Extracranial contribution to cerebral oximetry in brain dead patients:: A report of six cases

The near infrared spectroscopy offers a noninvasive method to monitor regional brain oxygenation. The problem with the technique appears to be possible extracranial contribution to the measurements. As a part of another study, we monitored regional saturation (rSO(2)) in six brain dead patients either during the test for spontaneous respiration or in those not eligible for organ donation, after discontinuation of mechanical ventilation. Relatively normal rSO(2) values were obtained after brain death, and the values decreased concomitantly with the hemoglobin saturation of oxygen (SpO(2)) after the discontinuation of mechanical ventilation. A corresponding decrease in SpO(2) and rSO(2) suggests extracranial contribution to the measured rSO(2). The diagnosis of brain death cannot be made based on this technology; furthermore the presence of extracranial contribution may limit its potential value even in other applications.