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.

Cardiovascular effects and placental passage of dantrolene in the maternal-fetal sheep model.

Using the chronic maternal-fetal sheep preparation, nine pregnant ewes were studied to determine the effects of intravenous dantrolene sodium on maternal and fetal physiology, with particular reference to its placental passage, and its effects on uterine blood flow and uterine tone. Two doses of dantrolene sodium were studied: 1.2 mg/kg and 2.4 mg/kg. After 2.4 mg/kg, maternal cardiac output increased 29% (P less than 0.05) after 1 min and returned to normal after 30 min. Maternal mean arterial pressure increased 13% after 1 min and remained significantly elevated (P less than 0.01) for 3 h. No significant changes (P greater than 0.05) were observed in maternal heart rate, uterine artery blood flow, or central venous pressure. Maternal arterial pH declined from 7.42 to 7.39 (P less than 0.01) after 1 min and returned to baseline values after 10 min. Fetal heart rate decreased 24% (P less than 0.01) after 3 min and returned to normal after 10 min; the mean fetal arterial pressure remained unchanged (P greater than 0.05). Fetal arterial pH declined from 7.29 to 7.27 (P less than 0.05) after 1 min and remained significantly decreased for 120 min. Similar changes of lesser magnitude and shorter duration were seen following the 1.2 mg/kg dose. Maternal levels of dantrolene were less than 3 micrograms/ml. Although an equilibrium between maternal and fetal plasma dantrolene concentrations was apparent at 5 min, the fetal levels of dantrolene were approximately 10% of the mother's. The results indicate that the administration of intravenous dantrolene at 1.2 mg/kg or 2.4 mg/kg has no clinically significant adverse effect on mother or fetus in the sheep model.