2. Pain lecture
Module Title: Anaesthesia Management III
Course Title:- ICU and Pain Management
Course Number:- Anst 5172
Credit Hours:- 3
Course Description:- This course is designed to enable the anaesthetist to
effectively assess and manage pain as well as identify, assess and manage
patients who are critically ill.
21/08/09 2
3. Cont..
Course Objectives:-
By the end of the course the student will be able to:
Define pain & explain the physiology of pain
Competently assess & manage acute post operative and non post-operative
pain.
Understand the basics of chronic pain management
21/10/20
09 3
4. Pain…
What is the real definition of pain?
And what is pain management??
How can this information help me???
18/8/09
4
5. Group Assignment
G1. Describe the characteristics and genesis of pain
G2. Explain the categories of pain
G3.Manage pain Effectively
G4.Consequences of untreated pain
Submit after a week.
6. Definition of Pain
An Unpleasant Sensory and Emotional
Experience Associated with Actual or
Potential Tissue Damage, or Described
in Terms of Such Damage.
7. Physiology of Pain
INTRODUCTION
Pain is defined by the International Association for
the Study of Pain (IASP) as ‘an unpleasant sensory
and emotional experience associated with actual
or potential tissue damage or described in terms of
such damage’.
Pain has objective, physiological sensory aspects
as well as subjective, emotional and psychological
components.
The term ‘nociception’ is used only to describe the
neural response to traumatic or noxious stimuli.
8. What areas in the CNS are involved
in pain generation and perception?
Afferent pathways,
CNS and efferent pathways.
Nociceptors transmit pain sensation to
the dorsal horn of the spinal cord
(substantia gelatinosa, laminae) across
to the contralateral spinal cord and
through spinothalamic tracts to the
thalamus 21/o8/20
09
8
9. PERIPHERAL TRANSMISSION
Transmission occurs from the peripheral
receptor to the brain as one continuous
process, for convenience this section is divided
into peripheral and central transmission.
Peripheral transmission of pain consists of
production of electrical signals at pain nerve
endings (transduction) followed by
propagation of those signals through the
peripheral nervous system (transmission).
10. Transduction
The primary sensory structure that
accomplishes transduction is the nociceptor.
Most nociceptors are free nerve endings that
sense heat, mechanical and chemical tissue
damage. Several types are described:
1. mechanoreceptors, which respond to
pinch and pinprick,
2. silent nociceptors which respond only in
the presence of inflammation, and
3. polymodal mechano-heat nociceptors.
12. The pain experience begins with the
nociceptors.
These are afferent nerves that respond to
noxious stimulation.
Different nociceptors may preferentially react
to a specific kind noxious stimuli, such as
mechanical or temperature sensation.
Different types of nociceptors may be found
in different sites: for example, the most
common cutaneous receptor is the polymodal
C fiber, which responds to pressure,
temperature and chemical stimuli, whereas
skeletal muscle contains mostly
chemoreceptors.
13. Cont..
All nociceptors have an initial high threshold
to noxious stimuli, which decreases with
repeated stimuli.
It is tempting to stop at this point and treat
pain as a simple reflex, in which the
nociceptor receives a noxious response and
transmits it to the brain. Much pain
treatment is based on this naive assumption.
It is, in reality, a long and complicated
journey between the nociceptor and the
brain. Signals from the nociceptor are
transmitted to the spinal cord.
14. Cont..
This is done mainly by two fibers: Ad fibers
and C fibers.
Ad fibers are myelinated and provide the
initial pain response.
C fibers are unmyelinated and probably
cause the slower response felt several
seconds after an injury.
Most of these fibers enter the spinal cord
through the dorsal root ganglion and
terminate in the dorsal horn of the spinal
cord.
15. cont
Generally they terminate ipsilaterally, but a
small number will cross to the contralateral
side.
The clinical significance of this is not clear, but
it may explain the incomplete pain relief seen
after unilateral surgical ablation of this area.
The dorsal horn is organized into areas, called
laminae, and certain pain fibers will
predictably go to specific laminae
16. Cont..
In the laminae the fibers synapse with
second order neurons, which take various
pathways to the brain.
