Download EO_004.12 Manage Acute and Chronic pain

Pain Management
EO 004.12
Learning Objectives
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Describe the principles of pain management
for acute and chronic pain that impact on
patient care
Select the most appropriate analgesic for an
individual patient to maximize the benefits
that can be expected from therapy
Communicate important aspects of
analgesic therapy to patients to improve the
odds of therapy being successful
References
• Therapeutic Choices
– Chapters 11,12
• Current Medical Diagnosis and
Treatment
– Chapters 20, 24
Outline
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Pain Definitions
Epidemiology
Pathophysiology
Pain Pathways
Drug Treatment
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Mild Analgesics
Opioid Analgesics
Adjuvant Analgesics
Miscellaneous Analgesics
Cases
Pain Definitions
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What is pain?
What purpose does pain serve?
How can I assess an individual’s pain?
What are the implications of poorly
managed pain?
Analgesia, Anesthesia And Pain
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Analgesia
Anesthesia
Pain
1.
2.
3.
4.
5.
Acute
Chronic
Neuropathic
Bone
Palliative Care
Acute And Chronic Pain
Characteristic
Relief of Pain
Dependence and
Tolerance to Medication
Psychological Component
Organic Cause
Environmental
Contributions and Family
Involvement
Insomnia
Treatment Goal
Acute Pain
Highly
Desirable
Unusual
Chronic Pain
Highly
Desirable
Common
Usually Not
Present
Common
Often a Major
Problem
Often Not
Present
Small
Significant
Unusual
Cure
Common
Functionality
Somatic, Visceral And
Neuropathic Pain
Characteristic
Location
Patient Description
Somatic Pain
Localized
Pin Prick or
Stabbing or Sharp
Visceral Pain
Generalized
Ache or Pressure or
Sharp
Mechanism of Pain
A-delta Fiber
Activity Located in
the Periphery
Superficial
Laceration,
Superficial Burns,
IM Injections,
Venous Access,
Otitis Media,
Stomatitis,
Extensive Abrasion
Cold Packes,
Tactile Stimulation,
Acetaminophen,
NSAIDs, Opioids,
Local Anesthetics
(Topical or by
Infiltration)
C-Fiber Activity
Involved Deeper
Innervation
Periosteum, Joints,
Muscles, Colic and
Muscle Spasm Pain,
Sickle Cell,
Appendicitis, Kidney
Stone
Clinical Examples
Most Responsive
Treatment
NSAIDs, Opioid Via
Any Route, Intraspinal
Local Anesthetic
Agents
Neuropathic Pain
Radiating or Specific
Burning or Prickling or Tingling or
Electric or Shock-like or
Lancinating
Dematomal (peripheral) or nondematomal (central)
Trigeminal Neuralgia, Avulsion
Neuralgia, Post-traumatic
Neuralgia, Peripheral Neuropathy
(Diabetes, HIV), Limb
Amputation, Herpetic Neuralgia
Anticonvulsants, Tricyclic
Antidepressants, Neural
Blockade
Pain Epidemiology - Overview
• Fifty million Americans are partially or totally
disabled because of pain
• Fifty percent of seriously ill hospitalized
patients report pain (15% had moderate to
severe pain at least 50% of the time)
• Seventy percent of chronic pain patients in
nursing homes had pain despite treatment
• Fifty percent of people in a British study of
community-dwelling patients had pain (in
50% of those the pain was significant)
Epidemiology – Neuropathic Pain
Pain pathways
• Ascending stimulating pathways
– Noxious stimulus activates afferent
neurons
• A fibres – fast transmission, sharp stinging –
acute pain
• C fibres – slow transmission, dull, aching –
chronic pain
– Stimulate the CNS via spinal interneurons
• Substance P and Glutamate
Pain Pathways
• Descending inhibitory pathways
– Originate in midbrain
– Release inhibitory neurotransmitters
• Serotonin and norepinephrine
• Enkephalins
• Gate hypothesis
– Pain transmission up the ascending
pathway can be modulated by activity of
other neurons
Pain Perception
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Nociceptive process
Physiologic response
Emotional response
Psychological framework
Assessing Pain
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Provocative causes/Palliative aids
Quality
Radiation
Severity
Timing
An Approach To Acute Pain
Patient (pt) has
pain or is likely to
have pain
Critical first step:
detailed history and
focused physical exam
Determine
mechanism of pain –
pt may report more
than one type
Arrange diagnostic
workup and treat
pain per
information
available
Next
page
Pt reports
localized pin
prick, sharp or
stabbing pain
Pt reports
generalized ache
or pressure
Pt reports
radiating,
burning, tingling
or lancinating
pain
Somatic Pain
Visceral Pain
Neuropathic Pain
1.
