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Perinatal medicine

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G28 LONGITUDINAL CHANGE IN LACTATE, PH, AND BASE EXCESS IN BLOOD FROM CLAMPED AND UNCLAMPED UMBILICAL CORD VESSELS

L. Armstrong, B. Stenson.The Simpson Centre for Reproductive Health, Edinburgh, UK

Introduction: Umbilical cord lactate is a clinically useful prognostic marker of neurological morbidity. Umbilical cord samples are often delayed, or taken from placental vessels, yet there are no data on how this practice may affect lactate measurement. We studied the effect of delayed sampling in vessels isolated from (clamped), and in continuity with the placenta (unclamped).

Methods: Umbilical cords of placentas obtained immediately after delivery were clamped at five locations. Paired samples were taken from clamped and unclamped vessels at 0, 20, 40, and 60 minutes, and analysed for lactate, pH, PCO2, and BE. Data were analysed as change from time 0 at 20, 40, and 60 minutes.

Results: n = 38. Lactate was higher than at time zero after 20 minutes in both clamped (p<0.001) and unclamped vessels (p = 0.005). pH is unchanged over 60 minutes in clamped vessels (p = 0.54) but reduces in linear fashion in unclamped vessels (p<0.001), see fig 1. Base excess widened in both clamped and unclamped vessels by 20 minutes (p<0.05). Venous and arterial blood had similar findings. Change in unclamped vessels was greater than in clamped vessels.

Figure 1

 Mean Δ arterial lactate and pH (±2SD) over 60 minutes, in clamped (solid bars) and unclamped (dotted bars) vessels.

Conclusion: Obstetric guidelines state that blood from doubly clamped cord vessels can be reliably sampled for pH and blood gases upto one hour after delivery. Our study shows that cord blood continues to undergo anaerobic glycolysis, and is thus unreliable for lactate and base excess after only 20 minutes, even if the vessel has been doubly clamped. Delayed sampling from unclamped vessels is unreliable for all measurements. Fetal metabolic acidosis has important clinical and medico-legal implications. Guidelines should reflect these findings to avoid serious misinterpretation of cord …

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