The area under the curve of l-lactate in neonatal foals from birth to 14 days of age

Background: Prior studies have shown the prognostic utility of measuring l-lactate in critically ill neonatal foals, both as single (at admission) and serial measurements. Greater prognostic sensitivity and specificity may be achieved by use of the area under the l-lactate versus time curve (LAC_Area) over the first 24 hours of hospitalization, which captures both severity and duration of hyperlactatemia. Prior to application of this concept in sick equine neonates, a reference interval for LAC_Area should be determined. Methods: The concentration of lactate [LAC] was measured in blood obtained via direct jugular venipuncture from clinically normal foals on Days 1 (birth-24 h of age), 3, 7, and 14 following birth at 6-hour intervals for each 24-hour period. LAC_Area was calculated using the trapezoidal method. Differences in LAC_Area by Day were determined by MANOVA with a priori Bonferroni correction, P ≤ 0.05. Results: LAC_Area differed by Day (P = 0.001), being largest on Day 1, followed by Day 3. Days 7 and 14 were smallest and not different from each other. Conclusion: LAC_Area decreases substantially and predictably over the first week of life in normal neonatal foals. Knowing how LAC_Area normally changes over the first 2 weeks of life will aid in future study of LAC_Area as it applies to sick neonatal foals, allowing for consideration of maturational changes potentially unrelated to disease.