Medico veterinario

Veterinary Anaesthesia and Analgesia, 2009, 36, 173–179

doi:10.1111/j.1467-2995.2008.00445.x

RESEARCH PAPER

Castration of horses under total intravenous anaesthesia: analgesic effects of lidocaine
Karine G Portier* DVM, CertVA, MSc, PhD, DVSc, Laetitia Jaillardon* DVM, Elizabeth A Leece  BVSc, CertVA, Diplomate ECVAA & Catherine M Walshà BSc, BVSc, DVA, Diplomate ECVAA
´ ´ ´*Universite de Lyon, Lyon, France; Ecole Nationale Veterinaire de Lyon, Equine Department, Marcy L’Etoile, France  The Animal Health Trust, Lanwades Park, Newmarket, Suffolk, UK àVRCC Veterinary Referrals, Southfields, Laindon, Essex, UK

´ ´ ´ Correspondence: Karine G Portier, Universite de Lyon, Lyon F-69003, France; Ecole Nationale Veterinaire de Lyon, Equine Department, Marcy L’Etoile F-69280, France.E-mail: k.portier@vet-lyon.fr

Abstract Objective To evaluate the effects of local anaesthesia with lidocaine for castration of horses under intravenous anaesthesia. Study design Prospective, randomized, blinded clinical trial. Animals Fifteen equidae, scheduled to undergo castration under total intravenous anaesthesia, were randomly distributed in two groups. One group received lidocaineinjections (group L: two ponies, four horses, two donkeys) and the other received saline (group S: two ponies, three horses, two donkeys). Methods Behaviour, heart rate (HR) and respiratory rate (fR) were evaluated prior to anaesthesia. Body mass was measured using an electronic scale and testicular volumes were estimated. The animals were anaesthetized with acepromazine intramuscularly and romifidineintravenously followed 10 minutes later by ketamine. Following romifidine administration lidocaine or saline was administered subcutaneously along the incision line and by intratesticular and intrafunicular injection. Based on clinical observations (movement, fR, and cranial nerve reflexes) incremental intravenous doses of ketamine and romifidine were administered. HR, fR, oscillometric mean arterialblood pressure (MAP), duration of surgery, movement and additional doses

were recorded. Surgical conditions were assessed using a visual analogue scale (VAS) and a simple descriptive scale (SDS). Recovery was assessed by two assistants, unaware of treatment, acting separately using a VAS and a SDS. Group means were compared using Mann–Whitney and Wilcoxon tests and the Kruskal–Wallis signed ranktest for matched pairs used to compare groups at different points (p < 0.05). Results The number (median, range) of incremental doses (4 [1–5] compared to 1.5 [1–4]) and movements (1 [1–5] compared to 0 [0–1]) were higher (p = 0.01 for both) in the control group than in the lidocaine group. Groups were similar for other recorded variables. Conclusions and clinical relevance These results show theeffectiveness of lidocaine used as a local anaesthetic adjunct to intravenous anaesthesia in horses undergoing castration. Keywords castration, horses, nociception, TIVA. local anaesthesia,

Introduction It has been shown that castration under anaesthesia in ponies increases nociceptive activity (Murrell et al. 2003) and it is suggested that the prevention of nociception during surgery isbeneficial for recovery (Hellyer et al. 2007; Pyati & Gan 2007).
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Local lidocaine in castrated horses under TIVA KG Portier et al.

Several studies have shown that the administration of a local anaesthetic, lidocaine, decreases pain associated with this procedure in horses, piglets, calves and lambs (Wood et al. 1991; Stafford et al. 2002; Haga & Ranheim 2005; Haga et al. 2006). Despite thewidespread use of local anaesthetic for analgesia for performing castration in the standing horse (Green 2001), its use during castration under general anaesthesia is relatively rare in practice (Price & Nolan 2001; Price et al. 2002; Hughes et al. 2003). One study demonstrated that 75% of veterinary surgeons used local anaesthetics during standing castration whereas only 40% used it during...