Safety of Apnea Testing in Pregnant Persons Undergoing Evaluation for Brain Death/Death by Neurologic Criteria

Brain death, or death by neurologic criteria (BD/DNC), is the permanent loss of brain function, defined by coma with loss of capacity for consciousness and complete brainstem areflexia, including the inability to breathe spontaneously. The 2023 American Academy of Neurology/American Academy of Pediatrics/Child Neurology Society (CNS)/Society for Critical Care Medicine guidelines state that pregnancy is not a contraindication for BD/DNC evaluation. Clinical evaluation of BD/DNC includes an apnea test to demonstrate the absence of spontaneous respiratory effort in response to hypercapnia and acidosis. The safety of apnea testing to the fetus in pregnant patients remains uncertain.We convened a panel of experts in BD/DNC, neurocritical care, maternal-fetal medicine, neonatology, fetal/neonatal/child neurology, and pediatric/fetal anesthesiology to perform a scoping review of apnea testing in pregnant persons. We found no studies directly assessing safety of apnea testing on the fetus. Apnea testing consists of fetal exposure to parental hyperoxia and hypercapnia; therefore, we searched for evidence related to these conditions in pregnancy. Case reports, series, and literature on physiologic changes induced during apnea testing and their potential effects on placental, fetal systemic, and fetal cerebral circulations were identified. In reported cases of BD/DNC in pregnant persons, some authors described explicitly avoiding apnea testing because of safety concerns, but whether apnea testing was performed at all was inconsistently reported. Evidence from studies evaluating hyperoxia and hypercapnia in healthy pregnant persons and in other animal models suggested possible adverse effects caused by reduced uteroplacental blood flow, fetal metabolic acidosis, and hypercapnia-induced cerebral hyperperfusion. Further possible complications of apnea testing, such as hypotension or hypoxemia in pregnant persons, could also contribute to fetal injury. These potential detrimental risks to the fetus raise the question as to whether apnea testing should be deferred if a fetus may be viable. Ancillary tests, such as radionuclide cerebral blood flow imaging or transcranial Doppler ultrasonography, can be used if the remainder of the BD/DNC evaluation and neurologic examination is otherwise consistent with BD/DNC. Further research is essential to assess the physiologic consequences of apnea testing in pregnant persons and potential risks to the fetus.