Challenges of Brain Death and Apnea Testing in Adult Patients on Extracorporeal Membrane Oxygenation—A Review

Brain death determination in patients with veno-arterial extracorporeal membrane oxygenation: A systematic study to address the Harlequin syndrome

PURPOSE

The Harlequin syndrome may occur in patients treated with venoarterial extracorporal membrane oxygenation (VA-ECMO), in whom blood from the left ventricle and the ECMO system supply different parts of the body with different paCO2-levels. The purpose of this study was to compare two variants of paCO2-analysis to account for the Harlequin syndrome during apnea testing (AT) in brain death (BD) determination.

MATERIALS AND METHODS

Twenty-seven patients (median age 48 years, 26-76 years; male n = 19) with VA-ECMO treatment were included who underwent BD determination. In variant 1, simultaneous arterial blood gas (ABG) samples were drawn from the right and the left radial artery. In variant 2, simultaneous ABG samples were drawn from the right radial artery and the postoxygenator ECMO circuit. Differences in paCO2-levels were analysed for both variants.

RESULTS

At the start of AT, median paCO2-difference between right and left radial artery (variant 1) was 0.90 mmHg (95%-confidence intervall [CI]: 0.7-1.3 mmHg). Median paCO2-difference between right radial artery and postoxygenator ECMO circuit (variant 2) was 3.3 mmHg (95%-CI: 1.5-6.0 mmHg) and thereby significantly higher compared to variant 1 (p = 0.001). At the end of AT, paCO2-difference according to variant 1 remained unchanged with 1.1 mmHg (95%-CI: 0.9-1.8 mmHg). In contrast, paCO2-difference according to variant 2 increased to 9.9 mmHg (95%-CI: 3.5-19.2 mmHg; p = 0.002).

CONCLUSIONS

Simultaneous paCO2-analysis from right and left distal arterial lines is the method of choice to reduce the risk of adverse effects (e.g. severe respiratory acidosis) while performing AT in VA-ECMO patients during BD determination.

Using extracorporeal membrane oxygenation in donations after cardiac death or brain death: A single-center experience and long-term outcome

Aims

The use of extended criteria donors is a routine practice that sometimes involves extracorporeal membrane oxygenation (ECMO) in donations after cardiac death or brain death.

Methods

We performed a retrospective study in a single center from January 2006 to December 2019. The study included 90 deceased donor liver transplants. The patients were divided into three groups: the donation after brain death (DBD) group (n = 58, 64.4%), the DBD with ECMO group (n = 11, 12.2%) and the donation after cardiac death (DCD) with ECMO group (n = 21, 23.3%).

Results

There were no significant differences between the DBD with ECMO group and the DBD group. When comparing the DCD with ECMO group and the DBD group, there were statistically significant differences for total warm ischemia time (p < 0.001), total cold ischemia time (p = 0.023), and split liver transplantation (p < 0.001), and there was significantly poor recovery in regard to total bilirubin level (p = 0.027) for the DCD with ECMO group by repeated measures ANOVA. The 5-year survival rates of the DBD, DBD with ECMO, and DCD with ECMO groups were 78.1%, 90.9%, and 75.6%, respectively. The survival rate was not significantly different when comparing the DBD group to either the DBD with ECMO group (p = 0.435) or the DCD with ECMO group (p = 0.310).

Conclusions

Using ECMO in donations after cardiac death or brain death is a good technology, and it contributed to 35.6% of the liver graft pool.

Subtypes and Mechanistic Advances of Extracorporeal Membrane Oxygenation-Related Acute Brain Injury

Extracorporeal membrane oxygenation (ECMO) is a frequently used mechanical cardiopulmonary support for rescuing critically ill patients for whom conventional medical therapies have failed. However, ECMO is associated with several complications, such as acute kidney injury, hemorrhage, thromboembolism, and acute brain injury (ABI). Among these, ABI, particularly intracranial hemorrhage (ICH) and infarction, is recognized as the primary cause of mortality during ECMO support. Furthermore, survivors often suffer significant long-term morbidities, including neurocognitive impairments, motor disturbances, and behavioral problems. This review provides a comprehensive overview of the different subtypes of ECMO-related ABI and the updated advance mechanisms, which could be helpful for the early diagnosis and potential neuromonitoring of ECMO-related ABI.

