Apnea Testing for the Determination of Brain Death: A Systematic Scoping Review

Apnea is one of the three cardinal findings in brain death (BD). Apnea testing (AT) is physiologically and practically complex. We sought to review described modifications of AT, safety and complication rates, monitoring techniques, performance of AT on extracorporeal membrane oxygenation (ECMO), and other relevant considerations regarding AT. We conducted a systematic scoping review to answer these questions by searching the literature on AT in English language available in PubMed or EMBASE since 1980. Pediatric or animal studies were excluded. A total of 87 articles matched our inclusion criteria and were qualitatively synthesized in this review. A large body of the literature on AT since its inception addresses a variety of modifications, monitoring techniques, complication rates, ways to perform AT on ECMO, and other considerations such as variability in protocols, lack of uniform awareness, and legal considerations. Only some modifications are widely used, especially methods to maintain oxygenation, and most are not standardized or endorsed by brain death guidelines. Future updates to AT protocols and strive for unification of such protocols are desirable.

The effect of incorporating an arterial pH target during apnea test for brain death determination

BACKGROUND

Persistent apnea despite an adequate rise in arterial pressure of CO₂ is an essential component of the criteria for brain death (BD) determination. Current guidelines vary regarding the utility of arterial pH changes during the apnea test (AT). We aimed to study the effect of incorporating an arterial pH target < 7.30 during the AT (in addition to the existing PaCO₂ threshold) on brain death declarations.

METHODS

We performed retrospective analysis of consecutive adult patients who were diagnosed with BD and underwent AT at the Cleveland Clinic over the last 10 years. Data regarding baseline and post-AT blood gas analyses were collected and analyzed.

RESULTS

Ninety-eight patients underwent AT in the study period, which was positive in 89 (91%) and inconclusive in 9 (9%) patients. The mean age was 50 years old (standard deviation [SD] 16) and 54 (55%) were female. The most common etiology BD was hypoxic ischemic brain injury (HIBI) due to cardiac arrest (42%). Compared to those with positive AT, patients with inconclusive AT had a higher post-AT pH (7.24 vs 7.17, p = 0.01), lower PaO₂ (47 vs 145, p < 0.01), and a lower PaCO₂ (55 vs 73, p = 0.01). Among patients with a positive AT using PaCO₂ threshold alone, the frequency of patients with post-AT pH < 7.30 was 95% (83/87).

CONCLUSION

Implementing a BD criteria requiring both arterial pH and PaCO₂ thresholds reduced the total number of positive ATs; these inconclusive cases would have required longer duration of AT to reach both targets, repeated ATs, or ancillary studies to confirm BD. The impact of this on the overall number BD declarations requires further research.

Special considerations in the assessment of catastrophic brain injury and determination of brain death in patients with SARS-CoV-2

INTRODUCTION

The coronavirus disease 2019 (Covid-19) pandemic has led to challenges in provision of care, clinical assessment and communication with families. The unique considerations associated with evaluation of catastrophic brain injury and death by neurologic criteria in patients with Covid-19 infection have not been examined.

METHODS

We describe the evaluation of six patients hospitalized at a health network in New York City in April 2020 who had Covid-19, were comatose and had absent brainstem reflexes.

RESULTS

Four males and two females with a median age of 58.5 (IQR 47-68) were evaluated for catastrophic brain injury due to stroke and/or global anoxic injury at a median of 14 days (IQR 13-18) after admission for acute respiratory failure due to Covid-19. All patients had hypotension requiring vasopressors and had been treated with sedative/narcotic drips for ventilator dyssynchrony. Among these patients, 5 had received paralytics. Apnea testing was performed for 1 patient due to the decision to withdraw treatment (n = 2), concern for inability to tolerate testing (n = 2) and observation of spontaneous respirations (n = 1). The apnea test was aborted due to hypoxia and hypotension. After ancillary testing, death was declared in three patients based on neurologic criteria and in three patients based on cardiopulmonary criteria (after withdrawal of support (n = 2) or cardiopulmonary arrest (n = 1)). A family member was able to visit 5/6 patients prior to cardiopulmonary arrest/discontinuation of organ support.

