The effect of CGRP-induced hypotension on organ blood flow during halothane anesthesia in dogs: a comparison with trimetaphan.

Abstract

Calcitonin gene-related peptide (CGRP) is an endogenous 37-amino-acid peptide which is a powerful vasodilator of the splanchnic circulation. To elucidate the effects of CGRP-induced hypotension on the organ blood flow, we compared the renal, hepatic, and pancreatic organ flows of CGRP-induced hypotension with those of trimetaphan (TMP) in halothane-anesthetized dogs. Systemic hemodynamics and organ blood flow were determined in 18 mongrel dogs allocated to one of two groups: CGRP group (n=10) and TMP group (n=8). CGRP of TMP was infused at a rate sufficient to decrease the mean arterial pressure (MAP) to near 60 mmHg from the baseline values for a 60 min-hypotensive period. Organ blood flow was measured using the hydrogen clearance technique. The decrease in MAP was approximately 50% of baseline values (P<0.01). The hypotension induced by either CGRP or TMP was associated with a reduction (P<0.01) in systemic vascular resistance in both groups. Cardiac index (CI) in the CGRP group did not change significantly throughout the experiment. On the other hand, CI decreased at 30 min (P<0.01) and 60 min (P<0.01) during the hypotensive period in the TMP group. No changes were observed in renal, hepatic, and pancreatic blood flows in the CGRP group. Renal blood flow in the TMP group did not change significantly throughout the experiment. In contrast, hepatic blood flow resulted in a significant decrease (P<0.01) during TMP-induced hypotension. Pancreatic blood flow decreased during the hypotensive period (P<0.01) and at 30 min (P<0.05) after termination of TMP. These findings show that CGRP does not adversely affect renal, hepatic, and pancreatic organ blood flows even in the presence of profound hypotension in halothane-anesthetized dogs. The results of this study suggest that CGRP may preserve organ blood flow during induced hypotension.