The best understood pathways are the
spinothalamic and spinoreticular
pathways.
These pathways are named after their
points of origin and termination.
17. Modulation of the Stimulus.
Local chemicals.
No "pain transmitter" has been identified. However,
many substances can modulate a nociceptor's response
to noxious stimuli.
The best understood is substance P, which may work
indirectly through vasodilatory effects.
Other chemicals that have a role in pain modulation
include prostaglandin, serotonin, histamine,
acetylcholine, bradykinin, slow-reacting substance of
anaphylaxis (SRS-A), calcitonin-gene-related peptide
(CGRP), and potassium.
18. Higher down-modulation.
Virtually every part of the pain system can
reciprocally affect other parts, and the
system should be envisioned as bidirectional.
The cortex, in particular, can influence all
previous stages of pain transmission through
a variety of means.
The most obvious is through attentional
processes. Most of us are familiar with
stories of combat victims who performed
heroic acts after injury, apparently unaware
of their pain until hours later.
19. Cont..
More common are reports from chronic pain
patients that their pain seems to get worse
at night, presumably when there is less
distraction.
The meaning of pain can also influence its
perception--for example, pain perceived as
jeopardizing health (e.g.. cancer pain) can
seem worse than pain that is not life
threatening.
Finally, a variety of learned phenomena,
such as cultural factors, can affect one's
perception and expression of pain.
21. Assessment of Pain
Immediate Pain, Physical Functioning, Psychological Factors Pain
Behaviors, Objective Correlates and Pain is always subjective.
It is the result of a variety of factors.
The assessment of pain, therefore, must rely on methods that are
necessarily subjective and multidimensional.
Currently there is no universal "gold standard" for pain assessment,
and it is not the purpose here to outline a blueprint for such an
assessment.
However, any approach must acknowledge the many different
dimensions of the pain experience.
These dimensions are discussed in the following slides and include
the areas bulleted above.
22. Cont..
Thus, the take home is that pain is very
complex.
It is not like other senses. There are
multiple systems involved, and they are
reciprocally influenced by what appears
to be a central control over the
process.
24. Intensity.
Most commonly, we wish to quantify the intensity of the pain.
We might give the patient a list of adjectives to describe
the pain, usually listed in order of increasing intensity.
Alternately, we might ask the patient to give a numerical
value to the pain intensity.
In the latter case, we often ask patients to rate the pain
from one to 10, one being no pain and 10 the most pain
they can imagine.
The latter approach is particularly practical in that it
rapid and easy to do, and most patients can readily
understand the task.
This can help us track changes in intensity over time, for
example, in response to treatment.
26. Introduction
Pain Signal Processing:
Pain perception is a complex phenomenon
involving sophisticated transmission
pathways in the nervous system
With many pain signal transmission points,
there exists opportunity!
27. Acute Pain
Pain in Perioperative Setting
Pain in Patients with Severe or Concurrent
Medical Illnesses (Pancreatitis)
Acute Pain Related to Cancer or Cancer
Treatment
Labor Pain
28. Acute Perioperative Pain
Pain that is Present in a
Surgical Patient Because of
Preexisting Disease, the
Surgical Procedure, or a
Combination of Both
29. Why Treat Pain?
Basic human right!
↓ pain and suffering
↓ complications –
↓ likelihood of chronic pain development
↑ patient satisfaction
↑ speed of recovery → ↓ length of stay → ↓
cost
↑ productivity and quality of life
31. Importance of
Pain Management
Adequate Pain Control
Reduce the Risk of Adverse
Outcomes
Maintain the Patient’s Functional
Ability, as well as Psychological Well-
being
Enhance the Quality of Life
Shortened Hospital Stay and Reduced
Cost
32. Adverse Outcomes Associated with
Management ofAcute Pain
Respiratory Depression
Circulatory Depression
Sedation
Nausea and Vomiting
Pruritus
Urinary Retention
Impairment of Bowel Function
33. Adverse Outcome of Undertreatment
of Acute Pain
Thromboembolic or Pulmonary
Complications
Needless Suffering
Development of Chronic Pain
34. Adverse Effects of Poor Pain Control
“… it remains a common misconception amongst
clinicians that acute postoperative pain is a
transient condition involving physiological
nociceptive stimulation, with a variable
affective component, that differs markedly in its
pathophysiological basis from chronic pain
syndromes.”
