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.