This document discusses acute perioperative pain management. It defines pain and its classification, and explains why treating pain is important for patient outcomes and recovery. It covers pain assessment methods, non-pharmacological and pharmacological treatment options including the WHO analgesic ladder and multimodal analgesia. Specific pain medications like acetaminophen, NSAIDs, opioids, gabapentin and regional anesthesia techniques are described. Management of side effects and opioid overdose is also summarized.

1. Acute Perioperative Pain
Management

2. Introduction
What is Pain?
• Pain is an unpleasant sensory and emotional
experience associated with actual or
potential tissue damage, or described in
terms of such damage
IASP – International Association for the Study of Pain 2011

3. Introduction
Classification of Pain
– Acute or Chronic
– Nociceptive or Neuropathic

4. 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!

5. Why Treat Pain?

6. 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

7. Adverse Effects of Poor Pain Control
– CVS: MI, dysrhythmias
– Resp: atelectasis, pneumonia
– GI: ileus, anastomotic failure
– Endocrine: “stress hormones”
– Hypercoagulable state: DVT, PE
– Impaired immunological state
• Infection, cancer, wound healing
– Psychological:
• Anxiety, Depression, Fatigue
Chronic Post-surgery/trauma Pain

8. “… 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.”
Cousins MJ, Power I, and Smith G.
Regional Analgesia and Pain Medicine, 25 (2000) 6-21
Adverse Effects of Poor Pain Control

9. Pain Assessment

10. Pain Assessment
Pain History
– O – Onset
– P – Provoking / Palliating factors
– Q – Quality / Quantity
– R – Radiation
– S – Severity
– T – Timing

11. 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

12. Pain Assessment
Visual Analogue Scale

13. Current Pain Medications
– Accuracy and detail are very important!
• Name, dose, frequency, route
– Don’t forget to re-order or factor in patient’s pre-
existing pain Rx usage when writing orders
Conflicts
– Renal disease → avoid morphine, NSAID’s
– Vomiting → avoid oral forms of medication
– Short gut/high output stomas → avoid controlled
release formulations

14. 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!

15. Methods to Treat Pain

16. Methods to Treat Pain
• Pharmacologic
– Medications (po, iv, im, sc, pr, transdermal)
• Acetaminophen
• NSAIDs
• Opioids
• Gabapentin
• NMDA antagonists
• Alpha-2 agonists
– Procedures
• Regional Anesthesia
• LA infiltration at incision site
• Surgical Intervention
• Non-Pharmacologic / Non-Surgical

17. WHO Analgesic Ladder

18. 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

20. Pre-emptive analgesia
• Formulated by Crile and Wolf started animal studies
• It is a antinociceptive treatment that prevents
establishment of altered processing of afferent input,
which amplifies postoperative pain
• It has the potential to be more effective than a
similar analgesic treatment initiated after surgery

21. Preemptive analgesia has been defined as
treatment that:
 Starts before surgery;
 Prevents the establishment of central
sensitization caused by incisional injury
(covers only the period of surgery);
 Prevents the establishment of central
sensitization caused by incisional and
inflammatory injuries (covers the period of
surgery and the initial postoperative
period).

22. • When preemptive analgesia was studied by
comparing preincisional versus postincisional
treatment groups, many authors found no
difference in the pain outcome
• However, some of the previous positive clinical
studies in combination with basic science
results are probably sufficient to indicate that
preemptive analgesia is a valid phenomenon
• Preemptive analgesia continues to have
promise for the effective treatment of
postoperative pain

23. Acetaminophen
• First-line treatment if no contraindication
• Mechanism: thought to inhibit prostaglandin
synthesis in CNS → analgesia, antipyretic
• Only available in po form in Canada
• 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

24. NSAIDs
• Also, first-line treatment
• Mechanism
– Block cyclooxygenase (COX) enzyme → ↓
prostaglandin synthesis
– COX-2 → Prostaglandins → pain,
inflammation, fever
– COX-1 → Prostaglandins → gastric
protection, hemostasis

25. 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?

26. 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

27. Side Effects
– Nausea / Vomiting
– Sedation
– Respiratory Depression
– Pruritus
– Constipation
– Urinary Retention
– Ileus
– Tolerance

28. 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)

29. • 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 costly
– PO form only
– Percocet (oxycodone + acetaminophen)

30. • 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

31. 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

32. Opioid Equianalgesic Table
Drug Equianalgesic Dose Initial Adult Dose (>50kg)
IV/SC/IM Oral IV/SC/IM Oral
Morphine 10 mg 20-30 mg 2-10 mg q4h 5-20 mg q4h
Hydromorphon
e
1.5 mg 4-7.5 mg 0.5-2 mg q4h 1-4 mg q4h
Oxycodone N/A 10-20 mg N/A 5-10 mg q4h

33. Opioids – PCA
• Patient-controlled analgesia
• 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

34. Opioids – PCA

35. 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

36. Management of Side Effects
• Nausea / Vomiting
– Ondansetron (Zofran)
– Dimenhydrinate (Gravol)
– Metoclopramide (Maxeran)
– Changing medication(s) / ↓ dose
• Pruritus
– Diphenhydramine (Benadryl)
– Changing medication(s) / ↓ dose

37. Regional Anesthesia

38. 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

39. 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

40. • Neuraxial Techniques
– Spinal (subarachnoid) anesthesia
– Epidural anesthesia (lumbar and thoracic)

41. 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

42. 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?

43. 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

44. Management of
Opioid Overdose

45. Management of
Opioid Overdose
• For ↓LOC, somnolent patient:
– Stimulate patient
– Vitals/Monitors/Lines
– Airway
– Breathing
– Circulation
– CODE BLUE? CCRT? ICU? APS

46. • 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

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

48. 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