Comparison of extracapillary and endocapillary blood flow oxygenators for open heart surgery in dogs: efficiency of gas exchange and platelet conservation.

The goal of the current study was to compare the efficiency of gas exchange and platelet conservation of a new extracapillary blood flow oxygenator versus an endocapillary blood flow oxygenator during open heart surgery with extracorporeal circulation in dogs. Dilation and remodeling of the right ventricular outflow tract of dogs was performed using a patch graft technique to simulate pulmonary stenosis. Sequential pre- and post-operative blood analysis revealed that gas exchange efficiency and platelet conservation was significantly greater with the extracapillary blood flow oxygenator than with the endocapillary blood flow oxygenator. However, the priming volume of the extracapillary blood flow oxygenator was significantly greater, leading to hemodilution. We conclude that while the extracapillary blood flow oxygenator provided benefits in terms of gas exchange and platelet conservation, development of a smaller extracapillary blood flow type oxygenator to reduce hemodilution effects would be beneficial.

Cardiopulmonary bypass in the cat.

OBJECTIVE: To assess the physiologic response to, and acute survival of, cats undergoing cardiopulmonary bypass (CPB) and to evaluate the efficacy of a commercial human pediatric oxygenator system on cats weighing less than 6 kg. STUDY DESIGN: Experimental study. ANIMALS: Six intact male cats METHODS: Cats were placed on cardiopulmonary bypass by cannulating the cranial and caudal vena cavae and the carotid artery. The pediatric CPB circuit was primed with 150 mL of a balanced crystalloid solution. Venous drainage was enhanced by a controlled, vacuum-assist system. A cross-clamp was placed on the ascending aorta and cardiac arrest was induced by antegrade infusion of a cold cardioplegia solution. After 45 minutes of arrest time, the cross-clamp was removed and the cats were weaned off bypass and decannulated. No blood products were administered. Heart rate, mean arterial pressure (MAP), central venous pressure, arterial blood gas, hematocrit (HCT), total plasma protein concentration (TP), serum electrolyte concentrations, and activated clotting time (ACT) were measured at baseline period (BL), during CPB, 60 minutes after CPB (CPB 60) and 90 minutes after CPB (CPB 90). A complete blood count (CBC), blood chemistry profile, and urinalysis were performed at BL, during CPB, and CPB 90. Cats were euthanatized after CPB 90. RESULTS: Cardiopulmonary bypass resulted in a significant (P <.05) decrease in mean HCT (18.0%) and TP (2.3 gm/dL) at CPB 90 when compared to BL (30.5% and 6.0 gm/dL, respectively). The MAP at CPB 90 (54 mm Hg) was decreased from BL (94 mm Hg). The ACT increased from a mean of 124 seconds to > 400 seconds with heparinization and was reversed to 300 seconds with protamine. Mean platelet counts decreased from BL (369,000 /microL) to CPB 90 (94,500 /microL). Mean white blood cell counts decreased from 13,200 /microL at BL to 2,200 /microL at CPB 90. Upon reperfusion, 1 cat fibrillated but was successfully defibrillated. CONCLUSIONS: Cardiopulmonary bypass was performed successfully in 6 cats weighing less than 6 kg. Acute survival to 90 minutes after CPB was achieved in all 6 cats CLINICAL RELEVANCE: The ability to perform CPB in the cat may allow intracardiac repair of various heart defects in this species.

Microbubble elimination during priming improves biocompatibility of membrane oxygenators.

We tested the hypothesis that platelet loss following blood contact with foreign materials is partly related to the presence of microbubbles of gas (gas nuclei) trapped in surface defects on the membrane material. Extracorporeal membrane oxygenator perfusions were conducted in two groups of sheep, with use of standard priming techniques for the oxygenator in one group and a new vacuum priming technique in the other group. The vacuum priming technique was developed to eliminate gas nuclei from the oxygenator surface. With denucleation priming, platelet loss during perfusion was markedly reduced, as was thrombus formation on the membrane surface. The platelet particle-size distribution curve showed a shift consistent with platelet aggregation with the standard priming technique but not with the vacuum priming technique. We conclude that the elimination of trapped gas nuclei from the membrane surface during priming reduces the initial interaction between blood elements and the foreign surface.