Challenges in determining death by neurologic criteria in extracorporeal membrane oxygenation - A single center experience

INTRODUCTION

Apnea test (AT) in patients on extracorporeal membrane oxygenation (ECMO) support is challenging, leading to variation in determining death by neurologic criteria (DNC). We aim to describe the diagnostic criteria and barriers for DNC in adults on ECMO in a tertiary care center.

METHODS

A retrospective review of a prospective observational standardized neuromonitoring study was conducted in adult VA- and VV-ECMO patients at a tertiary center from June 2016 to March 2022. Brain death was defined according to the 2010 American Academy of Neurology guidelines and following the 2020 World Brain Death Project recommendations for performing AT in ECMO patients.

RESULTS

Eight (2.7%) ECMO patients (median age = 44 years, 75% male, 50% VA-ECMO) met criteria for DNC, six (75%) of whom were determined with AT. In the other two patients who did not undergo AT due to safety concerns, ancillary tests (transcranial doppler and electroencephalography) were consistent with DNC. An additional seven (2.3%) patients (median age = 55 years, 71% male, 86% VA-ECMO) were noted to have absent brainstem reflexes but failed to complete determination of DNC as they underwent withdrawal of life-sustaining treatment (WLST) before a full evaluation was completed. In these patients, AT was never performed, and ancillary tests were inconsistent with either neurological exam findings and/or neuroimaging supporting DNC, or with each other.

CONCLUSION

AT was used safely and successfully in 6 of the 8 ECMO patients diagnosed with DNC and was always consistent with the neurological exam and imaging findings, as opposed to ancillary tests alone.

A descriptive evaluation of causes of death in venovenous extracorporeal membrane oxygenation

Veno-venous extracorporeal membrane oxygenation (VV ECMO) has become an important support modality for patients with acute respiratory failure refractory to optimal medical therapy, such as low tidal volume mechanical ventilator support, early paralytic infusion, and early prone positioning. The objective of this cohort study was to investigate the causes and timing of in-hospital mortality in patients on VV ECMO. All patients, excluding trauma and bridge to lung transplant, admitted 8/2014-6/2019 to a specialty ICU for VV ECMO were reviewed. Two hundred twenty-five patients were included. In-hospital mortality was 24.4% (n = 55). Most non-survivors (46/55, 84%) died prior to lung recovery and decannulation from VV ECMO. Most common cause of death (COD) for patients who died on VV ECMO was removal of life sustaining therapy (LST) in setting of multisystem organ failure (MSOF) (n = 24). Nine patients died a median of 9 days [6, 11] after decannulation. Most common COD in these patients was palliative withdrawal of LST due to poor prognosis (n = 3). Non-survivors were older and had worse predictive mortality scores than survivors. We found that death in patients supported with VV ECMO in our study most often occurs prior to decannulation and lung recovery. This study demonstrated that the most common cause of death in patients supported with VV ECMO was removal of LST due MSOF. Acute hemorrhage (systemic or intracranial) was not found to be a common cause of death in our patient population.

Brain death post cardiac surgery: A modified apnea test to confirm death by neurologic criteria for a patient on extracorporeal membrane oxygenation

Death by neurologic criteria (DNC) requires coma, absent brainstem reflexes, and the inability to breathe independently during apnea testing (AT). For patients on extracorporeal membrane oxygenation (ECMO), this clinical determination is more challenging. Herein, we report the case of a patient with DNC on ECMO post cardiac surgery, highlighting various considerations to the process and modifications required for AT.

