Intro to Pain Management Flashcards
negative consequences of pain
- hyperalgesia
- sympathetic stimulation
- decreased appetite
- increased anesthetic drug requirements
- serious behavioral, nuerohumoral, metabolic and immunological effects
- unseen changes to CNS
definition of pain
an unpleasant sensory and emotional experience with actual or potential tissue damage
how is pain perceived
- throughout CNS, primary afferent nerve fibers provide info to the higher centers of the brain
- most animals have sensory afferent nerve fibers that respond to noxious stimuli
- protective means for reflexive withdrawal to noxious stimuli
adaptive pain-inflammatory
spontaneous pain and hypersensitivity to pain in response to tissue damage and inflammation
occurs with tissue trauma, injury, surgery
adaptive pain-nociceptive
transient pain in response to noxious stimulus
small aches and pains that are relatively innocuous and that protect the body from the environment
allodynia
- pain caused by a stimulus that does not normally result in pain
- manifestation of peripheral nerve and tissue injury that induces changes in CNS
analgesia
absence of pain in response to stimulation that would normally be painful
anesthesia
medically induced insensitivity to pain
the procedure may render the patient unconscious (general anesthesia) or consist of local anesthesia
dysphoria
a state of anxiety or restlessness, often accompanied by vocalization
hyperalgesia
- an increased response to a stimulus that is normally painful and reduced threshold for pain
maladaptive pain-neuropathic
spontaneous pain and hypersensitivity to pain in association with damage to or a lesion of the nervous system
maladaptive pain-central neuropathic pain
pain initiated or caused by a primary lesion or dysfunction in the CNS
“central pain”
multimodal analgesia
use of more than one drug with different actions to produce optimal analgesia
peripheral neuropathic pain
pain initiated or caused by a primary lesion or dysfunction in the peripheral nervous system
preemptive analgesia
administration of an analgesic before painful stimulation
wind-up pain
- perceived increase in pain intensity over time when a painful stimulus is repeatedly delivered above a critical rate
- frequency dependent increase in excitability of spinal cord neurons (afferent C fibers) - central sensitization
nociception
- process of detection of potentially or actually damaging stimuli and the transmission of that information to the brain
- includes five processes:
- transduction, transmission, modulation, projection, perception
transduction
the conversion of noxious stimuli to an AP at the level of the nociceptors
transmission
the propagation of APs by primary afferent neurons to the spinal cord
modulation
process by which nociceptive info is augmented or inhibited
projection
delivery of nociceptive information from the spinal cord to the brain
perception
integration of the nociceptive information by the brain
overall conscious emotional experience of pain
nociceptors
unspecialized nerve cell endings that initiate the sensation of pain, sense and transduce electrical signals at the site of tissue disruption
nociceptive afferents
- transmitted to the dorsal horn of the spinal cord via primary sensory A-beta, A-gamma and c nerve fibers
- respond to heat, cold, mechanical and chemical stimuli
peripheral sensitization
localized inflammation at site of tissue injury, in peripheral tissues, causes hyperexcitability of nociceptors due to a reduction in threshold and an increased responsiveness to noxious stimuli
chronic pain
pain which lasts beyond the expected time period of healing
acute pain
usually temporary and has a specific causes such as surgery, injury or infection
painful chemical/physical stimuli to APs
- sensory pain receptors located on peripheral ends of sensory nerve fibers convert painful chemical or physical stimuli in APs
- these APs cause gated ion channels to open causing an influx of Na or Ca ions to diffuse across a diffusion gradient leading to depolarization of cell membrane and an AP
- pain receptors respond to stimuli that have the potential to cause cell damage
release of inflammatory mediators leads to peripheral sensitization by three main mechanisms:
- depolarization of pain sensing nerve endings
- lowering the threshold in which depolarization occurs in primary afferent nerves
- vasodilation and increased permeability of blood vessels that results in an increased number of leukocytes and inflammatory mediators at site of injury
somatosensory cortex is responsible for:
- discrimination of pain signals
- recognition, learning and memory of painful experiences
somatic pain
pain related to the wall of the body cavity
musculoskeletal
visceral pain
pain that is often poorly localized and associated with mechanical/chemical/thermal stimuli or ischemia
accompanied by changes in somatic muscle tone and autonomic responses
assessing pain in cats
- posture, orientation in a cage, facial expression, loss of normal behaviors and response to palpation of a surgical site should be evaluated
simple descriptive pain scales
- first pain scales to be used in animals
- 3 to 5 point scale with answers ranging from mild, moderate to severe
- very basic and not validated
University of Melbourne Pain Scale
- numerical rating scale
- assesses different behavioral and physiological indices to categorize pain after surgery in dogs
Colorado State University canine and feline acute pain scales
- numerical pain scales
- used clinically
- may fail to capture the full details of a case
visual analog scale (VAS)
- designed to improve assessment by trying to capture the subtle nuances of pain that may go unrecognized with the use of other scales
- semi-objective scale that consists of a 100 mm horizontal line that represents the painfulness of a patient (no pain-0, worst pain possible-100)
- very simple to use and provides assessor info on trends in patient’s pain level and treatment
- prone to observer variability and bias
Glasgow University Veterinary School
- composite pain scoring system for pain assessment in dogs
- validated and reliable
- questionnaire that examines numerous behavioral traits and then a pain score is derived
- six categories and 30 descriptors on the form
- descriptors are ranked numerically within each category according to pain severity
preemptive perioperative analgesic administration
should be instituted before surgery and application of noxious stimuli
benefit of decreased drug requirement during maintenance and recovery of anesthesia
multimodal therapeutic plan
should be instituted and includes the use of drugs that are directed at treating specific mechanisms of pain
allows for reduction in the dose of each drug used while also reducing potential side effects or toxicity
