Diltiazem withdrawal before coronary artery bypass surgery

The authors studied the effects of withdrawing oral diltiazem therapy on the subsequent course of coronary artery bypass graft surgery. Patients with severe coronary artery disease were divided into three groups using a prospective, controlled, randomized protocol. In group D (diltiazem-continuation) patients, diltiazem was administered 2.1 ± 0.1 hours (mean ± SEM) before anesthetic induction (n = 10). Group DW (diltiazem-withdrawal) patients received their final diltiazem dose 17.3 ± 2.9 hours before anesthesia (n = 10). Group R was a reference group of patients not receiving diltiazem (n = 11; not randomized). Anesthesia was induced and maintained with fentanyl and pancuronium without use of halogenated anesthetics. No clinically important differences were detected in measured hemodynamics or drug requirements. Group D patients did not have a lower systemic vascular resistance (SVR) index (P > 0.31) or mean arterial pressure (P > 0.08) compared with group DW. Also, no evidence for a diltiazem withdrawal response was found, because group DW did not have either a higher SVR index (P = 0.99) or a higher pulmonary vascular resistance index (P = 0.99) compared with group R, and no severe myocardial ischemia, coronary artery spasm, or postoperative heart block were seen. Plasma diltiazem concentrations decreased significantly during CPB (P < 0.0001), but showed overlap between groups D and DW. Plasma diltiazem concentration did not correlate significantly with simultaneous SVR. These data show the benign effects of both diltiazem administration and its acute withdrawal before coronary artery bypass surgery with high-dose fentanyl anesthesia.