CONCLUSION

It is feasible to evaluate patients with catastrophic brain injury and declare brain death despite the Covid-19 pandemic, but this requires unique considerations.

[Irreversible loss of brain function-Part 1: pitfalls in clinical diagnosis]

A significant change in the fourth update of the German guidelines on determining brain death is that it includes an explicit profile of requirements on physicians involved in ILBF diagnosis. These requisite qualification criteria have also been formulated due to the fact that, in many hospitals, ILBF diagnosis is only rarely carried out and, as a result, uncertainty frequently arises. Typical difficulties emerge at all stages of ILBF diagnosis, and numerous relevant pitfalls arise that need to be taken into consideration and which might also be relevant in the selection of the method(s) to detect irreversibility. The approaches presented here are suited to achieving a valid result in the evaluation of equivocal ILBF.

Clinical Determination of Brain Death in Children Supported by Extracorporeal Membrane Oxygenation

BACKGROUND/OBJECTIVE

Children supported by extracorporeal membrane oxygenation (ECMO) are at risk of catastrophic neurologic injury and brain death. Timely determination of brain death is important for minimizing psychological distress for families, resource allocation, and organ donation. Reports of successful determination of brain death in pediatric patients supported by ECMO are limited. The determination of brain death by clinical criteria requires apnea testing, which has historically been viewed as challenging in patients supported by ECMO. We report eight pediatric patients who underwent a total of 14 brain death examinations, including apnea testing, while supported by veno-arterial ECMO (VA-ECMO), resulting in six cases of clinical determination of brain death.

METHODS

We performed a retrospective review of the medical records of pediatric patients who underwent brain death examination while supported by VA-ECMO between 2010 and 2018 at a single tertiary care children's hospital.

RESULTS

Eight patients underwent brain death examination, including apnea testing, while supported by VA-ECMO. Six patients met criteria for brain death, while two had withdrawal of technical support after the first examination. During the majority of apnea tests (n = 13/14), the ECMO circuit was modified to achieve hypercarbia while maintaining oxygenation and hemodynamic stability. The sweep flow was decreased prior to apnea testing in ten brain death examinations, carbon dioxide was added to the circuit during three examinations, and ECMO pump flows were increased in response to hypotension during two examinations.

CONCLUSIONS

Clinical determination of brain death, including apnea testing, can be performed in pediatric patients supported by ECMO. The ECMO circuit can be effectively modified during apnea testing to achieve a timely rise in carbon dioxide while maintaining oxygenation and hemodynamic stability.

Legal and Ethical Considerations for Requiring Consent for Apnea Testing in Brain Death Determination

The past decade has witnessed escalating legal and ethical challenges to the diagnosis of death by neurologic criteria (DNC). The legal tactic of demanding consent for the apnea test, if successful, can halt the DNC. However, US law is currently unsettled and inconsistent in this matter. Consent has been required in several trial cases in Montana and Kansas but not in Virginia and Nevada. In this paper, we analyze and evaluate the legal and ethical bases for requiring consent before apnea testing and defend such a requirement by appealing to ethical and legal principles of informed consent and battery and the right to refuse medical treatment. We conclude by considering and rebutting two major objections to a consent requirement for apnea testing: (1) a justice-based objection to allocate scarce resources fairly and (2) a social utility objection that halting the diagnosis of brain death will reduce the number of organ donors.

Comparison of Two Apnea Test Methods, Oxygen Insufflation and Continuous Positive Airway Pressure During Diagnosis of Brain Death: Final Report

Introduction

Deterioration of the pulmonary function after the apnea test (AT) conducted with the classic oxygen insufflation AT (I-AT) is often observed during the brain death (BD) diagnosis procedure. In the present study, two AT methods were compared before a method is recommended for the currently revised Polish BD criteria.

