Venous Plasma L-Lactate is a Prognostic Indicator of Survival in Neonatal Foals
Plasma L-lactate (lactate) can be used in the assessment of hydration, acid-base, and oxygenation status of critically ill neonatal foals. While many factors contribute to the final outcome of survival, earlier information about the overall systemic status of each foal may help to formulate a more accurate prognosis on an individual basis. Our objective was to assess the use of plasma L-lactate concentration and the change in lactate over time as prognostic indicators for development of septicemia and survival to discharge in the population of neonatal foals seen at our referral facility.
Foals less than 2 weeks old admitted to Purdue University Veterinary Teaching Hospital from January 2005 through July 2006 were enrolled in this prospective, observational study. Information for a minimum database was collected at admission and a sepsis score calculated. Venous blood was drawn for plasma lactate concentration measurement at admission, 12-16 hours later, and 36-40 hours later. Foals were classified according to development of septicemia and survival to discharge. The Wilcoxon rank sum test was used to compare lactate concentrations between septicemic (sepsis score > 11) and nonsepticemic (sepsis score < 11) foals and between foals that survived and those that did not survive to discharge. Multivariate logistic regression was used to create separate models for predicting septicemia and non-survival. Receiver-operator characteristic curves were generated to suggest cut-off points for lactate concentrations to predict non-survival.
Septicemic foals had higher lactate concentrations at admission (P < 0.001) and at 12-16 hours (P = 0.007) than non-septicemic foals; there was no difference in the change in lactate concentrations over time. Non-surviving foals had higher lactate concentrations at admission (P = 0.001), 12-16 hours (P = 0.001), and 36-40 hours (P = 0.005) than surviving foals; there was no difference in the change in lactate concentrations over time. Lactate concentration was not a significant predictor of septicemia in a multivariate model, based on sepsis scores. In another multivariate model, increasing lactate concentrations were associated with a 1.65-fold increase in the chance of death.
A lactate concentration cut-off of > 5.3 mmol/L is suggested to predict non-survival in neonatal foals, but a useful cut-off point for lactate could not be established for predicting septicemia. Venous blood L-lactate concentrations should be assessed early in the treatment of critically ill neonatal foals to assist in formulating a prognosis for survival.