Pain Management Flashcards
(29 cards)
Definition of pain.
An unpleasant sensory + emotional experience associated with actual or potential tissue damage or describe in terms of such damage.
How is pain classified?
Duration: acute / chronic
Site of injury: nociceptive / neuropathic / nicoplastic
How does one differentiate between acute and chronic pain?
Acute: duration < 6 weeks, pain is associated with trauma, surgery or acute illness. Usually limited to areas of damage and resolves with healing.
Chronic: duration > 6 weeks, pain no longer associated with normal tissue healing process, persists beyond usual course of acute illness/injury
Clarify the meaning of the following terms:
- nociceptive pain
- neuropathic pain
- nociplastic pain
Nociceptive - pain arises from actual or threatened damage to non-neural tissue and is due to the activation of nociceptors
Neuropathic - pain caused by a lesion/disease of the somatosensory nervous system
Nociplastic - pain arises from altered nociception despite no clear evidence of actual or threatened tissue damage causing activation of peripheral nociceptors
Describe the quality and localisation of somatic nociceptive pain.
Quality - sharp, dull, aching, throbbing
Localised
Describe the quality and localisation of visceral nociceptive pain.
Quality - gnawing, squeezing, cramping
Localisation - diffuse, poorly localised and referred pain
Describe the quality, localisation and associated symptoms of neuropathic pain.
Quality - burning, electric shocks, allodynia
Localisation - dermatomal or diffuse
Associated symptoms - tingling, pins + needles, numbness , itching
What is meant by the term “hyperanalgesia”?
Increased pain from a stimulus that normally provokes pain.
What is meant by the term “allodynia”?
Pain due to a stimulus that does not normally provoke pain.
Outline the management of chronic pain.
Physician can prescribe medication - gabapentinoids (gabapentin + pregabalin), low dose TCA (amitriptyline), SNRIs (venlafaxine + duloxetine)
Physiotherapist
Psychologist/psychiatrist
Describe the component of the analgesic ladder.
Simple analgesics - paracetamol, aspirin, NSAIDS
Weak opioids - tramadol, codiene, dihydrocodiene
Strong opioids - morphine, oxycodone, fentanyl, diamorphine
Explain the MOA of NSAIDs.
Cause inhibition of COX enzymes which are crucial in the synthesis of prostaglandins, therefore reduce conversion of arachidonic acid into prostaglandins, reducing inflammation, pain and fever
COX 1 - housekeeping enzyme, assist with physiological functions (renal blood flow, mucosal integrity, platelet function)
COX 2 - play a role in inflammation and pain (induceable, expressed when tissue tissue damage occurs)
List examples of NSAIDs
Inbuprofen, diclofenac, indomethacin, ketorolac
What are the side effects of NSAIDs?
COX 1: Gastric irritation, renal dysfunction, platelet dysfunction
COX 2: Bronchospasm, hepatotoxicity, myocardial infarction
Why is prolonged NSAID use a problem in asthmatics? Explain fully.
When COX enzymes are inhibited, there’s an accumulation of arachidonic acid which gets shunted into LOX pathway.
LOX converts arachidonic acid into leukotrienes which results in bronchospasms, thereby worsening asthma symptoms
How does long term use of COX 2 inhibitors increase the risk of myocardial infarction?
COX 2 plays a role in production of prostacyclin in vascular endothelial cells - vasodilators and anti-thrombotic.
COX 1 produced thromboxane in platelets which is pro-thrombotic, causing platelet aggregation and vasoconstriction.
Therefore, selective COX 2 inhibitors reduced prostacyclin while thromboxane production is maintained, leads to pro-thrombotic + vasoconstrictive state (increased risk of MI)
Provide examples of long acting and short acting opioids.
Long - morphine (takes 20 min for effect but lasts 4-6 hours)
Short - fentanyl and its derivatives (takes 3 min for effect but lasts 20 min)
Usually given together
What are the side effects of opioids?
Nausea + vomiting
Constipation
Urinary retention
Itchiness/pruritis
Respiratory depression
Sedation
Histamine release (morphine)
Bradycardia
Muscle rigidity
Which drug can be given when suspecting opioid overdose? And what are the side effects of this drug?
Naloxone - opioid antagonist
Side effects:
- arrhythmias
- pulmonary oedema
- hypertension
- anti-analgesic
Most opioids act on which receptors?
MOP - mu receptors located in the CNS
What are the major + useful effects of opioids?
Centrally mediated analgesia (decreased neural discharge + intense in nature)
Decreased sympathetic response
Sedation (can contribute to anaesthesia + in very high doses, LOC)
Cough suppression (methadone + codeine)
Outline the uses of opioids in anaesthesia.
Intraoperative analgesia (mainly fentanyl + morphine)
Pre-emptive analgesia
Dampening intubation response (alfentanil)
Additive to LA in neuraxial blockade
Target controlled infusion of remifentanil
Opioid based anaesthesia in case of VCS instability (trauma, emergency, cardiac surgery)
Morphine can be administered IV, IM and orally. When is each mode chosen?
IV - intraoperative analgesia, post op in high care + ICU setting, patient controlled analgesia (PCA) pump
IM - post op in ward, given 4-6 hourly, labour
Orally - severe chronic pain, palliative care, cancer pain
How is codeine metabolised?
Pro drug - metabolised by liver in to morphine
