Effects of Body Mass Index on Intra-abdominal Pressure and Regional Cerebral Oxygen Saturation in Lumbar Spine Surgery in the Prone Position

Introduction: This study aimed to investigate whether the prone position could affect near-infrared spectroscopy (NIRS) values in patients with a high body mass index (BMI).

Methods: A total of 40 patients with the American Society of Anesthesiology physical status I–III who underwent lumbar disc hernia repair for one or two levels were included in this prospective study. NIRS monitorization was performed on all patients after routine monitoring. The patients were allocated equally to two groups according to BMI: Group I (BMI ≥30 kg/m2) and Group II (BMI <30 kg/m2).

Results: The mean intra-abdominal pressure (IAP) measured at the prone position was higher in Group I (p=0.005). There was a statistically significant positive correlation between BMI and IAP values at the prone position (r=0.471, p =0.002). A total of 8 patients suffered a ≥20% decrease in regional cerebral oxygen saturation, with 6 in Group I and 2 in Group II.

Discussion and Conclusion: Intragroup IAP values increased over time and were significantly higher in obese patients. Regional cerebral oxygen saturation dropped in both groups until the 20th minute of the prone positioning and then was stabilized. These findings might be used for anesthetic management of patients undergoing lumbar surgeries within the first 20 min.

Keywords: Anesthesia, prone, oxygenation, lumbar surgery, body mass index, intra-abdominal pressure