Preliminary Investigations of Pain and Analgesia Assessment in Horses Administered Phenylbutazone or Placebo After Arthroscopic Surgery

Authors

  • M. RAEKALLIO DVM, PhD,

    Corresponding author
    1. Faculty of Veterinary Medicine, Department of Clinical Sciences, University of Helsinki, Finland; Animal Health Trust, Newmarket, Suffolk; Department of Clinical Veterinary Medicine, University of Cambridge, Cambridge, England; Department of Surgery and Radiological Sciences, University of California, Davis, CA
      Faculty of Veterinary Medicine, Department of Clinical Sciences, PO Box 57, FIN-00014, University of Helsinki, Finland.
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  • P.M. TAYLOR MA Vet MB, PhD, DVA, Diplomate ECVA, MRCA, MRCVS,

    1. Faculty of Veterinary Medicine, Department of Clinical Sciences, University of Helsinki, Finland; Animal Health Trust, Newmarket, Suffolk; Department of Clinical Veterinary Medicine, University of Cambridge, Cambridge, England; Department of Surgery and Radiological Sciences, University of California, Davis, CA
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  • R.C. BENNETT MA, VetMB, CertVA, MRCVS

    1. Faculty of Veterinary Medicine, Department of Clinical Sciences, University of Helsinki, Finland; Animal Health Trust, Newmarket, Suffolk; Department of Clinical Veterinary Medicine, University of Cambridge, Cambridge, England; Department of Surgery and Radiological Sciences, University of California, Davis, CA
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Faculty of Veterinary Medicine, Department of Clinical Sciences, PO Box 57, FIN-00014, University of Helsinki, Finland.

Abstract

Twenty-five horses undergoing arthroscopic surgery were studied to develop a schemeor assessing pain in horses while investigating the effects of phenylbutazone (PBZ) analgesia. Fifteen of the 25 horses received PBZ 4 mg/kg intravenously (IV) before surgery and 2 mg/kg (IV) every 12 hours thereafter until 60 hours; the remaining 10 (placebo group) were given a corresponding volume of saline. In both groups, venous blood samples were collected for catecholamine, β-endorphin, and Cortisol assays before premedication and up to 72 hours after surgery. Postoperative pain was evaluated by measuring predefined behavioral and physiological variables. A total postoperative pain severity index (TPPSI) was calculated using all variables. There were no differences between PBZ and placebo groups in plasma β-endorphin or catecholamine concentrations, but the TPPSI was higher in the placebo group than in the PBZ group, suggesting that perioperative treatment with PBZ has some analgesic benefit. This study shows the difficulties associated with pain assessment in horses.

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