2025/07/08 by Shanna Wong, Jordyn M. Boesch, Stephen Parry +3 · 2 voices
Medicine · Veterinary · #Anesthesia and Pain Management #Veterinary Orthopedics and Neurology #Veterinary Pharmacology and Anesthesia
paper · doi:10.2460/ajvr.25.03.0107
openalex publication_date 2025/07/08 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/22
Objective: To determine the distribution of injectate (iohexol) at the feline sacrococcygeal space using CT and thereby identify the volume necessary to reach the 10th thoracic intervertebral foramina (T10-T11), where nociceptive neurons from the ovaries enter the spinal cord. Methods: 7 healthy, purpose-bred, 1- to 2-year-old intact female domestic shorthair cats were anesthetized and positioned in sternal recumbency. After baseline vertebral column CT, a stimulating needle connected to a nerve stimulator (current, 0.2 mA; frequency, 2 Hz; pulse width, 0.1 milliseconds) was inserted at the sacrococcygeal space. After distal tail twitching was observed, a syringe driver injected iohexol (44 mg/mL; 0.25 mL/kg over 30 seconds). Computed tomography was performed 30 seconds after the injection ended. This was repeated 3 times, with 4 minutes separating the start of each injection. A linear mixed-effects model was constructed to determine if the number of vertebrae traversed as the iohexol distributed cranially could be predicted as a function of injectate volume, side of vertebral column, and their interaction (cat as a random effect). Results: The association between injectate volume and number of vertebrae traversed was significant. The volume required to reach the T10-T11 intervertebral foramen bilaterally was 0.75 mL/kg in 3 cats and 1.0 mL/kg in 3 cats; in 1 cat, 1.0 mL/kg did not reach this level. Conclusions: Sacrococcygeal epidural injection of 0.75 to 1.0 mL/kg or more of local anesthetic may be required for segmental analgesia for feline ovariohysterectomy. Clinical Relevance: The volume required is greater than the volume injected epidurally in previous studies and could increase the risk of producing hemodynamic side effects.