Effects of Halothane Anesthesia on Blood Cholinesterase Activity in Cats

Abstract

Abstract : The effect of halothane anesthesia on blood cholinesterase activity was assessed in 24 adult cats. Blood samples were taken both before and during the course of halothane anesthesia. Acetylcholinesterase activity was depressed from 7 percent to 54 percent (average 19.5 percent) in 16 subjects, increased in 2 (9 percent and 11 percent), and was unchanged in the other 6. The mean acetylcholinesterase change for the entire population was a 12.3 percent decrease. Pseudocholinesterase (butyrylcholinesterase) activity was depressed from 7 to 24 percent (average 12.2 percent) in 19 subjects, and was unchanged in the other 5. The mean butyrylcholinesterase depression for the entire population was 11 percent. There was no apparent correlation between the weight or gender of the animal, or the length of time on halothane, and the amount of depression in cholinesterase activity. Neither was there close agreement between changes in acetylcholinesterase and butyrylcholinesterase activity in a single cat. These results demonstrate that halothane has an inhibitory effect on blood cholinesterase activity in many cats (96 percent of those tested when counting either acetyl- or butyrylcholinesterase). The lack of agreement between changes in acetylcholinesterase and butyrylcholinesterase activity in the same animal suggests that the mechanisms may be different. It remains to be determined whether the amount of enzyme inhibition following halothane is functionally significant.