Comparison of three sitting positions for combined spinal - epidural anesthesia: a multicenter randomized controlled trial

Background and objectives: The aim of this prospective, multi-centered and multi-arm parallel randomized trial was to test the hypothesis that modified sitting positions including hamstring stretch position (HSP) and squatting position (SP) would reduce needle - bone contact events and increase the success rate of combined spinal - epidural anesthesia (CSEA) compared to traditional sitting position (TSP) in patients undergoing total knee or hip arthroplasty. Patients and methods: Three hundred and sixty American Society of Anesthesiologists (ASA) I-III patients, aged between 45-85 years were randomly allocated to one of three groups using computer-generated simple randomization: group TSP (n = 120), group HSP (n = 120), and group SP (n = 120). Primary outcome measures were the number of needle-bone contact and success rates. Secondary outcome measure was the ease of interspinous space identification. Results: Seven patients in group SP and four of HSP could not tolerate their position and were excluded. Number of needle-bone contact, success rates, and grade of interspinous space identification were similar between groups (p = 1.000). Independent of positioning, the success rates were higher in patients whose interspinous space was graded as easy compared to difficult or impossible (p < 0.001). Success rates reduced, interspinous space identification became more challenging, and number of needle - bone contact increased as patient's body mass index (BMI) increased (p < 0.001). Conclusion SP and HSP may be used as alternatives to the TSP. BMI and ease of interspinous space identification may be considered important determinants for CSEA success. (C) 2020 Published by Elsevier Editora Ltda. on behalf of Sociedade Brasileira de Anestesiologia.