Investigations into pain and its clinical management, in dogs and cats

Student thesis: Doctoral ThesisDoctor of Philosophy (PhD)

Abstract

Five papers are submitted to support an application for the award of PhD by published work. These papers describe work carried out over a six-year period at the University of Bristol. The focus of all of the publications is the investigation of clinical pain mechanisms and strategies for its management in dogs and, to a lesser extent, cats in the United Kingdom. The publications employ a range of methodological approaches, as appropriate to the research question; and considered as a whole they examine clinical pain topics ranging from acute to persistent forms of pain, and from individual to population level.
On admission to the Royal College of Veterinary Surgeons, members promise and solemnly declare that “my constant endeavour will be to ensure the health and welfare of animals committed to my care” . However, historically acute perioperative pain has been undertreated by Veterinary Surgeons in a number of countries, including the UK. Persistent (“chronic”) pain in humans currently represents the one of the greatest healthcare burdens and significantly decreases quality of life in affected people yet is often poorly responsive to common analgesic interventions. Similarly, painful conditions such as osteoarthritis which cause persistent pain in people are common in dogs and cats and have been identified as one of the top three welfare issues in pet dogs. Robust examination of pain and analgesic strategies intended to manage pain in animals, and communication of the resulting findings to an appropriate audience therefore have the potential to improve welfare for a significant number of animals undergoing veterinary treatment; and this consideration has motivated the research presented within this work.
Paper 1 reports a evaluation of the analgesic efficacy of two opioid drugs with marketing authorisation for use in dogs in a highly clinically relevant model of orthopaedic surgery, within a standardised and pertinent anaesthetic management protocol. This research has contributed to an evidence base enabling, for example, the recommendation of full µ agonist opioids in preference to partial agonists for major surgery in dogs (Murrell, 2014), which would be expected to improve the provision of perioperative analgesia and animal welfare.
Paper 2 details a cross-sectional survey of perioperative analgesic prescribing practices amongst UK veterinary surgeons and draws comparisons with previous surveys. The results indicate significant improvement in the use of perioperative opioid and non-steroidal anti-inflammatory drugs for management of perioperative pain, and highlights areas such as local analgesia and postoperative administration of non-steroidal anti-inflammatory drugs to cats where prescribing could be improved.
Paper 3 considers the adverse events associated with administration of analgesics, specifically non-steroidal anti-inflammatory drugs. A number of challenges were encountered in accessing and interpreting the data which are discussed, however the work documents the state of our knowledge in respect of adverse event reporting in dogs and cats, and presents opportunities for further investigations.
Papers 4 and 5 resulted from a 3 year experimental investigation into changes in spinal cord processing of nociceptive stimuli in client owned dogs with osteoarthritis. Paper 4 details the development of a suitable technique in laboratory dogs to probe spinal nociceptive processing under general anaesthesia – a prerequisite for humane data collection in client owned animals. Electromyographic responses to nociceptive stimuli are recorded as a quantifiable estimation of spinal nociceptive processing. Paper 5 describes the application of the technique to a population of client owned animals diagnosed with pelvic limb osteoarthritis, and documents increases in nociceptive processing in affected animals, compared to a control group of unaffected client owned dogs. Additionally, in a subgroup of animals recruited, a technique for eliciting a form of endogenous analgesia (diffuse noxious inhibitory controls, DNIC) is described in dogs for the first time, and less effective DNIC is identified in animals affected by osteoarthritis. These results corroborate previously published evidence of widespread somatosensory sensitisation in dogs affected by osteoarthritis, and further identify that one mechanism which may contribute to sensitisation is a reduced efficiency of DNIC. These findings are consistent with investigations into people affected by osteoarthritis, and thus further validate canine osteoarthritis as a potential model for the human disease.
Considered together these five papers represent a significant contribution to our understanding of the management of pain in cats and dogs.
Date of Award26 Nov 2020
Original languageEnglish
Awarding Institution
  • The University of Bristol
SupervisorEmma J Love (Supervisor)

Keywords

  • Pain
  • Dog
  • Cat

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