Transcript Perioperative Pain Management

Acute Perioperative
Pain Management
Dr. Mahmoud Abdel-Khalek
What is pain?
An unpleasant sensory and emotional
experience associated with actual or
potential tissue damage, or described in
terms of such damage
IASP Pain Definition (1994, 2008)
IASP: International Association for the study of Pain
Introduction: Nociception
Introduction: Nociception
 Refers to the detection, transduction and transmission of
noxious stimuli
 Substances generated from thermal, mechanical or
chemical tissue damage, activate free nerve endings,
which we refer to as nociceptors
 These afferent fibers have their cell body located in the
dorsal root ganglion
 From DRG axons go into dorsal horn of the spinal cord
where axons synapse with the second order neuron as
well as with regulatory interneuron. In addition synapses
occur with the cell bodies of the sympathetic nervous
system and ventral motor nuclei, either directly or
through the internuncial neurons
 The cell body of the
second order neuron
lies in the dorsal horn.
Axonal projections of
this neuron cross to
the contralateral
hemisphere of the
spinal cord and
ascend to the level of
the thalamus
 In the thalamus, the
second order neuron
synapses with a third
order afferent neuron,
which sends axonal
projections into the
sensory cortex
Postoperative Pain
Postoperative pain can be divided into
acute pain and chronic pain:
Acute pain is experienced immediately after
surgery (up to 7 days);
Pain which lasts more than 3 months after
the injury is considered to be chronic.
Why Treat Pain?
Basic human right!
↓ pain and suffering
↓ complications – next slide
↓ likelihood of chronic pain development
↑ patient satisfaction
↑ speed of recovery → ↓ length of stay
→ ↓ cost
↑ productivity and quality of life
Adverse Effects of Poor Pain Control
CVS: MI, dysrhythmias
Respiratory: atelectasis, pneumonia
GI: ileus, anastomotic failure
Endocrine: “stress hormones”
Hypercoagulable state: DVT, PE
Impaired immunological state:
Infection, cancer, delayed wound healing
Psychological:
Anxiety, Depression, Fatigue
Pathophysiology
Inadequately treated pain following chest&
abdominal incisions → diaphragmatic
muscle splinting → ↓ ability to cough&
clear secretions → atelectasis,
hypoxemia& pneumonia
Nociceptive stimuli reaching the spinal
cord → sympathetic stimulation →
hypertension, tachycardia → ↑ heart work
load → ↑ oxygen demand → myocardial
ischemia in vulnerable patients&
myocardial infarction
Pathophysiology
Also increased sympathetic tone → ↑
intestinal secretions& slows gut motility& ↑
smooth muscle tone → gastric stasis,
nausea and vomiting, ileus and urinary
retention
Poorly controlled acute pain → initiation
and maintenance of stress response seen
with the trauma of major surgery →
hypercoagulability → DVT, p. embolism,
MI, ↓ immunity, hypermetabolism,
Hyperglycemia, protein catabolism and
delayed wound healing
Pain Assessment
Pain History
O – Onset
P – Provoking / Palliating factors
Q – Quality / Quantity
R – Radiation
S – Severity
T – Timing
Pain Assessment
Severity: Visual Analogue Scale
Severity of postoperative pain
Pain Assessment
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Current Pain Medications
 Accuracy and detail are very important: Name,
dose, frequency, route i.e. Oxycontin 10mg PO
TID
 Co-existing conditions
 Renal disease: avoid morphine, NSAID’s
 Vomiting: avoid oral forms of medication
 Drug allergies
 Document drug, adverse reaction and severity
 Intolerances
Nausea / vomiting, hallucinations,
disorientation, etc.
Methods to Treat Pain
 Pharmacologic
 Medications (po, iv, im, sc, pr, transdermal)
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Acetaminophen
NSAIDs e.g. Aspirin, diclofenac, ibuprofen.. etc.
Opioids e.g. Morphine, pethidine, fentanyl, codeine.. etc.
Gabapentin
NMDA antagonists e.g. ketamine
Alpha-2 agonists
 Procedures
 Regional Anesthesia
 LA infiltration at incision site
 Surgical Intervention
 Removal of cause of pain e.g. distended urinary bladder
WHO Analgesic Ladder
Acetaminophen (aka Paracetamol)
 First-line treatment if no contraindication
 It is relatively safe
 It is analgesic and antipyretic
 Mechanism: thought to inhibit prostaglandin synthesis in
CNS → analgesia, antipyretic
 It does not cause gastric irritation
 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
NSAIDs
Also, first-line treatment
Mechanism
 Block cyclooxygenase (COX) enzyme → ↓ prostaglandin
synthesis
 COX-2 → Prostaglandins → pain, inflammation, fever
 COX-1 → Prostaglandins → gastric protection, hemostasis
NSAIDs
Warnings: ↓dose / avoid if
 GI ulceration
 Bleeding disorders / Coagulopathy
 Renal dysfunction
 Asthma
 Allergy
Opioids
 They are highly effective class of analgesics
which operates at several levels in the nervous
system
 Intramuscular morphine or meperidine on prn
basis remains the most popular form of acute
postoperative pain management at most
hospitals
Opioids: mechanism of action
 They dampen the transmission of nociceptive
stimuli by binding to opioid receptors within
substantia gelationsa of the dorsal horn of spinal
cord
 They release inhibitory neurotransmitters such as
noradrenaline, serotonin and GABA
 Decrease inflammatory response in the periphery
 Affect mood and anxiety
Intramuscular opioid administration limitations
 Responsibility for management of pain is delegated to the nursing
staff, who err on the side of caution in the administration of opioids.
