Impact of Delayed Arterial Cord Blood Sampling for Lactate Assay A Prospective Observational Study

Background: Umbilical cord sampling at delivery provides important data on the newborn's metabolism. Objective: To evaluate the impact of delayed sampling on arterial cord blood lactate values. Methods: Observational study of 168 consecutive deliveries at a tertiary teaching hospital. Arterial cord blood lactate was determined with a test strip method on paired samples obtained immediately and 5-30 min after birth. At least 90 paired measurements were necessary to show a difference in lactate levels of 6 0.5 mmol/l between the first and second samples. Lactate levels according to the time interval between birth and sampling. Results: One hundred and two paired samples were available for analysis. The lactate value was always higher in the second sample than in the first. Lactate levels increased linearly with time, by 0.062 mmol/l per min. The degree of increase was independent of the initial lactate level and the route of delivery. Delayed sampling resulted in abnormal lactate levels in 16% of neonates born with normal lactate levels. Conclusions: Our results show that delayed sampling of arterial cord blood is unreliable for neonatal lactate assay. Cord blood sampling and lactate assay should therefore be performed immediately after delivery. Copyright (C) 2008 S. Karger AG, Basel