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pain is highly complex and subjective experience that originates from CNS or PNS or both; has nociceptors
specialized nerve endings that detect painful sensations from periphery, transmit them to CNS
How do Nociceptors carry pain?
carry signal to 2 primary sensory (or afferent) fibers: A(gamma) and C fibers
A (gamma) fibers
myelinated, larger diameter so transmit pain signal rapidly to CNS; pain sensation is localized, short-term, sharp
unmyelinated,small; transmit signal more slowly; "secondary" sensations are diffuse, aching, last longer after initial injury;
Where do primary afferent fibers enter spinal cord?
primary afferent fibers( A-delta and C fibers) terminate in the dorsal horn of the spinal cord unless blocked by a sodium channel inhibitor.
What happens when pain is poorly controlled?
over extended period, cells within dorsal horn become altered in size and function, this damage turns future pain signals into more exaggerated or hypersensitive processed signals
Nocioceptive Processing - Transduction
occurs when noxious stimulus in form of traumatic or chemical injury, burn, incision, or tumor takes place in periphery (includes skin, somatic and visceral structures)
Nocioceptive Processing - Transmission
pain impulse moves from leel of spinal cord to brain; at synaptic cleft, there are opiod receptors that can block pain signaling w/our own endogenous opiods or with exogenous opiods if they are adminstered
Nocioceptive Processing - Perception
indicates the conscious awareness of painful sensation; coritical structures like limbic system account for emotional response to pain, and somatosensory areas can characterized sensation; only when noxious stimuli are interpreted in higer cortical structures can this sensation be identified as "pain"
Nocioceptive Processing - Modulation
Neurons originating in the brainstem descend to the spinal cord and release substances(endogenous opioids) that inhibit nociceptive impulses.
Neuropathic Processing of Pain
pain that does not adhere to typical and rather predictable phases in nociceptive pain; implies abnormal processing of pain message from injury to nerve fibers; often perceived long after site of injury heals (can start 2-3 yrs later)
How do you test for Neuropathic Pain
pain is sustained on neurochemical level. Identify by electromyography and nerve-conduction studies
Abnormal processing of neuropathic pain
impules can be continued by PNS or CNS; proposed mechanism is that injury to peripheral neurons can result in spontaneous and repetitive firing of nerve fiber (almost seizure like) and sustained centrally in phenomenon known as neuronal 'wind-up'; in dorsal horn, neurons thought to be transformed into hyperexcitable state and minimal stimulus can ultimately spiral into much larger painful stimuli
Source of Pain - Viceral
pain originates from larger interior organs (kidney, stomach, intestine, gallbladder, pancreas); can stem from direct injury to organ or from stretching of organ from tumor, ischemia, distention, or severe contraction; pain impulse transmitted by ascending nerve fibers along w/nerves from autonomic NS; that is why visceral pain often presents along w/ autonomic responses (vomitin, nausea, pallor, diaphoresis)
Source of Pain - Deep Somatic Pain
comes from sources such as blood vessels, joints, tendons, muscles, and bone; injury may result from pressure, trauma, or ischemia
Source of Pain - Cutaneous
derived from skin surface and subcutaneous tissues; injury is superficial, w/sharp, burning sensation
Source of Pain - Mental
outdated and derogatory; psychogenic pain or psychogentic; linking pain to mental disorder negates pts pain report; lack of awareness and understanding of neuropathic pain may contribute to mislabeling
Source of Pain - Referred
pain felt at a particular site but originates from other location; both sites are innervated by same spinal nerve, and is difficutl for brain to differentiate point of origin; may originate from visceral or somatic structure; ex - inflamed appendix in right lower quad may have referred pain in periumbilical area
Types of Pain
can be classified by its duration into acute or chronic (persistent - carries less negative, malingering connotation) categories; duration provides information on possible underlying mechanisms and teatment decisions;
Types of Pain - Acute
short-term and self-limiting, often follows predictable trajectory, and dissipates after injury heals; serves a self-protective purpose; warns individual of actual or potential tissue damage; ex - surgery, trauma, kidney stones
Types of Pain - Acute Incident Pain
