Pain Management

Christine Nevins-Herbert, MD

Disclosures

Nothing to disclose

Objectives

Understand the basic physiology of pain Review different types of pain and how to

assess pain Focus on appropriate pain management

with opioids

*Not a lecture on opioid addiction/ misuse, long term outpatient opioid prescribing, or determining who is appropriate for opioids

What is Pain?

An unpleasant sensory and emotional experience associated with actual or potential tissue damage

- International Association for the Study of Pain (IASP)

Concept of Total Pain

Physical Emotional Social/interpersonal Spiritual/existential

Pathophysiology of Pain

Detected by peripheral nociceptors – Nociceptors – primary sensory neurons that

respond to painful stimuli – In skin, muscle, joints, viscera – A delta fibers – immediate, sharp pain – C fibers – delayed, longer lasting dull pain

Nociceptors send afferent signals through dorsal horn of spinal cord to brain

Spinothalamic Pathway

Multiple ascending pathways involved Signals sent via spinothalamic tract –

synapses in thalamus Neurons in thalamus project to primary

somatosensory cortex

Acute vs. Chronic Pain

Acute Pain – Serves a purpose, time limited – Cause often known – Diminishes as healing takes place – May have observable signs

Chronic Pain – Purposeless, cyclical, irreversible – Vegetative, depressive signs – Autonomic adaptation

Why Treat Pain?

Promote healing Patient experience/satisfaction Improve quality of life Alleviate suffering Avoid evolution to chronic pain

Consequences of Undertreatment in Elderly Depression Anxiety Social isolation Cognitive impairment Immobility Sleep disturbances Delirium

Types of Pain

Nociceptive – Somatic – Visceral

Neuropathic Mixed Psychogenic

Nociceptive Pain

From actual or potential tissue damage Somatic

– Nociceptor activation in body surface or musculoskeletal tissue

– Easy to localize – “sharp, stabbing, aching, throbbing”

– Examples: arthritis, wounds, bone mets

Nociceptive Pain

Visceral – Nociceptor activation due to compression,

obstruction, infiltration, ischemia, stretching, or inflammation of viscera

– Difficult to localize – “cramping, gnawing, pressure”

– Examples: SBO, angina, liver mets, urinary retention, constipation

Neuropathic Pain

Direct injury or dysfunction of peripheral or central nervous system

“Burning, shooting, tingling” Examples: diabetic neuropathy,

postherpetic neuralgia, radiculopathy, phantom pain, post-mastectomy or post-thoracotomy pain syndromes

Assessing Pain

O – Onset – When did it begin? How long does it last?

How often does it occur?

P – Provoking/palliating – What makes it worse? What makes it

better?

Q – Quality – What does it feel like? Can you describe it?

Assessing Pain

R – Region/Radiation – Where is it? Does it go anywhere else?

S – Severity – How intense is the pain (0-10 scale)? Right now?

At its worst? At its best?

Assessing Pain

T – Treatment – What medications are being used? How effective

are they? Any side effects? What have you tried in the past?

U – Understanding/Impact – What do you think is causing the pain? How is the

pain affecting you? Functional impairment? Impaired quality of life?

V – Values – What is your goal? What level of pain would be

acceptable for you?

Barriers in the Elderly

Under-reporting by patients Atypical manifestations of pain in the

elderly – Changes in function or gait – Withdrawn, agitated, confused

Misconceptions about tolerance and addiction to opioids

Reluctance to use opioids

Opiates

Receptors involved – Mu, kappa, delta

Mechanism of action – Bind to receptors – Modulate pain by inhibiting calcium

channels – Prevent or induce release of

neurotransmitters

Opiates – Adverse Effects

GI – constipation, nausea, vomiting Autonomic – dry mouth, urinary

retention, postural hypotension Cutaneous – itching, sweating CNS – sedation, confusion, dizziness,

hallucinations, delirium Pulmonary – respiratory depression True allergy is rare

Definitions

Tolerance – physiologic state; effectiveness of drug has decreased due to chronic use; need higher dose to achieve same effect

Physical dependence – how body experiences physiologic adaptation; withdrawal if stopped abruptly

Definitions

Addiction – behavior; compulsive use of drugs often for inappropriate reasons; continued use despite harmful consequences

Pseudoaddiction – behavior that mirrors addiction; often due to inadequately controlled pain

Opioid Calculation and Conversion

Getting Started

Consider scheduled tylenol “Start low, go slow” especially in elderly Tempting to use tramadol and lidocaine

patches in elderly – Tramadol: dizziness, lowers seizure threshold,

med interactions – Lidocaine patches: cost, works topically, does

not penetrate bone or joint space

Getting Started

Start with short acting opiates in opiate naïve patient

Long acting opiates should only start after 24hr need is assessed

Breakthrough dose should be 10-15% of total daily dose

Breakthrough Dose?

