[Clinical study of optimal bypass flow for temporary bypass with centrifugal pump in surgical treatment of aneurysm of the descending thoracic aorta].

Since 1987, 33 patients were operated on for aneurysm of the descending thoracic aorta using temporary bypass with a heparin-coated centrifugal pump and heparin-coated tubes at Kobe University Hospital. Sixteen patients had true aneurysms of the descending thoracic aorta, 7 had thoraco-abdominal aneurysms and 10 had aortic dissection (DeBakey's type III). Heat exchanger and oxygenator were not included in the bypass circuit in all cases. Perfusion time was from 42 to 205 minutes (average 90 minutes). Left heart bypass was established with 1 mg/kg of systemic heparinization in 5, 0.5 mg/kg in 5, and 0 mg/kg in 23 cases. There were no complications such as perioperative embolism, acidosis, or hypothermia. During aortic cross-clamping, the arterial pressure of the lower extremity was maintained over 70 mmHg, but there was no relationship between the distal perfusion pressure and bypass flow. The urine output during temporary bypass was significantly related to the distal perfusion flow by centrifugal pump (r = 0.455, p < 0.01). Seven out of 23 patients who were bypassed under 40 ml/kg/min of distal perfusion flow showed transient renal dysfunction postoperatively, and two developed postoperative renal failure, while the other patients bypassed over 40 ml/kg/min of pump flow stayed in the normal range of the renal function, where there were statistically differences (p < 0.05). Postoperative paresis occurred in 2 patients who were also perfused under 40 ml/kg/min of bypass flow. Therefore, it is concluded that temporary bypass with centrifugal pump is a safe and well acceptable circulatory support in the surgical treatment of aneurysm of the descending aorta.(ABSTRACT TRUNCATED AT 250 WORDS)