Abstract
We aimed to determine whether optical methods based on bolus tracking of an optical contrast agent are useful for the confirmation of cerebral circulation cessation in patients being evaluated for brain death. Different stages of cerebral perfusion disturbance were compared in three groups of subjects: controls, patients with posttraumatic cerebral edema, and patients with brain death. We used a time-resolved near-infrared spectroscopy setup and indocyanine green (ICG) as an intravascular flow tracer. Orthogonal partial least squares-discriminant analysis (OPLS-DA) was carried out to build statistical models allowing for group separation. Thirty of 37 subjects (81.1%) were classified correctly (8 of 9 control subjects, 88.9%; 13 of 15 patients with edema, 86.7%; and 9 of 13 patients with brain death, 69.2%; p < 0.0001). Depending on the combination of variables used in the OPLS-DA model, sensitivity, specificity, and accuracy were 66.7–92.9%, 81.8–92.9%, and 77.3–89.3%, respectively. The method was feasible and promising in the demanding intensive care unit environment. However, its accuracy did not reach the level required for brain death confirmation. The potential usefulness of the method may be improved by increasing the depth of light penetration, confirming its accuracy against other methods evaluating cerebral flow cessation, and developing absolute parameters for cerebral perfusion.
Highlights
We aimed to determine whether optical methods based on bolus tracking of an optical contrast agent are useful for the confirmation of cerebral circulation cessation in patients being evaluated for brain death
The results of the measurements carried out in patients with brain death were analyzed together with the results obtained in the control group and those obtained from patients with posttraumatic cerebral edema
We demonstrated that an optical method based on the tracking of an optical dye (ICG) bolus through the brain was able to discriminate between healthy subjects, patients with posttraumatic edema, and patients with brain death, with moderate accuracy
Summary
We aimed to determine whether optical methods based on bolus tracking of an optical contrast agent are useful for the confirmation of cerebral circulation cessation in patients being evaluated for brain death. Due to limited absorption of light at near-infrared wavelengths and pronounced scattering, photons can penetrate through the skull and cerebral tissue. They can be detected in reflectance geometry a few centimeters apart from the emission point on the surface of the head. A few NIRS studies assessing cerebral oximetry as an indicator of cerebral blood flow (CBF) have been performed for confirmation of brain death[18,19]. Measurements of rSO2 have not proven useful for the confirmation of brain death, as the values of cerebral oximetry in some cases remain within the normal range even when cessation of CBF is confirmed[18,19,22]
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