Regional blood flow during isoflurane and halothane anesthesia.

ABSTRACT

Cardiac output distribution and regional blood flow in 18 dogs during isoflurane and halothane anesthesia were studied in dose-related fashion. Surgical preparation consisted of left thoracotomy and placement of catheters in the left atrium and aorta through a femoral artery. Regional blood flow was studied one week after surgical preparation using a microsphere technique at the three stages awake, 1 MAC, and 2 MAC of inhalation anesthesia. At each stage of the experiment, two sets of microspheres (15- and 9-micron diameter), labeled with different isotopes, were used simultaneously. Both anesthetics increased cerebral blood flow, decreased blood flow through preportal area, and preserved renal blood flow. Isoflurane increased hepatic artery blood flow at both levels of anesthesia, while halothane preserved the flow during 1 MAC and decreased it at 2 MAC. Apparently, isoflurane provided better oxygenation to the liver than halothane. Myocardial blood flow was increased during isoflurane (despite decrease in blood pressure and cardiac output) and decreased during halothane anesthesia. Isoflurane appears to be a coronary vasodilator with potential beneficial (improvement in myocardial blood supply) as well as hazardous ("steal effect") effects on the heart.