Methods

Classic I-AT and continuous positive airway pressure AT (CPAP-AT) were performed in 60 intensive care unit patients. I-AT was performed at the end of two series of clinical tests, and approximately 1–1.5 h later, after BD was confirmed, a different method, CPAP-AT with 100% FiO₂ and CPAP value of 10 cm H₂O provided by a ventilator in CPAP mode was performed. The patients in I-AT and CPAP-AT groups were further divided into two subgroups: non-hypoxemic (NH) with good lung function before AT (PaO₂/FiO₂ index ≥ 200 mmHg) and hypoxemic (H) with poor lung function (PaO₂/FiO₂ index < 200 mmHg). PaO₂ and PaCO₂ were recorded prior to I-AT and CPAP-AT at time-point one (T1), 5 min after each test at time-point two (T2), and after 10 min prior to the end of tests at time-point three (T3). The I-AT NH subgroup consisted of 50 patients, and CPAP-AT NH subgroup 43 patients. The I-AT H subgroup consisted of 10 patients, and the CPAP-AT H subgroup 17 patients.

Results

In the I-AT NH subgroup, a gradual decrease in PaO₂/FiO₂ was observed throughout the AT but not in the CPAP-AT NH subgroup. The PaO₂/FiO₂ ratio during the AT in the CPAP-AT H group was stable with a slight tendency to increase but not in the I-AT H group. During the first 5 min of the AT, the mean increase in CO₂ was approximately 5 mmHg/min. Most patients in all groups met the AT criteria after 5 min of the test.

Conclusions

The results from the study show that I-AT may compromise pulmonary function in some cases and is one of the reasons for the recommendation of a safer option, CPAP-AT, in the currently revised Polish BD criteria. During AT, the mean CO₂ increase rate was 5 mmHg/min, which, in most patients, would allow the test to be completed after just 5 min.

Primary Posterior Fossa Lesions and Preserved Supratentorial Cerebral Blood Flow: Implications for Brain Death Determination

BACKGROUND

Patients with primary posterior fossa catastrophic lesions may clinically meet brain death criteria, but may retain supratentorial brain function or blood flow. These patients could be declared brain-dead in the United Kingdom (UK), but not in the United States of America (USA). We report the outcome of adult patients with primary posterior fossa lesions without concurrent major supratentorial injury.

METHODS

Henry Ford Hospital database was reviewed over a period of 88 months in order to identify all adult patients with isolated brainstem or posterior fossa lesions. We excluded patients with concurrent significant supratentorial pathology potentially confounding the clinical brain death examination. One more patient from a different hospital meeting these criteria was also included.

RESULTS

Three patients out of 161 met inclusion criteria (1.9% of all brain deaths during this period). With the addition of a fourth patient from another hospital, 4 patients were analyzed. All four patients had catastrophic brainstem and cerebellar injuries meeting the clinical criteria of brain death with positive apnea test in the UK. All had preserved supratentorial blood flow, which after a period of 2 h to 6 days disappeared on repeat testing, allowing declaration of brain death by US criteria in all four. One patient became an organ donor.

CONCLUSIONS

Patients with primary posterior fossa catastrophic lesions, who clinically seem to be brain-dead, evolve from retaining to losing supratentorial blood flow. If absent cerebral blood flow is used as an additional criterion for the declaration of death by neurological criteria, these patients are not different than those who become brain death due to supratentorial lesions.

Prevention of Hypoxemia During Apnea Testing: A Comparison of Oxygen Insufflation And Continuous Positive Airway Pressure

BACKGROUND

Apnea testing is an essential step in the clinical diagnosis of brain death. Current international guidelines recommend placement of an oxygen (O₂) insufflation catheter into the endotracheal tube to prevent hypoxemia, but use of a continuous positive airway pressure (CPAP) valve may be more effective at limiting arterial partial pressure of O₂ (PO₂) reduction.

