A Comparison of Two Techniques for Ultrasound-guided Caudal Injection: The Influence of the Depth of the Inserted Needle on Caudal Block

Abstract

BackgroundCaudal epidural injections have been commonly performed in patients with low back pain and radiculopathy. Although caudal injection has generally been accepted as a safe procedure, serious complications such as inadvertent intravascular injection and dural puncture can occur. The present prospective study was designed to investigate the influence of the depth of the inserted needle on the success rate of caudal epidural blocks.MethodsA total of 49 adults scheduled to receive caudal epidural injections were randomly divided into 2 groups: Group 1 to receive the caudal injection through a conventional method, i.e., caudal injection after advancement of the needle 1 cm into the sacral canal (n = 25), and Group 2 to receive the injection through a new method, i.e., injection right after penetrating the sacrococcygeal ligament (n = 24). Ultrasound was used to identify the sacral hiatus and to achieve accurate needle placement according to the allocated groups. Contrast dyed fluoroscopy was obtained to evaluate the epidural spread of injected materials and to monitor the possible complications.ResultsThe success rates of the caudal injections were 68.0% in Group 1 and 95.8% in Group 2 (P = 0.023). The incidences of intravascular injections were 24.0% in Group 1 and 0% in Group 2 (P = 0.022). No intrathecal injection was found in either of the two groups.ConclusionsThe new caudal epidural injection technique tested in this study is a reliable alternative, with a higher success rate and lower risk of accidental intravascular injection than the conventional technique.

Vertical Small-Needle Caudal Epidural Injection Technique

“…This success rate may exceed that of fluoroscopically guided injections. With use of ultrasound guidance to place the needle with a cephalad orientation through the cornua 9/29 (31%) had initial blood return in one study (14) and at least 5/25 (25%) in another (15). However, although aspiration for blood likely reduces the incidence of intravascular drug injection, it is not sufficient to prevent intravascular injection (5).…”

“…Two studies have suggested that caudal epidural injection may be more safely performed with Doppler monitor than with fluoroscopic guidance through decreasing the risk of intravascular injection, one by use of Doppler flow confirmation of an epidural pattern (5) and one by injecting immediately after penetrating the sacrococcygeal membrane to avoid contact with the venous plexus (15). This study adds another method to avoid intravascular injection, by inserting the needle at a 90 degree angle to the plexus.…”

“…If the needle is not advanced above the level of the cornua, fluid may not ascend as high in the epidural space. The cephalad extent of flow with this vertical method or with cephalad insertion immediately after penetrating the sacrococcygeal membrane (15) is likely to be volume dependent.…”

Failed caudal block in a child with pelvic neuroblastoma

“…Sir —The incidence of caudal block failure is about 1% and anatomical variation is a major contributing factor . We had an experience of caudal block failure in an 18‐month‐old male (16 kg) child with a pelvic neuroblastoma.…”

“…Ram Doo et al . during fluoroscopic‐guided injection of dye in the caudal space found an atypical pattern due to adhesions and fibrosis.…”