36. Pain Assessment
Origin of Pain
Acute Pain
ie. Incisional pain, acute appendicitis
Chronic Pain
ie. Chronic back pain
Acute on Chronic Pain
Acute and chronic causes may or
may not be related to each other
37. Pain Assessment Tools
In Pediatric Patients:
Physiologic and Behavioral Indicators
of Pain ( Infants, Toddlers, Nonverbal
or Critically Ill Children)
Face Scale (Age 3-10 yrs)
Visual Analogue Scales (Age 10-18)
41. Pain Assessment
Current Pain Medications
Accuracy and detail are very important!
Name, dose, frequency, route
ie. Oxycontin 10mg PO TID
Don’t forget to re-order or factor in patient’s pre-
existing pain Rx usage when writing orders
Conflicts with HPI(Hx, of pr. Illness) PMH(past med. Hx)
Renal disease → avoid morphine, NSAID’s
Vomiting → avoid oral forms of medication
Short gut/high output stomas → avoid CR
formulations
42. Pain Assessment
Allergies / Intolerances
Drug allergies
Document drug, adverse reaction and
severity
Intolerances
Nausea / vomiting, hallucinations,
disorientation, etc.
Very important to differentiate between an allergy and an intolerance!
43. Methods to Treat Pain
Pharmacologic manegement
Alter Nerve Conduction (Local
Anesthetics)
Modify Transmission in the Dorsal Horn
(Opioids, Antidepressants)
51. Multimodal Analgesia
Using more than one drug for pain control
Different drugs with different mechanisms/sites
of action along pain pathway
Each with a lower dose than if used alone
Can provide additive or synergistic effects
Provides better analgesia with less side effects
(mainly opiate related S/E)
Always consider multimodal analgesia when
treating pain
52. Acetaminophen
First-line treatment if no contraindication
Mechanism: thought to inhibit prostaglandin
synthesis in CNS → analgesia, antipyretic
Typical dose: 650 to 1000 mg PO Q6H
Max dose: 4 g / 24 hrs from all sources
Warning: ↓ dose / avoid in those with liver damage
54. NSAIDs
Warnings: ↓dose / avoid if
GI ulceration
Bleeding disorders / Coagulopathy
Renal dysfunction
High cardiac risk – COXII inhibitors
Asthma
Allergy
?Avoid celecoxib if allergic to Sulpha
Concern for anastomotic leaks?
55. Opioid Analgesics
Bind to Opioid Receptors:
Mu, Delta and Kappa
Morphine, Hydromorphone, Meperidine,
Fentanyl, Codeine, Methadone,
Oxycodone, Hydrocodone, Tramodol
Opioids may be Combined with NSAIDs
to Enhance the Opioid Analgesic Effect
56. Opioids
Key Points:
Centrally acting on opioid receptors
No ceiling effect
High dose/response variability in non-opiate
users
Previous dependence creates a challenge in
acute on chronic pain management cases
Balancing safety and efficacy can be difficult
(OSA patients)
Side effects may limit reaching effective dose
58. Opioids
Morphine
Most commonly prescribed opioid in hospital
Metabolism:
Conjugation with glucuronic acid in liver and kidney
Morphine-3-glucuronide (inactive)
Morphine-6-glucuronide (active)
Impaired morphine glucuronide elimination in renal failure
Prolonged respiratory depression with small doses
Due to metabolite build-up (morphine-6-glucuronide)
59. Opioids
Hydromorphone (Dilaudid)
Better tolerated by elderly, better S/E profile
Preferred over morphine for renal disease
patients
Low cost, IV and PO forms available
Oxycodone
Good S/E profile, but $$
PO form only
Percocet (oxycodone + acetaminophen)
60. Opioids
Codeine
1/10th Potency of morphine
Metabolized into morphine by body
Ineffective in 10% of Caucasian patents
Challenge with combination formulations
Meperidine (Demerol)