acute type that happens predictably when certain movements take place; ex - lower back upon standing or shoulder pain when arms raised
Types of Pain - Persistent (chronic)
diagnosed when pain continues for 6 mo or longer; can last 5, 15, 20 yrs or more; can be divided into malignant and nonmalignant; does not stop when injury heals and persists after predicted trajectory; many pts are not believed and often are labeled as malingers, attention seekers, drug seekers
Types of Pain - Chronic Malignant Pain
cancer-related; often parallels the pahtology created by tumer cells; is induced by tusse necrosis or stretching of organ by growing tumor; pain fluctuates w/disease
Types of Pain - Chronic Nonmalignant Pain
often associated w/musculoskeletal conditions such as lower back pain, arthritis, fibromyalgia
Types of Pain - Breakthrough Pain
pain that starts again or excalates before next scheduled analgesic dose; pain breaks through when is is expected to be controlled by pain meds
increasing the dose beyond an upper limit provides no greater analgesia - true for nonopioid analgesics
Name 3 Characteristics common to Nonopioids
1. analgesic ceiling
2. do not produce tolerance or physical dependence
3. many available OTC
ex. acetaminophen, aspirin, NSAIDs
the phenomenon of nonopioids allowing for effective pain relief using lower opioid doses thereby causing fewer opioid side effects
is transient, moderate to severe pain that occurs in pts. whose pain is otherwise well controlled, Pain that occurs between doses of pain medication.
a transient increase in pain that is caused by a specific activity or event that precipitates the pain (ex. dressing changes, movement, catherterization)
involves the conversion of a noxious mechanical, thermal, or chemical stimulus into an electrical signal called an action potential, caused by cell damag
noxious stimuli in pain
Harmful, stimuli that elicit tissue damage and activate nociceptors.
prostaglandins, bradykinin, serotonin, substance P, histamine
Name 5 substances that activate nociceptors and lead to the generation of action potentials at transduction stage
prostaglandins, bradykinin, serotonin, substance P, histamine
An inflammatory mediator released when a cell is damaged. They cause vasodilation and stimulate inflammation.
What type of of opioid therapy should a cancer patient receive?
both long-acting and short-acting opioid
What can unrelieved pain lead to?
unrelieved pain is dangerous and can lead to many physical and psychological complications
How are nociceptors stimulated?
can be stimulated directly by trauma or injury or secondarily by chemical mediators that are released from site of tissue damage
Crescent shaped projection of gray matter within the spinal cord where sensory neurons enter the spinal cord
Name the descending pathways neurotransmitters that impeded pain impulse producing an analgesic effect.
Descending pathways from brainstem to spinal cord produce 3rd set of neurotransmitters that slow down or impede pain impulse, producing analgesic effect: serotonin, norepinephrine, neurotensin, y-aminobutyric acid (GABA), and our own endogenous opiods: B-Endorphins, enkephalins, dynorphins
pain message is inhibited through modulation; our bodies have built-in system that will eventually slow down or stop the processing of a painful stimulus; if not, we would continue to experience pain from childhood injuries and beyond;
"relaxes the lower esophageal sphincter, blocks the release of stomach acid and pepsin, and regulates GI contraction and relaxation (pg. 58)"
comes from sources such as the blood vessels, joints, tendons, muscles and bone. Injury may result from pressure, trauma or ischemia (local decrease in blood supply)
Why does visceral pain present with automonic responses?
pain impulse transmitted by ascending nerve fibers along w/nerves from autonomic nervous system ---often result in vomiting, nausea, pallor diaphoresis
an IV delivery system or demand analgesia that is delivered when the patient decides a dose is needed. they receive a bolus infusion of analgesic. (morphine and hydromorphone commonly used)
Advantage--Narcotic moves directly from epidural space into spinal fluid and binds with opiate receptors in the spinal cord to block pain perception. Lower doses are required
1) Catheter inserted by anesthesiologist
2) Inserted between L3 and L4 or L4 and L5.
a) If placed in subarachnoid space it is Intrathecal delivery
b) Doses are extremely small. (1/10 the epidural dose, 1/100 the IV dose)
Care for pt. wtih epidural.
a) Assess for epidural catheter placement--
-1- Check site for swelling, redness, drainage (catheter dislodgement or abscess)
-2- Shooting pain down leg may be sign of nerve irritation from catheter.