Investigation of Apnea Testing During Brain Death Determination in China

Apnea testing (AT) is one of the key steps for brain death (BD) diagnosis and confirmation. However, the completion rate of AT is not well in China. The aim of this study was to investigate the completion rates of the AT during BD determination in China and analyze the determinant factors. We reviewed and analyzed potential BD patients registered in our database from 2013 to 2019. The patients were divided into those with completed and aborted AT. Preconditions and organ function status were compared between the two groups. A total of 1,531 (1,301 adults and 230 pediatrics) cases of potential BD were extracted, and BD determination was performed 2,185 and 377 times in adults and pediatrics respectively. The nonperformance and aborted rates of AT were 12.2% and 34.5% in adults, and 11.7% and 44.4% in pediatrics respectively. Compared with the completed group, the aborted group had a lower PaO2, systolic blood pressure, PaO2/FiO2 ratios, and higher alveolar-arterial (A-a) gradient both in adults and pediatrics, and higher PaCO2 and higher heart rates in adults. PaO2 and A-a gradient had higher predictive efficacy for AT completion in both adults and pediatrics. The implementation and completion rates of AT are not ideal in China. PaO2 and A-a gradient are important factors for the successful completion of AT and should be optimized before AT.

Modification strategies to improve the membrane hemocompatibility in extracorporeal membrane oxygenator (ECMO)

ABSTRACT

Since extracorporeal membrane oxygenator (ECMO) has been utilized to save countless lives by providing continuous extracorporeal breathing and circulation to patients with severe cardiopulmonary failure. In particular, it has played an important role during the COVID-19 epidemic. One of the important composites of ECMO is membrane oxygenator, and the core composite of the membrane oxygenator is hollow fiber membrane, which is not only a place for blood oxygenation, but also is a barrier between the blood and gas side. However, the formation of blood clots in the oxygenator is a key problem in the using process. According to the study of the mechanism of thrombosis generation, it was found that improving the hemocompatibility is an efficient approach to reduce thrombus formation by modifying the surface of materials. In this review, the corresponding modification methods (surface property regulation, anticoagulant grafting, and bio-interface design) of hollow fiber membranes in ECMO are classified and discussed, and then, the research status and development prospects are summarized.

Brain Injury in Extracorporeal Membrane Oxygenation: A Multidisciplinary Approach

Extracorporeal membrane oxygenation (ECMO) represents an established technique to provide temporary cardiac and/or pulmonary support. ECMO, in veno-venous, veno-arterial or in extracorporeal carbon dioxide removal modality, is associated with a high rate of brain injuries. These complications have been reported in 7 to 15% of adults and 20% of neonates, and are associated with poor survival. Thromboembolic events, loss of cerebral autoregulation, alteration of the blood-brain barrier, and hemorrhage related to anticoagulation represent the main causes of severe brain injury during ECMO. The most frequent forms of acute neurological injuries in ECMO patients are intracranial hemorrhage (2-21%), ischemic stroke (2-10%), seizures (2-6%), and hypoxic-ischemic brain injury; brain death may also occur in this population. Other frequent complications are infarction (1-8%) and cerebral edema (2-10%), as well as neuropsychological and psychiatric sequelae, including posttraumatic stress disorder.

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.

Enigma of apnea test for brain death on ECMO—an ongoing discussion—case study and review of literature

Coma, absent brain stem reflexes, and apnea are considered the neurological criteria of brain death. As membrane oxygenator does almost entire gas exchange in patients with severely diseased lungs who are on extracorporeal membrane oxygenation (ECMO), it is not possible to carry out apnea test in routine manner. We described the difficulties we faced conducting the apnea test and the other ancillary tests in our patient on veno-venous ECMO who suffered a major cerebral insult and reviewed the literature of brain death testing in patients on ECMO.

