Pain is an unpleasant and uncomfortable feeling that signals actual or possible tissue damage. It has both physical and emotional components, which is why different people experience pain differently. It may arise from injury, inflammation, nerve damage or internal disease.
According to the American Academy of Pain Medicine, pain is “an unpleasant sensation and emotional response to that sensation.” Dr. Don Ranney also describes pain as a perception, influenced not just by nerves but also by the mind. Pain can be triggered by harmful stimuli or even by conditions affecting the brain and spinal cord.
Types of Pain
Pain is broadly classified into two major categories.
1. Nociceptive Pain
Caused by stimulation of pain receptors (nociceptors) in tissues. Common examples include:
- Burns
- Bone fractures
- Appendicitis
- Post-surgical pain
- Heart ischemia (heart attack-related pain)
2. Neuropathic Pain
Caused by damage or disturbance in nerves or nerve pathways. Examples include:
- Diabetic neuropathy
- Nerve compression or nerve injury
- CNS lesions
Nociceptive pain is usually sharp and responds to normal painkillers, while neuropathic pain is chronic and more difficult to manage.
Pathophysiology
Pain begins when tissues are damaged by mechanical injury (cut, fall), heat or chemicals. This damage stimulates nerve endings, causing release of chemicals like:
- Potassium and hydrogen ions
- Serotonin
- Bradykinin
- Substance P
- Histamine
- Thromboxanes and leukotrienes
- Nerve growth factor
These chemicals cause inflammation, swelling and sensitivity at the site of injury. They activate nociceptors which send pain signals to the spinal cord. Neurotransmitters like glutamate and aspartate act on NMDA receptors and increase pain transmission.
Pain signals travel through spinal cord pathways such as:
- Spinothalamic tract
- Spinoreticular tract
- Spinomesencephalic tract
These pathways carry pain to the brain, where it is recognized and interpreted.
Clinical Presentation
Pain varies from person to person. It may be described by patients as:
- Sharp, dull or aching
- Burning or tingling
- Shooting or radiating
- Throbbing
- Electric shock-like
Non-specific symptoms associated with pain include:
- Anxiety
- Depression
- Fatigue
- Insomnia
- Anger or fear
Acute pain may present with temporary signs like:
- Increased heart rate
- High blood pressure
- Sweating
- Enlarged pupils
- Pale skin
Pain is always subjective, so the patient’s description and history are essential for proper assessment.
Management of Pain
Pain management depends on the type, severity and cause. It includes medicines and non-drug methods.
Management of Acute Pain
1. Non-Steroidal Anti-Inflammatory Drugs (NSAIDs)
These medicines block prostaglandins, reducing inflammation and pain.
- Aspirin: 325–650 mg every 4 hours
- Paracetamol: 650 mg every 6 hours
- Ibuprofen: 400 mg every 8 hours
2. Opioid Analgesics
Used for moderate to severe pain.
- Morphine group: Morphine, Hydromorphone, Oxymorphone
- Meperidine group: Meperidine, Fentanyl
- Methadone group: Methadone, Propoxyphene
- Agonist–antagonist drugs: Pentazocine, Butorphanol, Nalbuphine
- Opioid antagonist: Naloxone
Key notes:
- Morphine is a first-line drug for severe pain. May cause nausea and respiratory depression.
- Meperidine is less potent; its metabolite may cause tremors or seizures.
- Methadone is preferred for chronic and cancer pain.
- Naloxone reverses opioid overdose (0.4–2 mg IV/IM/SC).
3. Central Analgesics
- Tramadol: 50–100 mg
Useful for moderate pain and neuropathic pain. May cause seizures in rare cases.
Management of Chronic Pain
Depends on the underlying cause.
- NSAIDs for musculoskeletal pain
- Methadone for long-term cancer pain
- Epidural clonidine for severe, unresponsive pain
- Tricyclic antidepressants and anticonvulsants (for neuropathic pain)
Non-Pharmacological Measures
Non-drug approaches are important, especially for chronic pain.
Physical Methods
- Physiotherapy
- Heat or cold application
- Massage
- Hyper-stimulation techniques
- Nerve blocks
- Biofeedback
- Surgery (in selected cases)
Psychological Methods
- Counseling
- Stress management
- Hypnosis
- Behavioral therapy
- Relaxation techniques
- Art and music therapy
Social Support Techniques
- Community support groups
- Occupational therapy
- Self-help groups
Detailed Notes:
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