Lumbosacral (LS) epidural volume can be based on body weight (BW) or length from the occipital crest to the sacrococcygeal space (LE), but calculated volumes can differ in dogs < 15 kg. We compared the rostral spread using CT imaging and responses to nociceptive stimulation.
Methods: Six female Beagles (BW: 7.5–10.2 kg; LE: 46–56 cm) randomly assigned in a crossover block design to two treatment groups received: group BW- 0.2 mL kg-1 and group LE- 0.05 mL cm-1 ( < 50 cm) or 0.07 mL cm-1 (50 to < 70 cm) at LS. Dogs were mask-induced with isoflurane, positioned in sternal recumbency, and an epidural catheter advanced into LS 1–2 cm. The volume of injectate (1:1 mixture of bupivacaine 0.5% and iopamidol 30%) was administered over 20 seconds, and within 5 minutes the vertebral column was scanned to determine the number of vertebrae reached by the contrast. The dog was recovered and kept in sternal recumbency until fully conscious to start assessing analgesia from the tail to the thoracic limb using a hemostat or clamp, motor function, indirect blood pressure, heart rate, respiratory rate, and rectal temperature until return to normal. Comparisons between groups were completed with a mixed linear model (p < 0.05).
.jpg "Flavio A. V Freitag, DVM, MSc, DVSc photo")