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

Abstract

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. 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. 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. 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.