Lampl et al1 correctly state that an inadequate transtemporal window may falsely indicate no blood flow, especially in older women, thus decreasing the sensitivity of transcranial Doppler (TCD) in confirming brain death. They suggest that the routine additional use of the transorbital approach when using TCD to confirm brain death increases the efficacy of the examination.
We believe that routine use of the transorbital approach may be a double-edged sword. We carried out a prospective study of TCD in confirming brain death, in which the flow pattern in the internal carotid artery (ICA) siphon was evaluated in 45 patients. The ICA siphons were insonated using the transorbital approach at a depth of 60 to 70 mm from the surface. The patients were aged 2 to 81 years (mean age, 42.9 ± 19.4 years), and 24 were men. Causes of brain death included head injury (17 patients), subarachnoid hemorrhage (17 patients), intracerebral hemorrhage (4 patients), cerebral infarction (3 patients), anoxic encephalopathy (2 patients), and other (2 patients). In 8 patients (22%), the pattern of flow had a diastolic forward component in the ICA siphon despite blood flow changes compatible with cerebral circulatory arrest in all other intracranial arteries. The final results of our study2 were published after the submission of this letter.