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Predictive Hypoxemic Threshold for Tolerating the Apnea Test While Assessing Death by Neurological Criteria
Daniel Aviram1,2,3, Daniel Hikri4,5, Michal Aharon6
1Division of Anesthesia, Pain Management and Intensive Care, Tel Aviv Sourasky Medical Center, Tel Aviv, Israel. d.aviram@nhs.net.
Neurocritical Care
|September 19, 2024
Summary
A pre-apnea test (AT) oxygen level below 300 mmHg may indicate a higher risk of test failure. This finding helps clinicians avoid potential complications during the diagnosis of brain death.
Area of Science:
- Neurology
- Critical Care Medicine
- Clinical Diagnostics
Background:
- The apnea test (AT) is crucial for diagnosing brain death by assessing respiratory drive.
- The test involves disconnecting ventilation, which can lead to hypoxemia and hemodynamic instability, necessitating careful monitoring.
- Uncertainty exists regarding the optimal pre-AT oxygen levels to predict test failure.
Purpose of the Study:
- To identify pre-apnea test (AT) oxygen partial pressure (PaO2) levels associated with an increased risk of test failure.
- To determine a safe threshold for commencing the AT to prevent adverse events.
Main Methods:
- A retrospective cohort study was conducted from 2010 to 2022 at Tel Aviv Medical Center.
- Included patients suspected of brain death undergoing the apnea test.
- Primary outcome: arterial partial O2 pressure (PaO2) ≤ 60 mmHg at the conclusion of the AT.
Main Results:
- Among 70 patients, 7 met the primary outcome criteria.
- Patients with PaO2 ≤ 60 mmHg at AT conclusion had significantly lower initial median PaO2 (243.7 mmHg) compared to others (374.8 mmHg).
- Receiver operating characteristic (ROC) curve analysis showed pre-AT PaO2 levels had good discriminatory ability for low PaO2 outcomes (AUC = 0.76).
Conclusions:
- Arterial oxygen partial pressure (PaO2) at the end of the apnea test correlates with initial PaO2 levels.
- A pre-AT PaO2 cutoff of approximately 300 mmHg may help prevent oxygen saturation drops below 90%.
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