Transcript Pain Management

Pain Management
Lalan S. Wilfong, MD
March 25, 2004
What is Pain?
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Definition by the International Association
for the Study of Pain
 Unpleasant sensory and emotional
experience
 Associated with actual or potential tissue
damage
 Or described in terms of such damage
Physiology of Pain
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Primary afferent nociceptors
– Nerves that respond to painful stimuli
– Can respond to many different types of stimuli
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Sensitization
– Intense, repeated or prolonged stimuli
– Threshold for activating nerves is lowered
– Inflammatory mediators such as bradykinin,
prostaglandins, and leukotrienes
Physiology of Pain
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Central pathways
– Axons of primary nociceptors enter the spinal
cord via the dorsal root
– Transmits pain signal to brain sites
– Axon of each primary contacts many spinal
neurons
– Each spinal neuron receives convergent input
from many primary afferents
Referred Pain
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All spinal neurons receive
input from viscera and
skin
Convergence patterns are
determined by the spinal
segment of the dorsal root
ganglion
For example both the
diaphragm and the skin of
the shoulder have same
dorsal root
Types of Pain
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Somatic
– Nociceptors in cutaneous or deep tissues
– Dull or aching but well-localized pain
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Visceral
– Nociceptors from involvement of the viscera
– Poorly localized and described as deep, squeezing, and
pressure-like
– Can be associated with nausea or sweating
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Neuropathic
– Injury to peripheral or central nervous system
– Often severe and described as burning or shock-like
Acute Pain
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Well-defined temporal pattern of onset
Associated with subjective and objective physical
signs
Hyperactivity of the autonomic nervous system
Usually self-limited
Responds to analgesics and treatment of the
underlying cause
Two types
– Subacute – comes on over several days with increasing
intensity
– Episodic – occurs during confined periods of time
Chronic Pain
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Persistence of pain for more than 3 months
 Autonomic nervous system adapts
 Patients lack objective signs of pain
 Leads to changes in personality, lifestyle
and functional ability
 Treatment requires control of pain and its
multidimensional aspects
Chronic Pain
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Causes are multiple
– Trauma, surgery
– Cancer, medical conditions
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Baseline pain
– Average pain intensity for 12 or more hours in a
24 hour period
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Breakthrough pain
– Transient increase in pain from any cause
Measurement of Pain
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Important to determine but hard to define
 Many scales are used
– Mild, moderate, severe, excruciating
– Numeric scales: 1 (no pain) – 10 (worst
possible pain)
– Visual analog scales: faces, 10cm line
– All of these are validated instruments
Clinical Assessment
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Believe the patient's complaint of pain
Take a careful pain history
Evaluate the patient’s psychological state
Perform a careful medical and neurological
examination
Order appropriate diagnostic studies
Treat the pain
Reassess response to therapy
Pain History
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Description of site of pain
Quality of pain
Exacerbating and relieving factors
Temporal pattern
Associated symptoms and signs
Interference with ADL’s
Effect on psychological state
Response to previous and current therapies
Three-Step Analgesic Ladder of the World Health Organization
Levy, M. H. N Engl J Med 1996;335:1124-1132
Management
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Modalities
– Analgesic drugs
– rehabilitation
– psychotherapy
– cognitive
– surgical
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Individualize treatment plan
Nonopioid Analgesics
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Tylenol
– Main serious side effect is liver toxicity
– Counsel patients on all Tylenol containing drugs
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NSAIDS
– Main serious side effect is GI ulcers
– Risk factors: steroid use, advanced age, higher doses,
history of ulcer disease
– Most inhibit platelets
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Analgesia limited by a ceiling effect
 Tolerance and physical dependence do not occur
 Mechanism of action is inhibiting prostoglandins
Opioid Drugs
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Morphine is the prototype
 Vary in potency, efficacy, and adverse effects
 Produce analgesia by binding to discrete opiate
receptors in the peripheral and central nervous
systems
 Do not have a ceiling effect, but care is needed to
balance analgesia vs. side effects
– Nausea, mental clouding, sedation, constipation,
tolerance, physical dependence, and myoclonus
Principles of Opioid Therapy
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Start with a specific drug for a specific type of
pain
Know the equianalgesic dose of the drug and its
route of administration
Administer analgesics regularly after initial
titration
Gear the route of administration to the patient’s
needs
Use a combination of drugs
Anticipate and treat side effects
Points
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Morphine is the prototype drug
Oxycodone has street value
Hydromorphone has poor oral availability
Methadone is a great drug, but
– Negative pre-conceived notions
– Long half-life that is unpredictable
Demerol not a good drug for pain as it’s inactive
metabolite can cause seizures
 Fentanyl only comes in a patch
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– Great for patients who cannot take po
– Hard to titrate
Side Effects
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Sedation
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– Medullary chemoreceptor
– Discontinue all other drugs
that can cause this
– Use drug with shorter ½ life
– Ritalin, caffeine or an
amphetamine can help
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trigger zone
– Tolerance develops
– Switching drugs can help
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Constipation
– START REGULAR
Respiratory depression
BOWEL REGIMEN!!