METHODS

We performed a multicenter study assessing consecutive apnea tests in 14 intensive care units (ICUs) in two cities utilizing differing protocols. In one city, O₂ catheters are placed and arterial blood gases (ABGs) performed at intervals determined by the attending physician. In the other city, a resuscitation bag with CPAP valve is attached to the endotracheal tube, and ABGs performed every 3-5 min. We assessed arterial PO₂, partial pressure of carbon dioxide (PCO₂), pH, and blood pressure at the beginning and termination of each apnea test.

RESULTS

Thirty-six apnea tests were performed using an O₂ catheter and 50 with a CPAP valve. One test per group was aborted because of physiological instability. There were no significant differences in the degree of PO₂ reduction (-59 vs. -32 mmHg, p = 0.72), rate of PCO₂ rise (3.2 vs. 3.9 mmHg per min, p = 0.22), or pH decline (-0.02 vs. -0.03 per min, p = 0.06). Performance of ABGs at regular intervals was associated with shorter test duration (10 vs. 7 min, p < 0.0001), smaller PCO₂ rise (30 vs. 26 mmHg, p = 0.0007), and less pH reduction (-0.20 vs. -0.17, p = 0.0012). Lower pH at completion of the apnea test was associated with greater blood pressure decline (p = 0.006).

CONCLUSION

Both methods of O₂ supplementation are associated with similar changes in arterial PO₂ and PCO₂. Performance of ABGs at regular intervals shortens apnea test duration and may avoid excessive pH reduction and consequent hemodynamic effects.

Apnea testing using the oxygen insufflation method for diagnosis of brain death may compromise pulmonary function

INTRODUCTION

The aim of our study was to compare the reliability and safety of the classical I-AT with the continuous positive airway pressure apnea test (CPAP-AT).

MATERIAL AND METHODS

In the group of 48 patients (group O), an I-AT was performed at the end of BD diagnostic procedures, and approximately 1-1.5h later CPAP-AT with 100% FiO₂ and CPAP of 10cm H₂O, provided by ventilator in CPAP mode. After pre‑oxygenation with 100% FiO₂ for 10min, the PaO₂/FiO₂ ratio was recorded prior to I-AT at time-point one (T1) and prior to CPAP-AT at time-point two (T2). Group O was categorized into subgroup N-H (non-hypoxemic), consisting of 41 patients with good lung function, and subgroup H (hypoxemic) consisting of 7 patients with poor lung function. Within each subgroup PaO₂/FiO₂ at T1 and T2 were compared.

RESULTS

In Group O, PaO₂/FiO₂ decreased from 321±128mmHg at T1 to 291±119mmHg at T2 (p=0.004). In subgroup N-H, PaO₂/FiO₂ declined from 355±103 to 321±100mmHg (p=0.008), and in subgroup H, PaO₂/FiO₂ remained almost unchanged. Additionally, in 4 patients from subgroup N-H, PaO₂/FiO₂ decreased below 200mmHg at T2.

CONCLUSIONS

Our study indicates that I-AT may compromise pulmonary function and this may support the recommendation of safer CPAP-AT alternative.

Prolonged duration of apnea test during brain death examination in a case of intraparenchymal hemorrhage

Objective:

Apnea test is required as part of the brain death examination. The duration of the apnea test is variable but typically requires 8–10 min. Prolonged apnea tests have been reported in the setting of hypothermia. Here, we describe a case of prolonged duration of apnea test secondary to a phenomenon called cardiac ventilation.

Methods:

The patient presented in coma with brainstem areflexia after having an intracerebral hemorrhage resulting in subfalcine, central, uncal, and tonsillar herniations. Confounding variables were excluded. Brain death testing was performed, and she was found to have brainstem areflexia. Pre-requisites for apnea test were then met.

