Page 9 - BSAVA Guide to Pain Management in Small Animal Practice

BSAVA Guide to Pain Management in Small Animal Practice

VetBooks.ir surgeons take an oath to ensure the welfare of are sub ect to a high degree of plasticity and
alteration depending on the disease status
animals committed to my care , as per the Royal
of the animal. owever, it is useful to
College of Veterinary Surgeons RCVS . In
addition, most small animals are companion appreciate the ma or steps in the transmission
animals, and rely on us to protect their welfare, of pain to the central nervous system CNS , as
including their day to day re uirements and this allows the udicious application of
freedom from pain. It has been argued that multimodal analgesia A . A refers to
animal pain is worse than human pain. Animals the concept of using multiple analgesic agents
are thought to live in the now and, unlike a acting at di erent sites in the pain pathway. In
human being in pain, are not aware that the pain this way, the dose of any one agent, and hence
is only temporary and will be relieved given the potential side e ects, is kept to a minimum,
time or treatment Robertson, . yet the analgesic e ect is often enhanced
In addition to the ethical arguments, there leading to better clinical pain control. An
are a number of well recogni ed physiological example of A in small animal practice is the
conse uences of untreated pain. hese include use of a centrally acting opioid given as part of
a premedication protocol for a dog admitted
■ Release of catecholamines and pituitary for dental extractions followed by a suitable
hormones and, therefore, a catabolic state dental block using local anaesthetic. In this
leading to weight loss and potential wound case the block is designed to stop
breakdown transmission of the pain sensation from the
■ yperglycaemia and insulin resistance periphery, whereas the opioid works centrally
■ Leucocytosis neutrophilia to decrease the pro ection and appreciation of
■ Cytokine production any pain within the CNS.
■ Poor immune function he physiology of pain can be divided into
■ Poor appetite four processes transduction, transmission and
■ Impaired respiratory function pro ection , modulation and perception.
■ Increased blood pressure.
Transduction is the process by which
It is also likely that failure to manage pain a erent nerve endings participate in translating
may lead an animal to self traumati e, noxious stimuli e.g. a pinprick into nociceptive
potentially leading to the development of impulses igure .1 . Signal transduction can
chronic pathological pain. only be initiated by a mechanical, thermal or
In general, these physiological changes are chemical stimulus. hese stimuli can be
likely to lead to an increase in postoperative converted into an electrical signal at a
complications in surgical patients with poorly nociceptor via a stimulus gated ion channel.
controlled pain, as well as client dissatisfaction Nociceptors are present on speci c nerve
with the veterinary practice. Indeed, the endings spread throughout the body and
economic and time losses alone could be respond to potentially painful inputs, thus
signi cant as complications are generally allowing pain perception and locali ation.
treated by the practice at a reduced rate. i erent a erent nerve bres see below have
di ering nociceptors. Aδ bres possess thermal
and mechanical nociceptors with higher
The physiological basis activation thresholds than A touch receptors.
of pain: neural pathways C bre nociceptors are polymodal receptors
with even higher activation thresholds than Aδ
and where they can be bre receptors and respond to all three stimulus
interrupted types. An example of such a nociceptor is the
transient receptor potential vanilloid 1 receptor
he ma or physiological pathways involved in RPV 1 , which responds to capsaicin in chilli
mammalian pain, although well characteri ed, peppers to give a burning sensation.

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