Apnea Testing for the Determination of Brain Death: A Systematic Scoping Review

Abstract

Apnea is one of the three cardinal findings in brain death (BD). Apnea testing (AT) is physiologically and practically complex. We sought to review described modifications of AT, safety and complication rates, monitoring techniques, performance of AT on extracorporeal membrane oxygenation (ECMO), and other relevant considerations regarding AT. We conducted a systematic scoping review to answer these questions by searching the literature on AT in English language available in PubMed or EMBASE since 1980. Pediatric or animal studies were excluded. A total of 87 articles matched our inclusion criteria and were qualitatively synthesized in this review. A large body of the literature on AT since its inception addresses a variety of modifications, monitoring techniques, complication rates, ways to perform AT on ECMO, and other considerations such as variability in protocols, lack of uniform awareness, and legal considerations. Only some modifications are widely used, especially methods to maintain oxygenation, and most are not standardized or endorsed by brain death guidelines. Future updates to AT protocols and strive for unification of such protocols are desirable.

Optimal Duration of the Apnea Test for Determining Brain Death: Benefit of the Short-Term Apnea Test

“…In the 1st apnea test in this study, PaO 2 was signi cantly changed every minute, but its value was ≥ 90 mmHg (Table 2). Previous studies have con rmed that MAT did not negatively affect apnea test results and allowed a safer completion of the tests [19,20]. MAT was also performed in the present study.…”

Brain death post cardiac surgery: A modified apnea test to confirm death by neurologic criteria for a patient on extracorporeal membrane oxygenation

“…AT is a key component in DNC. However, AT can cause complications including, hypotension (6%–39%), hypoxemia (5%–32%), arrhythmia (0%–3%), cardiac arrest (0%–0.7%), and rarely pneumothorax, pneumomediastinum, and pneumoperitoneum 2 . These sequelae and baseline physiologic instability may preclude safe completion or performance of AT, respectively.…”

“…Various MATs have been proposed in an attempt to shorten the test and reduce complications. 2 Despite modifications, F I G U R E 2 CT angiography demonstrating good blood flow in extracranial vasculature (*) with no intravascular flow on initial scans (A), but faint opacification in the left middle cerebral artery (green arrowhead) and right transverse sinus (red arrow) on delayed scans (B). CT, computer tomography F I G U R E 3 Technetium-99m ethyl cysteinate radionuclide brain perfusion scintigraphy demonstrating no cerebral perfusion performing AT and determining DNC is more challenging in patients who are on ECMO.…”

How I do a brain death examination: the tools of the trade

“…Next is the apnea test. Keep it simple [7]. Review the chest X-ray and blood gas and pre-oxygenate to PaO 2 > 200 mmHg.…”

“…Conventionally, time of death is the time of the second blood gas result. Complications, usually minor with good preparation, become major with bad or non-standard preparation [7][8][9][10]. Our decades-long experience with this oxygen diffusion technique has been safe and aborted in only 3% of 212 tests [9].…”