Paravertebral brachial plexus block in sheep: a cadaveric and in vivo study

The Objective of the present study was to evaluate paravertebral brachial plexus block in sheep. A group of 13 healthy sheep with 20.10 ± 2.20 kg weight and five months of age were used. In phase I, in five sheep, an insulated needle attached to a nerve stimulator was directed to the location of C6, C7, C8 and T1 nerves and a 1.50 mL of a solution containing 1:1 methylene blue 1.00% and lidocaine 1.00% was injected at each site. Then, the cervical and thoracic areas were dissected and assessed in the cadavers. In phase II, cervical paravertebral block with 2.00% lidocaine and subsequent assessments were done in eight live sheep. Cadaveric evaluations revealed dye spread in C6 to T1 nerves: 61.75 ± 5.50, 72.75 ± 9.18, 40.75 ± 2.99 and 18.75 ± 3.30 mm, respectively. In three sheep, dye distribution in the anterior mediastinum was observed. In phase II, the onsets of anesthesia were determined within 10 and 15 min for sensory and motor blocks, respectively. Anesthesia at axillary, musculocutaneous, radial and ulnar skin sites and motor block lasted for 67.50 ± 15.80, 63.70 ± 16.00, 55.00 ± 21.70, 56.70 ± 19.70 and 76.40 ± 24.30 min, respectively. In three sheep, no anesthesia was observed for radial and ulnar skin sites. In conclusion, paravertebral brachial plexus block in sheep provided an acceptable block for the upper parts of the elbow joint, however, it was not effective and reliable for more distal structures.