ACE-INHIBITORS, CALCIUM-ANTAGONISTS AND LOW SYSTEMIC VASCULAR-RESISTANCE FOLLOWING CARDIOPULMONARY BYPASS - A CASE-CONTROL STUDY

Objective: To investigate whether the syndrome of low systemic vascular resistance (SVR) following cardiac surgery and cardiopulmonary bypass (CPB) is more common in patients taking angiotensin-converting enzyme inhibitors (ACE-inhibitors) or calcium antagonists. Design: A case-control study, with cases (''low SVR syndrome'') identified from intensive care unit observation charts. These cases were each matched to two controls identified from the same group of charts during the same time period. Exposure (ACE-inhibitors or calcium antagonists) was determined in a blinded fashion from the patient's medical record. Setting: Cardiothoracic surgical unit in a teaching hospital. Participants: We identified 42 cases of low SVR syndrome; these were matched to 84 controls. Results: There was no association between therapy with ACE-inhibitors and the low SVR syndrome following CPB (odds ratio [OR], 1.33; 95% confidence interval [CI], 0.53-3.34), nor with calcium antagonists (OR, 0.49; 95% Cl, 0.21-1.13). The incidence of the low SVR syndrome was 7.4%. Patients who develop the low SVR syndrome are more likely to be treated with noradrenaline, adrenaline and dopamine, and spend more time in the cardiothoracic intensive care unit. Conclusion: The ''low SVR syndrome'' following CPB is not associated with preoperative therapy with ACE-inhibitors or calcium antagonists.