Chapter 44 pain management

Transduction

A painful stimulus, such as an injury, activates pain receptors and is converted into an electrical signal.

Transmission

The pain signal travels through peripheral nerves and the spinal cord to the brain.

Perception

The brain recognizes and interprets the signal as pain.

Modulation

The nervous system increases or decreases pain signals through inhibitory or facilitating pathways.

Gate-control theory

Stimulating larger sensory fibers, such as A-beta fibers, can reduce the transmission of pain signals carried by smaller fibers. This helps explain why massage, rubbing an injured area, or applying certain forms of skin stimulation may reduce pain.

Acute pain

Usually begins suddenly

Often associated with injury, surgery, or illness

Usually serves as a warning of tissue injury

May cause increased pulse, blood pressure, or respirations

Priorities include relief and identifying the cause

Chronic pain

Persists or continues over time (more than 3-6 months)

May be associated with long-term conditions

Can continue to affect function and quality of life

Vital signs may be normal even when pain is severe

Priorities include improving function, sleep, activity, and quality of life

Episodic pain

Occurs in episodes rather than continuously

Cancer pain

Associated with cancer, cancer treatment, or its effects

• Pain from metastatic disease

Somatic nociceptive pain

Arises from skin, muscles, bones, or connective tissue

• Fracture or muscle injury

Visceral nociceptive pain

Arises from internal organs

• Abdominal pain

Neuropathic pain

Results from nerve damage or dysfunction

• Peripheral neuropathy

Nociplastic pain

Associated with altered pain processing without clear evidence of tissue damage or a lesion of the somatosensory system explaining the pain

• Some chronic widespread pain conditions 

Breakthrough cancer pain 

A temporary flare of pain that occurs even when baseline cancer pain is relatively well controlled.

Numeric Rating Scale (NRS)

Patient rates pain from 0 (no pain) to 10 (worst pain imaginable). Appropriate for patients who understand and can use numbers. 

Wong-Baker FACES Scale

Uses facial expressions to help patients communicate pain intensity. The patient should select the face that best represents their pain.

Visual Analog Scale (VAS)

The patient marks a point along a line representing the level of pain.

PAINAD, Abbey, and NOPPAIN

Behavioral tools used when patients cannot reliably communicate their pain, including some patients with dementia or cognitive impairment.

Nonopioids

Used for many types of mild to moderate pain. NSAIDs also reduce inflammation.

• Examples: acetaminophen, aspirin, ibuprofen, naproxen, and ketorolac.

Opioids

act on receptors in the brain and spinal cord to modify pain perception. 

Used for moderate to severe pain when appropriate. Require careful monitoring for sedation, respiratory depression, and other adverse effects.

• Examples: morphine, codeine, hydromorphone, fentanyl, oxycodone, and hydrocodone.

Adjuvants (coanalgesics)

Often used for neuropathic pain or to enhance other pain treatments.

• Examples: gabapentin, nortriptyline, certain corticosteroids, and other medications with pain-relieving properties.

Acetaminophen

• Action: Reduces pain and fever but does not significantly reduce inflammation. 

• Major risk: Liver injury (hepatotoxicity). 

NSAIDs

Examples: ibuprofen, naproxen, aspirin, and ketorolac. 

Action: Inhibit cyclooxygenase (COX), reducing prostaglandin production and inflammation. 

Important risks: 

• Gastrointestinal irritation and bleeding. 

• Reduced renal blood flow and kidney injury. 

• Potential allergic reactions, including in some patients with aspirin sensitivity or asthma. 

Tolerance

The same dose produces less effect over time, so a higher dose may be needed for the same effect.

Physical dependence

The body adapts to regular opioid use; sudden discontinuation can cause withdrawal.

Opioid use disorder (OUD)

A problematic pattern of opioid use that causes significant impairment or distress.

Multimodal analgesia

combines medications or therapies with different mechanisms of action to improve pain control and potentially reduce the dose and adverse effects of any one medication.

Patient-controlled analgesia (PCA)

Allows the patient to self-administer preset doses using a programmed pump. Monitor sedation and respirations.

Topical analgesics

Applied to the painful area; generally act locally. Monitor for skin reactions.

Transdermal analgesics

Absorbed through the skin into the bloodstream for systemic effects. Follow medication-specific instructions.

Epidural analgesia

Medication is delivered into the epidural space. Monitor respiratory status, blood pressure, motor function, and the catheter site.

asses sensation from toes up to shoulders

local injection

uses medication to temporarily block nerve signals or reduce inflammation in a specific target area, providing rapid relief without causing unconsciousness.

perinural infusion

a medical technique that delivers local anesthetics through a small, flexible tube (catheter) placed next to a peripheral nerve or nerve plexus.

intrathecal pump

is a small, hockey-puck-shaped medical device surgically implanted under the skin of the abdomen. It continuously delivers medication directly into the cerebrospinal fluid in the intrathecal space surrounding the spinal cord

Pain specialist

Evaluates complex or difficult-to-control pain

Palliative care team

Helps manage symptoms and improve quality of life in serious illness

Hospice team

Focuses on comfort and quality of life near the end of life