2.
3.
4.
5.
6.
Treatment
Choices:
tactile
stimulation
cold packs
acetaminophen
NSAIDs
opioids
local
anesthetics
(topical or
infiltration)
Treatment
Choices:
1. opioids
2. NSAIDs
3. local
anesthetics
(intraspinal)
See
next
page
1.
2.
3.
4.
Treatment Choices:
anticonvulsants
tricyclic antidepressants
neural blockade
opioids
Specific interventions:
1. Titrate medication dose up/down
2. Patient education
3. Further diagnostic workup
4. Specialty consult (surgery, etc.)
5. Procedures (neural blocks)
6. Behaviour and cognitive
interventions
7. Adjuvant therapy
Side effect
manageme
nt
Yes
Select an
alternative
treatment
Yes
Yes
Side
effects?
Adequat
e pain
relief?
No
Confident
of pain
mechanism
?
No
No
Follow-up
patient
instructions
Revisit
“critical
first
steps”
End
An Approach To Chronic Pain
Approach To Chronic Pain
Knowledge Of
Disease
Quality Of Pain
 Burning
 Lancinating
 Aching
 Movementrelated
Quantity Of Pain
 Pain Intensity
Scale
 Rated By Patient
 Rating Of 1-5
Diagnosis Of
Etiology
 Nerve
 Bone
 Soft
Tissue
See
Next
Page
Approach To Chronic Pain
Treatment Plan Guide
 Modified WHO
Analgesic
Ladder
Mild Pain
(1-2)
Moderate Pain
(2-3)
Non-opioid
+/Adjuvant
Weak Opioid
+/- NSAID
+/- Adjuvant
Reassess
Relief And
Modify Plan
If Needed
END
Severe
Pain
(4-5)
Strong
Opioid
+/- NSAID
+/- Adjuvant
Assessing An Individual’s Pain
Assessing An Individual’s Pain
Analgesics
• Mild
– Acetaminophen, ASA, NSAIDS
• Opiates
– Moderate – codeine
– Severe - morphine, meperidine and others
• Adjuvants
– Tricyclic Antidepressants (TCAs)
– Anti-Epileptic Drugs (AEDs)
• Miscellaneous
– Local Anesthetics, Capsaicin, Cannabis
Acetaminophen
• Works by inhibiting the synthesis of
prostaglandins in the central nervous system
and peripherally by blocking pain impulse
generation
• Has no significant anti-inflammatory effects
• Is most responsive to somatic type pain of
mild to moderate intensity
• Has an opioid sparing effect when used in
combination with narcotics
ASA
• Works by irreversibly acetylating
cyclooxygenase (COX) to inhibit
prostaglandin synthesis
• Similar efficacy, potency, and time-effect
curve as acetaminophen
• Is most responsive to somatic type pain of
mild to moderate intensity
• Largely replaced by equally or more effective
but safer NSAIDs for most analgesic
indications
NSAIDs
• NSAIDs are indicated for mild to moderate pain,
especially if there is an inflammatory or boney
component
• NSAIDs work by non-covalently binding to COX
• There is a high inter-patient variability in response to
NSAIDs, so a trial of a different NSAID may be
appropriate if a patient doesn’t respond to an initial
course
• In single full doses, most NSAIDs are more effective
than A.S.A. or acetaminophen and some have shown
equal or even greater analgesic effect than usual
doses of oral opioids
Mild Analgesics – Summary
Benefits:
1. Useful for mild to
moderate somatic
pain
2. Well tolerated
3. Available in many
forms
4. Low abuse
potential
Limitations:
1. Ceiling effect
2. Not useful for more
severe pain,
especially
neuropathic or
visceral type pain
3. Frequently require
multiple daily
doses for analgesia
Opioids - Background
• Opioids are used for all types of
moderate to severe pain but are most
effective for visceral and somatic pain –
much less so for neuropathic pain, often
necessitating adjuvant therapies
• Opioids do not decrease sensitivity to
touch, sight or hearing at therapeutic
doses
Opioids – Summary
Opioid
Morphine
Morphine
Controlled
Release
Hydromorphone
Codeine
Oxycodone
Oxycodone
Controlled
Release
Levorphanol
Meperidine
Methadone
Fentanyl
Parenteral Dose
(mg)
(IV/IM/SC)
10
10
Oral Dose
(mg)
Interval
(h)
30
30
4
8-12
1.5
130
-
7.5
200
15-30
15-30
4
4
4
8-12
2
4
4
75
300
2-3
5
5
6-8
0.1-0.2
1-2
Transdermal Fentanyl – Rember 1:2:3
25mg/day morphine IV = 50 mcg/hr q72h fentanyl patch = 75mg/day morphine PO
Opioids –Benefits And Limitations
Benefits:
1. Useful for moderate to
severe pain of somatic
or visceral origin
2. No ceiling effect for
most agents
3. Available in many
forms, including
extended release
4. Predictable adverse
effect profile
Limitations:
