HEMODYNAMIC AND CARDIODYNAMIC INTERACTION S BETWEEN NIMODIPINE AND PROPOFOL IN CHRONICALLY INSTRUMENTED DOGS

Nimodipine is frequently used for treatment of cerebral vasospasm in p atients undergoing intracerebral vascular surgery and during intensive care therapy of patients with subarachnoid haemorrhage. Propofol is b eing increasingly used as a hypnotic drug in neuroanaesthesia and for sedation in critically ill patients. There is evidence of a propofol e ffect on voltage-dependent calcium channels; hence,the administration of propofol may interact with the haemodynamic effects of nimodipine. We investigated the haemodynamic interactions of both compounds in chr onically instrumented dogs. Methods: Five mongrel dogs were chronicall y instrumented for measurement of heart rate (HR), left atrial (LAP), aortic (ABP), a nd left ventricular pressure (LVP), LV dP/dt, cardiac output (CO), systemic vascular resistance (SVR), coronary bleed Row ve locity (CBFV),and myodardial wall-thickening fraction (WTF). After com plete recovery from surgery and assessment of normal resting blood gas values and temperature, ail animals received on separate days either propofol 30 mg/kg.h (P), nimodipine in two maintenance doses in the aw ake state (N), or the combination of nimodipine and propofol (N+P). Th e maintenance doses of nimodipine in N and N+P were 1 and 2 mu g/kg.mi n for 40 min each after a bolus of either 10 or 20 mu g/kg.min over 2 min. Measurements were performed as controls, in the middle (20 min), and at the end (40 min) of each maintenance infusion of nimodipine or at equivalent points in time in group P (Fig. 1). Animals receiving pr opofol were mechanically ventilated after endotracheal intubation. Blo od gas Values were kept within the normal range. All data were analyse d with repeated measures of ANOVA followed by student's t-test with Bo nferroni correction. Results: There was no statistically significant d ifference for any of the measured parameters between N and N+P or betw een the two maintenance doses of nimodipine (Table 1). HR was signific antly higher with both doses of nimodipine in the awake state compared to the control values (123+/-7.1 and 146+/-6.4 vs 78+/-2.4/min). The administration of nimodipine with and without propofol led to a signif icant increase in CBFV (Fig. 2). However, there was no difference in C BFV between nimodipine in the awake state and in combination with prop ofol (Fig. 2). Conclusions: We conclude that administration of propofo l does not alter the systemic haemodynamic and regional myocardial eff ects of a nimodipine infusion in a dose of 1 or 2 mu g/kg min in chron ically instrumented dogs.