Background and Objectives: Imaging studies in humans have shown that intraneural injection of local anesthetic may be relatively frequent. The incidence of intraneural catheterization is unknown. We speculated that early neural blockade after the injection of a small dose of local anesthetic might be a common finding produced by unintended intraneural catheterization. We investigated the clinical effect of a small dose of local anesthetic injected through a stimulating sciatic catheter, and also the placement of the tip of the catheters by computed tomography (CT) scan.

Methods: In this descriptive study, a dose of 3 to 5 mL of 1.5% mepivacaine was injected through a stimulating sciatic catheter in 45 patients undergoing hallux valgus repair. Patients with early neural blockade at the foot, within 5 minutes after injection, were suspected to have an intraneural placement of the catheter. A CT scan of the thighs was performed in 10 additional patients to assess catheter tip placement.

Results: Nine of 45 patients had early neural blockade with the small dose of local anesthetic. Seven patients underwent surgery without further supplementation. There was a statistically significant lower intensity of stimulating current through the catheter in the group of patients with early neural blockade. Of 10 CT scans, 3 showed clear intraneural placement of the catheter. No postoperative sequelae were observed.

Conclusions: Intraneural catheterization of the sciatic nerve may be a frequent finding and was not followed by nerve injury under the conditions of our small pilot study.