Perfusion
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Reduction of priming volumes of the cardiopulmonary bypass (CPB) circuit in neonatal cardiac surgery to decrease haemodilution and blood transfusion requirements can be achieved with the use of neonatal low prime oxygenators and smaller diameter tubing. We have further reduced our prime volume with the use of a custom-designed arm allowing for remote positioning of a double-headed roller pump. ⋯ Results showed a 29% decrease in priming volume and a 58% reduction in blood utilization during CPB. This reduction in priming volume is clinically significant as it lowers the ratio of priming volume to patient blood volume and reduces homologous blood requirements.
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Femoral venous cannulae (17-28 French) were tested to compare flows obtained by their placement in a simulated inferior vena cava (IVC) or right atrium (RA) and by varying drainage pressures using gravity siphon drainage or a centrifugal pump in the venous line. The circuit consisted of conventional tubing and equipment including a segment of thin-walled latex tubing to simulate the IVC connected to a flexible reservoir to simulate the RA. The test fluid was a 40% glycerin solution. ⋯ When negative pressure was applied with the centrifugal pump, flow increased 10% and 18% (IVC and RA positions, respectively) compared to gravity siphon drainage conditions. There also was a tendency for flow to plateau or cease when the centrifugal pump was used at higher levels of negative pressure or when larger cannulae were used. We conclude: (1) position of smaller cannulae in the RA yield better flows than when the cannulae are larger and placed in the IVC; (2) smaller-sized cannulae are capable of achieving higher flows when the centrifugal pump is used; (3) cannulae must be properly positioned to achieve maximum flow; (4) the centrifugal pump will augment flow, but should be regulated to avoid extreme negative pressures; and (5) cannula design has no demonstrable effect on flow.
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Conventional cardiopulmonary bypass (CPB) in neonates results in increased transfusion requirements and hemodilution. There has been little advancement in CPB for the neonatal population. There is evidence that increased priming volumes and blood product transfusion enhances inflammatory response to CPB and increases myocardial and pulmonary dysfunction. ⋯ Among all parameters tested, except for blood requirement and hematocrit post-CPB, there were no significant differences between the two circuits. VAVD makes asanguineous prime in neonates feasible. When used in this study to miniaturize a conventional-CPB circuit, VAVD with a reconfigured neonatal CPB console and circuit resulted in no detrimental effects, and allowed for markedly decreased priming volumes and blood transfusion requirements.