[Hemodynamic changes in infusion with nimodipine]

The haemodynamic effects of 0.03 mg/kg bwxh (approximately equal to 0.5 microgram/kg bwxmin) and 0.06 mg/kg bwxh (approximately equal to 1.0 microgram/kg bwxmin) nimodipine as an infusion has been studied in 64 patients undergoing aorto-coronary-bypass surgery. The measurements were performed at 4 different times: 1. before induction of anaesthesia, 2. after induction of anaesthesia, 3. before cannulation of the aorta, 4. during extracorporeal circulation (ECC). After ECC haemodynamics were controlled in detail as a follow-up study. Each group was compared to a control group having received 0.9% NaCl as placebo. Preoperative infusion of 0.03 mg/kg bwxh nimodipine caused no relevant influence on haemodynamics, whereas 0.06 mg/kg bwxh led to a decrease in arterial blood pressure, peripheral and pulmonary vascular resistance and to a simultaneous increase in cardiac index. Similar haemodynamic effects were registered intraoperatively with both dosages. There was no relevant influence on contractility. During ECC nimodipine led to a decrease in arterial perfusion pressure and oxygenator volume, thus indicating arterial vasodilation and venous pooling. After ECC the investigation revealed a stabilization in cardiac rhythm and myocardial function. With respect to haemodynamics 0.03 mg/kg bwxh nimodipine, a dosage being used in neurosurgery, can be classified as safe. When higher dosages are necessary continuous haemodynamic and cerebral monitoring are recommended in order to avoid a hazardous drop in arterial blood pressure with a consecutive decrease in myocardial and cerebral blood flow (steal phenomena) in spite of better global perfusion.