Which Predictor, SctO2 or SstO2, Is more Sensitive for Postoperative Cognitive Dysfunction in Spine Surgery: A Prospective Observational Study?

OBJECTIVE: Patients undergoing spinal surgery in the prone position may experience venous stasis, often resulting in edema in dependent areas of the body, including the head, and increased postoperative cognitive dysfunction (POCD). Not only does POCD present challenges for post‐operative care and recovery, it can also cause permanent damage to the patient's brain and increase mortality and social costs. We aimed to clarify the incidence of POCD in patients with hypertension after prone spine surgery and to further determine the association between intraoperative somatic tissue oxygen saturation (SstO2)/cerebral tissue oxygen saturation (SctO2) and POCD. METHODS: Patients with hypertension scheduled for open prone spine surgery from January 2020 to April 2021 were included in this single‐center, prospective, observational study. SctO2 and SstO2 were monitored by near‐infrared spectroscopy continuously throughout the surgery. The primary outcome was POCD assessed using the Mini‐Mental Status Examination (MMSE). The association of SstO2 and SctO2 with POCD was evaluated with unadjusted analyses and multivariable logistic regression. RESULTS: One hundred and one of 112 identified patients were included, 28 (27.8%) of whom developed POCD. None of the investigated SctO2 indices were predictive of POCD. However, the patients with POCD had greater decreases in intraoperative absolute SstO2 and relative SstO2 than the patients without POCD (P = 0.037, P = 0.036). Moreover, three SstO2 indices were associated with POCD, including a greater absolute SstO2 decrease (P = 0.021), a greater relative SstO2 decrease (P = 0.032), and a drop below 90% of the baseline SstO2 (P = 0.002), independent of ASA III status, preoperative platelets and postoperative sepsis. In addition, there was no correlation between intraoperative SctO2 and intraoperative SstO2 or between their respective absolute declines. CONCLUSION: Twenty‐eight (27.7%) of 101 patients developed POCD in patients with hypertension undergoing prone spine surgery, and intraoperative SstO2 is associated with POCD, whereas SctO2 shows no association with POCD. This study may initially provide a valuable new approach to the prevention of POCD in this population.