1. Not as efficacious vs.
neuropathic pain
2. Titration required due
to physical tolerance
3. Numerous adverse
effects including
physical and
psychological
dependence
4. Special prescribing
and dispensing
practices may apply
TCAs – Background
• These medications are used as
complementary therapy to primary analgesics
in neuropathic pain
• Meta-analyses indicate TCAs are
approximately 50% effective for patients with
a number of painful neuropathic conditions
• TCAs are first line due to low cost and
efficacy when the alternatives like AEDs are
considered (although there are exceptions;
notably trigeminal neuralgia)
TCAs - Indications
•
Pain syndromes responsive to TCAs
include:
1. Post-herpetic neuralgia
2. Peripheral neuropathy (i.e. diabetic
neuropathy, HIV neuropathy, idiopathic
neuropathy, etc)
3. Central pain (damage specifically to the
brain or spinal cord from strokes, multiple
sclerosis, limb amputations or trauma)
TCAs - MOA
•
Postulated mechanisms include:
1. Blockade of norepinephrine,
2. Antagonism of histamine and muscarinic
cholinergic receptors,
3. Alpha-adrenergic blockade, or
4. Suppression of C-fiber afferent-evoked
activity in the spinal cord
AEDs – Background
• These medications are used as
complementary therapy to primary analgesics
in neuropathic pain
• Meta-analyses indicate AEDs, although
widely used in chronic pain (approximately
5% of all AEDs prescribed in the U.S. are for
pain management), have surprisingly few
trials to show analgesic effectiveness
AEDs – Background
• There is no evidence AEDs are effective for
acute pain
• In chronic pain syndromes other than
trigeminal neuralgia, AEDs should be
withheld until other interventions are tried
• Number-needed-to-harm for major effects
weren’t significant for any drug vs. placebo
• Number-needed-to-harm for minor effects
ranged from 2.5 (confidence interval [CI] 2.03.2) for gabapentin to 3.7 (CI 2.4-7.8) for
carbamazepine
AEDs - Indications
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AEDs have different indications
Carbamazepine is the intervention of choice
for trigeminal neuralgia
Pain syndromes AEDs are used in include:
1.
2.
3.
4.
5.
Trigeminal neuralgia
Peripheral neuropathy
Central pain
Post-herpetic neuralgia
Complex regional pain syndrome (formerly reflex
sympathetic dystrophy)
AEDs - MOA
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The precise mechanism of action of
AEDs remains uncertain
The standard explanations include
1. Enhanced gamma-aminobutyric acid
(GABA) suppression
2. Stabilization of neural cell membranes or
possibly
3. Action via N-methyl-D-aspartate (NMDA)
receptor sites
AEDs – Summary
Agent
Indications
Carbamazepi
ne
(Tegretol ®)
Central Pain (CP),
Peripheral Neuropahty
(PN),
Trigeminal Neuralgia
(TN)
Gabapentin
(Neurontin ®)
Complex Regional Pain
Syndrome (CRPS),
Post-Herpetic
Neuralgia (PHN), PN,
Post-Stroke Pain,
Spinal Cord Injury, TN
CP, PHN, PN
Phenytoin
Contraindications
Liver
abnormalities,
bone marrow
suppression,
hypersensitivity
to TCAs
Hypersensitivity
Most Common Side
Effects
Sedation, dizziness,
ataxia, confusion,
nausea, liver toxicity,
blod dyscrasias,
Stevens-Johnson
Syndrome
Sedation, dizziness,
confusion, peripheral
edema, weight gain
Bradycardia 2°3° heart block,
hypersensitivity
Sedation, dizziness,
ataxia, confusion,
nausea, gingival
hyperplasia,
peripheral
neuropathy,
Stevens-Johnson
Syndrome
Adjuvant Analgesics – Summary
Benefits:
1. May improve pain
control in conditions
resistant to other
analgesics
2. May allow for dosage
reduction of other
analgesics
3. Can be used in the
long term
management of
chronic pain and
associated conditions
(i.e. depression)
Limitations:
1. Not effective for acute
pain
2. Not useful as
monotherapy
3. Poor evidence
supporting use in
many conditions
4. Adverse effects often
occur before
therapeutic effects
Local Anesthetics
• Can provide relief of acute or chronic pain
• Are administered by injection (into the joints,
epidural or intrathecal space, along nerve
routes or in a nerve plexus) or topically (ex.