Not very potent
Decreases seizure threshold, dystonic reactions
Neurotoxic metabolite (normeperidine)
Avoid in renal disease
61. Opioids - Formulations
Short acting forms
Need to be dosed frequently to maintain
consistent analgesia
Controlled Release forms
Provides more consistent steady state level
Helpful for severe pain or chronic pain situations
Never crush / split / chew controlled release pills
62. Opioids
Drug PO
mg
IV
mg
Starting
Oral Dose
mg
Comments
Morphine 30 10 15-30 MS Contin, Release 8-12 hrs
MSIR for BTP
Hydro-
morphone
7.5 1.5 4-8 Duration Slightly Shorter
than Morphine
Meperidine 300 75 Duration Slightly Shorter
than Morphine
Normeperidine Causes CNS
Toxicity
Methadone 20 10 5-10 Qd Long Half-Life, 24-36 hrs
Accumulates on Days 2-3
Fentanyl 0.02-
0.05
Fentanyl Patch, 12 hrs Delay
Onset and Offset
63. Dose Regimens for PCA
Drug Bolus Dose
(mg)
Lock-Out
(Minutes)
Morphine 0.5-2 5-15
Hydromorphone 0.1-0.2 5-10
Fentanyl 0.01-0.02 5-10
66. Opioids – PCA
Allows patient to reach their own
minimum effective analgesic
concentration (MEAC)
Rapid titration (Morphine 1mg IV
every 5 min)
Better analgesia and less side
effects than IM prn
67. Gabapentin
Anti-epileptic drug, also useful in:
Neuropathic pain, Postherpetic neuralgia,
CRPS
Blocks voltage-gated Ca channels in CNS
Additive effect with NSAIDs
Reduces opioid consumption by 16-67%
Reduces opioid related side effects
Drowsiness if dose increased too fast
72. Anatomy of
Epidural Space
Surrounds the Dural
Sac
Anteriorly: Post.
Long. Ligament
Posteriorly:
Ligamentum Flavum
Laterally: Pedicles and
Intervertebral Foramina
73. Anatomy of Epidural Space
AP Dimension of the Epidural Space is Largest
in the Lumbar Region, 5-6 mm
In Thoracic Region the AP Dimension
Decreases but the Space is More Continuous
80. Regional Anesthesia
Involves blockade of nerve impulses using local anesthetics (LA)
LA bind sodium channels preventing propagation of action potentials
along nerves
Wide variety of LA with different characteristics:
ie. Lidocaine – fast onset, short duration of action
ie. Bupivacaine (Marcaine) – slow onset, longer duration
82. Benefits of
Epidural Analgesia
Superior analgesia to IV PCA in open abdominal procedures &
specifically in colorectal surgery
Reduce incidence of paralytic ileus
Blunt surgical stress response
Improves dynamic pain relief
Reduces systemic opiate requirements
Facilitates early oral intake, mobilization and return of bowel fx
when part of fast track protocols
83. Epidural Analgesia
Recommended as part of ERAS/fast track protocols for
colon/colorectal surgery
Increased incidence of hypotension and urinary retention
Management of postoperative hypotension?
84. Contraindications to
Neuraxial Blockade
Absolute:
Pt refusal or allergy to LA
Uncorrected hypovolemia
Infection at insertion site
Raised ICP
? Coagulopathy
Relative:
Uncooperative patient
Fixed cardiac output states
Systemic infection/sepsis
Unstable neurological disease
Significant spine abnormalities or surgery
87. Opioid Overdose Management
Opioid Reversal
Naloxone - opioid antagonist
Reverses effects of opioid overdose (for 30-45min)
MUST BE diluted before use:
0.4mg ampule
Dilute: 1mL Naloxone + 9mL Saline = 0.04 mg/mL
Give 0.04 to 0.08 mg (1 to 2 mL) IV q3-5 minutes
If no change after 0.2mg, consider other causes
88. Opioid Overdose Management
Ddx:
Seizure, stroke
Hypoxia, Hypercarbia
Hypotension
Other medication effect
Severe electrolyte or acid base abnormalities
MI
Sepsis
…..etc.
