Needle bevel orientation does not affect the cranial spread of injectate in a lumbosacral epidural in canine cadavers.

Tuohy needle bevel orientation does not significantly affect cranial epidural spread in canine lumbosacral injections.

This cadaveric study investigated whether Tuohy needle bevel orientation (cranial vs. caudal facing) influences the cranial and circumferential spread of contrast medium during lumbosacral epidural injections in dogs. Five canine cadavers per group received iohexol (240 mg/mL) diluted 1:3 with saline at volumes of 0.1 mL/kg and 0.2 mL/kg. CT imaging was used to assess the number of vertebral bodies reached and the estimated circumferential coverage of the epidural space at each volume. At 0.1 mL/kg, both cranial and caudal bevel orientations produced comparable spread, reaching a median of 1 vertebral body with 100% circumferential coverage, 7 bodies with ≥50% coverage, and approximately 9–10 bodies with ≥1% coverage. At 0.2 mL/kg, results were similarly equivalent between groups. No statistically meaningful difference in cranial injectate spread was identified between the two bevel orientations at either volume. The contrast medium was diluted to approximate the physical properties of local anesthetics, improving the clinical relevance of the model. These findings suggest that anesthesiologists need not alter their technique based on bevel direction when performing lumbosacral epidurals in dogs. However, the authors caution that this was a small cadaveric study, and physiological factors present in live patients—such as epidural pressure and vascular absorption—may influence results. Further prospective studies in living animals are warranted before definitive clinical recommendations can be made.

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