Prediction of bilateral cerebral oxygen desaturations from a single sensor in adult cardiac surgery: A prospective observational study

BACKGROUND Monitoring 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. OBJECTIVE To evaluate the efficacy of using a single lateral or medial probe to detect substantial desaturations on both sides. DESIGN A prospective observational study. SETTING Tertiary university teaching hospital. PATIENTS Seventeen adult patients undergoing elective cardiac surgery monitored with three near-infrared spectroscopy probes (two lateral and one medial) using an INVOS 5100C monitor. INTERVENTIONS The 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 MEASURES The 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. RESULTS We 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. CONCLUSION In 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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