Results:

Apnea testing, however, was prolonged at 110 min. When reconnected to ventilator, it was noted that she had small (30–35 cc) tidal volumes at a rate of her heart rate without respiratory effort. Ancillary testing with four-vessel cerebral angiogram confirmed cerebral circulatory arrest.

Conclusions:

To our knowledge, this is the longest reported case of apnea testing during brain death testing. Variables known to cause a delay in the rise of carbon dioxide (PaCO₂) levels were excluded. We suspect the hyperdynamic cardiac state caused cardiac ventilations resulting in slow increase in carbon dioxide levels.

Brain stem death certification protocol

Transplantation of Human Organs is guided by laid down specific Laws in India. The organs which are targeted to be transplanted are liver, kidney and cornea. The waiting list is enormous but the donor pool is meagre. This document has been made with a view that the donor pool can be enlarged by identifying patients who are 'Brain Dead' while still not having 'Cardiac Death'. The steps include the prerequisite conditions which must be satisfied by patients who have suspicion of being brain dead, detailed examination of the patient, confirmation of the Brain Death and Counselling of the relatives for organ donation.

[Apnea test for assessment of brain death under extracorporeal life support]

BACKGROUND

The fourth edition of the German guideline for the assessment of brain death, published in 2015 by the German Medical Council (Bundesärztekammer), emphasizes the importance of an apnea test. It is also now required under all circumstances of extracorporeal life support.

OBJECTIVES

This article is an instruction for the guideline-conforming performance of an apnea test in general and also in cases of extracorporeal life support in different configurations.

MATERIALS AND METHODS

A literature review was performed.

CONCLUSIONS

The apnea test is an essential part of the bedside examination for the clinical diagnosis of brain death. It is required for all kinds of extracorporeal life support and can be easily performed without endangering the patient. More accurate recommendations for its performance should be considered for the next version of the German guideline for brain death assessment.

Brain death and true patient care

The "brain death" standard as a criterion of death is closely associated with the need for transplantable organs from heart-beating donors. Are all of these potential donors really dead, or does the documented evidence of patients destined for organ harvesting who improve, or even recover to live normal lives, call into question the premise underlying "brain death"? The aim of this paper is to re-examine the notion of "brain death," especially its clinical test-criteria, in light of a broad framework, including medical knowledge in the field of neuro-intensive care and the traditional ethics of the medical profession. I will argue that both the empirical medical evidence and the ethics of the doctor-patient relationship point to an alternative approach toward the severely comatose patient (potential brain-dead donor). Lay Summary: Though legally accepted and widely practiced, the "brain death" standard for the determination of death has remained a controversial issue, especially in view of the occurrence of "chronic brain death" survivors. This paper critically re-evaluates the clinical test-criteria for "brain death," taking into account what is known about the neuro-critical care of severe brain injury. The medical evidence, together with the understanding of the moral role of the physician toward the patient present before him or her, indicate that an alternative approach should be offered to the deeply comatose patient.

Apnea testing with continuous positive airway pressure for the diagnosis of brain death in a patient with poor baseline oxygenation status

Apnea testing is a key component in the clinical diagnosis of brain death. Patients with poor baseline oxygenation may not tolerate the standard 8-10 min apnea testing with oxygen insufflation through tracheal tube. No studies have assessed the safety and feasibility of other methods of oxygenation during apnea testing in these types of patients. Here, we safely performed apnea testing in a patient with baseline PaO2 of 99.1 mm Hg at 100% oxygen. We used continuous positive airway pressure (CPAP) of 10 cm of H2O and 100% oxygen at the flow rate of 12 L/min using the circle system of anesthesia machine. After 10 min of apnea testing, PaO2 decreased to 75.7 mm Hg. There was a significant rise in PaCO2 and fall in pH, but without hemodynamic instability, arrhythmias, or desaturation. Thus, the apnea test was declared positive. CPAP can be a valuable, feasible and safe means of oxygenation during apnea testing in patients with poor baseline oxygenation, thus avoiding the need for ancillary tests.