12.5 Death by Neurologic Criteria: Examination & Apnea Testing
Key Takeaways
- The 2023 US guideline requires two independent pediatric examinations at least 12 hours apart and two apnea tests, one after each examination.
- Core temperature must be at least 36 C and pediatric SBP and MAP must be at least the fifth percentile for age before evaluation.
- An apnea test supports BD/DNC only with no breaths, pH below 7.30, PaCO2 at least 60 mmHg, and a rise at least 20 mmHg above baseline.
12.5 Death by Neurologic Criteria: Examination & Apnea Testing
Death by neurologic criteria (BD/DNC) is the permanent loss of function of the entire brain, including the brainstem, resulting in coma, brainstem areflexia, and apnea. The 2023 AAN/AAP/CNS/SCCM consensus guideline unifies adult and pediatric practice. Clinicians must also follow governing law and institutional policy.
Prerequisites and Observation for Permanency
The record must show a catastrophic, permanent brain injury with a mechanism known to cause BD/DNC, and neuroimaging should fit that mechanism and severity. Before testing, exclude conditions that can mimic loss of brain function.
| Prerequisite | Pediatric requirement |
|---|---|
| Temperature | Core temperature maintained at 36 C or higher |
| Blood pressure | SBP and MAP at or above the fifth percentile for age, or near a known chronic baseline |
| Drugs | Exclude intoxication and allow adequate clearance of CNS depressants; account for organ dysfunction, hypothermia, and interactions |
| Paralysis | Exclude residual neuromuscular blockade, using a peripheral nerve stimulator when needed |
| Metabolic state | Correct severe electrolyte, acid-base, endocrine, hepatic, or renal derangements capable of confounding the examination |
If core temperature was 35.5 C or lower, wait at least 24 hours after rewarming to at least 36 C; ancillary testing cannot bypass this wait. For patients younger than 24 months, wait at least 48 hours after the acute brain injury before beginning the evaluation. For patients 24 months or older after acute hypoxic-ischemic brain injury, wait at least 24 hours. Other injuries and interventions require a sufficient pathophysiology-based observation period.
Pediatric Examination
Two qualified clinicians must perform separate and independent pediatric examinations, separated by at least 12 hours regardless of the child's age. Each evaluates unresponsiveness and all assessable brainstem functions: pupillary response, ocular movements, corneal reflexes, facial movement to noxious stimulation, gag and cough, motor response, and age-appropriate sucking and rooting in neonates. Spinally mediated movements can occur and must be distinguished from brain-mediated activity.
If any finding reflects brain-mediated activity, the patient does not meet BD/DNC criteria and ancillary testing must not be used to override it. If trauma or anatomy prevents accurate assessment of a required element while all assessable findings remain consistent, ancillary testing is required.
Pediatric Apnea Testing
Children require two apnea tests, one after each examination. Before each test, confirm acceptable temperature and blood pressure, correct hypovolemia, and establish normal PaCO2 35-45 mmHg and pH 7.35-7.45 unless chronic hypercarbia changes the baseline. Preoxygenate with 100% oxygen for at least 10 minutes to a PaO2 above 200 mmHg when achievable.
In children, provide apneic oxygenation with CPAP on the ventilator or a flow-inflating resuscitation bag with a functioning PEEP valve. The tracheal insufflation catheter technique is an adult option in the 2023 guideline and should not be presented as the standard pediatric method. Stop mandatory breaths while directly observing the chest and abdomen and continuously monitoring oxygen saturation, ECG, and blood pressure.
Obtain an arterial blood gas after approximately 8 to 10 minutes, earlier if instability is developing. A test supports BD/DNC when there are no respirations, arterial pH is below 7.30, and PaCO2 is at least 60 mmHg and at least 20 mmHg above the pretest baseline. With known chronic CO2 retention, compare with the known chronic premorbid baseline. If chronic retention is suspected but the baseline is unknown, meeting the gas targets also requires ancillary testing.
Abort for any spontaneous respiration, progressive saturation below 85%, SBP or MAP below the fifth percentile for age despite support, or a hemodynamically unstable arrhythmia. If instability is imminent, obtain an ABG before reconnecting when feasible. Stabilize and then repeat with a safer method or use an acceptable ancillary test when indicated.
Separating the Three Time Rules
Candidates must keep three clocks distinct. First, observation after injury establishes permanency: at least 48 hours after acute injury when the child is younger than 24 months, and at least 24 hours after acute hypoxic-ischemic injury at 24 months or older. Second, significant hypothermia creates a rewarming clock: after a core temperature of 35.5 C or lower, wait at least 24 hours after reaching 36 C. Third, the two pediatric examinations are separated by at least 12 hours regardless of age. These intervals serve different purposes and are not interchangeable.
An apnea test is not simply a timed ventilator disconnect. The clinician establishes a safe baseline, uses a pediatric oxygenation method that preserves functional residual capacity, observes for respiratory effort, and confirms both carbon-dioxide and pH targets. If one spontaneous breath occurs, the test is inconsistent with BD/DNC. If instability forces termination before targets, the result is not positive merely because no breaths were seen.
A 7-year-old child with severe hypoxic-ischemic brain injury following an unwitnessed submersion event is being evaluated for brain death in the pediatric intensive care unit. The patient is comatose, has absent brainstem reflexes, and has been normothermic (core temperature 36.8°C) and normotensive for 24 hours off all sedation. An apnea test is performed. Prior to disconnection from the mechanical ventilator, the baseline arterial blood gas on an FiO2 of 1.0 is: pH 7.41, PaCO2 39 mmHg, and PaO2 310 mmHg. Apneic oxygenation is provided with CPAP and 100% oxygen using a method appropriate for children. At 7 minutes of apnea, the child exhibits no spontaneous respiratory effort. The arterial line monitor displays an acute blood pressure decline from 96/60 mmHg to 54/28 mmHg, and the pulse oximeter falls to 81%. What is the immediate, mandatory clinical action?
A 6-week-old full-term infant with non-accidental trauma and catastrophic diffuse intracranial hemorrhage is being evaluated for brain death. The first clinical neurological examination confirms coma, flaccidity, and the complete absence of all brainstem reflexes, followed by a positive apnea test. According to the 2023 AAN/AAP/CNS/SCCM pediatric brain-death/death-by-neurologic-criteria guideline, what is the mandatory observation period before the second clinical examination and apnea test can be performed, and what prerequisite must be confirmed?