The short answer is that you cannot. Brain death diagnosis requires the presence of 3 conditions: persistent coma, absence of brainstem reflexes, and lack of ability to breathe independently. If portions of the clinical exam or apnea test cannot be performed, ancillary testing is necessary to make t...

Our institutional policy allows for confirmatory testing with bedside TCDs demonstrating small systolic peaks in early systole without diastolic flow or a reverberating flow pattern. I believe some institutions may allow EEG as ancillary testing.

Very nice review in Greer et al., PMID 32761206. Certainly for those situations when apnea testing cannot be done, confirmatory/ancillary testing may be reasonable (and no, not all such patients are definitively terminal, e.g. high cord injury, CNS depressant agents that may mimic brain death). Opti...

If the patient is so ill, the outcome of death is the same. If death has already occurred or will occur during withdrawal of life support leads to the same result. Get your DNR and WOLS signed and proceed.

I agree you do need ancillary testing. You should investigate whether nuclear brain flow testing is available at your institution. This study can typically be completed at the bedside.