-3- Cath may stay in place 1 - 5 days post-op.
-4- Position pt. in low or semi-Fowler's to keep level from rising up to chest- especially if an anesthetic is used
-5- Monitor same as for PCA plus sensation and movement to lower extremities
Care for pt. with PCA
*teach patient to self-administer before intensity is greater than the pt. desired pain intesity goal
*pt. cannot overdose
Name 3 categroies of nonopioid analgesics more commonly used.
nonsalicylate (acetaminophen, Tylenol)
State nursing considerations for nonsalicyate.
*rectal suppository available
*doses above 4 g per day may cause gastric irritation and bleeding
*acute overdose: acute liver failure
*chronic overdose: liver toxicity
(nonopioid, acetaminophen, Tylenol)
State nursing considerations for salicyate.
*rectal suppository available
*Possibility of upper GI bleeding
* used more commonly in low doses as a cardioprotective measure than for its analgesic properties
Name 8 opioid agonists (effective for moderate to severe pain).
6. hydromorphone (Dilaudid)
7. oxymorphone (Opana, Opana ER)
8. levorphanol (Levo-Dromoran)
How do opioids produce their effects?
by binding to receptors in the CNS which result in
1. inhibition of the transmission of nociceptive input from the periphery to the spinal cord
2. altered limbic system activity
3. activation of the descending inhibitory pathways that modulate transmission in the spinal cord
How are opioids catergorized?
by physiologic action (agonist or antagonist) and binding at specific opioid receptor (mu, kappa, delta)
Why are pure opioid agonists effective for moderate and severe pain?
potent, have no analgesic ceiling and can be administered through several routes
a circumscribed hypersensitive area within a tight band of muscle, caused by acute or chronic muscle strain and can often be felt as a tight knot under the skin.
occurs when pain is recognized, defined, and responded to by the individual experienceing the pain. In the brain, nociceptive input is perceived as pain.
overwhelming involvement with obtaining and using a drug for its psychic effects, not for approved medical or social reasons. (Psychological dependence)
Name the typical medications used for epidural dosage.
epidural dosage (preservative free)
a) Morphine (Duramorph)-- 5mg/250ml (0.02 mg/ml)
b) Fentanyl (Sublimaze)--1250 mcg/250ml
c) Marcaine (a local anesthetic agent)
Most common adverse reactions to epidural analgesic
Respiratory depression, urinary retention, pruritis (atarax), nausea and vomiting
Special nursing requirement for epidurals.
Injected intermittently or infused continuously often requires a special "Nursing competency" and 2 RN signature
Advantage for using PCA.
• Decreases patient's need for opioids
• Can walk sooner
• Are able to be discharged home sooner
• Easily removed by the nurse or patient.
What should be moniotred when using PCA?
local anesthetic toxicity: peri-oral numbness, blurred vision, ringing in the ears (tinnitis), metallic taste in mouth, N & V, confusion, seizures.
The development of drug-seeking behaviors among pain patients due to inadequate pain management.
After repeated administration of a narcotic, a given dose begins to lose its effectiveness; duration of action decreases & then the effectiveness of the analgesia.
After repeated administration of a narcotic, withdrawal symptoms occur when the drug is not taken. Affects are physiologic.
Pain theory by McCaffery
"Pain is whatever the experiencing person says it is and exists whenever he says it does". (McCaffery, 2002).
Pain theory based on Descartes
Pain is the stimulus. Response is the attempt to withdraw from the painful response. This theory ignores the emotional, psychological and cultural aspects of pain.
