The association of blood lactate concentration with outcome in dogs with idiopathic immune-mediated hemolytic anemia: 173 cases (2003-2006)

Objective - To determine the association of blood lactate with outcome and response to transfusion therapy in dogs with idiopathic immune-mediated hemolytic anemia (IMHA). Design - Retrospective study. Setting - Urban veterinary small animal emergency hospital. Animals - One hundred and seventy-three client-owned dogs with IMHA. Interventions - None. Measurements and Main Results - Serial blood lactate concentration, therapeutic interventions, and outcome were recorded. Nonsurvivors were defined as those that died or were euthanized. One hundred and thirty-three dogs (77%) survived, 35 (20%) were euthanized, and 5 (3%) died. One hundred forty-five dogs (84%; 145/173) had a lactate concentration above the laboratory reference interval [0.46-2.31 mmol/L] on presentation. Blood lactate at presentation was higher in the nonsurvivors (median 4.8 mmol/L; 0.5-13.6) compared with survivors (median 2.9 mmol/L; 0.3-13.2) (P<0.01). All dogs presenting with hyperlactatemia that normalized (<2.0 mmol/L) within 6 hours of admission survived, whereas, 71% of dogs that had a persistent hyperlactatemia at 6 hours survived (P=0.034). Lactate was positively correlated with age, BUN, and alkaline phosphatase, and inversely correlated with PCV. Receiver operating curve analysis for lactate concentration at admission as a test for outcome had an area under the curve of 0.69 with an optimal lactate cutoff concentration of 4.4 mmol/L correctly predicting outcome 73% of the time (sensitivity 60%, specificity 77%). Conclusions - Lactate concentration at presentation was significantly higher in nonsurvivors than survivors. Lactate was significantly correlated with previously reported outcome variables but lactate concentration at admission, as a predictor for outcome was less than optimal. However, serial lactate concentration measurements may be more predictive as patients with persistent hyperlactatemia 6 hours after admission were less likely to survive. Prospective studies evaluating serial lactate concentration while controlling for other variables may provide further insight into lactate measurement as a prognostic indicator in animals with IMHA.