After confirmation of brain death by Electroencephalogram (EEG), is an apnea test the next step?

From the Guidelines

After brain death is confirmed by electroencephalogram (EEG), the apnea test is typically the next step in the brain death determination process. The apnea test is a crucial component of brain death confirmation as it specifically evaluates the function of the brainstem's respiratory centers. During this test, the patient is temporarily disconnected from the ventilator while oxygen is delivered passively, and physicians observe whether the patient makes any spontaneous respiratory efforts despite rising carbon dioxide levels in the blood.

Key Considerations for Apnea Testing

• Before conducting the apnea test, the patient should be preoxygenated with 100% oxygen for about 10 minutes, and arterial blood gases should be checked to ensure PaCO2 is normal or slightly elevated and PaO2 is at least 200 mmHg, as recommended by 1.
• The test is considered positive for brain death if no respiratory movements occur despite PaCO2 rising above 60 mmHg or increasing by more than 20 mmHg from baseline, as stated in 1 and 1.
• This confirms the absence of brainstem-mediated respiratory drive, which is incompatible with life without mechanical ventilation support.

Prerequisites for Apnea Testing

• The apnea test should only be performed after other prerequisites for brain death determination have been met, including:
  • Establishing the cause of coma
  • Excluding confounding factors
  • Confirming the absence of brainstem reflexes, as outlined in 1.

Safety Considerations

• Apnea testing must be performed safely, and if it cannot be completed safely, an ancillary study should be performed, as recommended by 1 and 1.
• The patient's heart rate, blood pressure, and oxygen saturation should be continuously monitored during the apnea test, and the test should be terminated if the patient shows any signs of distress or instability, as noted in 1.

From the Research

Apnea Test After Brain Death Confirmation by EEG

• The apnea test is a mandatory examination for determining brain death (BD) as it provides an essential sign of definitive loss of brainstem function 2.
• After brain death is confirmed by EEG, the apnea test is the next step in the diagnosis process.
• The apnea test involves disconnection from the mechanical ventilator, but this can pose risks, especially in hypoxemic patients 3.
• Alternative methods, such as using continuous positive airway pressure (CPAP) or continuous mechanical ventilation, can be used to maintain oxygenation during the apnea test 3, 4.

Safety and Complications of Apnea Test

• The apnea test can be associated with potential complications, such as severe hypotension, pneumothorax, excessive hypercarbia, hypoxia, acidosis, and cardiac arrhythmia or asystole 2.
• However, when an appropriate oxygen-diffusion procedure is used, the apnea test can be safe 2.
• The use of CPAP or mechanical ventilation during the apnea test can help minimize the risk of complications and maintain oxygenation 3, 4.

Modifications and Variations of Apnea Test

• There are various modifications and variations of the apnea test, including the use of CPAP, mechanical ventilation, and oxygen insufflation 3, 5, 4.
• These modifications can help improve the safety and efficacy of the apnea test, especially in patients with underlying respiratory or cardiac conditions 3, 4.
• However, there is a need for standardization and uniformity in the protocols and guidelines for the apnea test 5.