Download - Conceptualizing pain
CONCEPTUALIZING PAIN
Kyle P. Edmonds, MDAssistant Clinical Professor
Doris A. Howell, MD, Palliative Care ServiceUC San Diego Health Sciences
Adapted from the Palliative Care International Curriculum Series Editor, Frank R. Ferris, MD
OBJECTIVES
• Pain may be nociceptive, neuropathic or both and the history tells you which.
• A standardized approach to the assessment of pain helps prevent miscommunication.
• For constant pain, schedule dose using data.
• For breakthrough pain, use PRN dose.
PAIN
“Pain is whatever the person says it is…”
- Margo McCaffery
MECHANISM OF PAIN- DESCARTES
BASIC STEPS: PAIN PROCESSING
• Transduction
• Transmission
• Perception
• Modulation
NOCICEPTOR
• Nerve cell
• Activation• Thermal • Chemical• Mechanical
• Transmits signal
PAIN TRANSDUCTION
• Response to noxious stimuli
• Carried by A-delta and C-fibers
TRANSMISSION: 3 STAGES
• Stimulus to cord
• Cord to brain stem
• Brain stem to higher cortex
• Sensation
• Somatosensory cortex
• Emotional response
• Frontal cortex
• Limbic system
TRANSMISSION
PERCEPTION
• Experience• Conscious
• Multidimensional
• Interaction of transmission / transduction
“TOTAL PAIN”
MODULATION
• Changing
• Inhibiting
• Spinal cord level
PAIN PROCESSING
• Transduction
• Transmission
• Modulation
• Perception
CLASSIFICATION OF PAIN
• Physiologic• Nociceptive
• Neuropathic
• Mixed
• Temporal• Acute
• Chronic
NOCICEPTIVE PAIN
• Somatic• Skin
• Soft tissue
• Bone
• Visceral
NEUROPATHIC PAIN
• Damaged or dysfunctional nerves
• Central
• Peripheral
MIXED PAIN
• Experiencing • nociceptive and
• neuropathic
CLASSIFICATION OF PAIN
• Physiologic• Nociceptive
• Neuropathic
• Mixed
• Temporal• Acute
• Chronic
TEMPORAL CLASSIFICATION: ACUTE
• Sudden or recent onset
• Identifiable cause
• Short duration
• Sympathetic response
TEMPORAL CLASSIFICATION: CHRONIC
• Persistent
• No obvious cause
• Functional impairment
• No sympathetic response
INTERVAL SUMMARY
Understanding the pathophysiologyleads to improved assessment and
targeted management that will improve outcomes
PAIN ASSESSMENT
1. Location2. Description (type)3. Change over time4. Severity (0 – 10)5. Effect of
treatments• Benefit (+)• Unwanted effects (-)
• Constant
• Breakthrough
• Intermittentacute
3. CHANGE OVER TIME
PAIN ASSESSMENT TOOLS
• Self Report
• NRS (adult)
• Behavioral Pain Scales
• Checklist of Non-Verbal Pain Indicators (CNPI) – non-critical care units
• Critical-Care Pain Observation Tool (CPOT) – ICUs
• Assumption that Pain is/will be Present (APP)
INTERVAL SUMMARY
Assessment of pain requires a thoughtful history and physical. This step helps you to tailor & target your treatment options.
FEEDBACK? QUESTIONS?
• New Opioid Naïve Pain Orders Set
• What’s working?
• Not working?
• More pages? Less?
• Easier? Harder?
• Next steps?
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AbsorptionExcretion
First Order KineticsWhen biological effect
follows plasma concentration
MILD PAIN / MULTIMODAL PAIN
• Mild Pain: pain score 1-4• UCSD guidelines are to avoid use of opioids for
mild pain
• Multi-modal analgesic guidelines
• Scheduled vs PRN non-opioid agents
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Principle: Scheduled Dosing Steady State
Pain control
Unwanted effects
MODERATE / SEVERE PAIN ORDERS
• Moderate (VAS=5-7) & Severe (VAS=7-10)
• Behavioral Scale/APP set to moderate dose
• Nurse reassessment around analgesic peak
• PO peak 1 hour
• IV peak 30 minutes
• Rescue dose available at reassessment
• Breakthrough
• Intermittentacute
PAIN CHANGE OVER TIME
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IV
PO / PR60min
Time to MaximumConcentration ( t Cmax )
10min
RESCUE OPTIONS
• Rescue is EITHER PO or IV
• No more than 3 (oral or IV) in 24 hrs.
• Used with EITHER moderate or severe pain after reassessment at the peak of the PRN drug administered.
PRINCIPLE:ACUTE PAIN PRN MED
• Treat rapidly & safely
• Short-acting dosed at point of maximum effect (Cmax)
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Cmax
Acute Pain Principle
PO / PR≈ 1 hr
Cmax
• Constant
• Breakthrough
PAIN CHANGE OVER TIME
PRINCIPLE:CONTINUOUS PAIN SCHEDULED
MED
• To achieve steady-state
• Schedule non-opioid
• Opioid use guided by data
• PRN usage or
• Short-acting meds scheduled on the T½
CONTINUOUS PAIN PRINCIPLE
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Dosing every half-life ( t ½ )Oral morphine = 4 hours
164 8 12Time ( hours )20 24
50%75%
87.5%93.75%
97%100%
Pla
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Steady state after 5 half-lives≈ 20 hours
Pain control
Unwanted effects
Pla
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0
Time to Drip ( or Long-acting ) Steady State
164 8 12Time ( hours )20 24
50%75%
87.5%93.75%
97%100%
Pain Control
Change GTT12+ more hours!
Pla
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…20 Time
Steady State ~ 20 hours
Concentration needed to
control pain
Concentration where side-effects
start to occur
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STAGES OF RESPIRATORY DEPRESSION
Sedation
Bradypnea
Death
Awake & in Pain
PASERO OPIOID SEDATION SCALE (POSS)
• S = Asleep, easy to arouse
• 1 = Awake & Alert
• 2 = Slightly drowsy, easily aroused
• 3 = Frequently drowsy, arousable, drifts off to sleep during conversation
• 4 = Somnolent, minimal or no response to stimulation
SUMMARY
• Pain may be nociceptive, neuropathic or both and the history tells you which.
• A standardized approach to the assessment of pain helps prevent miscommunication.
• For constant pain, schedule dose using data.
• For breakthrough pain, use PRN dose.
PALLIATIVE CARE IS…
• A team that can help your patients and families manage the pain, symptoms, and stress of serious illness.
• Available at any age and at any stage in a serious illness and can be provided along with curative treatment.
• Expert communication for challenging situations.
• Partnering with you for better outcomes by helping your patients tolerate curative treatment.