Changes in plasma cortisol concentration by ages in dogs under ketamine and thiopental anesthesia

In order to examine the change in adrenocortical responses with age in dogs, 36 healthy beagle dogs were divided by age into 6 groups and were treated with ketamine or thiopental. The plasma cortisol concentrations were determined before and after the treatment. The concentrations prior to the induction of anesthesia were 2.23 +/- 0.44 micrograms/dl (mean +/- SD) in pups (2 to 3 months old), 4.35 +/- 2.04 micrograms/dl in adults (2 years old), and 3.40 +/- 1.25 micrograms/dl in aged dogs (8 to 10 years old). This result indicated the following order of plasma cortisol levels in dogs: pups less than aged dogs less than adults. The plasma cortisol concentrations after ketamine administration tended to increase. This suggested that the adrenocortical function in the dog was stimulated by ketamine. In the ketamine treated dogs, significant differences were demonstrated among the age groups. Namely, a significantly lower response was noted in pups compared to adults or aged dogs (p less than 0.001). On the other hand, the plasma cortisol levels after the thiopental treatment showed a temporary slight increase in aged dogs but tended to decrease in pups and adults. Thiopental was found to have a suppressive effect on the adrenocortical function in dogs in contrast to ketamine.