Pain management Flashcards
definition of pain
“An unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage”
acute vs chronic pain
acute pain: new onset of pain
chronic pain: pain which is present for 3 months or more
basic pain physiology
two aspects to the experience of pain
- sensory: sensory signal is transmitted from the pain receptor
- affective: an unpleasant emotional reaction to the pain
pain is supposed to indicate underlyingtissue damage damage but can occurwithout this. it’s subjective and there are pain thresholds i.e allodynia- pain experienced with sensory inputs which do not normal cause pain like light touch
pain threshold and pain tolerance
pain threshold- the point at which sensory input is reported as painful
pain tolerance- a persons response to pain (i.e pt experiences little pain but is able to carry on DOAL whereas another person may expereince simlar pain and worry but take time off work and seek medical advice etc. so pain tolerance is influenced by biological, psychological and social factors
transmission of pain
- pain receptors (nociceptors) at the ends of nerves detect damage or potential damage to tissues.
- nerve signals are transmitted along the afferent nerves to the spinal cord.
- afferent sensory nerves that transmit pain signals are part of the peripheral nervous system and are called primary afferent nociceptors.
Two groups of nerve fibres transmit pain: C fibres (unmyelinated and small diameter) – transmit signals slowly and produce dull and diffuse pain sensations A-delta fibres (myelinated and larger diameter) – transmit signals fast and produce sharp and localised pain sensations
signal then travels in the central nervous system, up the spinal cord (mainly in the spinothalamic tract and spinoreticular tract) to the brain where it is interpreted as pain, mainly in the thalamus and cortex.
The main sensory inputs that generate a pain signal are:
Mechanical (e.g., pressure)
Heat
Chemical (e.g., prostaglandins)
However, when directly measuring activity in the peripheral afferent sensory nerves: Pain can be experienced without activity in the primary afferent nociceptors
Activity in the primary afferent nociceptors can be detected without the patient experiencing any pain
referred pain
pain experienced in a location way from the site of tissue damage (i.e MI pain in left arm / left side of the jaw)
possible explanations for referred pain:
Nerves may share the innervation of multiple parts of the body (e.g., the heart and left arm)
Pain in one area amplifies the sensitivity in the spinal cord to signals coming from other areas
Activation of the sympathetic nervous system in response to pain results in pain in other areas
neuropathic pain
s caused by abnormal functioning or damage of the sensory nerves, resulting in pain signals being transmitted to the brain. Typical features suggestive of neuropathic pain are:
Burning Tingling Pins and needles Electric shocks Loss of sensation to touch of the affected area
how to measure pain
subjective experience
- VAS- visual analoguse scale
- numerical rating scale (NRS)
visual analogue scale (VAS)
involves asking the patient to rate their pain along a horizontal line, where the left end indicates no pain and the right end indicates the worst pain imaginable. The distance along that line can be measured to get a numerical value to represent the pain (e.g., 75mm along a 100mm line).
numerical rating scale
(NRS) involves asking the patient to rate their pain on a numerical scale of 0 – 10, with:
0 being no pain at all
10 being the worst pain imaginable
WHO analgesic ladder
step 1: non opioid meds i.e paracetamol, NSAIDS
step 2: weak opioids i.e codeine, tramadol
step 3: strong opioids: morphine, oxycodone, fentanyl, buprenorphine
adjuvant medications
other medication combined with the analgesic ladder for additional effect (or can be used seperately to manage neuropathic pain)
TCA- amitryptline
SNRI- duloxetine
anticonvulsant- gabapentin, pregabalin
topical capasicin cream (in chili peppers)
NSAIDS side effects
Gastritis with dyspepsia (indigestion) (*PPI prescribe)
Stomach ulcers
Exacerbation of asthma
Hypertension
Renal impairment
Coronary artery disease, heart failure and strokes (rarely)
NSAIDS contraindications
Asthma Renal impairment Heart disease Uncontrolled hypertension Stomach ulcers
NSAIDS and PPI
PPI (omeprazole, lansaprozole) are to be co-perscribed with NSAIDS to reduce the risk of GI side effects (i.e acid reflux, gastritis, stomach ulcers)
