Pain Management Flashcards
What are the 3 main questions to ask when classifying pain?
How long has the patient had pain? Acute, chronic or acute on chronic
What is the cause? Cancer or non-cancer
What is the pain mechanism? Nociceptive (physiological) or neuropathic (pathological)
Distinguish between acute and chronic pain
Acute: pain of recent onset and probable limited duration
Chronic: pain persisting beyond healing of injury, often no identifiable cause, lasting >3/12
Distinguish between cancer and non-cancer pain
Cancer pain: progressive, may be mixture of acute and chronic
Non-cancer pain: many different causes, can be acute or chronic
What is the mechanism of nociceptive pain and how can it be further classified?
Obvious tissue injury or illness (“physiological pain”)
Can be further classified into superficial somatic, deep somatic or visceral
Give a clinical description of nociceptive pain
Can be sharp, aching, dull, throbbing, cramping, pressure, etc
What is the mechanism of neuropathic pain?
Nervous system damage or abnormality (“pathological pain”); tissue injury may not be obvious
Give a clinical description of neuropathic pain
Burning, shooting +/- numbness, parasthesia
Not well localised
What are the 4 steps in the physiology of pain?
Periphery: tissue injury results in release of chemicals which stimulate nociceptors and result in propagation of signal in A-delta or C nerve to spinal cord
Spinal cord: dorsal horn is the “first relay station” where the A-delta or C nerve synapses (connects) with the second nerve, and the second nerve travels up the opposite side of the spinal cord
Brain: thalamus is the “second relay station” with connections to many parts of the brain including the cortex, limbic system and brainstem (pain perception occurs in the cortex)
Modulation: descending pathway from brain to dorsal horn, typically decreases the pain signal
Where is the abnormality in neuropathic pain?
Peripheral nerves
Spinal cord or brain
What peripheral or central changes can result in neuropathic pain?
Peripheral: damaged nerves (e.g. trauma, DM), abnormal firing of nerves
Central: changes in “wiring”, abnormal firing, loss of modulation
Sensitisation can occur in peripheral and central nervous system; persistent central sensitisation is a possibe mechanism for some chronic pain conditions
What is the mechanism of action of paracetamol (acetaminophen)?
Unclear but acts in CNS
Inhibits peripheral prostaglandin synthesis
Analgesic and antipyretic
What are the indications for paracetamol?
Analgesia either alone or in combination
What is the main AE of paracetamol?
Hepatic necrosis
Describe important drug interactions of paracetamol with other pain medications
Effects are additive with NSAIDs
What monitoring is indicated for paracetamol?
What is the mechanism of action of NSAIDs?
Non-specific inhibition of COX1 and COX2 to inhibit PG synthesis
Analgesic, antipyretic, anti-inflammatory
What is the indication for NSAIDs?
Analgesia alone or in combination
List 5 adverse effects of NSAIDs
Peptic ulceration
Renal impairment
Anti-platelet action
Bronchospasm in asthmatics
Exacerbation of CCF
Name one drug interaction of NSAIDs with other analgesics
Reduce opioid requirements by 20-40%
What monitoring considerations are important with NSAIDs?
Care with renal impairment or hypovolaemia
What is the mechanism of action of opioids?
What are the indications for opioids?
Severe pain
List 8 AEs of opioids
Sedation
Respiratory depression
Nausea
Euphoria
Miosis
Bradycardia
Postural hypotension
Urinary retention
What drug interactions occur with the use of opioids for analgesia?
Interacts with other sedative agents
What kind of monitoring is important with use of opioid analgesics?
Sedation, CV and respiratory
What is the mechanism of action of tramadol?
Weak opioid effect plus inhibitor of serotonin and noradrenaline reuptake (modulation)
List 3 advantages and one disadvantage of tramadol
Advantages: less respiratory depression, can be used with opioids and simple analgesics, not a controlled drug
Disadvantages: N+V
What is the mechanism of action of amitriptyline as an analgesic?
Increases descending inhibitory signals (tricyclic antidepressant)
Outline 3 advantages and one disadvantage of amitriptyline for analgesia
Advantages: cheap, safe in low dose, good for neuropathic pain, also treats depression and poor sleep
Disadvantages: anti-cholinergic side effects (glaucoma, urinary retention)
What drugs can be used for neuropathic pain Mx?
Amitriptyline
Anti-epileptics: carbamazepine, sodium valproate, gabapentin/pregabalin
Tegretol
Carbamazepine
Epilim
Sodium valproate
What is the mechanism of anti-epileptics as analgesics?
“Membrane stabilisers”; reduce abnormal firing of nerves
Summarise commonly used analgesics and the types of pain they are best for
What is the RAT approach to pain?
Recognise
Assess
Treat
What methods are commonly used for pain measurement?
Verbal (e.g. mild, moderate, severe)
Numerical (0 to 10)
Visual (VAS, “faces” pain scale)
What non-drug treatments can be used to manage pain?
RICE
Nursing care, physiotherapy
Surgery, acupuncture, massage, TENS
Psychological (explanation and reassurance, input from SW/pastor, relaxation, imagery, distraction, coping strategies)
Describe the types of drug treatments commonly used for mild, moderate and severe nociceptive pain
Mild: paracetamol (+/- NSAID)
Moderate: paracetamol (+/- NSAID) + codeine/oxycodone/tramadol
Severe: paracetamol (+/- NSAID) + morphine/oxycodone, regional anaesthesia, adjuvants (alpha 2 agonists, NMDA agonists)
How should neuropathic pain be treated?
Traditional drugs may not be as useful
Use other drugs early: amitriptyline, carbamazepine, gabapentinoids
Don’t forget non-drug treatments!
