The use of ultrasound to assist epidural injection in obese dogs.

OBJECTIVE

To evaluate the use of ultrasound for identifying the site for needle puncture and to determine the depth to the epidural space in obese dogs.

STUDY DESIGN

Prospective study in dogs undergoing elective orthopedic surgery.

ANIMALS

A group of seven obese Labrador male dogs aged 6.93 ± 2.56 years and weighing 46.5 ± 4.1 kg (mean ± standard deviation).

METHODS

The anesthetic protocol for these dogs included epidural anesthesia. With the dogs anesthetized and positioned in sternal recumbency with the pelvic limbs flexed forward, ultrasound imaging was used to locate the lumbosacral intervertebral space. Intersection of dorsal and transverse lines about the probe identified the point of needle insertion. A 17 gauge, 8.9 cm Tuohy needle was inserted perpendicularly through the skin and advanced to the lumbosacral intervertebral space. The number of puncture attempts was recorded and needle depth was compared with skin to ligamentum flavum distance.

RESULTS

Epidural injection was performed in all dogs at the first attempt of needle insertion. The distance from skin to epidural space was 5.95 ± 0.62 cm measured by ultrasound and 5.89 ± 0.64 cm measured with the Tuohy needle. These measurements were not different (p = 0.26). A highly significant correlation coefficient of 0.966 between measurement techniques was obtained (p < 0.001).

CONCLUSIONS AND CLINICAL RELEVANCE

Ultrasound imaging identified the point of needle insertion for lumbosacral epidural injection in seven obese dogs. The results indicate that ultrasound can be used to locate the lumbosacral intervertebral space and identify an appropriate point for needle insertion to perform epidural injection.