Pain management / Flashcards

1
Q

How can pain be classified?

A

Based on duration: acute, chronic and acute on chronic
Based on nature: nociceptive, neuropathic, mixed, visceral, malignant

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2
Q

What is acute pain?

A

Physiologic response to tissue damage
Responds to traditional medicine model
Up to 3-6 months

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3
Q

What are the problems in assessing acute pain?

A

Taxonomies of postoperative pain does not adequately describe pain profile - multidimensionality and dynamics through 24 hour day

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4
Q

What are the challenges in management of acute pain?

A

Older age - more sensitive to opioids
Ethnicity
Psychological issues
Type of surgical procedure
The use of pre-emptive analgesics
Genetics: gene polymorphism

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5
Q

What is the impact of acute pain?

A
  • Increased hospital stay or frequent readmissions
  • Reduced QoL
  • Impaired physical function
  • Decreased functional recovery
  • Increased comoplications
  • Impaired sleep
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6
Q

What are the consequences of inadequate acute pain management?

A

Chronic pain may develop
50% suffer from chronic pain after common surgery

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7
Q

What is chronic pain?

A

Recurrent pain, lasting beyond course of acute illness, over 3-6 months
Adversely affecting patient’s well being

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8
Q

What are the areas that are impacted by chronic pain?

A

QoL: physical functioning, ability to perform daily activities, work, recreation
Social consequences: marital/family relations, intimacy, social isolation
Socioeconomic: healthcare costs, disability, lost work days
Psychological morbidity: depression, anxiety, anger, sleep distrubances, low self esteem

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9
Q

What is the treatment approach for chronic pain?

A

Underlying cause and pain disorder, outcome is often pain control, not cure

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10
Q

What is nociceptive pain?

A

Caused by activity in neural pathways in response to potentially tissue-damaging stimuli

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11
Q

What is neuropathic pain?

A

Initiated by primary lesion or dysfunction in nervous system

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12
Q

What are the peripheral mechanisms in pathophysiology of pain?

A

Peripheral nerve injury >
- Sensitisation by spontaneous activity by neurons, lowered threshold for activation, increased response to given stimulus
- Formation of ectopic neuronal pacemakers along nerve and increased expression of Na+ channels and VG Ca2+ channels
- Adjacent demyelinated axons can have abnormal electrical connections channels and increased neuronal excitability

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13
Q

What are the central mechanisms of pain ?

A

Sustained painful stimulus results in spinal sensitisation
- Increased spontaneous activity of dorsal horn neurons, reduced activation thresholds and enhanced responsiveness to synaptic inputs
- Expansion of receptive fields, death of inhibitory interneurons
- Central sensitisation mediated by NMDA receptors that further release excitatory amino acids and neuropeptides
- Sprouting of sympathetic efferents into neurons and dorsal root and ganglion cells

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14
Q

What receptors and NTs involved in pain modulation?

A

Opioid receptors: mu and kappa
Alpha 2 adrenergic receptors:
GABA - glycine receptors
Glutamate/NMDA
Ca2+ channels: in excess
Na channels: in excess
Neurotransmitters
Substance P, CGBP, NO

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15
Q

What is the WHO pain ladder?

A

Step 1: mild pain - non-opioid, with/without adjuvant analgesic
Step 2: mild-moderate pain - opioid, plus non-opioid, with/without adjuvant analgesic
Step 3: moderate-severe pain - opioid, plus non-opioid, with/without adjuvant analgesic

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16
Q

What is multimodal therapy?

A

Simultaneous administration of 2 or more pharmacological agents, each with distinct MOAs
Whenever possible, clinicians should use multimodal pain management therapy

17
Q

What is the rationale behind multimodal therapy?

A
  • Targeting different pathways
  • Synergism of multiple agents
  • Allows dose reduction of individual agents, reduces risk for adverse effects
18
Q

What are some perioperative techniques in pain management?

A

Non-opioid systemic analgesics e.g. paracetamol, oral NSAIDs, injectable NSAIDs
Systemic opioids e.g IM injections, IV injections, PCA with/without background infusion
Central regional analgesia e.g. intrathecal or epidural opioid
Peripheral regional analgesia e.g. peripheral nerve blocks, infiltration of incisions

19
Q

What are treatment goals?

A
  • Reduce and manage pain
  • Optimise medication use
  • Increase function and productivity
  • Reduce level of disability
  • Stop cure seeking
  • Reduce unnecessary healthcare
  • Prevent relapse
  • Minimise costs
20
Q

What are pain treatments with increasing invasive natures?

A

Psychological/physical approaches
Topical medications
Systemic medications
Interventional techniques

21
Q

What are non-pharmacological options for pain management?

A

Biofeedback
Relaxation therapy
Physical and occupational therapy
Cognitive/behavioural therapies
Acupuncture
TENS

22
Q

What are the different aims for mechanistic approaches to pain therapy?

A

Decrease inflammatory response e.g. NSAIDs, local anaesthetics, steroids
Decrease conduction e.g. local anaesthetics, opioids, gabapentin
Prevent centralisation e.g. COX2, opioids, ketamine
Increase inhibition e.g. SSRIs, TCAs
Modify expression e.g. anxiolytics

23
Q

How do pharmacological agents affect pain differently?

A

Target different areas
Peripheral sensitisation - before signals reach dorsal horn: local anaesthetics, topical analgesics, opioids
Central sensitisation - at the dorsal horn: anticoagulants, opioids
Descending modulation - leads to body responding to pain: anticonvulsants, opioids, antidepressants

24
Q

Opioid use for pain management

A

Select group benefit from opioids > pain reduction, improved physical and psychological functioning
These have minimal side effects and show increased activity levels and less pain
Others do poorly and have tolerance and side effects

25
Q

Ketamine action indication, side effects?

A

Action: NMDA receptor anatogonist
Indication: Protective analgesia, opioid tolerant patients
Side effects: dysphoria, nightmares, psychedelic effects

26
Q

What are types of interventional pain management?

A

Epidural/perineural injections of local anaesthetics
Sympathetic nerve blocks
Neural ablative procedures
Peripheral nerve stimulation
Spinal cord stimulation

27
Q

What is the gate control theory?

A

Sensory impulses are greater than pain impulses, the gate closes, preventing pain signals reaching the brain

28
Q

What is spinal cord stimulation?

A

Implanted device in epidural space that sends low level electrical impulses directly into the spinal cord to relieve pain
Stimulates pain inhibiting nerve fibres masking painful sensation with tingling sensation
Also works by:
- directly inhibiting spinothalamic neurons
- descending modulatory effects
- alteration of sympathetic activity
- neurochemical modulation