Pain

Notes

## Basic introduction

  • The subcommittee on taxonomy of the International Association for the Study of Pain (IASP) defined pain as “unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage”[a]
  • McCaffery's 1968 definition of pain is that 'Pain is whatever the experiencing person says it is, existing whenever he says it does”[b]
  • Poor management of pain can result in[c]:
  • Decreased physical and mental functioning
  • Lethargy
  • Depression
  • Insomnia
  • Pain that lasts for more than 3 months despite the treatment efforts is said to be chronic pain

## Pathogenesis of pain

  • Depending on the clinical characteristics, pain can be categorized generally into:
  • Nociceptive
  • Neuropathic
  • Psychogenic
  • Mixed
  • Idiopathic pains.
  • Nociceptive pain
  • is transmitted via classical pain receptors (also known as nociceptive receptors)
  • These receptors can be excited by thermal, mechanical and chemical stimuli to produce:

|||Visceral pain (that is usually “referred” pain)

|||Deep somatic pain (that is poor localized and dull)

|||Superficial somatic pain (that well localized and sharp).

  • Neuropathic pain
  • Results from conditions that affect any part of nervous system
  • When peripheral nervous system is affected the resultant pain is usually described with various words such as “pins and needles”, “burning,” “tingling,” “electrical,” or “stabbing,”
  • Psychogenic pain
  • Also known as psychalgia or somatoform pain
  • It results from mental, emotional, or behavioral factors.
  • Phantom pain
  • It is a form of neuropathic pain from a part of the body that has either been lost or from which the brain no longer receives signals.
  • Breakthrough pain
  • It is a form of pain that occurs in between two dose intervals of analgesics
  • With selective COX-2 inhibitors such, as celecoxib and meloxicam, inhibition of COX-2 provides therapeutic effects, as with other NSAIDs.
  • COX-1 activities responsible for gastric and renal side effects with NSAIDs are not markedly affected by COX-2 hence they cause fewer incidences of related side effects. Their main drawback is that they increase risks of thrombotic events such as myocardial infarction and stroke.
  • Management of pain needs to start with non-opioid analgesics and climb up the ladder to powerful opioids (as per the WHO analgesic ladder for cancer pain)
  • Other methods of management of pain include:
  • Physiotherapy
  • Chiropractic
  • Acupuncture
Symptoms
  • Pain
Diagnosis
  • Clinical review
Differential
  • Not applicable
Prevention
  • Treatment of underlying cause(s)
Reference
  1. Merskey, H. (1991). The definition of pain. European psychiatry
  2. McCaffery, M. (1968). Nursing practice theories related to cognition, bodily pain, and man-environment interactions. University of California Print. Office
  3. Control of pain in adults with cancer; Scottish Intercollegiate Guidelines Network - SIGN (November 2008).
Management
  • Pain due to biliary colic:
  • Morphine causes muscular spasm and should be avoided or be used with antispasmodics
  • Pethidine
  • Phenazocine
  • NSAIDs (aspirin, indomethacin, diclofenac etc.)
  • Glycerol trinitrate
  • Glucagon
  • Pain due to diabetic neuropathy
  • Management of diabetic mellitus
  • Anti-depressants (mostly tricyclic anti-depressants)
  • Anti-epileptics
  • Lignocaine
  • Pain due to during menstruation (dysmenorrhea)
  • NSAIDs [e.g. aspirin, ibuprofen; indomethacin, mefenamic acid; piroxicam etch]
  • Hyscine –N-butyl bromide
  • Alverine
  • Drotaverine
  • Camylofin
  • Otilonium bromide
  • Oral contraceptives.
  • Pain in cancer patients
  • Treatment follows 3-step 'analgesic ladder’
  • First step: Non-opiod analgesics like paracetamol, aspirin, and other NSAIDs
  • Second step:
  • Weak opiod analgesics like:

|||Codeine

|||Dextro-propoxyphene

|||They are generally used together with non-opiod analgesics and adjuvant drugs

  • Strong opiod analgesics like:

|||Oral morphine

|||Pethidine.

  • Pain, postherpetic neuralgia: see under postherpetic neuralgia.
  • Pain in postoperative cases
  • Morphine [pre-operative, peri-operative and post-operative]

|||Fentanyl

|||Pethidine

|||Diamorphine

  • NSAIDs that are used together opiod analgesics immediate post-operatively

|||Diclofenac

|||Piroxicam

|||Ketorolac

|||Other NSAIDs

  • Local anaesthetics
  • Nerve blocks
  • Local infiltration of anaesthetics at the site of operation
  • Central nerve block administered epidurally or intrathecally (mostly with bupivacaine)
  • Mixture of local anesthetic and opiod analegics epidurally or intrathecally.
  • Pain in renal or urethral conditions
  • Opiod analgesics without muscular spasm side-effect e.g. pethidine
  • NSAIDs
  • Treatment of underlying causes
  • Central post-stroke pain (CPSP)
  • Anti-depressants
  • Anti-epileptics
  • Mexiletine
  • Lignocaine
  • Pain due to bone metastasis
  • Corticosteroids
  • Radiotherapy
  •  
  • Pains due to muscle spasm

Muscle relaxants such as diazepam together with NSAIDs.

  • Pain due to nerve blocks
  • Transcutaneous electrical nerve stimulation (TENS)
  • Pain due to nerve compression
  • Corticosteroids such as dexamethasone that reduce edema around the tumors
  • Pain due to nerve irritation
  • Amitriptyline
  •  
  • Pain due to gastric distension
  • Antacid with anti-flatulent
  • Gastro-kinetics like domperidone, levosulpiride
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