[Apnea test essential in the diagnosis of brain death]

We experienced 11 cases of brain death for the past two years, in six of whom we performed the apnea test to confirm the cessation of the medullary respiratory functions. The cause of brain death was primary intracranial lesions in four, subarachnoidal hemorrhages in three and meningitis in one. Hypoxia of the brain secondary to cardiac arrest resulted brain death in the remaining two cases. Blood gases were analysed before (control) and after pre-oxygenation, after having adjusted PaCO2 around 40 mmHg, and every three minutes after disconnection from the respirator. Blood pressure and other vital signs were monitored through out the test. PaCO2 was brought to 40 mmHg by reducing the respiratory rate in three cases, by decreasing the tidal volume following the reduction of the respiratory rate in one case and by applying the bicarbonate gas in one case. The mean PaCO2 level was 46.2 +/- 6.0 mmHg. No one regained the respiration during 10 minutes of the apnea test. In one case, the oxygen catheter was not inserted deeply enough into the tracheal tube, resulting the fall of blood pressure and necessitating termination of the test six minutes after disconnection from the respirator. This case was not included for further analysis. The pH and PaCO2 did not change significantly after pre-oxygenation and after adjusting of PaCO2. Only the PaO2 increased significantly after preoxygenation. PaCO2 increased with the rate of 3.04 +/- 1.2 mmHg/min up to 73.4 +/- 15.6 mmHg and pH decreased with the rate of 0.016 +/- 0.007 down to 7.1 +/- 0.03 after disconnection from the respirator.(ABSTRACT TRUNCATED AT 250 WORDS)