Pre-procedural ultrasound-guided versus landmark-guided paramedian spinal anesthesia in obese patients: A prospective randomized controlled trial

Background: Obesity poses challenges to spinal anesthesia due to poorly palpable anatomical landmarks (LMs), complicating neuraxial block placement. Pre-procedural ultrasound (US) improves identification of neuraxial structures; however, evidence for its exclusive use with the paramedian approach in obese patients is limited. Aims and Objectives: This study compared the efficacy of preprocedural US-guided versus conventional LM-guided paramedian spinal anesthesia in obese patients. Materials and Methods: In this prospective, randomized controlled trial, 50 obese patients (Body mass index >30 kg/m2) scheduled for elective lower abdominal, perineal, or lower limb surgery under spinal anesthesia were randomized to receive either US-guided paramedian spinal anesthesia (US group, n=25) or LM-guided paramedian spinal anesthesia (LM group, n=25). The primary outcome was the number of puncture attempts for successful dural puncture. Secondary outcomes included needle passes, time for puncture site identification, time for spinal injection, and complications. Results: The median puncture attempts were significantly lower in the US group compared with the LM group (2 interquartile range [IQR 1–2] vs. 3 [IQR 2–4]; P<0.001). Needle passes were fewer in the US group (4 [IQR 3–4] vs. 5.5 [IQR 4–7]; P<0.001). US required longer site identification (78.35 vs. 38.19 s; P<0.001), but injection time was shorter (64.32 vs. 88.31 s; P=0.048). Conversion to general anesthesia was comparable (P=1.000). Conclusion: Pre-procedural US-guided paramedian spinal anesthesia reduced puncture attempts and needle passes in obese patients. Despite longer scanning time, US facilitated easier needle placement and improved procedural efficiency in difficult neuraxial anatomy.