• Christian Schmidt, Matthias Heringlake, Patrick Kellner, Astrid Ellen Berggreen, Holger Maurer, Sebastian Brandt, Bence Bucsky, Michael Petersen, and Efstratios I Charitos.
• Department of Anesthesiology and Intensive Care Medicine, University of Lübeck, Ratzeburger Allee 160, 23538, Lübeck, Germany.
• Can J Anaesth. 2018 Jul 1; 65 (7): 766-775.

PurposeThe present study aimed to test the hypothesis that cerebral oxygen saturation (ScO2) measurements with the INVOS-5100-C and the ForeSight-Elite cerebral oximeters vary in their correlation with mixed venous oxygen saturation (SvO2) upon changes in systemic oxygenation in extubated cardiac surgical patients. Additionally, we aimed to elucidate whether the ScO2 measurements of both devices can be used interchangeably to detect reduced SvO2.MethodsForty-eight spontaneously breathing patients extubated after cardiac surgery were included in this prospective observational study. The patients were exposed to both high (10 oxygen L·min-1 via face mask) and low (room air) inspiratory oxygen concentrations. Bi-hemispherical ScO2 was determined with the INVOS and ForeSight Elite cerebral oximeters. The SvO2 was measured with a pulmonary artery catheter.ResultsSignificant changes in oxygen delivery, ScO2 (by both cerebral oximeters), and SvO2 were observed upon variation of oxygenation. The minimum mean (standard deviation) ScO2 (ScO2min) using the INVOS and ForeSight did not differ significantly during high oxygen delivery [63.1 (8.6) % vs 65.8 (4.7) %, respectively; P = 0.07], but during low oxygen delivery, the INVOS value was significantly lower than that of the ForeSight oximeter [56.7 (8.9) % vs 61.3 (4.4) %, respectively; P = 0.003]. Both devices differed in the correlation between ScO2min and SvO2 for the combined oxygenation data (0.59, INVOS vs 0.28, ForeSight; correlation difference, 0.31; Bonferroni-adjusted 95% confidence interval [CI], 0.08 to 0.54; P = 0.008). The receiver-operating curve analysis revealed an area under the curve of 0.83 (95% CI, 0.74 to 0.9; P = 0.005) for detecting an SvO2 below 50% by ScO2min with the INVOS and 0.51 (95% CI, 0.41 to 0.62; P = 0.92), respectively, with the ForeSight.ConclusionsThese findings suggest that the cerebral oximeters tested react differently to variations in systemic oxygenation and in their relationship with SvO2 and thus give different information on cardiopulmonary function. These findings raise doubt about whether these devices should be used interchangeably.

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