Effects of certain anaesthetics on plasma metabolite concentrations in the baboon (Papio ursinus)

Four groups of 12 baboons each were sedated for a period of 3 hours by means of one of 4 anaesthetic treatments. The treatments involved repeated administration of either ketamine or phencyclidine, or initial sedation with one of these followed by pentobarbitone. A number of plasma metabolites were measured at 30 min intervals. With one exception, there were no significant differences between the 4 individual anaesthetic treatments; there was a small, but significant, decrease in plasma calcium (3.4%) in the group receiving phencyclidine followed by pentobarbitone. There were, however, significant changes with time. Plasma inorganic phosphorus and magnesium concentrations in all the groups rose similarly, reaching mean respective increases of 21.8% and 7.7% after 3 hours. In a number of cases divergent time trends were observed between the pair of groups given pentobarbitone and the pair receiving only ketamine or phencyclidine. Pooling the results from each of these pairs of treatment groups doubled the overall group sizes to 24 animals each and enabled significant differences between the divergent time trends to be detected. In the former pair plasma zinc increased (by a maximum of 16.1%) and protein decreased (by a maximum of 4.0%), while in the latter pair alkaline phosphatase and cholesterol levels both increased (up to maximums of 7.8% and 5.2%, respectively). No significant changes with time were found to be attributable to diurnal variation. Some of the changes in plasma metabolite concentrations following anaesthesia are such that due care should be exercised in their determination and interpretation in anaesthetised baboons.