Total intravenous anesthesia (TIVA) is obtained by infusion of several drugs with distinct actions within the body. When given together at appropriate doses, these drugs result in the four basic components of anesthesia: hypnosis, analgesia, muscular relaxation, and autonomic reflex control. However, data still lacks about the endocrine response in dogs undergoing TIVA. Therefore, this study aimed at evaluating the serum levels of cortisol in dogs submitted to TIVA with propofol and three different doses of sufentanil.

To allow developing the experiment, twelve adult female mongrel dogs (mean weight 18.21±2.81 kg) were divided into three different groups. General anesthesia was induced with propofol (5 mg/kg i.v.) following administration of intravenously acepromazine (0.05 mg/kg). Anesthesia was then maintained with continuous infusion of propofol (0.2 mg/kg/minute), associated with sufentanil, in three different doses, accordingly to the group the animal was assigned to: (A) 0.025 µg/kg/minute; (B) 0.05 µg/kg/minute; and (C) 0.1 µg/kg/minute. The infusion of sufentanil and propofol lasted 120 minutes and was discontinued simultaneously. Arterial blood samples were withdrawn right before, and 30, 60, 90, and 120 minutes after induction. Blood samples were also collected at 30, 60, 90, and 120 minutes after discontinuation of both drugs.

The groups did not differ each other significantly, despite a high variability of the means could have decreased the sensitivity of the statistical test. Nonetheless, it was observed that groups A and B developed a suppression of the hypothalamic-pituitary-adrenal axis along anesthesia, since a tendency of reduction in cortisol levels was detected, followed by a mild increase in the post-anesthetic period. However, these changes were not enough to be of clinical or statistical importance.

According to the results, it is possible to conclude that this anesthetic association did not result in stress endocrine response, but led to a mild reduction in plasma cortisol concentration. Furthermore, it was seem that the reduction in cortisol levels is not determined by the dose of sufentanil.