• Manuel de la Matta and Alejandro Domínguez.
• From the Department of Anaesthesia, Hospital General, Hospital Universitario Virgen del Rocío, Sevilla, Spain (M de la M, AD).
• Eur J Anaesthesiol. 2018 May 1; 35 (5): 365-371.

BackgroundMonitoring regional cerebral oxygen saturation (rcSO2) with near-infrared spectroscopy is increasingly being performed in patients scheduled for cardiac surgery. It is sometimes difficult to monitor both frontal lobes due to anatomical or space compromises. However, it remains unclear whether the use of only one lateral or medial probe can provide adequate bilateral monitoring.ObjectiveTo evaluate the efficacy of using a single lateral or medial probe to detect substantial desaturations on both sides.DesignA prospective observational study.SettingTertiary university teaching hospital.PatientsSeventeen adult patients undergoing elective cardiac surgery monitored with three near-infrared spectroscopy probes (two lateral and one medial) using an INVOS 5100C monitor.InterventionsThe value of rcSO2 was recorded up to 19 times during each procedure. Substantial desaturation was defined as an absolute rcSO2 value of 50% or less or a decrease of more than 20% compared with baseline values on spontaneous ventilation with 21% oxygen.Main Outcome MeasuresThe level of agreement between the three pairs of probes using the Bland-Altman method for repeated measures, and the grade of concordant and discordant results between the three pairs of probes by means of contingency tables and the κ coefficient.ResultsWe obtained 244 records per probe. Greater agreement was observed between the two lateral probes (mean ± SD of the differences between recordings was -0.9 ± 5.5); mean difference between left and medial, and right and medial probes was 2.4 ± 7.3 and 3.3 ± 6.7, respectively. The rate of discordant results between the two lateral probes was 5.7%, κ coefficient of 0.6 with 95% confidence interval (95% CI 0.4 to 0.8), and between the left and medial, and right and medial of 8.2 and 7.4%, with κ coefficients of 0.57 (95% CI 0.38 to 0.76) and 0.5 (95% CI 0.29 to 0.71), respectively.ConclusionIn cardiac surgery patients in whom there is difficulty in accommodating two rcSO2 probes, a single lateral probe can effectively measure bilateral rcSO2 in specific scenarios.

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