Identification of Hemodynamic Risk Factors for Apnea Test Failure During Brain Death Determination

An apnea test is essential step for diagnosing brain death and is known to be relatively safe. However, various complications such as hypoxia, arrhythmias, and hypotension could occur. Herein, we identified risk factors of failed apnea test and determined their optimal cutoff values.

We retrospectively analyzed 512 patients of apnea test to diagnose brain death and classified them into 2 groups according to success or failure of the test. Demographic characteristics, value of arterial blood gas analysis, and systolic blood pressure (SBP) were collected, and alveolar-arterial gradient (A-a gradient) and Pao₂/fraction of inspired oxygen ratio were calculated to evaluate the respiratory status.

A total of 484 patients completed the apnea test, and the test was aborted in 28 patients because of hypotension or refractory hypoxemia. The SBP, pH, Pao₂, and Pao₂/fraction of inspired oxygen ratio were higher in success group, whereas A-a gradient was lower. In multivariate analysis, low SBP (odds ratio [OR], 0.976; 95% CI, 0.958-0.994; P = .01), low pH (OR, 0.004; 95% CI, 0.000-0.184; P = .005), and elevated A-a gradient (OR, 1.005; 95% CI, 1.003-1.008; P = .001) were associated with apnea test failure. The optimal cutoff values to predict the test failure were 105.0 mm Hg for pretesting SBP, 7.326 for pretesting pH, and 556.4 mm Hg for pretesting A-a gradient.

Early recognition and aggressive management for the risk factors are important to reduce failure rates of apnea test and consequently improve outcomes of organ procurement.