Vasoplegia after cardiopulmonary bypass — FFICM MCQ

Correct answer: D — Post-cardiopulmonary bypass vasoplegic syndrome

The correct answer is D, post-cardiopulmonary bypass vasoplegic syndrome. This man has a normal-to-high cardiac index (3.9 L/min/m2), a low systemic vascular resistance, elevated lactate and warm peripheries despite refractory hypotension on two vasopressors, which is the classic haemodynamic signature of vasoplegia rather than pump failure or obstruction. TOE confirming good biventricular function and no tamponade excludes the cardiogenic and obstructive differentials, leaving a distributive (vasodilatory) shock state as the only pattern that fits. Vasoplegic syndrome is well recognised after cardiopulmonary bypass, driven by the systemic inflammatory response to bypass, nitric oxide and inflammatory mediator release, vasopressin depletion and adrenoreceptor desensitisation, producing profound vasodilation resistant to catecholamines and vasopressin. Refractoriness to both noradrenaline and vasopressin with preserved cardiac output is a recognised marker of severity requiring escalation (for example methylene blue or hydroxocobalamin as rescue therapy). Why the other options are wrong: E. Low-output cardiogenic shock: this requires a reduced cardiac index and impaired ventricular function on imaging, whereas this patient has a normal/high index and TOE-confirmed good biventricular function. B. Obstructive shock from tamponade: TOE has specifically excluded pericardial tamponade, and obstructive shock typically presents with a low cardiac output, not a high-output vasodilated picture. A. Tension pneumothorax: there are no signs described (tracheal deviation, absent breath sounds, raised airway pressures) and it would cause obstructive, low-output shock, inconsistent with the warm, vasodilated, high-index picture here. C. Severe hypovolaemic shock: hypovolaemia causes cold peripheries, high SVR and low cardiac index due to reduced preload, the opposite of the warm, low-SVR, normal-output state seen here. Key point: warm peripheries with low SVR, normal or high cardiac index and hypotension refractory to noradrenaline and vasopressin after bypass points to vasoplegic syndrome, not a low-output or obstructive cause.

Reference: Ltaief Z, Ben-Hamouda N, Rancati V, et al. Vasoplegic Syndrome after Cardiopulmonary Bypass in Cardiovascular Surgery: Pathophysiology and Management in Critical Care. J Clin Med 2022;11(21):6407. https://pmc.ncbi.nlm.nih.gov/articles/PMC9658078/