Responses to Pain and Autonomic Nervous System

Study Notes

The autonomic nervous system activates the fight-or-flight response when it interprets pain signals from the brain
Physiologic responses to pain include increased heart rate, respiratory rate, and blood pressure
Patients in pain may exhibit behaviors such as grimacing, moaning, and verbalizing pain or withdrawing

Most pain experienced in hospitals is acute pain
Acute pain follows the normal pathway for pain from nociceptor activation to the brain
Examples of acute pain include postoperative pain, renal colic pain, bone fractures, and pain in childbirth
Acute pain is temporary, and its cause is known and treatable; it subsides when healing takes place

Chronic pain is defined as pain that persists or recurs for more than 3 to 6 months
Chronic pain may be nociceptive (e.g., osteoarthritis) or neuropathic (e.g., nerve damage)
Neuropathic pain causes unusual sensations such as burning, shooting pain, and abnormal sensations
The cause of chronic pain is often unknown, and treatment may or may not be helpful in relieving the pain
Examples of chronic pain include cancer, arthritis, peripheral vascular diseases, and traumatic injuries

Chronic noncancer pain is persistent pain that interferes with sleep and function, resulting in possible disability and loss of health and normal lifestyle
Intractable pain is pain that cannot be relieved and has no known effective treatment
Phantom limb pain is an example of chronic neuropathic pain

Treatment of chronic pain often requires a multidisciplinary approach involving pain specialists and healthcare teams
Pharmacological options for neuropathic pain include serotonin and norepinephrine reuptake inhibitors, antiepileptics, and tricyclic antidepressants
Other treatment options for chronic pain include lidocaine patches, tramadol, capsaicin 8% patches, and strong opioids