Brain death

Brain death evaluation
Surveys have suggested that physicians in general have poor knowledge about brain death determination and are not necessarily performing brain death evaluations properly. Formal training has been recommended.

Apnea testing
The determination of brain death for patients on ECMO requires some modifications to be made to the apnea testing protocol. There is limited guidance on this, but the United Kingdom Faculty of Intensive Care Medicine have published a list of steps for how to appropriately perform the apnea test for patients on ECMO, which are as follows: Importantly, these steps can be followed for VA or VV ECMO. For peripheral VA ECMO, however, there is an issue of blood mixing, as the right hemisphere may see cardiac output from the heart itself, while the left hemisphere may instead see blood from the oxygenator, depending on the mixing point. By sampling blood from the right radial artery alone, these could have elevated levels of CO2 while the blood from the ECMO circuit could have CO2 levels below 60 mmHg, invalidating the test. Thus it is recommended that, in peripheral VA ECMO, the post-oxygenator circuit be sampled at the same time as the right radial ABG to ensure an accurate correlation and that both are above 60 mmHg.
 * 1) Ensure sweep gas FiO2 is 100%.
 * 2) Temporarily increase the sweep gas flow rate to maximum and then reduce again to ‘sigh’ the extracorporeal membrane and eliminate condensation
 * 3) Adjust ECMO blood flow to achieve PaO2 > 10 kPa at all times at all sampling sites. Note that the blood flow may need to be increased above previously established baseline rates.
 * 4) Reduce sweep gas flow rate by 0.5 L/minute every 5 minutes. Perform arterial blood gas analysis at each 5-minute point until the PaCO2 is ≥ 6.0 kPa and starting pH <7.4 or [H+] >40 nmol/L. In patients with an elevated bicarbonate, the PaCO2 may need to be further titrated to achieve the desired pH. Do not reduce the sweep gas flow rate below 0.5 L/min.
 * 5) Suction the patient’s airway to ensure it is clear of obstruction, secretions or soiling.
 * 6) Undertake a ventilator recruitment maneuver to optimize pulmonary gas exchange.
 * 7) Disconnect the ventilator circuit and attach a Water’s (Mapleson C) circuit with inline ETCO2 monitoring and valve adjusted to give approximately 10 cmH2O CPAP to the lungs.
 * 8) Reduce the sweep gas flow rate further by 0.5 L/minute every 5 minutes and perform an arterial blood gas at each 5-minute point until all measured PaCO2 values have risen by at least 0.5kPa above the starting level. Do not reduce the sweep gas flow rate below 0.5L/min.
 * 9) During the period of disconnection, observe for any respiratory effort – ETCO2, chest excursion and/ or movement of the circuit reservoir bag. This must be for a minimum of 5 (five) minutes.
 * 10) Abandon test if there is significant deoxygenation or cardiovascular instability, if respiratory effort is observed or if adequate rise in PaCO2 is not achieved.

If the patient has hypoxia with this method, one can consider adding 8% CO2 volume to the ECMO circuit to raise the pCO2 without lowering the sweep gas flow rate.