Obesity is prevalent among patients with lumbar degenerative disease and is a known risk factor for perioperative complications in spinal surgery. However, most existing evidence relies solely on body mass index (BMI) without distinguishing between central and peripheral obesity phenotypes. Central and peripheral fat distribution may have distinct biomechanical and hemodynamic consequences, particularly with respect to intraabdominal pressure (IAP) changes during prone positioning and intraoperative blood loss.
This prospective single-center observational study aims to evaluate the effect of obesity phenotype - classified as non-obese, centrally obese, or peripherally obese based on BMI and waist-to-hip ratio - on intraabdominal pressure, intraoperative blood loss, and other perioperative outcomes in adult patients undergoing major lumbar spinal surgery (decompression and/or instrumentation)
Age 18-80 years
ASA Physical Status Classification I-III
Scheduled for elective major lumbar spinal surgery (canal stenosis decompression and/or instrumented fusion)
No prior lumbar spinal surgery
- Pediatric patients (<18 years)
Pregnancy
Emergency surgical procedures
Pre-existing renal failure
Adult patients aged 18-80 years with ASA physical status I-III scheduled for elective major lumbar spinal surgery (decompression and/or instrumentation) at Marmara University Pendik Training and Research Hospital and Asaf Ataseven Hospital, Istanbul, Turkey. Patients are classified by obesity phenotype based on BMI and waist-to-hip ratio. Patients with renal failure, coagulation disorders, anemia, pregnancy, prior lumbar surgery, or emergency procedures are excluded.
Cohort
Prospective
Intraabdominal Pressure Measurement via Urinary Bladder Catheter
Other interventionIntravesical intraabdominal pressure measurement performed via indwelling urinary catheter at three standardized time points: supine position after intubation, prone position during surgery, and supine position at end of surgery. This measurement is performed as part of observational data collection within the scope of routine catheterization; no additional invasive procedure is applied.
Total Intravenous Anesthesia (TIVA)
Other interventionStandardized TIVA protocol applied uniformly to all patients per institutional neuromonitoring-guided spinal surgery protocol. Induction with propofol 2 mg/kg, fentanyl 2 µg/kg, and rocuronium 0.6 mg/kg; maintenance with propofol and remifentanil infusion. Adjusted body weight used for drug dosing in obese patients. No study-specific modification to routine anesthetic management is performed. Arm Label: All Groups (NO, PO, CO)
Intraoperative Blood Loss
Total estimated blood loss (mL) calculated from suction canister volume and surgical sponge weight.
Intraabdominal Pressure (IAP)
Intravesical IAP measurement (mmHg) via urinary bladder catheter at positional transitions during surgery
Intraoperative Transfusion Requirement
Number of units of packed red blood cells, fresh frozen plasma, and platelet concentrate administered intraoperatively
Postoperative Hemoglobin Drop
Difference between preoperative and postoperative hemoglobin levels (g/dL).
Vasopressor/Inotrope Requirement
Type and cumulative dose of vasopressor or inotropic agents administered intraoperatively.
Postoperative Transfusion Requirement
Postoperative blood product transfusion rate and indication (Hb \<7 g/dL, hemodynamic instability, ongoing bleeding).
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