Characteristics and physiological basis of falls in ventricular outputs after immediate cord clamping at delivery in preterm fetal lambs

Key points Controversy exists about the physiological mechanism(s) underlying decreases in cardiac output after immediate clamping of umbilical cord at birth. To define these mechanisms, four major determinants ventricular (afterload, preload, heart rate and contractility) were measured concurrently fetal lambs 15 s intervals over a 2 min period before ventilation following delivery. After clamping, right (but not left) fell by 20% initial 30 s, due to increased afterload associated with higher arterial blood pressures, but both outputs then halved 45 falling deteriorating contractility accompanying rapid declines oxygenation asphyxial levels. Ventricular subsequently plateaued from 75 120 rebound rises asphyxia-induced surges circulating catecholamines. These findings provide basis for clinical recommendation that effective should occur within 60 clamping. Abstract large anaesthetized preterm (127(1)d, n = 12) instrumented flow probes catheters central arteries, left (LV) micromanometer-conductance catheter. Following delivery, haemodynamics, LV (RV) outputs, during non-ventilatory period, aortic gases catecholamine (noradrenaline adrenaline) concentrations intervals. (1) RV LV) reduced stroke volume (2) next falls rate, pressures decline levels, (3) exponential are consistent time-dependent which comprised an initial, minor fall related altered loading conditions, ensuing combination bradycardia dysfunction emergence state, subsequent stabilization ongoing asphyxia, supported cardiovascular stimulatory effects marked sympathoadrenal activation.