Anticholinesterase-resistant neuromuscular blockade in sheep given amino-steroid muscle relaxants |
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| Authors: | RE Clutton GM Lawson T Hems∼ MA Glasby |
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| Institution: | Department of Veterinary Clinical Sciences, Royal (Dick) School of Veterinary Studies, Easter Bush, Roslin, Midlothian EH25 9RG;*Princess Margaret Rose Orthopaedic Hospital, Frogston Road West, Edinburgh, EH10 7ED;∼Department of Trauma, John Radcliffe Hospital, Headington, Oxford;+Department of Anatomy, University of Edinburgh Medical School, Teviot Place, Edinburgh EH8 9AG |
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| Abstract: | Three cases of anticholinesterase-resistant neuromuscular blockade in sheep are described. Neuromuscular blockade produced with pancuronium (n = 2) and vecuronium was only temporarily antagonised with anticholinesterases and signs of residual block-muscular weakness, recumbency, hypoventilation, dyspnoea, dysphagia, 'fade' in evoked responses to repetitive nerve stimulation and rapid exhaustion of cranial nerve reflexes - were observed. Responses to repeated edrophonium and, or neostigmine injections were incomplete and shortlived. These complications probably arose because high loading doses, incremental injections (pancuronium and vecuronium) and infusion (pancuronium) created high plasma drug concentrations at antagonism. This occurred because the facial nerve-levator nasolabialis muscle unit used to monitor drug effects proved resistant to blockade. The effects of relative overdose were probably augmented by the sensitivity of sheep to non-depolarizing neuromuscular blocking agents and the relative insensitivity of monitoring blockade using tactile and visual evaluation of evoked responses. |
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