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 vascula r resistance (SVR) following cardiac surgery and cardiopulmonary bypas s (CPB) is more common in patients taking angiotensin-converting enzym e inhibitors (ACE-inhibitors) or calcium antagonists. Design: A case-c ontrol study, with cases (''low SVR syndrome'') identified from intens ive care unit observation charts. These cases were each matched to two controls identified from the same group of charts during the same tim e period. Exposure (ACE-inhibitors or calcium antagonists) was determi ned in a blinded fashion from the patient's medical record. Setting: C ardiothoracic surgical unit in a teaching hospital. Participants: We i dentified 42 cases of low SVR syndrome; these were matched to 84 contr ols. Results: There was no association between therapy with ACE-inhibi tors 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 wa s 7.4%. Patients who develop the low SVR syndrome are more likely to b e 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 thera py with ACE-inhibitors or calcium antagonists.