Umbilical cord blood gas analysis at delivery: a time for quality data

Abstract

Objectives To address the practical problems of routine umbilical cord blood sampling, to determine the ranges for pH, pCO2 and base deficit and to examine the relationships of these parameters between cord vessels. Design An observational study of umbilical cord artery and vein blood gas results. Setting A large district general hospital in the UK. Subject One thousand nine hundred and forty‐two cord results from 2013 consecutive pregnancies of 34 weeks or more gestation, monitored by fetal scalp electrode during labour. Results Only 1448 (74.6%) of the 1942 supposedly paired samples had validated pH and pCO2data both from an artery and the vein; 54 (2.8%) had only one blood sample available, 90 (4.6%) had an error in the pH or pCO2 of one vessel and in 350 (18%) pairs the differences between vessels indicated that they were not sampled from artery and vein as intended. Only 60% of the cases with an arterial pH less than 7.05 had evidence of a metabolic acidosis (base deficit in the extracellular fluid 10 mmol/1 or more). Of all the cases, 2.5% had a venous‐arterial pH difference greater than 0.22 units. Conclusions Both artery and vein cord samples must be taken and the results screened to ensure separate vessels have been sampled. Interpretation of the results requires the examination of pCO2 and base deficit of the extracellular fluid from each vessel as well as the pH. Confusion about the value of cord gas measurements may be due to the use of erroneous data and inadequate definitions of acidosis which do not differentiate between respiratory and metabolic components.

Physiological development of a mixed metabolic and respiratory umbilical cord blood acidemia with advancing gestational age

“…Only pregnancies with singleton vertex presentations, complete information about all the investigated parameters, and validated cord blood samples, were included. The quality of paired umbilical arterial and venous blood samples was validated by excluding samples obtained from the same umbilical vessel according to the criteria that pH in the artery should be > 0.02 units lower than in the vein [6,7]. Single-vessel samples were excluded due to uncertain origin.…”

Cord blood sampling at delivery: do we need to always collect from both vessels?

“…It is therefore prudent to have normal blood gases on record for a baby who had a normal delivery but subsequently develops neurologic impairment, or even minor learning disabilities 1 . Authorities 2,3 have suggested that the routine collection of cord blood for blood gas analysis should include sampling from both artery and vein. Westgate et al 3 found that of 1798 paired samples, 350 (19.4%) had unphysiologic pH and carbon dioxide (CO 2 ) readings (compared with the artery, the oxygenated umbilical vein must have a higher pH and lower CO 2 ).…”

Access to computerised analysis of intrapartum cardiotocographs improves clinicians’ prediction of newborn umbilical artery blood pH

“…Cases were excluded from UAB pH analysis if paired samples were not obtained, if pH values between the two samples differed by less than 0.03 units or if values of partial pressure of CO 2 between the two samples differed by less than 7.5 mmHg. [9][10][11] Apgar scores were evaluated by the health professional responsible for immediate neonatal support, in the majority of cases this being the attending midwife.…”

“…11,13 All participants gave written informed consent for their clinical data and CTG files to be used for the purpose of research. No person-identifiable data were disclosed in the present study.…”