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Post-CPB Low Cardiac Output — FRCA Final MCQ

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ModerateCardiothoracic AnaesthesiaPost-CPB Low Cardiac OutputFRCA Final

A 58-year-old man undergoes coronary artery bypass grafting. Following separation from cardiopulmonary bypass, his cardiac index remains 1.6 L/min/m² despite optimized preload and a heart rate of 80 beats/min in sinus rhythm. His mean arterial pressure is 75 mmHg and systemic vascular resistance is elevated. Transoesophageal echocardiography shows global left ventricular systolic dysfunction without a new regional wall-motion abnormality, tamponade or another surgically correctable cause. A correctly functioning intra-aortic balloon pump is in situ. Which pharmacological agent is most appropriate to improve cardiac output?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: D — Milrinone

Milrinone is the best option. It inhibits phosphodiesterase III, increasing intracellular cAMP in cardiac myocytes and vascular smooth muscle. This produces positive inotropy and lusitropy together with systemic and pulmonary vasodilation. In this patient, it therefore addresses both global ventricular dysfunction and elevated afterload, increasing cardiac index despite an already functioning IABP. Blood pressure must be monitored because vasodilation can cause hypotension; noradrenaline may be added if pressure subsequently becomes inadequate. Noradrenaline is not the primary treatment here because MAP is adequate and SVR is already elevated. Phenylephrine, vasopressin and metaraminol predominantly increase vascular tone and afterload, so they may further impede ventricular ejection rather than correct the low-output state.

Reference: Wockhardt UK Ltd. Milrinone 1 mg/ml Solution for injection/infusion, Summary of Product Characteristics, sections 4.1 and 5.1; eMC, updated 21 November 2023. https://www.medicines.org.uk/emc/product/2625/smpc