3. Physiology and Pathophysiology of Pain Flashcards
What is the definition of pain?
“An unpleasant sensory and emotional experience, associated with actual or potential tissue damage, or described in terms of such damage” International Association for the Study of Pain (ISAP)
What do Molony and Kent 1997 define pain as?
“An adverse sensory and emotional experience representing awareness by the animal of damage or threat to the integrity of its tissues… producing a change in physiology and behaviour directed to reduce or avoid the damage, reduce the liklihood of recurrence and promote recovery”
What is the definition of chronic pain?
“Pain lasting longer than one month, associated with a wide range of often subset behavioural disturbance” (Wiseman-Orr et al. 2004)
When is pain experienced?
Pain is a subjective emotion and can be experienced even in the absence of obvious external noxious stimulation. It is also influenced by behavioural experiences eg- fear, memory, emotional stress
What is the Cerebral Cortex and how does it work?
The seat of the conscious experience of pain. A noxious stimulus not only activated several cortical areas, but also, as the intensity of the stimulus increases, an increasing number of sub cortical and cortical areas.
Exerts ‘top-down’ control on almost all nociceptive relays within the the central nervous system
What types of pain are there?
Nociceptive, inflammatory, neuropathic and functional (Woolf, 2004)
What is nociceptive pain and how does it work?
Special receptors that only respond to noxious stimulus and generate nerve impulses which the brain interprets as pain.
Conscious experience of acute pain resulting from a noxious stimulus.
Mediated by a high-threshold nociceptive sensory system.
Following tissue trauma, changes in the properties occur and may also transmit ‘pain information’
What is inflammatory pain?
When tissue damage occurs despite the nociceptive defence system which usually occurs via trauma, surgery or inflammatory disease.
The aim is to protect the injured region so that it can heal as an adaptive protective response.
With an acute inflammatory response, the pain should go once the painful stimulus has gone. However if the pain is chronic, it may be persistent
What is neuropathic and functional pain?
Pain that develops following injury to the peripheral or central nerves.
Functional pain is a specific type of neuropathic pain (irritable bowel syndrome)
How does neuropathic pain work?
Nerve injury can disrupt the electrical properties , neurochemistry and central conductivity of neurons. Eg- limb amputation and sciatica.
Difficult to control with standard analgesia- rarely diagnoses in animals
What is cancer pain?
Cancer is common in cats and dogs however not much is known at managing cancer pain. The emotional response in humans plays a big part in cancer pain.
Acupuncture and transcutaneous nerve stimulation can help.
What is post surgical pain?
In humans, persistent pain, despite ‘routine’ administration of analgesics, is a problem (Kellet et al. 2006)
Believed to be primarily neuropathic.
A study by Wiseman et al, 2001 and 2004, found that dogs with persistent pain due to chronic inflammation, had altered behaviour that affected their quality of life
What is hyperalgesia?
An exaggerated and prolonged response to a noxious stimulus
What is allodynia?
A pain response of low intensity, normally to an innocuous stimulus eg- light to the touch
Why are pain assessments important?
Relates directly to anaesthesia. Key to effective pain management which is often difficult in animal patients.
At present, a positive response to appropriate analgesic therapy is probably the best marker for effective diagnosis of pain.
