Brain death diagnosis and apnea test safety

Machado, Calixto; Pérez, Javier; Scherle, Claudio; Areu, Alejandro; Pando, Alejandro

doi:10.4103/0972-2327.56326

Cited by 22 publications

(15 citation statements)

References 43 publications

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“…6 However, relying on fixed durations, which are based upon the expected rise in PaCO 2 with apnea (3-4 mm Hg/min under normal physiologic conditions), may yield variable results, as the relationship of PaCO 2 and CO 2 production may vary greatly under conditions of terminal illness and brain death. 27 Because of this, the apnea testing may be continued until the arterial blood gas results are noted, as long as the patient remains hemodynamically stable and with an adequate SpO 2 . Continuing the apnea test for slightly longer periods (eg, up to 15 min) may be preferable to repeating the test.…”

Section: Methods Of Performing Apnea Testingmentioning

confidence: 99%

Apnea Testing During Brain Death Assessment: A Review of Clinical Practice and Published Literature

et al. 2013

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The diagnosis of brain death is a complex process. Strong knowledge of neurophysiology and an understanding of brain death etiology must be used to confidently determine brain death. The key findings in brain death are unresponsiveness, and absence of brainstem reflexes in the setting of a devastating neurological injury. These findings are coupled with a series of confirmatory tests, and the diagnosis of brain death is established based on consensus recommendations. The drive to breathe in the setting of an intense ventilatory stimulus (ie, respiratory acidosis) is a critical marker of brainstem function. As a consequence, apnea testing is an important component of brain death assessment. This procedure requires close monitoring of a patient as all ventilator support is temporarily removed and PaCO 2 levels are allowed to rise. A "positive" test is defined by a total absence of respiratory efforts under these conditions. While apnea testing is not new, it still lacks consensus standardization regarding the actual procedure, monitored parameters, and evidencebased safety measures that may be used to prevent complications. The purpose of this report is to provide an overview of apnea testing and discuss issues related to the administration and safety of the procedure.

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Section: Methods Of Performing Apnea Testingmentioning

confidence: 99%

Apnea Testing During Brain Death Assessment: A Review of Clinical Practice and Published Literature

et al. 2013

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“…The subsequent hypercarbia results in cerebral spinal fluid (CSF) acidosis, which stimulates the respiratory reflex in the medulla. Before initiating apnea testing, all patients must meet pre-requisite baseline characteristics including a body temperature >36°C, a systolic blood pressure >90 mmHg, the absence of hypoxia and acidosis, and a euvolemic state 1 . Declaration of apnea in brain death can, nonetheless, be harmful to patients due to the possibility of adverse events such as hypotension, hypoxia, acidosis, arrhythmias, asystole, and pneumothorax using conventional methods 2 .…”

Section: Introductionmentioning

confidence: 99%

The Modified Apnea Test During Brain Death Determination

Ahlawat

Carandang

Heard

et al. 2015

J Intensive Care Med

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Introduction Conventional apnea testing in patients with severe hypoxemia or hemodynamic instability with removal from ventilator support is unsafe. We describe an alternative approach to apnea testing, which may be used in hypoxic patients unable to undergo conventional apnea testing. Methods Case Report. A 42-year-old man suffered a severe traumatic brain injury resulting in diffuse cerebral edema and subarachnoid hemorrhage with herniation. His presentation was complicated by hypoxic respiratory failure from pulmonary contusions and hemorrhagic shock. On hospital day 2, the patient lost brainstem reflexes. Brain death testing with conventional apnea testing was attempted but aborted due to hypoxia. Results A modified apnea test was applied, which had been approved by appropriate hospital committees including critical care operations, ethics, and the brain death protocol council. Minute ventilation was gradually decreased by ≥50% to attain a PaCO2 level ≥20 mmHg above baseline. The ventilation mode was then switched from volume control to continuous positive airway pressure while observing the patient for signs of respiration for a duration of 60 seconds. Conclusion The modified apnea test does not require circuit disconnection and can be successfully applied to determine brain death without compromising safety in high-risk patients suffering from severe hypoxia.

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“…1,2 Complications of the apnea test include hypoxia, hypotension, cardiac arrhythmias, cardiac arrest, excessive hypercarbia, and pneumothorax. 2,[4][5][6][7][8] Interestingly, while the occurrence of pneumothoraces during the apnea test is believed to be rare, 9 several case reports have described pneumothoraces within minutes of initiating the apnea test. 3,[7][8]10 The case reports describe various oxygen flows, IC sizes, and the use of nasal-cannula tubing or oxygensupply tubing for the IC.…”

Section: Introductionmentioning

confidence: 99%

Apnea Testing: The Effects of Insufflation Catheter Size and Flow on Pressure and Volume in a Test Lung

Henry

Marshall

2013

Respir Care

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BACKGROUND:The apnea test is used to determine the absence of respiratory drive when determining brain death. Current guidelines for performing the apnea test do not specify the size of insufflation catheter (IC) to use with each endotracheal tube (ETT) size, despite case reports describing procedure-related complications with the use of various IC sizes. We studied the effect of the ratio of IC outer diameter to ETT inner diameter on the pressure and volume generated within the lungs during the apnea test. METHODS: We tested ETTs with inner diameters of 6.0 -10.0 mm, IC outer diameters of 10 -16 French, and oxygen-supply tubing, at oxygen flows of 6 -15 L/min, in an intubation manikin connected to a test lung. RESULTS: The multivariate analysis of variance method identified significant differences in the pressures and volumes during the apnea test (P < .001), and the Tukey method identified significant differences in the pressures and volumes associated with IC/ETT ratios > 0.7 and < 0.7 (P < .05). CONCLUSIONS: An IC with an outer diameter < 70% of the ETT inner diameter, at 6 L/min, may prevent inappropriate lung pressure and volume during the apnea test. This recommendation, coupled with current American Academy of Neurology guidelines for the determination of brain death, may reduce the risk of procedure-related complications.

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Brain death diagnosis and apnea test safety

Cited by 22 publications

References 43 publications

Apnea Testing During Brain Death Assessment: A Review of Clinical Practice and Published Literature

Apnea Testing During Brain Death Assessment: A Review of Clinical Practice and Published Literature

The Modified Apnea Test During Brain Death Determination

Apnea Testing: The Effects of Insufflation Catheter Size and Flow on Pressure and Volume in a Test Lung

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