Glucose Homeostasis (15)

Glucose Homeostasis (15)The study by Kuntschen et al also compared two groups of patients undergoing either hypothermic or normothermic CPB with bubble oxygenators. The patients undergoing hypothermic CPB had slightly greater body dimensions and probably a different diet (Switzerland vs south of France). At induction of anesthesia, they were administered fentanyl, 12.5 \l%/ kg (vs 2.5 fig/kg), and then nitrous oxide and enflurane. Cardiac arrest was obtained without cardioplegia (vs cold cardioplegic solution). By contrast, the present study used membrane oxygenators and a different anesthesia with higher doses of fentanyl but no anesthetic gases.

Our study confirms most of the results of Kuntschen et al suggesting that anesthesia and the type of oxygenator have less influence on glucose metabolism than the CPB temperature. In conclusion, during hypothermic and normothermic CPB, blood glucose increases substantially partly due to hormonal and metabolic changes. Hypothermic CPB is accompanied by lower hormone levels (insulin, glucagon, cortisol, catecholamines) than normothermic CPB. Rewarming is accompanied by increased glucose, insulin, glucagon, cortisol and norepinephrine levels, and by an increase in insulin/blood glucose ratio to a value twice as high as in normothermic CPB, suggesting a greater insulin resistance. Similarly, after completion of hypothermic CPB, higher blood glucose concentrations are observed despite a substantial increase in plasma insulin. Eventually the normothermic CPB resulted in a slow and steady increase in blood glucose with no significant change in insulin level, as opposed to the major perturbations that occurred with hypothermic CPB. Finally, it is suggested that more exogenous insulin should be administered after hypothermic CPB than after normothermic CPB in order to avoid hyperglycemia.