Open heart surgery was performed without perfusion under deep hypothermia in 343 patients with congenital heart defects aged from 1 year 3 months to 44 years. Cooling to a temperature of 26-25 degrees C in the oesophagus was achieved by covering the body with crushed ice. The patients were maintained under superficial ether narcosis and they were given morphine (0.5 mg/kg) and tubocurarine (0.5-1.0 mg/kg). The duration of circulatory arrest was 30 minutes in 190 and longer in 153 patients--60-77 minutes in 10 patients. It took an average of 7.6 minutes for resumption of normal cardiac activity after circulatory arrest prolonged beyond 60 minutes. Of the 343 patients operated on 32 (9.3%) died. Analysis of the mortality pattern showed that patients with acute cardiac insufficiency contributed most to the total number of deaths (19 patients, 5.5%); those with pulmonary oedema ranked second (4 patients, 1.2%) and those with brain oedema third (3 patients, 0.9%). Neurological complications were observed in 13 patients (3.8%). Their frequency was significantly related to the duration of circulatory arrest. Circulatory inadequacy in patients with poor myocardial function who had undergone extensive repair appeared to be a contributory factor. The results obtained without perfusion under deep (26-25 degrees C) hypothermic protection suggest that 75 minutes is a safe time, in terms of brain damage, for circulatory arrest. Under these conditions complex cardiac defects can be repaired.
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