Early derangements of arteriovenous anastomotic and capillary blood flow in the canine hindlimb induced by supplemental pentobarbital anesthesia

Abstract

Vasoactive effects of supplemental pentobarbital anesthesia in the canine hindlimb microcirculation were documented in two groups of animals previously anesthetized with 30 mg/kg pentobarbital: Group I with a 5 mg/kg intravenous (iv) bolus of pentobarbital (n = 8) and Group II with a 5 mg/kg 2-min iv infusion of pentobarbital (n = 7). In Group I, measurements at baseline (BL) and 5, 15, 20, and 30 min (min) following pentobarbital administration included cardiac output, mean arterial pressure, total peripheral vascular resistance, common femoral artery flow (CFAQ) and resistance (CFAR), percentage hindlimb arteriovenous anastomotic shunt (AVA%), absolute shunt flow (AVAQ), and hindlimb nutrient capillary flow (NCQ). In Group II these same measurements were made, but the study was continued until all hindlimb hemodynamic parameters returned to control values. CFAQ, AVA%, AVAQ, and NCQ were significantly increased, and CFAR was decreased in both groups. CFAQ and NCQ remained significantly elevated at 30 min in Group I. In Group II CFAR, AVA%, and AVAQ remained elevated at 30 min, but did return to BL by 40 min, as did all other hindlimb hemodynamic parameters measured. Pentobarbital resulted in both AVA and arteriolar dilation, with an increase in the percentage total flow distributed to AVAs. These alterations of microcirculatory flow should be considered during investigations of the distribution of peripheral blood flow, as well as during metabolic studies assessing arteriovenous substrate differences, if interpretative errors are to be avoided.