CEREBRAL OXIMETRY IN DEAD SUBJECTS

Near-infrared spectroscopy is a technique used to monitor cerebral oxy genation. To validate the method, we measured regional oxygen saturati on (rSo(2)) in the brains of 18 dead subjects (mean age, 74.4 +/- 14.6 years) 19.8 +/- 18.2 h (range, 1-73) after cessation of systemic circ ulation, and in 15 healthy probands (mean age, 34.2 +/- 8.7 years) wit h an INVOS 3100 cerebral oximeter. The mean (+/-SD) rSo(2) in the dead subjects was 51.0 +/- 26.8% [range, 6-88%; left, 48.4 +/- 28.0% (n = 21); right, 54.4 +/- 25.7% (n = 16)]. The mean rSo(2) in the control g roup was 68.4 +/- 5.2% (range, 60-76%; left, 68.1 +/- 5.0%; right, 68. 7 +/- 5.6%). After removal of the brain at autopsy in five of the dead subjects, the rSo(2) was 73.4 +/- 13.3% (15 measurements). Six of 18 of the dead subjects had val;es above the lowest values found in the h ealthy adults (greater than or equal to 60%). These findings raise con cerns about the validity of cerebral rSo(2) data in adults obtained by the INVOS 3100 system.