Original Article

Hematological Effects of a Low-Prime Neonatal Cardiopulmonary Bypass Circuit Utilizing Vacuum-Assisted Venous Return in the Porcine Model

Medical University of South Carolina, Department of Extracorporeal Circulation Technology, Charleston, South Carolina

^* Address correspondence to: Kevin Ahlberg, BS, CCP Sarasota Memorial Hospital Perfusion Department 1700 S. Tamiami Trail Sarasota, FL 34239

Abstract

Limiting hemodilution in neonates is difficult when extracorporeal circuits require priming volumes that are 2 to 3 times the blood volume of the newborn patient. This extreme hemodilution contributes to the development of significant postbypass coagulation disturbances. The purpose of this project was to design a low-prime neonatal bypass circuit and evaluate the coagulation status after reduced hemodilution. The null hypothesis stated there is no significant difference in the measured coagulation parameters between the low-prime circuit and the standard high-prime circuit.

Four neonatal piglets (2–4 kg) were divided into two groups and placed on cardiopulmonary bypass using either a low- (200 ml) or high-prime (500 ml) circuit. Both groups were cooled to 20°C, and, following cardioplegic arrest, underwent circulatory arrest for 20 minutes. The low-prime circuit used vacuum-assisted venous drainage, which permitted the circuit to be at the patient level. The high-prime circuit required fresh washed donor red blood cells to maintain the hematocrit in the desired range of 15–20%.

The platelet count on bypass decreased by 60 ± 1.0% in the low-prime group versus 79.6 ± 0.1% in the high-prime group. Following bypass, the platelet count was reduced by 38.3 ± 14.3% in the low-prime versus 60.2 ± 2.6% in the high-prime group. During rewarming, the mean heparinase activated clotting time (ACT) increased 5.1% above baseline in the lowprime group and 53.5% above baseline in the high-prime group. Mean plasma-free hemoglobin levels increased 40.4 mg/dl in the low-prime group versus 62.1 mg/dl in the high-prime group during bypass. This laboratory evaluation of a low-prime neonatal circuit demonstrates that coagulation disturbances often present in neonates can be reduced with the use of a low-prime circuit.