A randomised controlled trial comparing needle movements during combined spinal-epidural anaesthesia with and without ultrasound assistance

Ultrasound assistance for neuraxial techniques may improve technical performance; however, it is unclear which populations benefit most. Our study aimed to investigate the efficacy of neuraxial ultrasound in women having caesarean section with combined spinal-epidural anaesthesia, and to identify factors associated with improved technical performance. Two-hundred and eighteen women were randomly allocated to ultrasound-assisted or control groups. All the women had a pre-procedure ultrasound, but only women in the ultrasound group had this information conveyed to the anaesthetist. Primary outcomes were first-pass success (a single needle insertion with no redirections) and procedure difficulty. Secondary outcomes were block quality, patient experience and complications. Exploratory sub-group analysis and regression analysis were used to identify factors associated with success. Data from 215 women were analysed. First-pass success was achieved in 67 (63.8%) and 42 (38.2%) women in the ultrasound and control groups, respectively (adjusted p = 0.001). Combined spinal-epidural anaesthesia was difficult' in 19 (18.1%) and 33 (30.0%) women in the ultrasound and control groups, respectively (adjusted p = 0.09). Secondary outcomes did not differ significantly. Anaesthetists misidentified the intervertebral level by two or more spaces in 23 (10.7%) women. Sub-group analysis demonstrated a benefit for ultrasound in women with easily palpable spinous processes (adjusted p = 0.027). Regression analysis identified use of ultrasound and easily palpable spinous processes to be associated with first-pass success.