Pain Management Flashcards by Srishti D

Why should we treat pain?

Avoid physiological effects of untreated pain
- Sympathetic response
- Reduced function
- Poor mobility
- Ineffective cough
Avoid psychological effects of untreated pain
Humane thing to do

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What is acute pain?

Pain of recent onset and probable limited duration

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What is chronic pain?

Pain persisting beyond healing of injury
Often no identifiable cause
Lasting for >3 months

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What is nociceptive pain?

Obvious tissue injury/illness
Physiological
Protective function

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What are the different types of nociceptive pain?

Superficial somatic
Deep somatic
Visceral

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What is neuropathic pain?

Nervous system damage/abnormality
Pathological
Doesn't have protective function
Tissue injury not obvious
Not well localised

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What are the positive features of neuropathic pain?

Allodynia

Hyperalgesia

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What are the negative features of neuropathic pain?

Hypoesthesia

Numbness

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What happens in the periphery to first cause pain?

Tissue injury > release of chemicals > stimulation of nociceptors > signal travels in A-delta/C fibres to spinal cord

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What happens to pain information in the spinal cord?

Dorsal horn 1st synapse - site of decussation

2nd nerve travels up spinal cord

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What happens to pain information in the brain?

Thalamus = 2nd synapse
Connections to many parts of brain
- Cortex
- Limbic system
- Brainstem

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Where does pain perception occur?

Cortex

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What does pain modulation involve?

Descending pathway from brain to dorsal horn

Usually decreases pain signal

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What is the mechanism of action of paracetamol?

Unclear but acts in CNS
Inhibits peripheral prostaglandin synthesis
Analgesic and antipyretic

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What are the indications for paracetamol?

Analgesia alone/in combination

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What are the adverse effects of paracetamol?

Hepatic necrosis in overdose

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What are the interactions of paracetamol with other analgesics?

Additive with NSAIDs

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What is the mechanism of action of NSAIDs?

Non-specific inhibition of COX-1 and -2 > inhibits prostaglandin synthesis
Analgesic, antipyretic, and anti-inflammatory

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What are the indications for NSAIDs?

Analgesia alone/in combination

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What are the adverse effects of NSAIDs?

Peptic ulceration
Renal impairment
Anti-platelet action
Bronchospasm in asthma
Exacerbation of CCF

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What are the interactions of NSAIDs with other analgesics?

Reduce opioid requirements by 20-40%

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What is the mechanism of action of opioids?

Mu opioid receptors to produce analgesia
Sites of action
- Peripheral nociceptors
- Dorsal horn
- Cerebral cortex
- Descending tracts

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What are the indications for opioids?

Severe acute pain

Cancer pain

What are the adverse effects of opioids?

Sedation
Respiratory depression
Nausea
Euphoria
Miosis
Bradycardia
Postural hypotension
Urinary retention

What are the interactions of opioids with other analgesics?

Caution with other sedative agents

What is the mechanism of action of tramadol?

Weak opioid effect | Inhibition of serotonin and noradrenaline reuptake

What are the indications for tramadol?

Moderate pain

What are the adverse effects of tramadol?

Hypertension Nausea and vomiting Ceiling effect for analgesia Lowers seizure threshold

What are the interactions of tramadol with other analgesics?

Risk of serotonin syndrome with other serotonergic agents

What are two examples of tricyclic antidepressants?

Amitriptyline | Nortriptyline

What is the mechanism of action of tricyclic antidepressants?

Inhibit reuptake of NA and serotonin into pre-synpatic terminals Inhibit cholinergic, histaminergic, alpha1-adrenergic, and serotonergic receptors Increases descending inhibitory signals

What are the indications for tricyclic antidepressants?

Neuropathic pain Depression Poor sleep

What are the adverse effects of tricyclic antidepressants?

Anti-cholinergic side effects Postural hypotension Liver dysfunction QTc prolongation and arrythmia

What other drugs do tricyclic antidepressants interact with?

Monoamine oxidase inhibitors Selective serotonin reuptake inhibitors Tramadol

What should you monitor when a patient is using tricyclic antidepressants?

Liver function ECG Nortryptiline levels

What is the mechanism of action of gabapentin/pregabalin?

Exact mechanism unknown Binds to alpha-2 delta protein subunit of high threshold voltage-dependent Ca channels > reduces Ca influx > reduces neurotransmitter release

What are the indications for gabapentin/pregabalin?

Focal seizures | Neuropathic pain

What are the adverse effects of gabapentin/pregabalin?

Sedation

What are the drug interactions of gabapentin/pregabalin?

Other sedative drugs

What should you monitor when a patient is using gabapentin/pregabalin?

Reduce dose in renal impairment | Can cause raised bilirubin

What is the mechanism of action of ketamine?

Antagonises NMDA receptors Descending monoaminergic pain pathways Voltage-sensitive Ca channels and opioid receptors in brain and spinal cord

What are the indications for ketamine?

Anaesthesia | Pain

What are the adverse effects of ketamine?

``` Sedation Hyper-salivation Tachycardia Dysphoria - Relatively contraindicated in psychiatric patients ```

What are the drug interactions of ketamine?

Other sedative drugs

What should you monitor when a patient is using ketamine?

Dysphoria

What is the mechanism of action of clonidine?

Alpha-2 adrenoceptor agonist

What are the indications for clonidine?

Sedation Analgesia Antihypertensive Addiction medicine for opioid withdrawal management

What are the adverse effects of clonidine?

Sedation Hypotension Bradycardia

What are the drug interactions with clonidine?

Other sedative agents

What should you monitor when a patient is using clonidine?

Rebound hypertension | Reduce dose in renal impairment

What is the gold standard in the measurement of pain?

Self reporting

What are the non-drug treatments for pain?

``` RICE - Rest - Ice - Compression - Elevation of injuries Nursing care Physiotherapy Surgery Acupuncture Massage Psychological - Explanation and reassurance - Input from social worker/pastor - Relaxation - Coping strategies ```

What are the drug treatments for mild nociceptive pain?

Paracetamol +/- NSAID

What are the drug treatments for moderate nociceptive pain?

Paracetamol +/- NSAID +/- opioids; eg: - Codeine - Oxycodone - Tramadol

What are the drug treatments for severe nociceptive pain?

Strong opioids/regional anaesthesia + paracetamol +/- NSAID Adjuvants - Alpha-2 agonists - NMDA antagonists

What are the drug treatments for neuropathic pain?

``` Traditional drugs may not be useful, especially NSAIDs and chronic opioids Use other drugs early - Amitriptyline - Carbamazepine - Gabapentinoids ```