Preliminary Investigation of the Area Under the l-Lactate Concentration–Time Curve (LACAREA) in Critically Ill Equine Neonates

Background: A variety of measures of l-lactate concentration ([LAC]) in the blood of critically ill neonatal foals have shown utility as prognostic indicators. These measures, evaluating either the severity of hyperlactatemia or the duration of exposure to hyperlactatemia, perform fairly well and have correctly classified 75-80% of foals examined in several studies. The area under the l-lactate concentration versus time curve (LACArea) encompasses both severity and duration of hyperlactatemia and should improve correct classification of patient survival. Hypothesis/Objectives: LACArea is larger in nonsurviving critically ill neonatal foals. Animals: Forty-nine foals admitted for critical illness to 1 of 4 referral hospitals. Methods: Whole blood was obtained at admission and 6, 12, 18, and 24 hours after admission for measurement of l-lactate using a handheld lactate meter. LACArea was calculated for: admission-6, 6-12, 12-18, 18-24 hours, and admission-24 hours using the trapezoidal method and summing the 6-hours interval areas to determine total 24 hours area. Differences between survivors and nonsurvivors were determined using robust regression and Kruskal-Wallis testing, P < .05. Results: LACArea was significantly larger in nonsurviving foals (n = 9) than in surviving foals (n = 40) at all time periods examined. Conclusions and Clinical Importance: Differences in LACArea between surviving and nonsurviving critically ill neonatal foals are large and support further investigation of this method as an improved biomarker for survival in critically ill neonatal foals is indicated.