Pain in the Adult Flashcards
Definition of Pain
Pain is an unpleasant sensory and emotional experience associated with actual or potential tissue damage or described in such terms. Pain is whatever the person experiencing it says that it is; existing whenever s/he says that it does.
MARGO MCCAFFREY, 1969
Barriers to pain management
Only about 49% of patients with pain
achieve satisfactory control
Patients, healthcare providers, and the
healthcare system present barriers to
optimum pain control
Fear of addiction and dependence
Patients may be reluctant to report pain
Scales for measuring pain intensity are not
used correctly
Categorization of pain- important
Somatic- superficial of deep
Superficial-skin- prickly, sharp, burning
Deep- aching, throbbing, (joints, bones,
muscle, skin or connective tissue)
Visceral- internal organs, linings of body
cavities, thorax and abdomen.
Visceral nociceptors respond to
inflammation, stretching, and ischemia-
intense cramping
Examples of Nociceptive pain-
Surgical incisions
Broken bones, arthritis,
Pancreatitis, inflammatory bowel disease
Treatment-usually respond to NSAIDS,
opiods
Nociceptors
Specialized nerve endings that respond to threshold
stimulation by thermal, mechanical, or chemical stimuli.
Nociceptor activation causes opening of cation and Na
channels ? opening of voltage gated Na channels ?
action potentials (intensity depends on duration and
frequency of nociceptor stimuli) that are transmitted via
Ab- fast transmission?touch,vibration, rarely pain
Ad- fast transmission, pricking pain
C- slower transmission, slow burning pain
Nociception
Transduction
Conversion of thermal, chemical, mechanical stimulus to electrical activity at nociceptor
Na channels
Conduction
Passage of action potential along the first order neuron to dorsal horn of spinal cord
Nociception
Transmission
Transfer and modulation of
input from one neuron to
another
Substance P, Glutamate, Brain
derived neurotropic factor
Inhibitory interneurons
Perception
Awareness and meaning of pain
Modulation
Descending pathways inhibit
transmission of nociceptive
impulses
Endogenous opioids,
norepinephrine, serotonin
Neural Plasticity
Neurobiological process by which changes in the
nervous system can alter the response to stimuli
Modulation
Reversible change in the excitability of neurons
Modification
Long lasting change in expression of neurotransmitters,
receptors, ion channels; and structure and functionality of
neurons ? modification and distortion of the usual stimulus
response ? abnormal responses such as hyperalgesia and
allodynia
Peripheral Sensitization
Excitability threshold of nociceptors is lowered
Most important mediators are those of
inflammation
Bradykinin, serotonin, histamine, prostaglandin,
leukotrines, cytokines, nitric acid, protons, neurotropic
growth factors
Results in increased capacity of tactile, low level
stimuli to generate hyperexcitability of nociceptors
Central Sensitization
Increases responsiveness of dorsal horn neurons to
stimuli ? heightened excitability and sensitivity
extending beyond site of injury
Loss of modulating and inhibitory signals ?
exaggerated response to noxious stimuli
NMDA receptor activation is a main factor
Pain is not static
Active process involving peripheral and central
nervous system
Neural plasticity shifts threshold and
responsiveness to pain over time, so that
Pain may appear to occur spontaneously, in an
exaggerated or prolonged course, or in response to
innocuous stimuli
PAIN ASSMT:
P lace: Where?
A mount: How much?
I ntensifiers: Worse?
N ullifiers: Better?
E ffects: Medication effect/side effect? Effect on
QOL?
D escription: How does it feel?
+
Pain History
prior therapies, recent analgesic use
Medical History
Diagnosis, prognosis, other health problems
Psychosocial History
Physical Exam
Diagnostic test results if appropriate
Clinical Examples of Pain
Syndromes
Nociceptive
Surgery, trauma
Inflammatory
Bone metastases, arthritis, healing incision
Neuropathic
PHN, diabetic neuropathy, nerve root compression
Functional
IBS, Fibromyalgia
Rational Approach to Pain
Management
T reat treatable causes
O ptimize analgesic
medications
N on pharmacological
modalities
I nvasive procedures
Treatment of Pain
Whenever possible- oral preparations
The underlying cause of pain should be diagnosed
Ask about pain regularly, assess quality duration, location
Ask about goals for pain control and management preferences
Choose options appropriate for patient, family, and setting-
dosage, route, drug type, cost.
Frequent follow up
May need pain contract
Acetaminophen
Analgesic for mild-to-moderate pain
Ceiling dose: 1000 mg/dose
Maximum dose 2000-4000 mg/day
FDA maximum dose is still 4000 mg/day
McNeil lowered recommended maximum dose to 3000
mg/day
Lower dose in older adults and individuals with hepatic
impairment
Concerns regarding multiple OTC products containing
acetaminophen; use with alcohol
Liver toxicity if maximum dose exceeded
Tramadol (Ultram)
Opioid receptor agonist with inhibition of re-uptake of
serotonin and norepinephrine
Ceiling dose 300-400 mg/24 hours
Usual dose 50-100 mg q 6h PRN
Side effects: dizziness, constipation, sedation, nausea
Reduces seizure threshold
Combination with other opioids controversial
Studies show effectiveness in treatment of peripheral
neuropathy
INITIATING OPIOIDS IN THE
TREATMENT OF CNCP
When Acetaminophen, NSAIDs, and topical agents are no
longer effective
Patients have multiple co-morbidities, and not candidates for
corticosteriod injections
Neuropathic pain guidelines recommend tx with TCA, and
SSRI, gabapentin, lyrica
May be considered in moderate to severe pain impacting
quality of life.
Opioid Risk Evaluation
Assess risk- integral part of prescribing
Check validated risk evaluation tools
Opioid risk tool
Diagnosis, risk, itractability, risk, Efficacy score
Opioid assessment for Patients with Pain-Revised (SOAPP-R)
can aid in assessing risk of addiction
Pain contract
Urine drug testing- strongly recommended
Incomplete Cross Tolerance
A patient who is tolerant to the effect and
side effects of one opioid may not be
equally tolerant to the effects and side
effects of another opioid.
Converting to new opioid
Decrease equi-analgesic dose by 1/3 to 1/2
because of incomplete cross tolerance
90 mg oral morphine ? 30 mg = 60 mg oral
morphine/24 hours
New dose: 30 mg SR Morphine q12h
Opioid for Breakthrough* Pain
Determining the ?as-needed? dose:
Each ?as needed? dose should equal 10%-20% of the 24-hour dose
of background opioid
Opioid Selection
Patient preference and experience
Availability of appropriate dosing forms
and routes of administration
Drug pharmacokinetics
Cost and insurance coverage
Pharmacokinetic Considerations
Morphine is the standard opioid
Active metabolite
Hydromorphone (Dilaudid)
Active metabolite
Methadone
Long and variable half life necessitates careful
monitoring for sedation
Fentanyl
Liphophillic
Codeine
Analgesic ceiling effect
Transdermal Fentanyl
For stable, chronic pain
12-24 hours for onset and
discontinuation of action
Heat increases absorption
Hydration and nutritional status may
affect absorption
Methadone
Theorized action as NMDA receptor antagonist
makes it useful in neuropathic pain
Long and variable half life can lead to accumulation
of drug and sedation
In high dose, may cause Q-T prolongation
High dose is > 300mg/day
Inflammatory pain such as pain from bone
metastasis often responds to:
NSAIDs