Gate control theory
(1965): A pain stimulus of a certain intensity opens a neurological gate, allowing the pain stimulus to proceed through the nervous system to the brain to create the sensation of pain. Also considers the emotional component of pain.
Name the four steps in pain transmission
Steps in pain transmission include:
1). A pain stimulus from the body is carried by A delta and C nerve fibers to the dorsal horn of the spinal cord.
2) The gate is located in the substantia gelatinose in the dorsal horn of the spinal cord. It can facilitate or inhibit the transmission of the nerve impulse through the CNS.
3) If the painful stimulus if of sufficient intensity or persists, the pain sensation is transmitted to the brain via the limbic system.
4) In the brain, the stimulus is recognized as pain and a pain response is elicited.
nocioceptive pain name two types
somatic or visceral
Somatic - from skin, muscle, bone, joint, connective tissue.
Visceral pain -Internal organs and lining of body cavities.
Name two types of somatic pain
1) Superficial - from skin & SQ tissue- often described as sharp, burning, prickly
2) Deep- from receptors originating in bone, joints, muscles, tendons, etc. usually aching or throbbing.
What type of pain does visceral pain produce?
Referred pain -- pain perceived in an area other than from where stimulus originates; Due to complex multi-directional pathways of these fibers, pain from viscera may be perceived in a joint or skin, & vice versa.
Subjective assessment of pain the 5th vital sign.
document Patient's own words.
PQRST: quality, radiation, severity, time (duration)
b. Location: Try to isolate area; radiate?
1) Use scale of 0 - 10
2) Other scales available (Faces, colored analog, FLACC, etc.)
a) Faces may work with non-English speaking clients.
Assessing pain for comatose or cognitively impaired clients.
clients who cannot give a pain rating:
1) Assess & chart the client's behavior (e.g., moaning, restlessness, frowning, etc.)
2) Note & document any behavior change after pain med, Onset, alleviating or relieving factors, associated symptoms
Objective data for pain assessment (physical symptoms).
Manner of expressing pain
-Possible accompanying physical symptoms
a) Elevated BP, HR, RR --
e) Dilated pupils, etc.
Objective data for pain assessment (emotional symptoms)
Objective data for pain assessment (effects on activity and rest)
3) Effects on Activity and Rest
b) Inability to perform ADL's, ambulate, etc.
Objective data for pain assessment (cognitive effects)
a) Decreased concentration
b) Inability to learn
somatogenic vs. psychogenic pain
Somatogenic vs. psychogenic pain
a. Pure physical pain is rare.
b. Pure psychogenic pain is rare.
c. Most pain sensation is created by a combination of somatic and emotional / mental stimuli.
"One who pretends to be ill or suffering from a non-existent disorder to arouse sympathy."
-We must say, "I don't know why the patient hurts." & then we assess, report & treat the pain
-Lack of pain EXPRESSION does NOT mean lack of pain
Characteristics of non-opioids
a. Anti-inflammatory, antipyretic and analgesic effects
b. Have an analgesic ceiling
c. Mild to moderate pain
d. All can be used in combination with an opioid in mod-severe pain.
Name three classes of non-opioids
1) Salicylates (Aspirin)
2) Acetaminophen - antipyretic or analgesic; negligible anti-inflammatory effect.
OFIRMEV= IV Tylenol: infused over 15min. 4g/d max.
3) NSAIDs: anti inflammatories, inhibit prostaglandin synthesis.
Do not take the following NSAIDs if recent surgery
a) Ibuprofen -- (Motrin, Advil)
b) Naproxen - (Naprosyn, Anaprox, Aleve)
c) Celecoxib (Celebrex)
d) Ketorolac ( Toradol)- short term treatment of moderately severe pain (<5 days)
e) Indomethacin (Indocin)- moderate -severe OA, RA, gouty arthritis
-Selectively inhibits the enzyme COX-2 and inhibits prostaglandin synthesis to reduce inflammation, this relieves pain/inflammation in joins and smooth muscles (Celebrex, NSAIDs)
short term treatment of moderately severe pain (<5 days), -only for "acutely moderate severe pain (Toradol)
Indomethacin (Indocin)- moderate -severe OA, RA, gouty arthritis, Most preferred NSAID for RA
Bind to mu receptor sites & block the neuromediators that stimulate the nociceptors.