89. Acute Pain Service
Consult service for complex / specialized pain
management
Anesthesia Staff + Advanced Practice Nurses
Many post-op patients will be followed by APS
If APS involved, APS must write all pain Rx
Call for:
Advice
Difficult to manage cases
90. Summary
Accurate pain assessment
Make sure to continue or account for patient’s pre-hospital pain regimen
Use Multimodal pain management
Discharge pain management plan
Acute Pain Service available 24 hrs/day
91. Summary
Superior analgesia, ↓ side effects means:
Improved patient satisfaction
Better rehabilitation
Earlier functional return
Earlier discharge from hospital
↓ likelihood of chronic pain
Reduced health care costs
92. Why Treat Pain?
Basic human right!
↓ pain and suffering
↓ complications –
↓ likelihood of chronic pain development
↑ patient satisfaction
↑ speed of recovery → ↓ length of stay → ↓ cost
↑ productivity and quality of life
94. Importance of
Pain Management
Adequate Pain Control
Reduce the Risk of Adverse Outcomes
Maintain the Patient’s Functional Ability, as well as
Psychological Well-being
Enhance the Quality of Life
Shortened Hospital Stay and Reduced Cost
96. Outline
Definition
Common Pain Syndromes
Oral therapy
Opioids
Antidepressants
Anticonvulsants
Epidural Steroid injections
Trigger Point Injections
Non pharm: TENS unit, heat/cool
Spinal cord stimulator
Cancer Pain
97. Definition
Chronic Pain: pain that persists beyond the usual course
of an acute disease or after a reasonable time for
healing to occur
Often complex with patients having biologic disease that
coexists with congnitive, behavioural, and social factor
May be nociceptive, neuropathic, or both
Nociceptive: due to noxious stimulation of tissue that
activates nociceptors
Neuropathic: due to prolonged injury of the nerve
fiber/neural structures
98. Common Pain Syndromes
Low Back Pain
Neuropathic Pain
Diabetic Neuropathy
Post-herpetic neuralgia
Chronic Regional Pain Syndrome (CRPS)
Type I and Type II
99. Low Back Pain
One of the most common reasons people seek medical
attention
Between T12 to sacro-coccygeal joint
Conservative management
60-70% patients recover in 6 weeks
90% patients recover in 12 weeks
After 12 weeks, recovery in uncertain
100. Low Back Pain
Lumbosacral pain – localized to the back
Radicular pain – distributed in the area of a nerve
101.
102. Radicular Pain
Signs: numbness, weakness, loss of deep tendon
reflexes in area of affected nerve root
Acute Radicular Pain:
usually due to a herniated nucleus pulposus (“herniated
disc”) or foraminal narrowing that causes inflammation of
the nerve root
Chronic Radicular Pain:
requires indepth diagnostics to find source, often with MRI
103. Lumbosacral Pain
Acute: ususally due to myofascial injury
Chronic: may arise from injury of many parts of the
vertebral unit
i.e. sacroiliac joint, lumbar facts, intervertebral discs
Diagnostic nerve blocks into these areas by pain specialist
with local anesthetic may help figure out cause
104.
105.
