[Effect of dihydroergotamine (DHE) on blood volume and circulation in the calf in peridural anesthesia in the human].
Dihydroergotamine (DHE) preferentially constricts capacitance vessels in the skin and striated musculature, thereby redistributing blood in favor of the pulmonary vascular bed in the presence of neurogenic vascular tone. The aim of this study was to see if DHE would act likewise when neurogenic vascular tone is absent. Filling and blood flow of the calves were measured plethysmographically in six healthy, supine male volunteers before and during peridural anesthesia (PDA) to the level of at least T5 and, in the denervated state, after the injection of DHE 7.5 micrograms/kg intravenously. Arterial blood pressure, central venous pressure (CVP), and heart rate were also determined. Both blood flow (+2.2 ml/min per 100 ml tissue) and volume (+1 ml/100 ml tissue) of the calves increased while CVP and systolic arterial pressure decreased during PDA (Table 1). DHE did not affect the PDA-included increase in blood flow, but strongly reduced calf volume (-1.7 ml/100 ml tissue). This was accompanied by an increase in CVP and systolic blood pressure (Fig. 1). In the absence much as in the presence of neurogenic vascular tone, DHE preferentially constricts capacitance but not resistance vessels. Thus, DHE counteracts the vascular effects of PDA, as it improves cardiac filling and consequently raises arterial blood pressure by redistributing blood from the dilated capacitance vessels without curtailing blood flow. It would appear, therefore, that DHE is a rational alternative to fluid therapy for the prophylaxis of arterial hypotension during major conduction anesthesia.