Timing of cord clamping for blood gas analysis is of paramount importance

Abstract

Timing of cord clamping for blood gas analysis is of paramount importanceSir,We thank Prof. Di Tommaso and Vannuccini for their interest in our article. 1,2 We congratulate their group for the study "Blood gas values in clamped and unclamped umbilical cord at birth". 3 In their prospective observational study, published in 2014, 46 patients delivered vaginally at term; for each patient, cord blood gas analysis was performed after blood collection had been carried out in two different ways. The first two blood samples, arterial and venous, were obtained from the unclamped cord within 90 seconds from birth.After that, two other samples were taken from a 10-cm segment of a double-clamped cord. No significant differences were observed on arterial pH, pO 2 , pCO 2 , SaO 2 or hemoglobin concentration (ctHb) between the samples obtained within 90 seconds from birth and the clamped samples analyzed immediately after the previous sampling.In contrast, the venous SaO 2 , ctHb and BE turned out to be significantly different between the unclamped and clamped cord, although pH, pO 2 and pCO 2 were comparable.We apologize for not having cited their study, 3 which actually reinforces our hypothesis with experimental data. Di Tommaso et al demonstrate a statistically significant difference between the arterial BE by comparing the two methods. 3 The same trend toward a higher (ie, less negative) BE in the unclamped samples is present in the venous cohort. There may be a slight variation in the interpretation of these data. While Di Tommaso et al give main importance to the difference between the two techniques of umbilical cord blood collection, we instead give priority to the difference in timing of blood collection. In our opinion, timing is a crucial issue, especially in newborns at risk of intrapartum asphyxia. Timing of blood collection explains why the median BE level is higher in unclamped samples than in clamped ones. Since the blood collection in unclamped cords was performed within 90 seconds after birth, the BE correlates more closely with the intrapartum cord gas status. After this lapse of time, two variables may influence the efficacy of the cord blood gases: sampling after the onset of newborn's breathing 4 or sampling after a condition of hidden acidosis has been established in the newborn. 5Obviously, these slight changes in cord blood gases at birth may have a higher impact in those fetuses who suffered from a hypoxic stress during labor. We once again congratulate Di Tommaso et al on their important work, 3 and for the opportunity to even better delineate our clinical correlations.We therefore suggest performing cord blood sampling for gas analysis as soon as possible after birth. Further experimental studies are needed to establish the exact timing, and to evaluate whether best timing is even before onset of breathing. Surely, the technique of blood collection from the intact (unclamped) and still pulsating umbilical cord is a suitable method in clinical practice. 1. Di Tommaso M, Vannuccini S. Is pulsating co...

The effect of clamped and unclamped umbilical cord samples on blood gas analysis

“…In accordance with previous findings [12,15,17] the BE values showed the most critical changes [12]. As already demonstrated by other authors [17,18], these alterations could be time-dependant; umbilical cord arterial blood gas analysis parameters decrease when cord sampling is not immediately performed, showing even a further drop when collection occurs between 45 and 90 s from birth [19]. We are not aware about the exact time of sampling in our cohort, and can only report that blood has been collected within 60 s from birth, as per protocol.…”

Differences between umbilical blood gas in term and preterm newborns

“…Indeed, delayed cord clamping is the recommended procedure due to the reported benefits for term and preterm infants (16)(17)(18). Studies on the effects of delayed cord clamping on cord gas analysis have reported conflicting and non-definitive results (19,20). This study provides a basis for performing research in a larger population to be used as a useful tool to missing samples in high-risk deliveries and in infants subjected to birth asphyxia (21).…”