Background and purpose: Diagnosis of brain death requires confirmation of the clinical diagnosis by appropriate tests, generally electroencephalography (EEG) and angiography. The diagnostic limitations or logistical problems inherent to these tests indicate the need to develop other more appropriate methods. The results obtained with transcranial Doppler (TCD) led us to conduct this prospective study of TCD recordings in brain dead patients.
Methods: 130 patients, aged 2-88 years were diagnosed as brain dead between July 1987 and June 1993. Clinical criteria were confirmed in all cases by EEG (n=88) and or angiography (n=64). Intracranial anterior circulation was insonated via temporal windows or, when impossible, via a transorbital approach. The posterior circulation was studied only in more recent patients. Examinations were made as soon as possible after brain death diagnosis and repeated for about 30 min. Vital parameters and treatments were taken into account.
Results: There was only one false negative result, in a patient with an extended skull defect, who retained TCD and angiographic intracranial circulation despite confirmed irreversible brain death. All other patients displayed typical ultrasonic patterns of cerebral circulation arrest: an oscillating signal (n= 190, 73%), a systolic spike (n=62, 24%) or a unilateral absence of signal (n=5). Despite a total correlation for positive diagnosis, TCD and angiography may differ as to the level of circulation arrest. TCD is useful for patients under sedative drugs. No false positive result was encountered but we were unable to insonate any intracranial artery in 5 patients.
Conclusion: Data from previous studies and the results of this study indicate that TCD is a very sensitive and safe method for diagnosing cerebral circulatory arrest. TCD may be used as a confirmatory test alongside EEG and angiography. TCD is more widely applicable than EEG and may be earlier and safer than angiography.