Proposed cutoff for fetal scalp blood lactate in intrapartum fetal surveillance based on neonatal outcomes: a large prospective observational study

• Objective: Determination of lactate in fetal scalp blood (FBS) during labour has been recognised since the 1970s. The internationally accepted cutoff of >4.8mmol/l indicating fetal acidosis is exclusive for the point-of-care device (POC) LactatePro™, which is no longer in production. The aim of this study was to establish a new cutoff for scalp lactate based on neonatal outcomes with the use of the StatstripLactate®/StatstripXpress® Lactate system, the only POC designed for hospital use. Design: Observational study. Setting: January 2016 to March 2020 labouring women with indication for FBS were prospectively included from seven Swedish and one Australian delivery unit. Population: Inclusion criteria: singleton pregnancy, vertex presentation, ≥35+0weeks of gestation. Method: Based on the optimal correlation between FBS lactate and cord pH/lactate, only cases with ≤25minutes from FBS to delivery were included in the final calculations. Main outcome measures: Metabolic acidosis in cord blood defined as pH <7.05 plus BDecf >10mmol/l and/or lactate >10mmol/l. Results: A total of 3334 women were enrolled of whom 799 were delivered within 25minutes. The areas under the receiver operating characteristics curves (AUC) and corresponding optimal cutoff values were as follows; metabolic acidosis AUC 0.87 (95% CI 0.77–0.97), cutoff 5.7mmol/l; pH <7.0 AUC 0.83 (95% CI 0.68–0.97), cutoff 4.6mmol/l; pH <7.05 plus BDecf ≥12mmol/l AUC 0.97 (95% CI 0.92–1), cutoff 5.8mmol/l; Apgar score <7 at 5minutes AUC 0.74 (95% CI 0.63–0.86), cutoff 5.2mmol/l; and pH <7.10 plus composite neonatal outcome AUC 0.76 (95% CI 0.67–0.85), cutoff 4.8mmol/l. Conclusion: A scalp lactate level <5.2mmol/l using the StatstripLactate®/StatstripXpress® system will safely rule out fetal metabolic acidosis. Tweetable abstract: Scalp blood lactate <5.2mmol/l using the StatstripLactate®/StatstripXpress system has an excellent ability to rule out fetal acidosis.

Ämnesord

MEDICIN OCH HÄLSOVETENSKAP  -- Klinisk medicin -- Reproduktionsmedicin och gynekologi (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Clinical Medicine -- Obstetrics, Gynaecology and Reproductive Medicine (hsv//eng)

Nyckelord

Cardiotocography and point of care

fetal monitoring

fetal scalp blood

intrapartum asphyxia

lactate

metabolic acidosis

umbilical cord blood

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