What are the criteria that must be met prior to apnea testing in patients with suspected brain death?

From the Guidelines

Before conducting apnea testing to determine brain death, several criteria must be met to ensure accurate results, including normalization of the patient's pH and PaCO2, maintenance of core temperature above 35°C, normalization of blood pressure, and correction of factors that could affect respiratory effort, as recommended by the guidelines for the determination of brain death in infants and children 1, 2, 3, 4, 5.

Key Criteria

The following criteria must be met prior to apnea testing:

• Hypotension, hypothermia, and metabolic disturbances should be treated and corrected 1
• Medications that can interfere with the neurologic examination and apnea testing should be discontinued allowing for adequate clearance before proceeding with these evaluations 1
• The patient must have a normal arterial PCO2 (35-45 mmHg) or near-normal levels at baseline 3
• Euvolemia must be established, as hypovolemia can affect test results 3
• The patient should not be under the influence of CNS depressants, neuromuscular blocking agents, or other medications that could suppress respiratory drive 2
• Severe electrolyte, acid-base, or endocrine disturbances that could affect respiratory function must be corrected 2
• Preoxygenation with 100% oxygen for at least 5-10 minutes is necessary before initiating the apnea test to prevent hypoxemia during the test 3 ### Apnea Testing Apnea testing must be performed safely and requires documentation of an arterial PaCO2 20 mm Hg above the baseline PaCO2 and ≥ 60 mm Hg with no respiratory effort during the testing period to support the diagnosis of brain death 1, 4.

Additional Considerations

If the apnea test cannot be safely completed, an ancillary study should be performed to assist with the determination of brain death 1, 4. 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's oxygen saturation falls below 85% or if hemodynamic instability occurs 3.

From the Research

Criteria for Apnea Testing

To determine the criteria that must be met prior to apnea testing, several factors need to be considered:

• The patient's overall medical condition, including the presence of hypoxemia or hemodynamic instability 6
• The need for a standardized apnea test with a baseline PaCO2 of 40 mm Hg or greater to ensure efficiency and safety 7
• The use of appropriate prerequisites, such as minute ventilation and PaCO2 levels, to determine brain death 8
• The consideration of modifications to apnea testing, such as the use of continuous positive airway pressure or oxygen insufflation, to improve tolerance and safety 9, 10

Prerequisites for Apnea Testing

The following prerequisites should be met prior to apnea testing:

• The patient should be on a stable ventilator setting with a baseline PaCO2 of 40 mm Hg or greater 7
• The patient's oxygenation and hemodynamic status should be stable, with a median FiO2 of 0.5 and PEEP of 5 cm H2O 8
• The patient should not have any contraindications to apnea testing, such as severe hypoxemia or hemodynamic instability 6

Safety Considerations

Apnea testing should be performed with caution and careful monitoring to avoid complications, such as:

• Hypoxemia, which can occur in patients with severe lung disease or those who are unable to maintain adequate oxygenation 8, 10
• Hypotension, which can occur in patients with hemodynamic instability or those who are receiving vasopressors 8, 10
• Cardiac arrhythmias, which can occur in patients with underlying cardiac disease or those who are receiving certain medications 8