Effect of non-adrenal illness, anaesthesia and surgery on plasma cortisol concentrations in dogs.

Basal plasma cortisol concentrations in 25 dogs with non-adrenal illness were two to three times higher than in 25 normal dogs (158 +/- 25 nmol litre-1 compared with 65 +/- 22; mean +/- SD). In addition, plasma cortisol concentrations were measured in 12 animals undergoing major abdominal, thoracic or orthopaedic surgery and compared to a group of six anaesthetised dogs. Anaesthesia alone failed to significantly alter plasma cortisol levels, however, all forms of surgery produced a significant increase in plasma cortisol concentration which returned to normal 24 hours after completion of surgery.