Can pre-procedure neuroaxial ultrasound improve the identification of the potential epidural space when compared with anatomical landmarks? A prospective randomized study.

BACKGROUND: Regional epidural analgesia is considered the gold standard for pain treatment in labor. However, epidural catheter placement may be a challenging procedure because of the difficulty in the palpation of anatomical landmarks, particularly in pregnant women. Pre-procedural neuroaxial ultrasound may facilitate the procedure.

METHODS: A prospective randomized controlled study was conducted in a labor ward. Two groups of women undergoing epidural analgesia were randomized: Group A (N.=28), which was subjected to the loss of resistance technique, and Group B (N.=30) which was subjected to an ultrasound (US)-assisted procedure. The real depth of epidural space was calculated in both groups by measuring the needle skin-to-tip distance, while the US depth was measured only in Group B.

RESULTS: The mean number of attempts in group A (3.43±3.8) was significantly higher than in Group B (1.70±0.87, P=0.019). Analysis of data from Group B revealed a strong positive correlation between the epidural real depth and US depth (r=0.88, P<0.0001).

CONCLUSIONS: The US-assisted technique for epidural catheter placement for labor analgesia is safe, effective, easy to perform, and is a valuable aid to improve the identification of the epidural space compared with the palpation of anatomical landmarks and the loss of resistance technique. Pre-puncture ultrasound assessment shows the exact location of the intervertebral space, the optimal point of insertion and the tilt angle of the needle, the depth of the epidural space and any anatomical abnormalities of the spine, thereby increasing the success rate and reducing procedural complications of the blind approach.