The effect of arterial pressure alterations during halothane anesthesia on residual flow and infarct size with transient regional ischemia of the dog.

The present study was designed to determine if infarct size under halothane anesthesia could be reduced by increasing the pressure gradient across the collateral vascular bed, thereby increasing flow within the occluded vascular bed. Forty-nine mongrel dogs were anesthetized with halothane under identical physiologic conditions with the exception of systemic arterial blood pressure. The control group of 18 animals anesthetized with halothane was compared to two experimental groups. In one group of 15 dogs, the mean systemic pressure was raised 25% above control with phenylephrine (BP25). In the second group of 15 dogs, systemic pressure was raised 50% above control (BP50). Adjacent marginal branches of the left circumflex coronary artery were ligated for 90 minutes followed by 90 minutes of reflow. The area of the occluded vascular bed was similar in all groups, but the area of infarction as a percentage of the occluded vascular bed was reduced from 47.7 +/- 4.7% to 25.4 +/- 4.3% in the BP25 group (P < or = .05 v control) and to 33.1 +/- 5.0% in the BP50 group. Flow measurements using microspheres showed a larger zone of ischemic tissue receiving adequate residual flow in the BP25 and BP50 groups compared to the control. It is concluded that infarct size during halothane anesthesia in the dog can be reduced by increasing systemic blood pressure with phenylephrine.