lidocaine jelly, eutectic mixtures of local
anesthetics [EMLA ® = lidocaine and
prilocaine])
• Work by blocking nociceptive transmission
and interrupting sympathetic reflexes
• Are often combined with opioids for synergy
Local Anesthetics
•
Disadvantages in the use of local
anesthetics include:
1. Need for skillful technical application
2. Need for frequent administration
3. Need for highly specialized monitoring
and follow-up procedures
Capsaicin
• Indicated in the topical treatment of pain
associated with postherpetic neuralgia,
arthritis, diabetic neuropathy and
postsurgical pain
• May also be useful for psoriasis, chronic
neuralgias unresponsive to other
treatments and intractable pruritus
Capsaicin
• Commonly available as a cream of differing
strengths:
• Zostrix ® = 0.025%
• Zostrix-HP ® = 0.075%
• Induces the release of substance P from
peripheral neurons and after repeated
application depletes substance P and
prevents it’s reaccumulation
Capsaicin
• Onset of action = 14-28 days with regular
application (3-4 times daily)
• Maximum effect may take up to 6 weeks
• Duration of effect after an application =
several hours
• Transient burning occurs in > 30% of
patients, which usually diminishes with
repeated use
• Also causes itching, stinging, erythema and
cough in 1-10% of patients
Cannabis
• Three quarters of British doctors surveyed in
1994 wanted cannabis available on
prescription
• Humans have cannabinoid receptors in the
central and peripheral nervous system
• Cannabinoids are analgesic and reduce signs
of neuropathic pain in animal tests
• Some evidence suggests that cannabinoids
may be analgesic in humans
Cannabis
• No studies have been conducted on
smoked cannabis
• The predominant adverse effect was
central nervous system depression
which was common at higher doses
• Cardiovascular effects were generally
mild and well tolerated
Cannabis
• The best that can be achieved with single
dose cannabinoids is an analgesic effect
equivalent to 60mg of codeine (or a number
needed to treat of 16 patients for at least a
50% reduction in pain)
• Cannabinoids widespread introduction for
pain management is therefore undesirable
Conclusion
A Bill Of Rights
I have the right to have my reports of pain
accepted and acted on by health care
professionals
I have the right to have my pain controlled, no
matter what the cause or how severe it may
be
I have the right to be treated with respect at all
times. When I need medication for pain, I
should not be treated like a drug abuser
Principles Of Pharmacotherapy
• Always ask the patient if pain is present
and assess the characteristics of pain
• Identify the source of pain
• Select the most effective analgesic with
the fewest adverse effects
• Properly titrate the dose for each
individual and administer for an
adequate duration
Principles Of Pharmacotherapy
• Always consider around-the-clock (ATC)
regimens for acute and chronic pain
• Use as-needed (PRN) regimens for
breakthrough pain or when acute pain
displays great variability and/or has subsided
greatly
• Assess for adverse effects, particularly the
constipation seen with opioids
Principles Of Pharmacotherapy
• Avoid excessive sedation by titrating
opioids effectively
• Adjust the route of administration to
meet the needs of the patient
• Whenever possible use the oral route
• When converting from one opioid to
another, use the equianalgesic dose
and then titrate
Principles Of Pharmacotherapy
• Do not use placebo therapy to diagnose
psychogenic pain
• Consider the use of capsaicin, tricyclic
antidepressants and anticonvulsants
when treating neuropathic pain
• Use a multidisciplinary approach and
nonpharmacologic strategies when
possible
Pitfalls In Analgesic Therapy
1. Overestimating the analgesic efficacy of a
drug
2. Underestimating the analgesic requirement
of the patient
3. Prejudice against the use of analgesics that
may prevent objective therapy
4. Lack of knowledge in analgesic
pharmacology
Pitfalls In Analgesic Therapy
5. Patient non-compliance because of fear of
addiction
6. Patient not communicating with caregivers
for fear of being labeled a drug addict
7. Patient wants to please by not complaining
8. Patient does not know how or is afraid to
communicate with caregiver