Haemodynamic effects of umbilical cord milking in premature sheep during the neonatal transition

Abstract

ObjectiveUmbilical cord milking (UCM) at birth may benefit preterm infants, but the physiological effects of UCM are unknown. We compared the physiological effects of two UCM strategies with immediate umbilical cord clamping (UCC) and physiological-based cord clamping (PBCC) in preterm lambs.MethodsAt 126 days’ gestational age, fetal lambs were exteriorised, intubated and instrumented to measure umbilical, pulmonary and cerebral blood flows and arterial pressures. Lambs received either (1) UCM without placental refill (UCMwoPR); (2) UCM with placental refill (UCMwPR); (3) PBCC, whereby ventilation commenced prior to UCC; or (4) immediate UCC. UCM involved eight milks along a 10 cm length of cord, followed by UCC.ResultsA net volume of blood was transferred into the lamb during UCMwPR (8.8 mL/kg, IQR 8–10, P=0.01) but not during UCMwoPR (0 mL/kg, IQR −2.8 to 1.7) or PBCC (1.1 mL/kg, IQR −1.3 to 4.3). UCM had no effect on pulmonary blood flow, but caused large fluctuations in mean carotid artery pressures (MBP) and blood flows (CABF). In UCMwoPR and UCMwPR lambs, MBP increased by 12%±1% and 8%±1% and CABF increased by 32%±2% and 15%±2%, respectively, with each milk. Cerebral oxygenation decreased the least in PBCC lambs (17%, IQR 13–26) compared with UCMwoPR (26%, IQR 23–25, P=0.03), UCMwPR (35%, IQR 27–44, P=0.02) and immediate UCC (34%, IQR 28–41, P=0.02) lambs.ConclusionsUCMwoPR failed to provide placental transfusion, and UCM strategies caused considerable haemodynamic disturbance. UCM does not provide the same physiological benefits of PBCC. Further review of UCM is warranted before adoption into routine clinical practice.

Cord milking versus immediate clamping in preterm infants: a randomised controlled trial

“…Animal studies have shown the value of commencing ventilation and effective pulmonary circulation to improve the cardiac output, stabilise cerebral circulation and allow for a smoother cardiovascular transition at birth 35. A recent study by Blank et al demonstrated that milking the cord at birth resulted in swings in the arterial pressure and cerebral blood flow without increasing pulmonary blood flow in newborn lambs 36. This does not negate the potential value of UCM in improving haemoglobin levels and blood volume, especially in conditions where DCC may not be a viable option as in case of need for urgent resuscitation or in interrupted placental circulation 8 13 14.…”

Management of anaemia in pre‐term infants

“…While it has the potential advantage of rapidly achieving a placental transfusion, significant concerns remain over its effect on the infants’ cerebrovascular stability. Each ‘milking’ attempt results in significant fluctuations in the systemic blood pressure and cerebral blood flow (Blank et al , ). Due to the potential risk of harm and lack of robust evidence supporting its long‐term benefit, umbilical cord milking is currently not recommended.…”

European Consensus Guidelines on the Management of Respiratory Distress Syndrome – 2019 Update

“…Two randomised trials including 255 babies <33 weeks’ gestation offered broad reassurance that short-term outcomes are broadly equivalent [41], and one follow-up study suggested better cognitive and language scores in those randomised to cord milking [42]. However, animal studies show that cord milking causes considerable haemodynamic disturbance, and a recent clinical trial has shown quadrupling of the incidence of severe intraventricular haemorrhage with cord milking compared to delayed cord clamping in preterm infants calling into question the safety of this procedure [43]. After birth, the baby should be placed in a clear polythene bag and under a radiant warmer to maintain body temperature (see below).…”