Changes in plasma cortisol concentrations before, during and after analgesia, anaesthesia and anaesthesia plus ovariohysterectomy in bitches.

Plasma cortisol concentrations were determined before, during and after analgesia, anaesthesia and anaesthesia plus ovariohysterectomy in six New Zealand border collie cross bitches. The treatments were: control, analgesia with butorphanol, anaesthesia with thiopentone sodium, halothane and oxygen and anaesthesia plus surgery. In addition, each bitch was given an ACTH challenge. All the bitches showed transient increases in plasma cortisol concentrations and the integrated cortisol responses (calculated as the area under the cortisol curve above the pre-treatment concentration) for 6.25 hours after treatment increased in the order: control, anaesthesia, analgesia, surgery. The control group had increased cortisol concentrations attributable to the excitement from handling. The plasma cortisol concentrations of the group subjected to surgery were greater than the other groups for at least 6.25 hours, with an approximately four-fold increase above pre-treatment values, but they had returned to pre-treatment levels after 24 hours.