Cardiac Theatre for Residents: Vasoplegia, SAM and Pacing

Your noradrenaline is climbing, and climbing, and the pressure still won't hold. The tank's the right size and the pump is working — so what do you reach for next? In this episode Mike and Calum get scrubbed for the theatre half of the cardiac topic: the problems that show up on the table rather than on the unit, and the ones that catch people out. This is the companion to the ICU episode on heart failure and mechanical circulatory support. We start with vasoplegia — when to add vasopressin, why a femoral arterial line earns its place (the radiofemoral difference tracks the severity, and it takes days rather than hours to close), and the second-line agents: methylene blue at 1 mg/kg, why you warn the surgeon before you give it, and high-dose hydroxocobalamin when that isn't enough. Then a quick tour of the inotropes — and the honest admission that there is no perfect one, and essentially no evidence on which is best in acute heart failure. Then the moment everyone dreads: coming off bypass with a failing right ventricle. Get the rate up, get atrial wires in, nitric on, inotropes running — and choose Octaplex and fibrinogen over big volumes of FFP and cryo, because bleeding in the face of RV failure is one of the hardest balancing acts in the building. We cover SAM — systolic anterior motion — which is easy to miss, hard to manage, and can have you telling a surgeon there's a problem with a valve that's perfectly fine. Finally, a proper deep dive on pacing, from the epicardial wires up: why you nag for atrial wires, how to read the three-letter code, what AAI, DDD, VVI and the asynchronous modes actually do, and when diathermy forces your hand. We finish on the two dials everyone muddles — output and sensitivity — and the counterintuitive trap at the heart of it: turning the millivolt number up makes the box less sensitive, which is how you end up pacing onto a T wave. R-on-T is the commonest cause of cardiac arrest on a cardiac ICU, and NAP7 says so. Plus a closing bugbear about vascaths. Chapters (00:00) Cold open — the noradrenaline that won't hold (00:50) Vasoplegia: vasopressin, and the radiofemoral difference (02:20) Methylene blue and hydroxocobalamin (03:50) The inotropes — and why there's no perfect one (05:00) Cardiac output monitoring in theatre (06:00) Coming off bypass with a failing RV (07:40) SAM — systolic anterior motion (09:00) Pacing deep dive: the wires and the three-letter code (10:30) AAI, DDD, VVI — and the atrial kick (12:00) Asynchronous modes and diathermy (13:00) Output vs sensitivity — the trap that causes R-on-T (14:40) NAP7, and the daily bedside discipline (15:40) Permanent pacemakers: checks and mode agreement (16:20) The vascath bugbear (17:00) Wrap-up Key takeaways Escalate vasoplegia in order: noradrenaline → vasopressin → methylene blue → hydroxocobalamin A femoral arterial line earns its place — the radiofemoral difference tracks the degree of vasoplegia There is no perfect inotrope, and almost no evidence on which is best in acute heart failure A failing RV coming off bypass wants rate, atrial wires, nitric and inotropes — and low-volume factor concentrates rather than FFP and cryo SAM is dynamic LVOT obstruction — manage it by filling and pacing, not by blaming the valve Nag for atrial wires: no atrial wire means you're stuck in VVI Set output at 2–3× the capture threshold, and re-check daily as the wires fibrose Sensitivity is inverted — a higher millivolt setting makes the box less sensitive; undersensing causes R-on-T, the commonest cause of arrest on a cardiac ICU (NAP7) References / further reading Royal College of Anaesthetists. 7th National Audit Project (NAP7): perioperative cardiac arrest. 2023 Reade MC. Temporary epicardial pacing after cardiac surgery: a practical review. Anaesthesia 2007 (parts 1 and 2) Levin RL et al. Methylene blue reduces mortality and morbidity in vasoplegic patients after cardiac surgery. Ann Thorac Surg 2004 Shaefi S et al. Vasoplegia after cardiovascular procedures: pathophysiology and targeted therapy. J Cardiothorac Vasc Anesth 2018 Mathew R et al. DOREMI: milrinone vs dobutamine in cardiogenic shock. NEJM 2021 Mehta RH et al. LEVO-CTS: levosimendan in patients with reduced EF undergoing cardiac surgery. NEJM 2017 Ibrahim M et al. Modern management of systolic anterior motion of the mitral valve. Eur J Cardiothorac Surg 2012 Boer C et al. EACTS/EACTA Guidelines on patient blood management for adult cardiac surgery. 2017 This podcast is for medical education for healthcare professionals. It is not clinical advice — always follow your local protocols and your own centre's guidance.