[Cardiovascular effects of apnea test in the diagnosis of brain death]

Cardiovascular effects of apnea test were investigated in 12 patients suspected of brain death. Arterial blood gas and cardiovascular hemodynamics were measured just before and after 10-minute apnea. Apnea test induced respiratory acidosis without hypoxemia. Cardiac index increased by 34% (2.3 to 3.1 l.min-1.m-2; P less than 0.01) and systemic vascular resistance index decreased by 30% (3608 to 2519 dynes.sec.cm-5.m-2; P less than 0.01), whereas heart rate and mean arterial pressure were unchanged. Significant increases in mean pulmonary arterial pressure (17.6 to 29.1 mmHg; P less than 0.01), pulmonary vascular resistance index (381 to 616 dynes.sec.cm-5.m-2; P less than 0.01) and right ventricular stroke work index (4.0 to 10.5 g.m.m-2; P less than 0.01) suggest that apnea test increases right ventricular afterload.