Venous blood lactate evaluation in equine neonatal intensive care

The use of blood lactate concentration as an indicator of prognosis and disease severity has become a common practice in equine medicine, especially with the validation of handheld analyzers. However, few authors described lactate concentration in critically ill foals, and there are no published studies about the use of handheld analyzers in neonatal foals. In this study, for the first time in the equine neonate, we validated the Lactate Scout analyzer, both in healthy and in critically ill foals. The study also describes the normal range for blood lactate in 26 healthy neonatal foals during the first 72 h of life. Moreover, the utility of venous lactate measurement in 88 critically ill foals was determined, describing lactate values in the most common neonatal pathologies, evaluating serial blood lactate measurements, and investigating its prognostic value. The comparison with the enzymatic-colorimetric reference method showed that the Lactate Scout analyzer is reliable. The mean difference (bias +/-2SD) between the two methods was close to zero for all comparisons, and the SD of difference was +/-0.76 with a 95% confidence interval from -1.58 to 1.40 mmol/L. In healthy foals, blood lactate concentrations at birth and at 12h of life were statistically higher (P<0.01) than lactate concentrations measured at subsequent times. In critically ill foals, the highest lactate concentration at admission was found in hemorrhagic shock, septic shock, and complicated perinatal asphyxia syndrome (PAS). Our results showed that hyperlactatemia, although it does not provide diagnostic information, indicates the severity of illness and the need for an early and aggressive intervention. This could be very useful both during hospitalization and in the field to support veterinarians in making a decision about referral. Furthermore lactatemia proved to be a reliable prognostic parameter: In nonsurviving foals, hyperlactatemia persisted during the entire hospitalization, whereas in survivors there were no significant differences after 24h from admission. Because prognostic parameters have certain limitations, hyperlactatemia should not be used alone to decide whether to discontinue treatments in critically ill foals. A careful and complete clinical examination is always essential.