours of a dose, unlike warfarin. I would stop it 48 hours before surgery — two missed doses — for this major intra-abdominal procedure. His eGFR is 45, and because apixaban is only about 27 per cent renally cleared, 48 hours is adequate and I do not need to extend it the way I would for dabigatran, which is largely renally cleared. I would restart it once haemostasis is secure, typically 24 to 72 hours after a major resection. His CHA2DS2-VASc is high — age, hypertension, diabetes and vascular disease — so I would not interrupt anticoagulation any longer than necessary. If I needed to reverse apixaban in an emergency bleed, andexanet alfa is the specific reversal agent; if that were unavailable, four-factor PCC at 25 to 50 units per kilogram is the alternative." [1]

Examiner: "He is eight months out from a drug-eluting stent. How does that affect your plan?" [1]

"This is the single most dangerous part of his perioperative management. The minimum stent period for a drug-eluting stent is six months — or three to six months in selected stable patients — so he is just past the conservative floor for elective surgery, which is reassuring. The plan, which I would agree with cardiology, is to continue his aspirin through the surgery and to stop the clopidogrel five days before, for this moderate-to-high bleeding-risk cancer resection, restarting it as soon as haemostasis is secure and completing the full intended twelve-month dual antiplatelet course. The reason aspirin continues is that stent thrombosis carries a mortality of 30 to 50 per cent, and the bleeding risk of continuing aspirin alone is generally acceptable. I would not stop both agents, and I would not stop aspirin and continue the P2Y12 inhibitor — the logic is to keep one platelet blocker on board. POISE-2 showed aspirin did not reduce events in unselected surgical patients, but the coronary-stent population is the recognised exception." [1]

Examiner: "Walk me through his diabetes plan for the day of surgery." [1]

"First, I would stop his empagliflozin three days before surgery. The reason is the risk of euglycaemic diabetic ketoacidosis, which is precipitated by the combination of the SGLT2 inhibitor, fasting, surgical stress and dehydration, and which is frequently missed because the glucose may be only mildly elevated. On the day of surgery I would place him first on the list. I would continue his glargine — his basal insulin — at about 75 per cent of his usual dose on the night before and the morning of surgery, and omit the meal-time rapid-acting insulin while he is fasting. Because he is insulin-treated and facing a major resection with prolonged fasting, I would start a variable-rate intravenous insulin infusion with a glucose substrate fluid and hourly capillary glucose monitoring, targeting 6 to 10 millimoles per litre. The VRIII replaces the obsolete sliding scale, which produces erratic control with no basal cover. Once he is eating, I would overlap his first subcutaneous basal-bolus dose with the infusion and then stop the infusion, and restart the empagliflozin only when he is eating and drinking normally and clinically stable." [1]

Examiner: "His eGFR is 45. How does that change your LMWH prophylaxis?" [1]

"He is very high VTE risk by Caprini — active cancer, major abdominal surgery, age, obesity, immobility — so he absolutely needs pharmacological prophylaxis. Enoxaparin 40 milligrams once daily is acceptable down to a creatinine clearance of about 30, so at 45 I would use the standard 40 milligrams daily dose without reduction, given six to twelve hours postoperatively once haemostasis is secure. If his renal function were to deteriorate postoperatively, I would reassess — below a CrCl of 30 I would reduce to 20 milligrams daily or switch to unfractionated heparin. I would add mechanical prophylaxis with compression stockings and intermittent pneumatic compression during and after surgery, after checking his arterial circulation, and I would continue prophylaxis for the full hospital stay and consider extended prophylaxis for four weeks because this is cancer surgery." [1]

Examiner: "What is the most dangerous error a registrar could make in this patient?" [1]

"Stopping his aspirin around the surgery because of bleeding concerns, while he is within the stent period. Acute stent thrombosis is a frequently fatal event and the aspirin is the single most protective continuation in his regimen. The second most dangerous error is continuing the empagliflozin into the fasting and surgical-stress period, which risks euglycaemic DKA. The third is using a sliding-scale insulin regimen instead of a variable-rate intravenous insulin infusion." [1]

