pain and anesthesiology Flashcards
define pain
an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or describes in terms of such damage
characteristics of pain
- body’s warning system
- protects body from tissue damage
- perception is necessary for survival (but when it becomes maladaptive and outlasts its physiological usefulness it is pathological and becomes not just a symptom of disease/ trauma but a disease entity itself
what factors contribute to pain severity?
pathological mechanisms
- inflammation
- central or peripheral sensitization
History/ social
- Previous pain experiences
- Reaction to pain by significant other
Cognitive factors
- Interpretation of nociception
- Coping style
Emotional factors
- Fear of pain
- Degree of anxiety
The difference between nociception and pain
Nociception
- is a function of a specific sensory system
- This system is a warning system with an adequate stimulus
- Noxious stimulus threatens or damages normal tissue
- Nociception is modulated at spinal cord level and interpreted by higher cortical structures; resulting in discomfort and perception of pain
- third-person perspective
- stimulus related
- sensory discrimination
Pain
- is the result of network activity in the brain when nociception is modulated at spinal cord level and interpreted by higher cortical structures
- first-person perspective
- perception related
- suffering
describe nociceptive pain
- Pathological process in peripheral organ/tissue
- Pain projection into damaged body part or referred pain
- Pain caused by activation of nociceptive afferent fibres
- Also termed inflammatory pain because peripheral inflammation and inflammation mediators plays a major role in initiation and amplification
what is pain interpretation?
Pain perception is the final product of a complex information processing network and requires modulation from the cerebral cortex
Whether stimuli is perceived as painful depends on:
- Nature of stimuli
- Context in which it is experienced
- Individual’s memories and emotions
Classification of pain
Neuropathic pain
- Pain initiated or caused by a primary lesion or dysfunction in the peripheral or central nervous system
- Pathological process in the somatosensory system
- Pain projection into innervation territory
Complex regional pain syndrome
- Chronic arm or leg pain developing after injury, surgery, stroke or heart attack
- Cause is not well understood but may involve abnormal inflammation or nerve dysfunction
- It is complex neuropathic pain that follows soft-tissue or bone injury (type I) or nerve injury (type II) and lasts longer and is more severe than expected for the original tissue damage
Acute pain
- Somatic
o Transmitted via sensory fibres; discrete and intense
o Muscles, tendons, periostium, skin
- Visceral
o Transmitted via sympathetic fibres; diffuse poorly localised
o Organs and peritoneum
- Referred
o Pain perception in one part of the body that I actually caused in a different site
Angina radiating into the neck and left arm
what are the causes of neuropathic pain?
o Metabolism
DM
Beri-Beri
o Infections
Post herpetic neuralgia
HIV
Guillian-Barre
o Toxicity
Alcohol
Chemotherapy
Radiotherapy
o Trauma
SCI
Post surgery
o Multiple sclerosis, Syringomylenia, Post-Stroke pain
acute vs chronic pain
- Chronic: a disease entity on its own
- Disease with own aetiology, signs and symptoms
- Bio-psycho-social phenomenon
3 central questions to guide ax of pain
- What is the extent of the patient’s disease and physical impairment?
- To what extent is the patient’s disease impeding on usual activities?
- To what extent is the patient’s behaviour appropriate to the disease or injury?
what does a brief psychosocial screening during interview entail?
- Activities: how is the pain affecting you sleep/appetite/relationships?
- Coping: how do you cope/deal? What makes it better?
- Think: do you think your pain will get better?
- Upset: have you been anxious/depressed?
- People: how do people respond when you have pain?
what is chronic pain?
Traditionally pain lasting longer than 3 months
Persistent pain or pain that outlasts its physiological value
Persists beyond course of an acute disease or after a reasonable time for injury to heal
Bio-psycho-social problem
define hyperalgesia
- Increased response to a normally painful stimulus
define hyperaesthesia
- Increased sensitivity to stimulation
define allodynia
- Perception of a non-noxious stimuli as painful
define neural plasticity
- Property of the CNS and PNS that enables modification of function according to the alterations in conditions
define deafferentitation
- Elimination or interruption of afferent nerve impulses to the spinal cord by destruction of the afferent pathway
define hyperpathia
- Pain elicited by noxious stimuli that is delayed in onset and outlasts the stimulus duration and spreads beyond the site of the stimulus
define neuralgia
- Pain in the distribution of nerve(s)
define neuroma
- Peripheral nerve damage that initiates axon regeneration creating an area of hyperexcitability
How do we sense pain?
- In peripheral tissue, when (mechanical) damage occurs [stimulus] it’s transformed into electrical signal [transduction]
- This electrical signal is then carried up the nerve [transmission] to the CNS which starts at SC and goes to brain
- In brain we have perception of stimulus which is the emotional and sensory perception we have. Anything that goes together with the tissue damage, which can include tastes and smells we associate with it based on previous experiences
How brain contributes to pain
- Concurrent changes in brain
o Previously mentioned areas in the pain matrix
Maladaptive pain coping ability including substance abuse
Depression
anxiety
Name substances involved in inflammatory soup
- Helps nerves become more sensitive to dangerous stimuli
- Excites nerves to let you know that there is danger ahead
- Histamine
- Serotonin
- Bradykinin
- Adenosine-5-triphosphate
- Prostaglandin E2
- Sodium
- Potassium
- Hydrogen
- Pro-inflammatory cytokines
o IL-1B
o IL-6
o Nerve growth factor
o TNF-a - ‘neurogenic inflammation’/ ‘dorsal root reflex’
o Substance P
o Calcitonin gene-related peptide
o Neurokinin A
o Nitric Oxide
How SC can adapt to constant nociceptive stimuli and modulation of pain
- Inhibitory mechanisms that might immediately try to supress nociceptive stimulus from reaching the brain. This may be a protective response to stop one from overreacting to a small stimuli
o GABA
o Glycine
o Descending inhibitory pathways from the brain by supressing signal transmission from SC to brain
o Endogenous opioids
o Higher order brain functions
