Resting Cortisol Concentration as a Predictor of Illness Severity in Critically Ill Dogs With Systemic Inflammatory Response Syndrome.

OBJECTIVE: To determine the use of resting serum cortisol concentration as a marker of outcome and illness severity as assessed by the Acute Patient Physiologic and Laboratory Evaluation (APPLE) full and fast scores in critically ill dogs with and without systemic inflammatory response syndrome (SIRS). DESIGN: Prospective, observational study. SETTING: University teaching hospital. ANIMALS: Client-owned dogs were enrolled into three different groups: SIRS (30 dogs), non-SIRS (25), and healthy controls (19). Dogs with acute critical illness (<48 h) admitted to the ICU were enrolled and classified into SIRS and non-SIRS groups. Healthy dogs were enrolled as controls. Resting serum cortisol concentrations were measured before treatment. APPLE full and fast scores were calculated at admission, with outcome recorded for each dog. INTERVENTIONS: None. MEASUREMENTS AND RESULTS: Resting serum cortisol concentrations were higher in the SIRS and non-SIRS groups compared with the control group (p < 0.001); however, there was no significant difference (p = 0.59) between the SIRS and non-SIRS groups. APPLEfull scores were higher in the SIRS group compared with the non-SIRS (p < 0.0001) and control (p < 0.0001) groups. The APPLEfull scores increased by 1 (95% CI: 0.6-1.4) for every increase of 62.5 nmol/L (2.2 µg/dL) in resting serum cortisol concentration. Resting serum cortisol concentrations were not associated with mortality (p = 0.33). There was moderate evidence that APPLEfull scores can predict mortality (p = 0.03). CONCLUSIONS: Resting serum cortisol concentrations can be used as a marker of illness severity in critically ill patients with SIRS. Further studies enrolling larger numbers of cases may clarify its potential as a marker of outcome.