Use of Lactate ProTM2 for measurement of fetal scalp blood lactate during labor - proposing new cutoffs for normality, preacidemia and acidemia: a cross-sectional study

Objective: Measurement of fetal scalp blood lactate is a supplementary tool to cardiotocography in the case of a non-reassuring tracing. Several hand-held lactate meters have been launched, all with differentials in absolute values. Therefore, the reference intervals must be calculated for each device. The internationally accepted reference interval is based on measurement with Lactate Pro(TM) with recently got out of production. The aim of this study was to propose cutoffs for normality, preacidemia, and acidemia in fetal scalp blood for Lactate Pro(TM)2 based on the comparison of lactate values measured with Lactate Pro(TM) and Lactate Pro(TM)2.Design: Seven hundred one fetal scalp blood samples were analyzed simultaneously. The conversion equations were retrieved from the linear regression model. On the basis of the cutoffs for Lactate Pro(TM) cutoffs for Lactate Pro(TM)2 were calculated.Results: The conversion equations obtained were Lactate Pro(TM)=-0.02+0.68xLactate Pro(TM)2 (SD: -0.09-0.07xLactate Pro(TM)2) and Lactate pro(TM)2 (LP2)=0.03+1.48xLactate Pro(TM) (SD: 0.16+0.17xLactate Pro(TM)). The correlation to umbilical arterial pH was identical for the two devices (r=-0.18), whereas the correlation to umbilical arterial lactate was better for Lactate Pro(TM) than for Lactate Pro(TM)2 (r=0.38, respectively, r=0.33). The correlation to umbilical arterial lactate was dependent on time from sampling to delivery.Conclusion: Proposed reference values for Lactate Pro(TM)2: scalp lactate <6.3mmol/L=normal, no indication for intervention; 6.3-7.1mmol/L=preacidemia, repeated testing has to be considered;>7.1mmol/L=acidemia, expedite delivery.