Delaying cord clamping until ventilation onset improves cardiovascular function at birth in preterm lambs

Area of Science:

• Neonatal Physiology
• Cardiovascular Research
• Perinatal Medicine

Background:

• Delayed cord clamping is known to improve circulatory stability in preterm infants.
• The precise physiological mechanisms underlying this benefit remain unclear.
• Understanding the timing of umbilical cord clamping relative to ventilation onset is crucial.

Purpose of the Study:

• To investigate the effects of umbilical cord clamping timing on cardiovascular function in newborn lambs.
• To compare clamping at delivery versus after ventilation onset.
• To elucidate the physiological changes during the transition period.

Main Methods:

• Prenatal surgery in lambs to implant cardiovascular monitoring catheters and probes.
• Delivery at 126 days gestation.
• Two groups: umbilical cord clamped before ventilation (Clamp 1st) or after ventilation (Vent 1st).
• Continuous monitoring of pulmonary and carotid blood flow, pressures, and cardiac output.

Main Results:

• Clamping before ventilation caused transient increases in pressure and flow, followed by significant reductions in heart rate and right ventricular output.
• Ventilation restored cardiovascular parameters in the early clamping group.
• Delaying cord clamping until after ventilation onset resulted in stable blood flows and pressures, with only a minor reduction in right ventricular output.
• Vent 1st group showed improved pulmonary blood flow before cord clamping.

Conclusions:

• Delaying umbilical cord clamping for 3-4 minutes until after ventilation is established significantly improves cardiovascular function in newborns.
• This practice enhances pulmonary blood flow prior to clamping, maintaining stable cardiac output.
• Delayed clamping facilitates a smoother cardiovascular transition, crucial for neonatal well-being.