Pain management / Flashcards
How can pain be classified?
Based on duration: acute, chronic and acute on chronic
Based on nature: nociceptive, neuropathic, mixed, visceral, malignant
What is acute pain?
Physiologic response to tissue damage
Responds to traditional medicine model
Up to 3-6 months
What are the problems in assessing acute pain?
Taxonomies of postoperative pain does not adequately describe pain profile - multidimensionality and dynamics through 24 hour day
What are the challenges in management of acute pain?
Older age - more sensitive to opioids
Ethnicity
Psychological issues
Type of surgical procedure
The use of pre-emptive analgesics
Genetics: gene polymorphism
What is the impact of acute pain?
- Increased hospital stay or frequent readmissions
- Reduced QoL
- Impaired physical function
- Decreased functional recovery
- Increased comoplications
- Impaired sleep
What are the consequences of inadequate acute pain management?
Chronic pain may develop
50% suffer from chronic pain after common surgery
What is chronic pain?
Recurrent pain, lasting beyond course of acute illness, over 3-6 months
Adversely affecting patient’s well being
What are the areas that are impacted by chronic pain?
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
What is the treatment approach for chronic pain?
Underlying cause and pain disorder, outcome is often pain control, not cure
What is nociceptive pain?
Caused by activity in neural pathways in response to potentially tissue-damaging stimuli
What is neuropathic pain?
Initiated by primary lesion or dysfunction in nervous system
What are the peripheral mechanisms in pathophysiology of pain?
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
What are the central mechanisms of pain ?
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
What receptors and NTs involved in pain modulation?
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
What is the WHO pain ladder?
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