Noninvasive and sensitive optical assessment of brain death

Brain death is an irreversible loss of all brain functions, and the assessment is crucial for organ supply for transplantation. The noninvasive, sensitive, universally available and timely ancillary method to assess brain death has not been established. Here, we attempted to explore a noninvasive way in brain death assessment. Eighteen brain-dead patients and 20 healthy subjects were measured by near-infrared spectroscopy (NIRS), with a multiple-phase protocol at varied fraction of inspired O₂ (FIO₂ ). We found that the concentration changes ratios of oxyhemoglobin to deoxyhemoglobin (Δ[HbO₂ ]/Δ[Hb]) in the cerebral cortex of brain-dead patients were significantly higher than those of healthy subjects. And, the Δ[HbO₂ ]/Δ[Hb] in low-to-high FIO₂ phase was most sensitive to distinguish brain-dead patients from healthy subjects, with a recommended threshold ranged in 1.40~1.50. The innovative incorporation of NIRS and a varied FIO₂ protocol was shown to be a noninvasive and reliable way in assessing brain death. This successful attempt of NIRS application is a help for fast and accurate evaluation of brain death, promptly offering quality-assured donor organs and indicate us a protocol-aided way to expand the use of NIRS.