Pulsatility improves hemodynamics during fetal bypass. Experimental comparative study of pulsatile versus steady flow

Area of Science:

• Cardiovascular Physiology
• Fetal Physiology
• Bypass Surgery

Background:

• Cardiopulmonary bypass (CPB) typically uses steady flow, which can increase systemic vascular resistance.
• Fetal bypass is associated with rising peripheral and placental vascular resistances, leading to hypoxemia.
• Pulsatile flow is hypothesized to mitigate these adverse effects in fetal bypass.

Purpose of the Study:

• To investigate the effects of pulsatile flow compared to steady flow during fetal bypass in lambs.
• To determine if pulsatile flow can prevent the rise in vascular resistance and hypoxemia observed with steady flow.

Main Methods:

• 17 fetal lambs underwent 30-minute fetal bypass via right atrial and main pulmonary artery cannulation.
• Two groups were studied: continuous steady flow (n=9) using a roller pump and pulsatile flow (n=8) using a centrifugal pump.
• Hemodynamic, oxymetric, and organ blood flow (using radiolabeled microspheres) parameters were recorded before and during bypass.

Main Results:

• Pulsatile flow (group 2) maintained significantly higher SaO2 and PaO2 at 10 minutes compared to steady flow (group 1).
• Pump flow and lower systemic vascular resistances were observed with pulsatile flow.
• Organ blood flow, including to the placenta, was significantly higher with pulsatile flow, and placental vascular resistance remained stable.

Conclusions:

• Pulsatile flow temporarily prevented hypoxemia during 30 minutes of fetal bypass in lambs.
• Pulsatile flow facilitated higher pump flow by decreasing systemic vascular resistance.
• Pulsatile flow improved organ perfusion, including placental blood flow, suggesting potential benefits for fetal cardiac surgery.