Delayed ACTH response to human corticotropin releasing hormone during cardiopulmonary bypass under diazepam-high dose fentanyl anaesthesia.

The inhibitory effect of high dose fentanyl (0.1 mg.kg-1) and diazepam (0.5 mg.kg-1) anaesthesia on the pituitary-adrenal response to coronary artery surgery during cardiopulmonary bypass was assessed by comparison of the adrenocorticotropic hormone and cortisol responses to intravenous boluses of either 0.1 mg (n = 14) or 0.2 mg (n = 14) human corticotropin releasing hormone administered 5 min after starting cardiopulmonary bypass, with the responses obtained in a control group (n = 14). Blood samples were taken before inducing anaesthesia, just before cardiopulmonary bypass and at 5, 20, 35, 50, 65 and 80 min thereafter. The administration of human corticotropin releasing hormone at both doses resulted in significantly greater plasma concentrations of adrenocorticotropic hormone at 50, 65 and 80 min compared to the control group; at the other sampling times there were no differences between the three groups. Plasma cortisol concentrations did not vary between the three groups at any sampling time. During cardiopulmonary bypass the early adrenocorticotropic responses to human corticotropin releasing hormone are blunted but later there is a good response, suggesting that the inhibitory effect of high dose fentanyl and diazepam anaesthesia takes place in the hypothalamus.