A Two-Point Ultrasound-Guided Injection Technique for the Transversus Thoracis Plane Block: A Canine Cadaveric Study.

The transversus thoracis plane (TTP) block desensitizes the intercostal nerves that run through this plane, providing analgesia to the ventral thoracic wall. Two canine cadavers were used to assess the feasibility of the transverse approach for the TTP (t-TTP) under ultrasound guidance to inject a solution at the third and sixth intercostal spaces. Eight cadavers were used to compare the spread and number of intercostal nerves that were stained when a low volume (LV) 0.5 mL kg-1 or a high volume (HV) 1 mL kg-1 of a dye-lidocaine solution was injected into the same hemithorax, injecting the volume equally at these intercostal spaces using the transverse approach. Fisher's exact test and Wilcoxon signed-rank test were used to contrast the spread of the different volume solutions. The injectate spread along the TTP after all injections, dying a median number (range) of 3 (2-5) and 6 (5-6) nerves with LV and HV, respectively (p = 0.011). The two-point injection of HV, using the t-TTP approach, is a feasible technique that provides a consistent staining from T2 to T7 intercostal nerves. The injection of HV instead of LV increases the spread and enhances the number of stained intercostal nerves.

Description of a novel ultrasound-guided approach for a dorsal quadratus lumborum block: a canine cadaver study.

OBJECTIVE: To describe an ultrasound-guided approach to the dorsal aspect of the quadratus lumborum muscle (D-QL) and to evaluate the spread of methylene blue dye in canine cadavers. STUDY DESIGN: Prospective, experimental anatomical study. ANIMALS: A total of 12 canine cadavers. METHODS: The ultrasonographic landmarks and injection technique for the D-QL approach were determined in two cadavers. Correct needle tip position was confirmed by computed tomography. Bilateral ultrasound-guided injections were performed in 10 cadavers between the QL muscle, the vertebral body and the ventrocaudal aspect of the transverse process of the first lumbar vertebra (L1) using two volumes of methylene blue: low volume (LV) 0.3 mL kg-1 or high volume (HV) 0.5 mL kg-1. Staining of the main thoracolumbar trunk, dorsal and ventral branches of the thoracic (T) and lumbar (L) spinal nerves, sympathetic trunk and epidural space were assessed following dissection. Data between groups were compared using Mann-Whitney U test. Data are presented as median (range). RESULTS: The ventral branches of spinal nerves T12, T13, L1, L2, L3 and L4 were stained in 10%, 70%, 100%, 90%, 60%, 0% and 30%, 100%, 100%, 100%, 50% and 30% after LV and HV injections, respectively. Multisegmental spread of the sympathetic trunk was found on 3 (3-4) and 5 (3-6) vertebral spinal levels following LV and HV injections, respectively (p = 0.005). The T13 segment of the sympathetic trunk was stained after all HV injections. Epidural spread was found in 20% and 30% of LV and HV injections, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: The injection of HV versus LV dye using the D-QL approach provided more consistent staining of the thoracolumbar nerve structures which innervate the abdominal wall and viscera. Clinical studies are required to evaluate the analgesic efficacy of the D-QL block for abdominal procedures in dogs in vivo.

Description of an Ultrasound-Guided Transverse Approach to the Transversus Thoracis Plane Block and Evaluation of Injectate Spread in Canine Cadavers.

Transversus thoracis plane (TTP) block has demonstrated to produce analgesia in humans undergoing median sternotomy. The objectives of the study were to describe an ultrasound-guided transverse approach to the transversus thoracis plane (t-TTP) and to evaluate the spread of two injectable volumes in canine cadavers. Two cadavers were used to describe relevant gross anatomy of the ventral thoracic area and sonoanatomy between the fifth and sixth costal cartilages. Then, eight cadavers were used to describe the ultrasound-guided injection into the TTP and were dissected to evaluate the injectate spread and the intercostal nerves staining with two different dye-lidocaine volumes: low volume (LV) 0.5 mL kg-1 and high volume (HV) 1 mL kg-1. To compare the spread between both volumes the Fisher's exact test and Wilcoxon signed-rank test were used. The solution spread along the TTP after all injections, staining a median number (range) of 3 (2-4) and 4 (3-5) nerves with LV and HV, respectively (p = 0.014). The injection of HV versus LV increases the number of stained nerves. Ultrasound-guided t-TTP is a feasible technique that provides staining of several intercostal nerves with a single injection site, so it could be useful to provide analgesia to the ventral chest wall.