Use of a Low-Prime Circuit for Bloodless Heart Transplantation in Xenotransplant of 5—7 Kilogram Primates

Abstract

There is a great effort to decrease blood product use during open-heart surgery in pediatrics. We were presented with a research challenge to accomplish heart xenotransplantation from donor cynomologous monkey (Macaca fascicularis) to recipient olive baboon (Papio anubis) of 5–7 kilograms without benefit of donor or banked blood products. The purpose of this study was to design and implement a practical, low-volume circuit to minimize hemodilution and avoid the use of blood products. A simple circuit was assembled using a low-volume oxygenator with hardshell venous reservoir, an 1/8-inch arterial line, an 1/4-inch venous line, and gravity drainage. Three xenotransplants were performed and evaluated. The mean recipient weights were 6.3 ± 0.7 kg. Circuit prime volume was 228 ± 5.8 mL, and bypass time was 85 ± 6.7 min. Blood flow rates were 585 ± 113 mL/min with postmembrane arterial line pressures of 344 ± 81 mmHg, and patient mean arterial pressures (MAP) of 51.4 ± 16.7 mmHg. Venous saturations were 63.7 ± 8.0%. The hematocrit prebypass was 37.4 ± 3.2, bypass 20.7 ± 0.9, post-MUF 27.8 ± 3.3, and 7 days postoperative 24.5 ± 7.5%. Platelet count was 289 ± 1.1 K/µL, 147 ± 37.1 K/µL, and 322 ± 292.7 K/µL prebypass, postbypass, and 7 days postoperative, respectively. Plasma-free hemoglobin prebypass was 7.5 ± 4.4 mg/dL and postbypass 22.2 ± 16.5 mg/dL with no noted hematuria during and after the procedure. All patients survived and were successfully weaned from cardiopulmonary bypass (CPB) with same day extubation. A low-prime circuit for bloodless heart surgery is possible. To achieve low reservoir levels, especially without the use of an arterial line filter (ALF), it is necessary to have a full armament of monitoring and alarm devices.