Different volumes of injectate using electrostimulator and blinded techniques for brachial plexus block in dogs

Abstract

To compare different volumes of injectate using electrostimulator (ES)-guided and blind brachial plexus blockade (BPB) techniques in dogs. Prospective, randomised, blinded study. Fifty-eight healthy adult purpose-bred beagle dogs. Animals were randomised into 4 groups based on the volume of methylene blue 0.1 per cent administered for BPB, three using ES technique: E1 (0.2 ml/kg, n=22), E2 (0.6 ml/kg, n=22), and E3 (1.0 ml/kg, n=14), and one using blinded technique B4 (1.0 ml/kg, n=14). After euthanasia, the axillary region was dissected and nerves identified by a blinded evaluator. Success was defined as 3/4 nerves stained, or presence of dye in the tissue immediately surrounding the plexus. There were no significant differences between groups when total nerve count, adjacent staining, success rate (92.8-100 per cent), or rate of haematoma were evaluated. The musculocutaneous nerve was significantly more targeted in B4 than E1 and E2, but not E3. Electrostimulator-guided BPB using lower volumes of injectate had similar success rate as the blinded technique using higher volume, thus, lower volumes can be used without compromising success. When an ES is not available, the blind technique with 1 ml/kg is also acceptable. However, when performing an ES-guided BPB, volumes as low as 0.2 ml/kg can be used. As volume is increased, the musculocutaneous nerve becomes more likely to be targeted.

Evaluation of an ultrasound-guided technique for axillary brachial plexus blockade in cats

“…25,26 A recent study compared the efficacy of different volumes of LA using electrolocation or a blind guided-technique to block the BP in canine cadavers. 23 It was concluded that under electrolocation the administration of a lower volume of injectate (0.2 ml/kg) had a similar success rate than the blinded technique using a higher volume of LA (1 ml/kg). As was mentioned above, with the use of US-guided techniques volumes as low as 0.15 ml/kg can be successfully employed in dogs.…”

“…A dangerously high plasma concentration can also be reached following an accidental intravascular injection or by an increased absorption from the injection site. 22,23 Blind approaches to the BP and large volumes of LA (1 ml/kg) are commonly used in veterinary medicine. The relatively large volume of LA necessary to achieve an effective block when blind techniques are used can lead to discomfort and an increased risk of side effects or overdose.…”

“…Possible complications include haematoma due to vessel laceration or puncture, pneumothorax, diaphragmatic hemiparesis (secondary to phrenic nerve block), intrathoracic injection and nerve damage. 7,23 In a recent study, two different positions for an US-guided axillary BP blockade were compared in feline cadavers. An axillary approach with the cat in dorsal recumbency and with the forelimb to be blocked abducted 90° was found to be the safest technique, as no complications were reported.…”

A rat model of nerve stimulator-guided brachial plexus blockade

“…This model differs from previously reported BPB models that did not discuss complications or reported relatively high complication rates. 5,15 The possible reasons for these differences included that the anatomical characteristics of the rat BP and the NS-guided technique improved the safety of the rat BPB model. The rat model of NS-guided BPB is a feasible, safe, effective and reproducible model.…”

“…Some regional anesthesia models have been developed in rats, cats, dogs and sheep. [3][4][5][6][7] Sciatic nerve blockade models in rats are the most widely used animal models in experimental studies because of their simplicity and reproducibility. However, a sciatic nerve block only provides dorsal limb anesthetization of the hind limb, whereas it cannot provide complete anesthetization of the hind limb (i.e., the dorsal and ventral limb) without including a femoral or saphenous nerve block (ventral limb anesthetization of the hind limb).…”