– Senna and colace most
useful
– Never gets better
– Occurs with other CNS
symptoms
– Tolerance develops
– Can reverse with naloxone
Nausea
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Pruritis
– Tolerance develops
– Use H1 blockers
Tolerance
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Effectiveness of analgesia diminishes over time
– Increase dose of drug
– Cross tolerance not complete; so can change drugs
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Taper drugs slowly
– Withdrawal – agitation, tremors, insomnia, fear,
hyperexcitability, and pain
– Slowly tapering drug can prevent these symptoms
Adjuvant Drugs
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Enhance analgesia
especially for neuropathic
pain
Antidepressants
– Tricyclic
 Enhance serotonin activity
– Paxil
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Anticonvulsants
– Stabilize membranes and
alter sodium and calcium
influx
– Gabapentin, tegretol,
dilantin
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Steroids
– Improves mood and
appetite as well
– Helpful in bone or
tumor pain
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Other
– Benzodiazepines
– Neuroleptics
– bisphosphanates
Other Techniques
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Psychotherapy
 Local anesthesia
 Nerve blocks
 Intrathecal Opioids
Examples
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Mr. H is a 50 y/o WM who presents
complaining of 2 day history of a painful
right great toe
 PE reveals a swollen right toe that is very
sensitive to the touch
 How do you treat him?
 NSAIDS such as Indocin
Case 2
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John is a 40 year old with AIDS. He has
been on AZT and ddc
 Presents with burning pain in his hands and
feet which he describes as severe and keeps
him awake at night
 What do you do?
 Consider gabapentin, TCA’s, opioids
Case 3
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David is a 67 y/o farmer with colon cancer
with liver metastases
 He reports increasing right upper quadrant
pain that he describes as a 4/10
 What do you give him?
 Tylenol or NSAIDS?
 Mild opioid combination such as Lortab
Case 3 part 2
David’s disease
progressed
 He is using 2 lortab
(5/500) every 6 hours and
2 Percodan (5/325) every
8 hours without relief
 What’s wrong with this?
 Tylenol toxicity
 You decide to place him
on a pure opioid. What do
you do?
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Figure total opioid dose
– 2 x 5 x 4 = 40mg
– 2 x 5 x 3 = 30mg
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Convert to equivalent dose
of new drug
– Both are 1:1 dosing with
morphine
– MsContin 30mg BID
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Add Breakthrough or
Rescue med
– 10% of total daily dose
– Lortab 1-2 every 6 hours
Case 3 part 3
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David now presents with acute n/v after
chemotherapy and worsening back pain
 Admitted for rehydration
 What do you do about his pain?
 MsContin 30mg bid and roughly 6 lortab
per day
 What do you do?
PCA
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Loading dose
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– Drug to control pain initially
– Nurse can give extra dose if
– Eg 5mg morphine every 10
patient in pain
– Nurse should assess patient
first for side effects
minutes
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Continuous dose
– Continuous infusion of pain
medication
– Don’t use for narcotic naïve
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PCA dose
– How much patient will get
when they hit the button
– Order dose and time interval
Booster dose
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Lockout dose
– Usually 4 hours
– How much is too much?
– Adjust based on patients
age, size, and history of
narcotic use
Case 3
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Total narcotic dose
– 30mg morphine 2x/day
– 6 lortab with 5mg hydrocodone per day
– Total oral dose of 90mg
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Convert to IV dose
– Morphine 3:1 oral to IV == 30mg morphine
– 1mg/hour continuous infusion of morphine
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Breakthrough dose
– 1 mg every 10 minutes PRN
– Booster dose by the nurses of 1-2 mg every 30 min
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Lockout dose – 4 hours max 20 mg
Case 3
Next day, David’s still in 5/10 pain and he
used a total of 50mg morphine.
 Why is he still in pain?
 Tolerance?
 Increase PCA dose to 2 mg
 Next day, David still in 5/10 pain and he
used 60 mg morphine
 Increase CI dose to 2 mg/ hour
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Case 3 (cont)
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Next day, David is better. He is eating well and
pain controlled on 50 mg total morphine
 You want to change to different oral narcotic such
as Oxycontin
 What do you do?
 Convert to oxycodone dose
– 50mg IV morphine = 150mg PO morphine
– morphine and oxycodone 3:2 equianalgesic
– Oxycontin 40 mg bid with oxycodone 5-10 mg every 4
hours for breakthrough
Don’t Forget
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Bowel regimen
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Senna/colace
Lactulose
MOM
Sorbitol
Miralax
Etc
Adjuvant drugs
Obligatory Kid Pic