ENDOCRINE AND METABOLIC RESPONSES IN SHEEP DURING HALOTHANE AND PENTOBARBITAL-ANESTHESIA WITH DOBUTAMINE INFUSION

The study investigated the stimulus to pituitary-adrenocortical activi ty (PACA) during halothane anaesthesia. Groups of six sheep were anaes thetized with thiopentone/halothane (TH group), acepromazine/thispento ne/halothane (ATH group) or pentobarbitone (P group). Dobutamine was i nfused in the TH and ATH groups to prevent hypotension (0.3-1.4 mu g/k g/min) and in the P group at 0.05 mu g/kg/min. Pulse rate. arterial bl ood gases and pressure (ABP) were measured and sequential blood sample s taken for assay of cortisol, adrenocorticotrophic hormone (ACTH), ar ginine vasopressin (AVP), glucose and lactate. Pulse rate increased in all groups. Arterial blood pressure decreased by 13% in TH, by 24% in ATH and remained stable in P. All three groups developed hypercapnia and acidosis but were well oxygenated. Cortisol increased in all group s: with ATH the sevenfold rise occurred earlier than with either TH (s ixfold rise) or P (fivefold rise), Adrenocorticotrophic hormone change s were as for cortisol but AVP increases were not consistent. Glucose and lactate were stable, but lactate was lowest with ATH. Dobutamine i nfusion failed to prevent hypotension during halothane anaesthesia and PACA appeared proportional to the hypotension. Dobutamine may have st imulated ACTH and cortisol release after 120 min. Halothane-induced hy potension may cause adrenocortical activity but a direct effect of hal othane cannot be ruled out.