They tend to give too small a dose of drug too infrequently because
of exaggerated fears of producing ventilatory depression or
addiction.
 Because the administration of drugs is left entirely to the discretion
of the nursing staff, the degree of empathy between nurse and
patient affects analgesic administration.
 Because the measurement of pain is difficult, it is seldom possible to
adjust the dose of drug to match the extent of pain.
 There are enormous variations in the extent of analgesic
requirements depending upon the type of surgery, pharmacokinetic
variability pharmacodynamic variability, etc.
Opioids: Side effects
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Nausea / Vomiting
Sedation
Respiratory Depression
Pruritus
Constipation
Urinary Retention
Ileus
Tolerance
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)
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)
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
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
Management of Opioid Overdose
Ddx:
 Seizure, stroke
 Hypoxia, Hypercarbia
 Hypotension
 Other medication effect
 Severe electrolyte or acid base abnormalities
 MI
 Sepsis
 …..etc.
Management of Opioid Overdose
For ↓level of consciousness, somnolent
patient:
Stimulate patient
Vitals/Monitors/Lines
Airway
Breathing
Circulation
CODE BLUE?
Management of Opioid Overdose
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
Opioids: PCA
 Patient-controlled analgesia (PCA) permits the patient to
administer the delivery of his own analgesic by activating a
button, which then triggers the intravenous delivery of a
predetermined dose of an opioid such as morphine.
 Limits are set on the number of doses per four-hour period
and on the minimum time that must elapse between doses
(lockout interval).
 The pharmacokinetic advantage of PCA is that by self
administering frequent, small doses, the patient is able to
come closer to achieving a steady state analgesic level in
the blood, avoiding the high peaks and low troughs that can
be found with intermittent (intramuscular) opioid
administration.
Benefits of PCA
 PCA has been shown to provide equivalent analgesia with
less total drug dose, less sedation, fewer nocturnal
disturbances and more rapid return to physical activity.
 In addition, patient acceptance is high since patients have a
significant level of control over their pain management.
 PCA analgesia is not without side effects, the most common
of which is nausea and vomiting, Excessive sedation and
pruritus
 Standardized orders provide “as needed” orders for
medications to counteract both nausea and pruritus.
Benefits of PCA
 Although it does not obviate the need for close monitoring,
PCA frees nursing personnel from administering analgesic
medication.
 Since patients titrate their own therapy with PCA, they
must be capable of understanding the principle, willing to
participate and physically able to activate the trigger.
Consequently, use is prohibited at the extremes of age as
well as in very ill or debilitated patients
 Typically, the PCA modality is used for 24-72 hours.
 The patient must be capable of oral (fluid) intake prior to
converting from PCA to oral analgesics
Opioids – PCA
Management of Opioid Side Effects
Nausea / Vomiting
 Ondansetron (Zofran)
 Dimenhydrinate (Gravol)
 Metoclopramide (Maxeran)
 Changing medication(s) / ↓ dose
Pruritus
 Diphenhydramine (Benadryl)
 Changing medication(s) / ↓ dose
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
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:
 i.e. Lidocaine – fast onset, short duration of action
 i.e. Bupivacaine (Marcaine) – slow onset, longer
duration
Central neuraxial analgesia
Central neuraxial analgesia involves the delivery of
local anesthetics and/or opioids to either the
intrathecal (spinal) space or the epidural space.
Opioids added to the (spinal) local anesthetic
solution provide long-lasting analgesia after a
single injection, lasting well into the post-operative
period
The duration of effect is directly proportional to the
water-solubility of the compound, with hydrophilic
compounds such as morphine providing the longest
relief
Epidural catheters are safe and easy to insert
Epidural Analgesia
 Epidural analgesia can be used to provide pain relief for
days through the infusion of a solution containing local
anesthetic, opioid or both. The infusion is usually delivered
continuously
 Continuous epidural infusions provide a steady level of
analgesia while reducing the side-effects associated with
bolus administration
 Overall, epidural analgesia can provide highly effective
management of post-operative pain
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
Regional Anesthesia
Peripheral Nerve Blocks
 Upper Limb:
Brachial plexus
 Lower Limb:
Femoral, sciatic, popliteal, ankle
 Abdomen:
TAP blocks
 Thoracic: Paravertebral, intercostal blocks
Use of Ultrasound Imaging has revolutionized
peripheral nerve blockade
 Safety?
 Accuracy / Improved Success
 Efficiency
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
Peripheral Nerve Blocks
 Almost any peripheral nerve that can be reached with a needle
can be blocked with local anesthetics
 The brachial plexus, intercostal and femoral nerves are examples
of nerves which are commonly blocked to provide post-operative
analgesia
 A block may be used as the sole method of post-operative
analgesia or it may be useful as an adjunct to decrease the
required dose of systemic opioids
 The major drawback of this method of post-operative analgesia is
that the duration of effect of a single block is limited, usually to less
than 18 hours
 A typical example of the use of a peripheral nerve block for postoperative pain would be the use of a femoral/sciatic nerve block
for a patient undergoing total knee arthroplasty. The block would
be augmented with oral opioids and other adjuncts
Summary
Accurate pain assessment
Use Multimodal pain management
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
Thank you