Short Case Viva — A Preoperative Medication Review

Examiner: "A 68-year-old woman with a mechanical mitral valve on warfarin, insulin-treated diabetes, and heart failure on an ACE inhibitor, beta-blocker and loop diuretic, is admitted for an elective hip replacement. Take me through the perioperative medication plan." [1]

*"I would take her drug by drug. The warfarin comes first because she has a mechanical mitral valve, which is the highest annual thrombotic risk of any indication and where a valve thrombosis is usually fatal — so she must be bridged. I would stop the warfarin five days before surgery, start therapeutic-dose LMWH about three days before, give the last LMWH dose 24 hours before, and restart warfarin on the evening of surgery with continued LMWH bridging until the INR is therapeutic again. The BRIDGE trial showed most atrial fibrillation patients do not need bridging, but mechanical mitral valves were excluded from that trial and remain a bridging indication. [1]

For her diabetes, I would stop any SGLT2 inhibitor three days before surgery, continue her basal insulin at 75 per cent of the dose, and use a variable-rate intravenous insulin infusion during the fasting and perioperative period, targeting 6 to 10 millimoles per litre. I would not use a sliding scale. [1]

For her heart failure therapy, I would continue her beta-blocker — abrupt cessation risks rebound tachycardia and ischaemia. I would hold the morning dose of her ACE inhibitor for this major surgery because of the intra-operative hypotension risk, and restart it once she is haemodynamically stable and her renal function is stable. I would hold her loop diuretic on the morning of surgery to avoid intra-operative hypovolaemia, and restart once she is taking oral fluids. I would give her a statin if she is not already on one. [1]

For VTE prophylaxis, hip replacement is very high risk — I would use LMWH plus mechanical prophylaxis, and continue for a full month after surgery because of the late-VTE risk in major orthopaedic surgery."* [1]

Examiner: "If she bled significantly intra-operatively and her INR had not fully normalised, how would you reverse the residual warfarin effect?" [1]

"I would give four-factor prothrombin complex concentrate plus intravenous vitamin K 10 milligrams. The PCC reverses the INR within minutes by directly replacing factors II, VII, IX and X — Sarode showed it was non-inferior to plasma for haemostasis and superior for rapid INR correction, with a smaller volume. The vitamin K takes 6 to 12 hours to enable hepatic synthesis of new factors and so sustains the reversal. Vitamin K alone would be too slow for active bleeding. I would not use idarucizumab or andexanet — those are for dabigatran and the factor Xa inhibitors respectively, not for warfarin." [1]

Examiner: "Why does the VRIII replace the sliding scale?" [1]

"The traditional sliding scale was reactive boluses of short-acting insulin given against a capillary glucose reading, with no background basal insulin. It produced erratic control with swings between hyper- and hypoglycaemia, and no basal cover, so the patient was effectively under-insulinised between boluses. The variable-rate intravenous insulin infusion is a continuous insulin infusion run alongside a glucose-containing substrate fluid — a glucose, potassium and insulin substrate — and titrated against hourly capillary glucose using a standard algorithm. It provides continuous background cover, smooth control, and the ability to respond to trends rather than react to single readings. It is the standard method for fasting surgical patients who need insulin." [1]

Key examiner-shaped takeaways

• Risk-stratify, do not 'clear'. Use the RCRI and functional capacity; test only when the result will change management. Do not revascularise, stress-test, or start a beta-blocker routinely.
• The mechanical mitral valve always bridges. Most atrial fibrillation does not.
• SGLT2 inhibitors stop three days before; sliding scale is obsolete; use the VRIII.
• Aspirin continues for a recent stent; the stent period must be respected.
• Warfarin major bleeding: PCC plus vitamin K, not vitamin K alone. Idarucizumab for dabigatran, andexanet for apixaban and rivaroxaban.
• VTE prophylaxis is universal in surgical and immobile medical patients — LMWH first-line, add mechanical, time the first dose against bleeding risk. [1]