Perioperative Pain Management

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Acute Perioperative Pain Management
Dr. Mahmoud Abdel-Khalek
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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

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Introduction Nociception
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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

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• 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

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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.

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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

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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

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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

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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

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Pain Assessment

• Pain History
• O Onset
• P Provoking / Palliating factors
• Q Quality / Quantity
• R Radiation
• S Severity
• T Timing

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Pain Assessment Severity Visual Analogue Scale
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Severity of postoperative pain
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Pain Assessment

• 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, NSAIDs
• Vomiting avoid oral forms of medication
• Drug allergies
• Document drug, adverse reaction and severity
• Intolerances
• Nausea / vomiting, hallucinations,
  disorientation, etc.

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Methods to Treat Pain

• Pharmacologic
• Medications (po, iv, im, sc, pr, transdermal)
• 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

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WHO Analgesic Ladder
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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

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NSAIDs

• Also, first-line treatment
• Mechanism
• Block cyclooxygenase (COX) enzyme ? ?
  prostaglandin synthesis
• COX-2 ? Prostaglandins ? pain, inflammation,
  fever
• COX-1 ? Prostaglandins ? gastric protection,
  hemostasis

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NSAIDs

• Warnings ?dose / avoid if
• GI ulceration
• Bleeding disorders / Coagulopathy
• Renal dysfunction
• Asthma
• Allergy

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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

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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

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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.

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Opioids Side effects

• Nausea / Vomiting
• Sedation
• Respiratory Depression
• Pruritus
• Constipation
• Urinary Retention
• Ileus
• Tolerance

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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
  )

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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)

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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

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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

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Management of Opioid Overdose

• Ddx
• Seizure, stroke
• Hypoxia, Hypercarbia
• Hypotension
• Other medication effect
• Severe electrolyte or acid base abnormalities
• MI
• Sepsis
• ..etc.

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Management of Opioid Overdose

• For ?level of consciousness, somnolent patient
• Stimulate patient
• Vitals/Monitors/Lines
• Airway
• Breathing
• Circulation
• CODE BLUE?

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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

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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.

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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.

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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

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Opioids PCA
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Management of Opioid Side Effects

• Nausea / Vomiting
• Ondansetron (Zofran)
• Dimenhydrinate (Gravol)
• Metoclopramide (Maxeran)
• Changing medication(s) / ? dose
• Pruritus
• Diphenhydramine (Benadryl)
• Changing medication(s) / ? dose

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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

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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

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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

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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

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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

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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

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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

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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 post-operative 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

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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

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Thank you