Distribution Pattern of the Drug and Analgesic Area by Paravertebral Block Using a Nerve Stimulator in Dogs

Abstract

Summary:The aim of this study was to investigate the pattern of drug distribution and analgesic area of a paravertebral block using a nerve stimulator in dogs. Six healthy adult beagles were used in the study. After anesthesia was induced and maintained with isoflurane, a paravertebral block was performed at the 11th, 12th, and 13th thoracic spinal levels. A 3 ml solution consisting of contrast media mixed with bupivacaine and saline was injected at each spinal level. Proper needle placement was confirmed using the nerve stimulator and a CT scan was performed to assess the distribution of the contrast media. After completion of the paravertebral block and CT scan, tetanic stimulation was applied at the paramedian region of the umbilicus (umbilical region), outside of the umbilical region, outermost umbilical region, upper abdomen, lower abdomen, and control (contralateral of the umbilical region). Changes in the heart rate and mean arterial pressure were simultaneously assessed. The contrast media distributed into the paravertebral space in 33 of 36 injections (91.6%). The median (range) of the longitudinal distribution was 4 (3-5) vertebrae. The tetanic stimulation at the umbilical region caused significantly lower increases in heart rate and mean arterial pressure than those at the control. In conclusion, the probability that local anesthetics distributed into the paravertebral space was high. In dogs, the umbilical region was effectively blocked when the paravertebral blocks between the 11th and 13th thoracic spinal levels were performed using the nerve stimulator. Key words: dog, drug distribution, nerve block, nerve stimulator, paravertebral block