Comparing Ultrasonography and Surface Landmark-Guided Lumbar Puncture in Patients with Obesity and Difficult Anatomy; a Randomized Controlled Trial

Introduction: Previous studies have shown higher lumbar puncture (LP) success rates when using ultrasound guidance. This study aimed to compare the first-attempt success rate of ultrasound-guided LP with blind technique of needle insertion using the palpable spinal surface landmark in patients with obesity or a difficult anatomy. Methods: This prospective randomized controlled study was performed at the emergency department of Ramathibodi Hospital, an academic tertiary university hospital, from August 2015 to July 2016. Results: 40 patients were enrolled (20 surface landmark-guided and 20 ultrasound-guided LPs). 52.5% of the patients were male with the mean age of 60.33 ± 4.24 years. The first-attempt success rate in the ultrasound-guided LP group was significantly higher than the landmark-guided LP group (80% vs. 35%, respectively), with risk difference (RD) of 45.00% (95% confidence interval (CI): 17.72%, 72.28%). This indicated absolute risk reduction and number needed to treat of 45.00% and 2.22, respectively. The median procedural duration required to achieve successful LP in the ultrasound-guided LP group was significantly shorter than the surface landmark-guided LP group (5 [IQR: 3–18] minutes vs. 13.5 [IQR: 5-30] minutes, respectively). Traumatic puncture as a complication occurred less frequently in the ultrasound-guided LP group than the surface landmark-guided LP group with risk ratio (RR) = 0.33 (95% CI: 0.08, 1.46) and RD = -20.00% (95% CI: -44.00%, 4.00%). This indicated absolute risk reduction and number needed to harm of 20.00% and 5.00, respectively. However, the difference was not significant. Conclusion: Using ultrasound to help localize the insertion point before LP increased the first-attempt success rate and improved other LP outcomes in Thai patients with obesity or a difficult anatomy. It also shortened the procedural duration and reduced the incidence of traumatic tap.