EFFICIENCY OF A CENTRIFUGAL PUMP FOR DISTAL CIRCULATORY SUPPORT DURING CROSS-CLAMPING OF THE DESCENDING THORACIC AORTA

To demonstrate efficiency and to determine the ideal circulatory suppo rt using the centrifugal pump, the authors designed an experimental st udy in 6 mongrel dogs 13.3 to 18.5 kg in weight. The descending thorac ic aorta was cross-clamped for two hours without the use of vasoactive drugs or blood products. They developed methods of optimizing use of the centrifugal pump to achieve satisfactory hemodynamic and metabolic efficiency. Aortic pressure proximal to the clamp was essentially mai ntained unchanged by regulating flow with the pump during cross-clampi ng. Bypass flow tended to decrease (from 83 +/- 13 to 53 +/- 22 ml/kg/ min) during prolonged clamping; distal nonpulsatile pressure was still maintained between 114 +/- 34 to 127 +/- 30 mmHg (mean +/- SD). Anima ls were observed for more than twenty-four hours postexperiment; 3 of six dogs were able to stand and walk normally, while the other 3 dogs were only able to move their hind legs but unable to walk normally or stand for more than twenty-four hours. The cause of the paraparesis wa s unclear. It may be related to spinal cord ischemia secondary to hepa tic steal. It also suggests that this method of circulatory support is not able to prevent paraplegia following two-hour cross-clamping of t he descending thoracic aorta.