Objective: To evaluate the onset time and duration of action of lidocaine, lidocaine-morphine, lidocaine-tramadol or bupivacaine for a neural blockade of the brachial plexus in fat-tailed lambs.
Study design: Prospective, randomized, crossover, experimental study.
Animals: Seven healthy female fat-tailed Ghezel lambs weighing 27.0 ± 2.2 kg (mean ± SD).
Methods: Each lamb was administered four treatments for brachial plexus block (BPB): lidocaine 2% (5 mg kg(-1)) (LID), lidocaine 2% combined with morphine (0.1 mg kg(-1)) (LIDMO), lidocaine 2% combined with tramadol (1 mg kg(-1)) (LIDTR) or bupivacaine 0.5% (1.25 mg kg(-1)) (BUP), for a total treatment volume of 0.25 mL kg(-1). The brachial plexus was located with a peripheral nerve stimulator, and the treatment volume was injected in increments. Treatments were randomized and separated by at least 7 days. Onset and duration of a sensory block of the distal thoracic limb were evaluated using superficial and deep pin pricks and pinching of the skin with haemostatic forceps.
Results: The mean duration of sensory block was 100 ± 38 minutes in LID, 103 ± 35 minutes in LIDMO, 79 ± 28 minutes in LIDTR, and 335 ± 134 minutes in BUP. The mean duration of sensory and motor blocks in BUP were significantly longer compared with other treatments (p < 0.05). No clinical signs of local anaesthetic toxicity were noticed, and the rectal temperature did not differ significantly from baseline values in any treatments.
Conclusions and clinical relevance: The addition of morphine or tramadol to lidocaine did not affect the duration of antinociception of lidocaine for brachial plexus block in fat-tailed lambs. Administration of bupivacaine provided a prolonged duration of action without obvious adverse effects.
Keywords: brachial plexus block; bupivacaine; lambs; lidocaine; morphine; tramadol.
© 2015 Association of Veterinary Anaesthetists and the American College of Veterinary Anesthesia and Analgesia.