106. Neuropathic pain
Pain following injury to the nervous system
Two common examples
Diabetic neuropathy
Postherpetic neuralgia
107. Diabetic Neuropathy
Occurs in advanced diabetes mellitus (both Type I and
Type II)
Peripheral – usually first presents in the feet
Pt having numbness, tingling, burning sensation
108. Postherpetic Neuralgia
Occurs 3-6 months after acute infection of herpes zoster
(also called varicella zoster or Shingles)
Usually in immunocompromised or elderly patients
Pts have episodic sharp pain in a dermatomal
distribution
Zoster infection can now be prevented by a vaccine
109. Complex Regional Pain
Syndrome (CRPS)
Due to a known injury
Pain disproportionate to original injury
Pain often severe and burning, pt may have joint stiffness,
atrophic changes in muscle
Accompanied by sympathetic nerve dysfunction
Changed in vasoconstriction and vasodilation, changes in
temperature, loss of hair in the affected region
2 Types
CRPS I: absence of known nerve injury
CRPS II: known nerve injury
111. Opioids
See “Acute Pain” lecture for mechanism
Oral Opioids include:
Morphine sulfate
Codeine
Hydromorphone
Tramadol
Oxycodone
Some opioids (morphine, oxycodone) come in
immediate and sustained release formulations
112. Opioids
Pt develop tolerance quickly and can require escalating
doses
May need to “rotate” opioids to have continued effect
Manage side effects
Constipation
Nausea, Vomiting
113. Antidepressants
Have an analgesic effect that occur at lower doses than
needed for their antidepressant action
Often helpful for neuropathic pain
Mechanism: blockade of presynaptic reuptake of
serotonin, norepinephrine, or both
Older tricyclic antidepressants are more effective
analgesics than newer SSRIs (selective serotonin
reuptake inhibitors)
Commonly use tricyclic antidepressants
Nortryptiline
Amitryptiline
114. Anticonvulsants
Useful for neuropathic pain
Mechanism: block voltage-gated sodium channels and
suppress spontaneous neural discharges
Examples:
Gabapentin
Carbamezapine (first line for trigeminal neuralgia, which
is a distinct syndrome from post-herpetic neuralgia)
115. Epidural Steroid Injections
Useful for patients with radicular back pain
Usually a combination of local anesthetic (lidocaine 1%)
and a steroid is given
Local Anesthetic provides rapid relief of pain
Steroid takes a couple days to work, but will reduce
inflammation of nerve root and provide more long term
relief
Typical Steroids: methylprednisolone or triamcinolone
Usually done with x-ray/fluoroscopy by pain specialist
Epidural needle is usually smaller gauge than typically
used in the OR.
116. Trigger Point Injection
Indication: Myofascial pain – often in upper or lower
back
Technique:
Identify “trigger points”: areas of the back that are
particularly tender to palpation and reproduce the back
pain
Mixture of lidocaine and bupivacaine
Syringe with 25g needle injects ~2ml of local anesthetic
into trigger point
While doing so, move the needle in many directions to
break up the muscle fibers
The main benefit is from the needle breaking up the
contracted muscle fibers.
117. Non-pharmacologic
Heat/Cool to affected area
Transcutaneous Electrical Nerve Stimulation (TENS Unit)
– a device that provides external vibration to the painful
area
Stimulates large afferent fibers
Thought to be a distracting input that will reduce the
amount of pain sensed
119. Non-pharmacologic
Heat/Cool to affected area
Transcutaneous Electrical Nerve Stimulation (TENS Unit)
– a device that provides external vibration to the painful
area
Stimulates large afferent fibers
Thought to be a distracting input that will reduce the
amount of pain sensed
120. Spinal Cord Stimulator
A small device is surgically implanted with electrodes in
the epidural space
Mechanism: activation of descending modulating
systems and inhibition of sympathetic outflow
Indications:
Spinal cord lesions, phantom limb pain, ischemic lower
extremity pain
Still an area with much research.
121. Cancer Pain
Pain is the most common presenting symptom of
undiagnosed malignancy
May be due to cancer invasion or cancer treatment
Infiltration into bone or nerves is especially painful
May also have pain from chemotherapy, radiation, or surgical
treatment
Primary focus is treatment of malignancy but may
require specific treatment of symptoms as well
122. Cancer Pain Treatment
Multimodal
Includes
Opioids – mainstay
Many routes of administration – pills, liquid, transdermal
patch, buccal, IV
Tricyclic antidepressants
Anticonvulsants
Implantable intrathecal drug delivery
Palliative sugery
Nerve blocks with agents that permanently lyse the nerves
Celiac plexus block for pancreatic cancer