Apnea test for the diagnosis of brain death in a patient undergoing extracorporeal membrane oxygenation

Extracorporeal membrane oxygenation is used as extracirculatory support for the care of patients with severe and reversible cardiac and/or respiratory failure. Neurological complications may be related to the procedure. Given the unfavorable neurological evolution and the need to perform a brain death protocol, the performance of an apnea test in this context remains a challenge. We report the use of an apnea test for the diagnosis of brain death post-cardiac surgery in a patient receiving venoarterial extracorporeal membrane oxygenation.

A 92 Days Run of Venovenous Extracorporeal Membrane Oxygenation

Background Venovenous extracorporeal membrane oxygenation (VV-ECMO) is an established life-saving procedure for severe acute respiratory failure due to various causes. In general, the duration of ECMO ranges from 1 to 2 weeks, with withdrawal recommended if no improvement is noted. We report a case of respiratory failure due to acute respiratory distress syndrome (ARDS) following influenza A infection, supported with a long ECMO run and the lessons learned from this experience.

Case Report A 40-year-old female weighing 120 kg with pneumonia following H1N1 influenza was transferred to our hospital on mechanical ventilation for worsening respiratory distress. On admission, she presented with bilateral diffuse infiltrates on chest X-ray and severe hypoxemia with a partial pressure of oxygen in arterial blood/fraction of inspired oxygen concentration ratio (PaO2/FiO2) of 85 at FiO2 of 0.8 on endotracheal intubation and mechanical ventilation. Acinetobacter Baumannii was isolated from respiratory secretions; antibiotics were revised as per sensitivity. Her respiratory status further deteriorated over next 96 hours in spite of maximally optimized mechanical ventilation. VV-ECMO was established on 4th day of mechanical ventilation in our hospital. Thereafter, she underwent a prolonged ECMO run with respiratory improvement starting to show some promise only by 86th day of ECMO. Weaning process was initiated gradually. However, on 88th day of ECMO the patient had an episode of seizure followed by low Glasgow Coma Scale (GCS) score (3T/15). The patient did not recover from the cerebral insult and based on clinical neurological examination including apnea test, brain death was determined within next 48 hours and the ECMO was called off.

Conclusions Prolonged ECMO therapy poses many challenges and might be considered if the primary cause of respiratory failure necessitating ECMO is expected to resolve or a feasibility of lung transplantation is contemplated. Good team dynamics and appropriate counselling to the family are of utmost importance managing the patients on prolonged ECMO.

Apnea test for brain death diagnosis in adults on extracorporeal membrane oxygenation: a review

Among the potential complications of extracorporeal membrane oxygenation, neurological dysfunctions, including brain death, are not negligible. In Brazil, the diagnostic process of brain death is regulated by Federal Council of Medicine resolution 2,173 of 2017. Diagnostic tests for brain death include the apnea test, which assesses the presence of a ventilatory response to hypercapnic stimulus. However, gas exchange, including carbon dioxide removal, is maintained under extracorporeal membrane oxygenation, making the test challenging. In addition to the fact that the aforementioned resolution does not consider the specificities of the diagnostic process under extracorporeal membrane oxygenation, studies on the subject are scarce. This review aims to identify case studies (and/or case series) published in the PubMed^® and Cochrane databases describing the process of brain death diagnosis. A total of 17 publications (2011 - 2019) were identified. The practical strategies described were to provide pretest supplemental oxygenation via mechanical ventilation and extracorporeal membrane oxygenation (fraction of inspired oxygen = 1.0) and, at the beginning of the test, titrate the sweep flow (0.5 - 1.0L/minute) to minimize carbon dioxide removal. It is also recommended to increase blood flow and/or sweep flow in the presence of hypoxemia and/or hypotension, which may be combined with fluid infusion and/or the escalation of inotropic/vasoactive drugs. If the partial pressure of carbon dioxide threshold is not reached, repeating the test under supplementation of carbon dioxide exogenous to the circuit is an alternative. Last, in cases of venoarterial extracorporeal membrane oxygenation, to measure gas variation and exclude differential hypoxia, blood samples of the native and extracorporeal (post-oxygenator) circulations are recommended.