Clinical utility and reliability of transcranial Doppler ultrasonography for the confirmation of brain death

Introduction

Clinical examination criteria have been established to determine brain death and subsidiary investigations such as electroencephalogram (EEG), arteriography and radionuclide scans have been used to determine the arrest of the cerebral circulation and to confirm the diagnosis of brain death. We examined in this study the clinical utility and reliability of transcranial doppler ultrasonography (TCD) as a confirmatory test for brain death.

Patients and methods

A total of 30 (20 male, 10 female and ranged in age from 2 to 80) consecutive comatose patients were studied by TCD and at the same time EEG recording was performed. Twenty-five of 30 patients clinically presented with brain death. Undetectable flow despite accurate bone window or the demonstration of isolated systolic spikes or diastolic reverse flow without forward flow in TCD examination and isoelectricity in EEG recording were accepted as confirmation of brain death. TCD examination was repeated in clinically brain death patients in whom TCD demonstrated initially systolodiastolic forward flow or diastolic forward flow and reverse flow in middle cerebral artery (MCA).

Results

Five of 25 patients who were brain death excluded from the study because of the lack of accurate bone window in TCD examination. In only 9 (45 %) of 20 patients who were clinically brain dead, three wave-form patterns that confirmed brain death were seen at the initial of TCD examination. Various wave-form patterns were detected in 11 patients in the first examination. Repeated TCD examination of 9 of these 11 patients who initially had forward flow patterns later demonstrated flow patterns which confirmed brain death. In 2 of 11 patients TCD examination could not be reperformed because of sudden cardiopulmonary arrest. In one of 5 patients who were not clinically brain death, TCD showed systolic spikes and no diastolic flow. The sensitivity and specificity of TCD for brain death were found to be 45% and 80%, respectively.

Discussion

TCD is a simple and noninvasive imaging modality that is easily performed at the patient's bedside in order to evaluate cerebral perfusion. A number of authors have presented very similar results concerning the specificity (100%) and sensitivity (91-100%) of this method [1,2]. However, we found 11 (55%) false negative and one false positive (20%) results which are higher rates than the results of previous studies [1,2]. Finally, in our study we interestingly found that the specificity and sensitivity of TCD examination in confirming brain death were lower than in previous studies.