Evaluation of canine plasma cortisol and C-reactive protein as measures of post-surgical stress and tissue trauma

Post surgical stress and tissue trauma have increasingly been evaluated through blood cortisol and C-reactive protein (CRP) assays. Cortisol release has numerous triggers compared with CRP and no comparison has previously been made between the discriminating ability of the assays. Forty five bitches were ovariohysterectomized by either an experienced surgeon (8) or veterinary student (37) under standardised conditions. Blood samples collected pre, 2, 4 and 6 hours post operatively were analysed for cortisol and CRP. Surgery times were four times longer, anaesthesia times double, post operative temperatures lower, and estimated blood loss was three times greater for student sterilised dogs. CRP and cortisol was found to increase significantly over time for all animals. Bitches sterilised by inexperienced surgeons had a significantly greater rise in CRP at 4 and 6 hours post surgically (P=0.046). Serum cortisol was not significantly affected by surgeon experience (P=0.242), or any other outcome variables assessed. Inexperienced surgeons caused more tissue trauma due to long surgical times, larger wounds, more bleeding and less precise tissue handling than experienced surgeons. This difference was only discernable in serum CRP concentrations. It was concluded that serum CRP is a more discriminating marker than serum cortisol when assessing post surgical trauma. Blood cortisol concentration may still be a useful, if less precise, measure of assessing patient perceived post surgical stress in dogs, but it was clearly inferior to CRP in terms of identifying differences between surgical procedures in this study.