Table 1.

Chronicity and type of pain

Pain	Details
Chronicity of pain
Acute pain	• Typically persists for <3 mo.
	• Associated with tissue damage.
	• Usually episodic with periods without pain.
	• Tends to last a predictable period, have no progressive pattern and subsides as healing occurs.
	• Tends to respond well to pharmacologic therapy: titrating analgesics against pain intensity usually works well.
Chronic pain	• Often defined as any painful condition that persists for >3 mo (8).
	• Usually initiated by tissue injury but is perpetuated by neurophysiologic changes, which take place within the peripheral and central nervous system leading to continuation of pain once healing has occurred.
	• Severity is often out of proportion with the extent of the originating injury.
	• More likely to result in functional impairment and disability, psychologic distress, sleep deprivation, and poor QOL than acute pain.
	• The pain experience may be affected substantially by mood, stress, and social circumstances.
	• May not respond well to analgesics, including opioids, except early in the course of treatment.
Recurrent pain	• Acute pain from tissue injury, which may occur over long periods of time (e.g., pain from needling fistulas, intradialytic steal syndrome, intradialytic headaches, and cramps).
	• Patient will also be free from pain for long periods.
	• More intrusive on everyday life than “acute pain.”
Type of pain
Nociceptive pain	• Results from tissue damage in the skin, muscle, and other tissues, causing stimulation of sensory receptors.
	• May be described as sharp or like a knife and often felt at the site of damage (e.g., joint pain from dialysis-related arthropathy).
	• With stimulation of visceral nociceptors, may be experienced as dull, aching, and poorly localized (e.g., gut ischemia).
	• Tends to respond to analgesics.
Neuropathic pain	• Results from damage to the nervous system resulting in either dysfunction or pathologic change.
	• May be felt at a site distant from its cause (e.g., in the distribution of a nerve).
	• Common descriptors include burning, shooting, and electrical.
	• May be associated with episodes of spontaneous pain, hyperalgesia, and allodynia; the presence of allodynia is pathognomonic.
	• Examples include peripheral neuropathy. Severe pain associated with limb ischemia and calciphylaxis tend to have substantial neuropathic components.
	• Responds poorly to analgesics and typically requires adjuvant therapy such as anticonvulsants (gabapentinoids or carbamazepine) and tricyclic antidepressants.

QOL, quality of life.