Patient is on MSContin 150mg q12hrs

What should breakthrough/short acting dose be?

Breakthrough Dose

Total daily dose is 300mg of PO morphine

Breakthrough dose should be MSIR 30-45mg q3-4hrs prn pain

Adjusting Long Acting Dose

Generally, if 3 or more breakthrough doses are used in 24hrs – Increase long acting opiate by 50-100%

of total amount of breakthrough med used in 24hrs

Long Acting Dose?

Patient is on MSContin 100mg q12hrs Has used 6 breakthrough doses of

MSIR 30mg in the past 24hrs

What should the new MSContin dose be?

Long Acting Dose

Patient used 180mg of breakthrough morphine

MSContin should be increased by 90-180mg = 145mg q12hrs - 190mg q12hrs

Based on patient’s pain intensity, side effects, and goals of care

Opioid Rotation

Intolerable side effects Poor analgesic effect despite aggressive

dose titration Drug-drug interactions Change in route Drug availability

Opioid Rotation

Dose of new opioid should be reduced by 25-50%

Accounts for incomplete cross-tolerance – Due to differing structures of individual

opioids and action at various receptors

Potency

IV opioids are more potent than oral opioids – Morphine 3:1 – Dilaudid 5:1

Dilaudid is far more potent than morphine – PO dilaudid 4x more potent than PO

morphine – IV dilaudid nearly 7x more potent than IV

morphine

Potency

Fentanyl patches – 50mcg fentanyl patch = 40mg IV morphine

= 120mg PO morphine

Caution

Long acting opioids (MSContin/ Oxycontin) should not be given any more frequently than q8hrs

Long acting opioids cannot be crushed Long acting opioids should never be

used for breakthrough pain

Breakthrough Pain

If separating PRN meds based on mild, moderate, severe pain – Make sure it makes sense equianalgesically – Make sure full range is covered

Fear of Respiratory Depression Principle of double effect Sedation will always precede respiratory

depression Consider use of holding parameters

– Hold for RR <10

Conversion Questions

MSContin to TD Fentanyl

1. 85 y/o M with lung cancer on MSContin 100mg q12hrs which has been effectively controlling pain for the past few months. He is now having trouble swallowing. What would be an appropriate dose of a fentanyl patch?

Decrease dose by 40% for incomplete cross tolerance.

MSContin to TD Fentanyl

Total daily dose of morphine = 200mg Decrease by 40% (80mg) = 120mg 120mg oral morphine = 50mcg fentanyl

patch

IV Morphine to PO MSContin

2. 78 y/o F with metastatic breast cancer on morphine drip at 4mg/hr in the hospital. She is getting ready to be discharged home and wants to switch to oral meds. What dose of MSContin would you recommend? (Comes in 15mg, 30mg, 60mg, and 100mg)

What would be an appropriate breakthrough dose?

IV Morphine to PO MSContin

4mg/hr x 24hrs = 96mg IV morphine/day IV:PO = 1:3 96mg x3 = 288mg PO morphine/day 288/2 = 144mg PO morphine q12hrs 145mg MSContin q12hrs Breakthrough dose 10-15% of total daily

dose ≈ 30mg MSIR q3-4hrs prn

Morphine drip to Hydromorphone drip 3. 71 y/o M with colon cancer has been

well controlled on morphine drip at 30mg/hr, but has developed uncomfortable itching. What would be an appropriate hourly rate of hydromorphone?

Decrease dose by 33% for incomplete cross tolerance.

Morphine drip to Hydromorphone Drip 30mg/hr IV morphine - 33% (10mg) =

20mg/hr IV morphine IV morphine:IV hydromorphone =

10:1.5 = 6.67 20/6.67 = 3mg/hr IV hydromorphone

TD Fentanyl to IV Morphine

4. 78 y/o F with ovarian cancer has been well controlled on 200mcg fentanyl patch, but has developed fevers. She also has difficulty swallowing and plan is to start morphine via pump. What would be an appropriate hourly rate of morphine?

Decrease by 40% for incomplete cross tolerance

TD Fentanyl to IV Morphine

200mcg fentanyl = 160mg IV morphine 160mg - 40% (64mg) = 96mg IV

morphine/day 96mg/24hrs = 4mg/hr IV morphine

Percocet to Oxycontin

5. 67 y/o M with renal cancer has been taking Percocet 5/325mg (oxycodone/ acetaminophen) 2 tabs every 4 hours, but does not wake up overnight to take a dose, and often wakes up in the morning in a lot of pain. Plan is to start Oxycontin q12hrs. What would be an appropriate starting dose of Oxycontin?

Percocet to Oxycontin

10mg oxycodone x6 = 60mg oxycodone/ day

60/2 = 30mg Oxycontin q12hrs

Reasonable to continue percocet 2 tabs PO q4hrs prn breakthrough pain

Questions??