Effects of Halothane Anesthesia Compared with Fentanyl Anesthesia and No Anesthesia during Coronary Ligation in Rats

The effects of halothane and fentanyl anesthesia on responses to ligation of a coronary artery in chronically prepared rats were compared with responses in conscious animals. A total of 86 rats were used; 24 were ligated under halothane anesthesia, 18 under fentanyl, and 23 were left conscious. Three other groups (each of seven rats) were identically prepared but not ligated. Non-ligated rats were left conscious or anesthetized with halothane or fentanyl. Ligation was performed with the aid of a permanently implanted snare around the left anterior descending coronary artery. The responses to ligation that were measured were: arrhythmias, blood pressure changes, heart rate changes, ECG changes, mortality rate, occluded zone, and infarcted cardiac tissue mass. It was found that 1% halothane anesthesia starting 30 min before and continuing for 4 h after permanent ligation, had an overall beneficial effect, when compared with controls. Fentanyl (200-1,000 micrograms/kg, iv) had no overall beneficial effect, compared with conscious controls. Halothane reduced arrhythmias and mortality rates, when compared with controls, while fentanyl did not. Halothane produced lower blood pressures, fewer ECG changes, and lower heart rates than those seen in conscious or fentanyl anesthetized rats. The occluded and infarcted zones produced by ligation were not influenced by the two anesthetics.