Evaluation of selection criteria for validating paired umbilical cord blood gas samples: an observational study.

Abstract

To compare six validation criteria for umbilical cord blood gas (UCBG) values in vigorous and nonvigorous neonates. Retrospective cohort study. Single tertiary obstetric centre, King Edward Memorial Hospital (KEMH), Perth, Western Australia. A total of 37,763 consecutive deliveries at >23 weeks of gestation. Six validation criteria were compared to evaluate the proportion of deliveries with 'valid' UCBG data; and the proportion of vigorous and nonvigorous neonates with metabolic acidaemia. Proportion of deliveries with 'valid' UCBG values; proportions of vigorous and nonvigorous neonates with normal, borderline and abnormal UCBG values. The criteria based on KEMH 5th centile arteriovenous pH and Pco(2) differences resulted in a higher proportion of neonates with 'valid' UCBG values than the previously described Westgate and Kro criteria. The increase in 'valid' UCBG values occurred across the entire study population including vigorous and nonvigorous neonates. Among neonates with short-term neonatal complications there was an increase in nonvigorous neonates with umbilical artery metabolic acidaemia. There was no corresponding increase in vigorous neonates diagnosed with abnormal UCBG values. Use of the KEMH criteria results in an increase in the proportion of nonvigorous term neonates with UCBG data considered 'valid' to aid clinicians in the management of the neonate shortly after delivery. This change occurs without increasing the rate of false-positive diagnoses of acidaemia in vigorous neonates. The KEMH 'validation' criteria were developed from an entire presenting population and provide a simple algorithm that can be universally applied to identify neonates with nonphysiological UCBG values.