Ultrasound-guided spinal anaesthesia in obstetrics: is there an advantage over the landmark technique in patients with easily palpable spines?

Data are scarce on the advantage of ultrasound-guided spinal anaesthesia in patients with easily identifiable bony landmarks. In this study, we compared the use of ultrasound to the landmark method in patients with no anticipated technical difficulty, presenting for caesarean delivery under spinal anaesthesia.

A total of 150 pregnant women were recruited in this randomized, controlled study. Ultrasound examination and spinal anaesthesia were performed by three anaesthetists with experience in ultrasound-guided neuraxial block. Patients were randomized to either the Ultrasound Group (n=75) or the Landmark Group (n=75). In both groups the level of L3-4 or L4-5 was identified by ultrasound (transverse and longitudinal approach) or palpation. The primary outcome was the procedure time, measured from the time of skin puncture by the introducer to the time of viewing cerebrospinal fluid at the hub of the spinal needle. Secondary outcomes were the number of skin punctures, number of passes, and incidence of successful spinal blockade.

The average procedure time, number of skin punctures and needle passes, were similar in both groups. The number of patients with successful spinal anaesthesia after one puncture was not statistically different between the groups.

The present results indicate that when performed by anaesthetists experienced in both ultrasound and landmark techniques, the use of ultrasound does not appear to increase the success rate of spinal anaesthesia, or reduce the procedure time or number of attempts in obstetric patients with easily palpable spines.