Utility of admission lactate concentration, lactate variables, and shock index in outcome assessment in dogs diagnosed with shock

Objective To determine whether admission venous plasma lactate concentration, calculated lactate variables, or shock index (SI) could discriminate hospital survivors from nonsurvivors in dogs admitted with shock. Design Prospective investigation performed over a 19-month period. Setting Large urban private teaching hospital. Animals Twenty-three dogs consecutively admitted to the ICU from January 2008 to July 2009 with initial peripheral venous plasma lactate concentration >2 mmol/L (18.0 mg/dL) and clinical and hemodynamic parameters consistent with shock. Interventions None. Measurements and Main Results Heart rate, systolic blood pressure, and venous plasma lactate concentrations were serially recorded at predefined time points and used to calculate SI (SI = heart rate/systolic blood pressure) and lactate variables, including lactime (time lactate > 2.0 mmol/L), lactate clearance ([lactate(initial) - lactate(delayed)]/lactate(initial) x 100), and LAC(AREA) (area under the lactate concentration versus time curve). Primary outcome was survival to discharge. Overall survival rate was 61%. Admission venous plasma lactate concentration did not differ between groups (P = 0.2). Lactime was shorter in survivors versus nonsurvivors (P = 0.02). Lactate clearance at 1, 10, 16, 24, and 36 hours, and final lactate clearance were greater in survivors versus nonsurvivors (P < 0.05). LAC(AREA) at time intervals 0-1, 1-4, 4-10, 10-16, 16-24, 24-30, and 30-36 hours was larger in nonsurvivors versus survivors (P < 0.05). Total LAC(AREA) did not differ between groups (P = 0.09). Admission SI and time to normalize SI (SI < 0.9) were not different between survivors and nonsurvivors (P > 0.05). Conclusions While admission venous plasma lactate concentration could not discriminate between hospital survivors and nonsurvivors, lactate variables showed clinical utility to predict outcome in dogs with shock. Further studies are needed to determine SI reference ranges and optimal SI cut-off values to improve its prognostic ability in sick dogs.