-1- Morphine --
Give PO, IM, SQ, IV, rectally, intrathecally (into epidural space).
MS Contin-- LA
-2- Hydromorphone - Dilaudid
-3- Oxycodone (Oxycontin) (LA)
-4- Fentanyl - IV, & as a duragesic patch
Mixed agonist and antagonist opioids
a) bind as agonists on kappa receptors and as weak antagonists or partial agonists on mu receptors
b) Less respiratory depression, but more agitation and dysphoria
Side effects of opioids
a. Respiratory depression
b. Sedation- drowsiness, confusion
d. N & V, constipation, occasional allergic reactions
e. decreased BP &/or bradycardia
Combination Analgesics (Opioids and Non-opioids)
a. Oxycodone/Tylenol - (Tylox)
b. Oxycodone/aspirin - (Percodan)
c. Oxycodone/acetaminophen (Percocet)
d. Hydrocodone /acetaminophen (Norco, Lortab, Vicodin)- Vicodin comes in many dosage combinations- CAUTION: watch dose ordered and the medication available
e. Codeine in combination with aspirin or acetaminophen
f. Codeine dose in #2, #3, #4
1) #2 =15 mg Codeine
2) #3 = 30 mg Codeine
3) #4 = 60 mg Codeine
Adjuvant Medications (Coanalgesics):
drugs that add to the action or effect of opioids. Often used for chronic &/or neurogenic pain. Treat symptoms that aggravate pain (depression, seizures, inflammation) & tx. neuropathic pain.
Refers to the relative potency of various opioid analgesics compared to a standard dose of parenteral morphine
Equianalgesia= Narcotic conversion chart ie: morphine 1mg=dilaludid 0.2mg
Principle of Pain Relief Dosage:
Start with the lowest amount that relieves pain & increase gradually as needed.
Example: WHO -- 3-Step Analgesic Ladder for Treatment of Cancer Pain
Question of addiction of opioid study showed
In a prospective study of 12,000 hospitalized medical patients who received at least one narcotic, only 4 became addicted (<1%)
In another study by Friedman (1990) of > 24,000 patients receiving opioids for pain, only 7 patients became addicted! (0.0003%)
Name 3 types of possible "potentiators" of analgesia
-1- Dextroamphetamine IM or PO -- rarely used.
-2- Ritalin PO --may be helpful in advanced cancer pain.
-3- Caffeine--100-200mg, combined with acetaminophen or ASA
Six Examples drugs that are "potentiators" of analgesia
1) Steroids -- Dexamethasone (Decadron), Prednisone -- bone, nerve pain.
2) Tricyclic antidepressants -- Amitriptyline (Elavil), Endep) -- used for nerve pain.
3) Anticonvulsants - (Tegretol, Neurontin)
4) Membrane-stabilizing drugs - (Flecainide, Catapres - Nerve pain.
5) Skeletal muscle relaxants—Flexeril
6) Antiemetics: ondansetron (Zofran)
Where are noericeptors located?
located within skin, connective tissue, muscle, and thoracic, abdominal and pelvic viscera;
How is a noericeptors process protective ?
it is warning signal that injury is about to or has taken place;
learn to move our hand away from burning flame, skinned knee, kidney stones, menstrual cramps, muscle strain, venipuncture, arthritis;
typically predictable and time limited based on extent of injury
What chemicals are released in noericeptor process 1st and 2nd set of neurotransmitters?
damaged tissue then releases variety of chemicals: substance P, histamine, prostaglandins, serotonin, bradykinin; chems are neurotransmitters that propagate pain message (action potential) along sensory afferent nerve fibers to terminate in dorsal horn of cord;
second set of neurotransmitters carry pain impulse across synaptic cleft to dorsal horn neurons: substance P, glutamate, ATP
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