Comparison between two approaches for the transversus abdominis plane block in canine cadavers

ObjectiveTo compare the dye distribution following either two lateral abdominal or one lateral abdominal and one subcostal ultrasound-guided transversus abdominis plane (TAP) injections of a clinically relevant volume of dye solution in dogs.Study designRandomized cadaveric study.AnimalsA total of eight canine cadavers.MethodsOn one side of each cadaver, two TAP injections were performed on the lateral aspect of the abdomen (approach LL), caudal to the last rib and cranial to the iliac crest. On the contralateral hemiabdomen, one subcostal (caudal to the costal arch) and one lateral abdominal injection (between last rib and iliac crest), were performed (approach SL). Side allocation was randomly determined. A spinal needle was introduced in-plane to the transducer for each injection of methylene blue (0.25 mL kg^?1). All cadavers were dissected to assess dye distribution and number of stained target nerves.ResultsAll injections were performed in the TAP. The proportion of target nerve staining was 53.5% versus 80.4% with approaches LL and SL, respectively (p = 0.005). Approach LL stained the first lumbar (L1) spinal nerve in 100% of injections and ninth thoracic (T9), T10, T11, T12, T13 and L2 were stained in 0%, 0%, 37.5%, 62.5%, 87.5% and 87.5% of injections, respectively. Approach SL stained T11, L1 and L2 in 100% of injections and T9, T10, T12 and T13 were stained in 37.5%, 87.5%, 75% and 62.5% of injections, respectively. Approach SL resulted in greater staining of nerves cranial to T12 compared with approach LL. The two approaches were equivalent in staining nerves caudal to T12.Conclusions and clinical relevanceApproach SL provided a broader distribution of the injected solution than approach LL, which may result in a larger blocked area in live animals undergoing celiotomy.     

Ultrasound-guided modified subcostal transversus abdominis plane block and influence of recumbency position on dye spread in equine cadavers

ObjectiveTo describe and evaluate an ultrasound-guided modified subcostal approach for the transversus abdominis plane (TAP) block in horse cadavers in lateral or dorsal recumbency.Study designProspective, experimental cadaveric study.AnimalsStudy of one preserved foal and eight fresh adult horse cadavers.MethodsThe lateral and ventral abdominal wall of a preserved cadaver was dissected to identify the muscles and nerves. A unilateral standard TAP block technique was performed (60 mL of methylene blue dye–bupivacaine) on a fresh cadaver in right lateral recumbency. A modified subcostal technique was performed on the opposite side using a linear ultrasound transducer and in-plane approach. Injection points (two 30 mL dye) were at the level of the TAP (between the rectus abdominis and transversus abdominis muscles and ventral to the cutaneous trunci muscle) perpendicular to: 1) the mid-point between the xiphoid cartilage and umbilical scar; and 2) at a point between the caudal and middle thirds of the abdomen measured from the first injection point to the umbilical scar. The modified subcostal approach was performed in seven additional cadavers in both hemiabdomens, with three cadavers in lateral and four cadavers in dorsal recumbency. Ultrasound guidance was used with all injections.ResultsThe standard approach stained the sixteenth to eighteenth thoracic nerves (T16–T18). The modified subcostal approach performed in lateral recumbency provided greater spread (T9–T17) than dorsal recumbency (T12–T18) (p = 0.016).Conclusions and clinical relevanceThe modified subcostal TAP approach resulted in extensive staining exceeding the standard approach. The nerves stained are consistent with production of ventral abdominal wall anesthesia in horses. Clinical studies are needed to verify these findings.     

Evaluation of the potential efficacy of an ultrasound-guided adductor canal block technique in dog cadavers

Objective

To evaluate an ultrasound-guided technique for adductor canal (AC) block by describing the distribution of methylene blue around the AC, popliteal fossa, saphenous, tibial and common fibular nerves in dog cadavers.

Lumbar erector spinae plane block: an anatomical and dye distribution evaluation of two ultrasound-guided approaches in canine cadavers

ObjectiveTo examine the anatomy of the lumbar epaxial region and to describe two different ultrasound-guided approaches for the lumbar erector spinae plane (ESP) block in dogs.Study designAn anatomical and experimental cadaver study.AnimalsA group of 19 canine cadavers.MethodsThe anatomy was described following dissection of two cadavers. Bilateral ultrasound-guided ESP injections with 0.4 mL kg^–1 of contrast dye were performed in 17 adult Beagle cadavers using either transversal (TVS) or parasagittal (PST) approaches. Computed tomography was performed to measure the total length of the contrast dye column and the epidural, intravascular, hypaxial and intra-abdominal migration. Dissections were performed to assess the spread of the contrast dye and to determine the degree of staining of the dorsal branches of the spinal nerves (DBSN). Mann–Whitney U and chi-square tests were used to compare data between groups.ResultsUsing both techniques, the contrast dye was observed within the ESP compartment. There was no difference in the total length of the contrast dye column between TVS and PST approaches (p = 0.056). Using the TVS approach, multisegmental staining of the DBSN was visible with 100% (17/17) of injections, while complete staining of the DBSN was achieved at 94% of the injection sites. Using the PST approach, these values were 29% (5/17) and 23% (4/17), respectively. The TVS approach stained more DBSN than the PST approach (p = 0.001), with a median (range) of 2 (2–3) versus 0 (0–3) DBSN, respectively. Using the TVS approach, epidural and intravascular migration were present in 2/17 (p = 0.485) and 3/17 (p = 0.227) injections, respectively.Conclusions and clinical relevanceBoth ultrasound-guided approaches resulted in a spread of the contrast dye within the ESP compartment. Although there were no differences in the total length of the contrast dye column, the TVS approach was superior to the PST approach in staining DBSN.     

Description of an ultrasound-guided thoracic paravertebral block technique and the spread of dye in dog cadavers

Objectives

To describe an ultrasound-guided thoracic paravertebral block and determine the distribution after injection of two volumes of methylene blue in dog cadavers.