A Protocol that Mandates Postoxygenator and Arterial Blood Gases to Confirm Brain Death on Venoarterial Extracorporeal Membrane Oxygenation

Abstract

The apnea test (AT) during clinical brain death (BD) testing does not account for different arterial gas tensions on veno-arterial extracorporeal membrane oxygenation (V-A ECMO). We aimed to develop a protocol and now report our experience with three patients. The protocol was developed and implemented in 2015 at a quaternary center in Australia, measures both right radial and postoxygenator carbon dioxide (CO2) and oxygen (O2) gas tensions during the AT, incorporates regular gas sampling and a gradual reduction in fresh gas flow to ensure patient oxygenation. Patient 1 remained apneic despite both right radial and postoxygenator CO2 gas tensions >60 mmHg. Patient 2, despite having CO2 levels in a right radial arterial sample high enough to diagnose BD, postoxygenator CO2 remained <60 mmHg. Patient 2 did not breathe but radiological tests confirmed BD. Patient 3 showed respiratory effort but only once CO2 levels rose high enough in both right radial and postoxygenator samples. No patient was hypoxic during the AT. Performance of a reliable AT on V-A ECMO requires measurement of both right radial and postoxygenator blood gases. A protocol, which measures both blood gas values, is feasible to implement, while being both safe and easy to perform.

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

“…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.…”

“…This is due to the moving relative position of the aortic "water shed" or "mixing point" compared to the cerebral vessel take-off orifices. Given that these differences in gas tensions may not be recognized simply by peripheral arterial gas sampling, a protocol measuring both radial and post-oxygenator carbon dioxide (PaCO 2 ) and oxygen (PaO 2 ) gas tensions during AT may be necessary to ensure homogenous gas tensions reach the brain without compartmentalization [80].…”

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

“…( 10 - 14 ) Hemodynamic instability was described by only three studies. ( 10 - 12 ) Of these, only one was abandoned due to refractoriness to rescue interventions. ( 12 )…”

“…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.…”

“…Although more frequent than arterial hypotension, it was described by only four studies. ( 10 , 12 , 13 , 23 )…”