The Physiology of the Apnea Test for Brain Death Determination in ECMO: Arguments for Blending Carbon Dioxide

Beam, William B.; Scott, Phillip D.; Wijdicks, Eelco F. M.

doi:10.1007/s12028-019-00784-7

Cited by 18 publications

(26 citation statements)

References 22 publications

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“…Not reliant on ventilator setting changes, this technique results in rapid and predictable rise of CO 2 without trying to estimate the change in sweep gas flow and/or multiple gas draws. This method differs from previous descriptions of AT on ECMO which advocated for decreasing the sweep gas flow to decrease CO 2 removal by the ECMO oxygenator [77].…”

Section: Carbogen or Co 2 Supplementationmentioning

confidence: 86%

“…Reduction of Sweep Gas Flow Madden et al [73] Saucha et al [74] Shah and Lazaridis [71] Lie and Hwang [75] Solek-Pastuszka et al [15] Giani et al [41] Carbogen or CO 2 supplementation Andrews et al [70] Madden et al [76] Beam et al [77] Blood Gas Monitoring Draw ABGs from two sites: radial and post-oxygenator site Ihle et al [80] should be done from two different sites. For patients on VA-ECMO, different gas tensions (i.e., PaCO 2 ) may exist at different arterial sampling sites.…”

Section: Blood Gas Monitoring While On Ecmomentioning

confidence: 99%

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

2020

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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.

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Section: Carbogen or Co 2 Supplementationmentioning

confidence: 86%

Section: Blood Gas Monitoring While On Ecmomentioning

confidence: 99%

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

2020

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“…In the absence of hemodynamic instability, as observed in the reviewed studies, the blood flow value should be kept fixed. ( 2 , 12 - 24 ) In cases of instability refractory to the recommended adjustments, the test should be abandoned.…”

Section: Discussionmentioning

confidence: 99%

“…Some advocate that oxygen supplementation during the test is not necessary for all patients on ECMO because adequate gas exchange is ensured if the device is programmed to provide blood flow at 75 - 80% of cardiac output - a management decision described by two studies. ( 2 , 18 ) However, most suggest that supplementary oxygen therapy should be provided to maintain potential donor stability. Therefore, the consensus recommendation is to perform adequate preoxygenation for approximately 10 minutes with fraction of inspired oxygen (MV) = 1.0 (100%) and fraction of supplied oxygen (ECMO) = 1.0 (100%).…”

Section: Discussionmentioning

confidence: 99%

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

Sady¹,

Junqueira²,

Veiga³

et al. 2020

Revista Brasileira De Terapia Intensiva

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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.

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In silico simulation of the liquid phase pressure drop through cylindrical hollow‐fiber membrane oxygenators using a modified phenomenological model

Tabesh

Rafiei

Mottaghy

2021

Asia-Pacific J Chem Eng

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Low blood pressure drop is an important performance characteristic of a hollow‐fiber membrane oxygenator (HFMO). While the application of natural blood corresponds to complex handling procedures, the in vitro investigation of liquid pressure drop is mainly done using water or similar fluids (e.g., normal saline solution [NSS]). In this study, a comprehensive phenomenological model has been proposed to predict the liquid pressure drop through a cylindrical HFMO, considering viscous and inertial resistances in porous media, derived from literature. The results demonstrate that approaches based on Darcy–Weisbach phenomenological equation correlate the most with in vitro experimental investigations using NSS and native porcine blood, in both pediatric and adult commercially available cylindrical HFMOs. Remarkably, this study corroborates theoretically and experimentally that approaches based on Ergun semi‐empirical equation fail to predict the liquid pressure drop in cylindrical HFMOs. Moreover, it is shown that the presented phenomenological model is also applicable to cylindrical hollow‐fiber heat exchangers, and subsequently, its noticeable effect on total liquid pressure drop through cylindrical HFMOs is demonstrated. The results reveal that this component may contribute to almost half of total blood pressure drop, and therefore, it should be redesigned using other approaches than hollow fibers.

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The Physiology of the Apnea Test for Brain Death Determination in ECMO: Arguments for Blending Carbon Dioxide

Cited by 18 publications

References 22 publications

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

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

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

In silico simulation of the liquid phase pressure drop through cylindrical hollow‐fiber membrane oxygenators using a modified phenomenological model

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