From June 1985 to December 1991, 21 patients (12 men and 9 women; mean age, 60 years) underwent total simultaneous aortic replacement that extended from the valve to the bifurcation. The causes of the diseased aorta were: medial degeneration with total aortic dilatation or multiple aneurysms (n = 7) and either acute (n = 4) or chronic (n = 10) dissection. Clinical evaluation and investigation in all patients consisted of computed tomography and magnetic resonance imaging as well as angiography. Only patients with combined thoracic and abdominal emergencies were selected, and these comprised worsening of cardiac conditions resulting from aortic regurgitation, and rapid dilatation of the ascending aorta and arch with impending rupture in conjunction with ischemia of the abdominal viscera, kidney, or either leg. The surgical technique consisted of inducing deep hypothermia by means of femoral vein-femoral artery cardiopulmonary bypass. During the cooling time, the aortic root was replaced under cardioplegia. Once lowering of the body temperature attained electroencephalographic silence, circulation was stopped and the aorta was replaced from the arch to the bifurcation. Circulation and rewarming were resumed only after the operation was completed. In our most recent patient, the operating time was reduced by opening the thoracic and the abdominal incisions during cooling; the cardioplegic solution as not injected but, instead, the myocardium was cooled down along with the whole body. In these patients, the hypothermy at electroencephalographic silence ranged from 14 degrees to 19 degrees C.(ABSTRACT TRUNCATED AT 250 WORDS)