Summary: Reasons for performing study: Evaluation of serial blood lactate concentrations [LAC] are of prognostic value for morbidity and mortality in critically ill human patients and neonatal foals, but have not been prospectively evaluated in a large multicentre study of critically ill neonatal foals. Objectives: To prospectively evaluate the prognostic value of sequential [LAC] analysis in critically ill neonatal foals with risk of mortality. Study design: Prospective, observational study. Methods: Thirteen university and private equine referral hospitals enrolled 643 foals over the 2008 foaling season and [LAC] was measured at admission ([LAC]ADMIT) and 24 ([LAC]24), 48 ([LAC]48), 72 ([LAC]72), 96 ([LAC]96) and 120h ([LAC]120) after admission. [LAC] changes over time ([LAC]Δ) were calculated between sampling points. Results: Nonsurvivors had significantly greater [LAC]ADMIT, [LAC]24 and [LAC]48 compared with surviving foals (P<0.001). In nonsurviving foals [LAC]Δ did not decrease over time while survivors showed significant positive [LAC]Δ between [LAC]ADM-24 and all other time periods (P<0.001). Logistic regression analysis showed that the odds of survival decreased for each 1mmol/l [LAC] increase at all time points for all critically ill foals, independent of major final diagnoses as potential confounders. Septic foals had significantly greater [LAC] at all time points compared with nonseptic foals (P<0.001) and [LAC]Δ in septic foals was significantly more positive (suggesting better clearance of lactate from the blood) only at [LAC]ADM-24 and [LAC]72-96 (P<0.01), while in nonseptic foals [LAC]Δ was significantly positive between [LAC]ADM-24 compared with all other time periods (P<0.001). Conclusions: Blood lactate concentration is a strong, independent biomarker used to predict mortality in critically ill foals. Lactate metabolism is impaired in nonsurviving and septic foals and [LAC]Δ can be utilised to identify patients at high risk for mortality.
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