INOTROPIC EFFECTS OF SODIUM-NITROPRUSSIDE - A CLINICAL-STUDY ON CORONARY SURGERY PATIENTS

Objective. Sodium nitroprusside (SNP) induces release of nitric oxide and is widely used as a vasoactive drug. Recent research analyzed effe cts of SNP on cardiac muscle and described variable inotropic effects. The present study evaluated effects of SNP on left ventricular (LV) f unction in patients undergoing coronary artery surgery. Methods. The s tudy was performed in 100 patients with a preoperative ejection fracti on >40%. LV pressures were measured with a fluid-filled catheter in th e LV cavity. Hearts were placed in AV sequential mode at a rate of 90 beats/min. Measurements were obtained at end-expiration and consisted of a control tracing and a tracing obtained after a 5 min infusion of SNP 0.5 mu g.kg(-1).min(-1). These measurements were obtained before a nd after cardiopulmonary bypass (CPB). An average of 5 consecutive bea ts was obtained for analysis. Ventricular function was assessed with L V pressure and dP/dt. Data were analyzed suing two factor analysis of variance for repeated measurements. Results. 1. Baseline patient data (n=80). Before CPB, a variable inotropic response to SNP was observed. The direction of the inotropic response was related to preoperative b eta-blocking medication. LVP and dP/dt(max) increased with SNP in pati ents without preoperative beta-blocking medication. In patients on pre operative beta-blocking medication, SNP dit not alter LVP and dP/dt(ma x). After CPB, a positive inotropic response was not observed in any o f the patients. 2. Postoperative patient data under dobutamine (n=20). Data of these separate observations were similar to baseline data bef ore CPB. After CPB and under dobutamine administration (5 mu g.kg(-1). min(-1)) all 20 patients developed a positive inotropic response to SN P. Conclusions. In coronary surgery patients, SNP induced a variable i notropic effect. The direction of the inotropic response appeared to b e modulated by the beta-adrenergic drive.