What is the definition of pain?
Pain is an unpleasant sensory and emotional experience associated with actual or potential tissue damage (subjective and influenced by biological, psychological, and social factors).
What are the main classifications of pain?
- Acute pain
- Chronic pain
- Nociceptive pain
- Neuropathic pain
- Psychogenic pain
What are common pain terminologies?
- Allodynia: pain from non-painful stimulus
- Hyperalgesia: increased pain response
- Paresthesia: abnormal sensation (tingling)
- Referred pain: pain felt elsewhere
- Radiating pain: spreads from source
What is Gate Control Theory?
Pain signals are modulated in the spinal cord; non-painful stimuli (e.g., rubbing) can “close the gate,” reducing pain transmission to the brain.
What is the difference between nociceptive, neuropathic, and psychogenic pain?
- Nociceptive: tissue damage (e.g., injury, inflammation)
- Neuropathic: nerve damage (burning, shooting)
- Psychogenic: psychological origin
Difference between acute and chronic pain?
- Acute: short-term, protective, resolves with healing
- Chronic: >3 months, persists beyond healing, often complex
What is the basic pain pathway?
- Transduction (stimulus → electrical signal)
- Transmission (via spinal cord)
- Perception (brain interprets pain)
- Modulation (inhibition/amplification)
Mechanism of action of opioid analgesics?
Bind to opioid receptors (mu, kappa, delta) in CNS → inhibit pain transmission and alter perception.
Acute adverse effects of opioids?
- Respiratory depression
- Sedation
- Nausea/vomiting
- Constipation
- Hypotension
Chronic adverse effects of opioids?
- Tolerance
- Dependence
- Constipation (persistent)
- Hormonal suppression
How do opioids relieve pain?
- Block pain signals in CNS
- Increase pain threshold
- Alter emotional response to pain
How does liver failure affect opioid use?
- Reduced metabolism → drug accumulation
- Increased risk of toxicity and overdose
- Dose adjustments required
Aim of general anaesthetic?
- Loss of consciousness
- Analgesia
- Muscle relaxation
- Amnesia
How does opioid tolerance develop?
Repeated use → receptor desensitisation → higher doses needed for same effect.
Pharmacodynamics of opioids?
- Act on CNS receptors
- Reduce neurotransmitter release
- Decrease pain signal transmission
Signs of opioid overdose?
- Respiratory depression
- Pinpoint pupils
- Unconsciousness
- Bradycardia
Nursing management of opioid overdose?
- Airway support (ABC)
- Administer naloxone
- Oxygen therapy
- Monitor vitals
- Prepare for repeated naloxone doses
Mechanism of action of naloxone?
Competitive opioid antagonist → displaces opioids from receptors → reverses effects.
Side effects of naloxone?
- Acute withdrawal symptoms
- Agitation
- Hypertension
- Tachycardia
What are NSAIDs and how do they work?
Non-steroidal anti-inflammatory drugs inhibit COX enzymes → reduce prostaglandins → decrease pain and inflammation.
Effects and risks of NSAIDs?
- Pain relief + anti-inflammatory
- Risks: GI bleeding, renal impairment, cardiovascular risk
Role of paracetamol in chronic pain?
- Mild–moderate pain relief
- Minimal anti-inflammatory effect
- Often used as first-line therapy
Benefits of combining opioid and non-opioid analgesics?
- Better pain control
- Lower opioid doses required
- Reduced side effects
What are adjunct pain medications? Give examples.
Medications used alongside analgesics:
* Antidepressants (e.g., amitriptyline)
* Anticonvulsants (e.g., gabapentin)
* Corticosteroids
