Evaluation of pulsed Doppler common carotid blood flow as a noninvasive method for brain death diagnosis: a...

Among the main causes for the relatively small number of organ donors, the delay in the diagnosis of brain death plays a major role. This prospective study was designed to evaluate whether pulsed Doppler mean and phasic common carotid blood flow (CCBF) combined with arterial and jugular venous blood gases could rapidly and specifically establish a diagnosis of brain death. CCBF was measured by an 8 MHz pulsed Doppler flowmeter, allowing measurement of the vessel diameter via a double transducer probe, which fixed the ultrasonic incidence angle. From an initial series of patients (n = 28) with an established diagnosis [brain death n = 14; severe coma with a Glasgow Coma Scale (GCS) less than 7, n = 14], the results of the logistic regression analysis process yielded the most discriminating parameters for brain death diagnosis: end-diastolic velocity (Ved - 1.4 vs. 12.7 cm/s; t = 7.67, P = 0.001) and blood flow (Qed - 13.6 vs. 121.4 ml/min). These parameters were then tested in a blind fashion on a second series of 28 comatose patients (GCS = 7). They resulted in correct diagnosis (brain death n = 14 or severe coma n = 14) for all patients. Brain death diagnosis was confirmed by clinical signs, EEG, and/or angiography. From the analysis of the overall population (n = 56), a value of Qed of less than 31.4 ml/mn indictes brain death. The authors conclude, that pulsed Doppler measurements of CCBF represent an early, low cost and noninvasive technique, the results of which may prompt legally accepted procedures, which in turn would reduce the delay required before brain death is diagnosed. Moreover, this technique could help in deciding on discontinuation of active therapy in severely injured patients.