Defining Vasoplegia in Cardiac Surgery: ACTACC UK National Audit

Abstract

Objective: Vasoplegic syndrome (VS) is a common complication after cardiac surgery, marked by low systemic vascular resistance and fluid-resistant hypotension despite preserved cardiac function. Its incidence, causes, management, and impact on outcomes remain poorly defined. This audit aimed to characterise its incidence, diagnosis, treatment, and outcomes across UK cardiac centres. Design and method: A prospective, one-month national audit was conducted across UK adult cardiac surgical centres under the ACTACC collaborative. All adult patients undergoing cardiac surgery were screened. Case reporting was triggered by: (i) noradrenaline dose 0.2mcg/kg/min or greater for more than 1 hour (ii) use of more than 1 vasopressor, or (iii) administration of a recognised rescue therapy (methylene blue, hydroxocobalamin, high dose vitamin C, cytokine adsorption). VS was defined using a pragmatic clinical definition consistent with the VANCS and ATHOS II trial criteria: mean arterial pressure 2.2 L/min/m2 or a central venous oxygen saturation >70% with central venous pressure >8 mmHg. Cases meeting trigger criteria but not formal definition formed the 'triggered cohort' (TC); those fulfilling VANCS/ ATHOS II physiology were the 'VANCS/ ATHOS II cohort' (VC). Centres submitted anonymised demographic, haemodynamic, treatment and outcome data. Institutional approval and Caldicott guardian registration were obtained (Barts Health Clinical Effectiveness No. 13971). Result(s) and Conclusion(s): Data was submitted by 20 of 35 (54%) cardiac centres, with 125 patients triggering inclusion out of a total of 1675 cases, therefore incidence of 7.5%. Thirty-six patients (29%, 2.1% overall incidence) fulfilled VC criteria. Cardiac output (CO) monitoring was employed in 56% with complete haemodynamic data available in 61 patients, 36 (59%) of whom met VC criteria. Shock dose steroids were administered in 54%, methylene blue in 9.6%, and hydroxocobalamin in 7.2%. Methylene blue use correlated with higher mortality (50% vs. 14.2%, p<0.01) and hydroxocobalamin showed a trend for higher mortality (37.5% vs. 16.2%, p=0.4). TC vs VC VC patients had lower EuroSCORE (median 3.2 vs. 7.6, p<0.01) yet demonstrated greater vasodilation (CRT<2s: 90% vs. 58%, p<0.01) and lower SVR (605 vs.1143dynes/sec/cm5) with preserved cardiac index (3.3 vs 2.3 L/min/m2, p<0.01). Although inotrope doses and incidence of moderate to severe LV dysfunction were similar, Milrinone use was more frequent (61% vs.28%, p<0.01). Overall hospital mortality was 19%, with median ICU and hospital stays of 18 and 24 days, respectively. In comparison to tC, VC patients had longer ICU stays but lower ICU and hospital mortality. Conclusions The first national audit of vasoplegia in UK cardiac surgery revealed a 7.5% incidence with 2.1% meeting VANCS/ATHOSII criteria. Only half had CO monitoring and a minority received rescue therapies, revealing wide practice variation. Inclusion identified a high risk group with 19% mortality and prolonged ICU/ hospital stay. The VC phenotype, despite more severe vasodilatation, was associated with lower mortality, suggesting standardised monitoring and management may improve outcomes. Large multi-centre studies are needed to validate definitions, optimise monitoring strategies and evaluate targeted therapies. Copyright © 2025