pain management

1. Acute Perioperative
Pain Management
AHMED HAMDY
Staff Anesthesiologist
St. Michael’s Hospital

2. Outline
Introduction
Why Treat pain?
Pain Assessment
Methods to Treat Pain
Management of Opiate Overdose
Acute Pain Service

3. Introduction
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)

4. Introduction
Classification of Pain
Acute or Chronic
Nociceptive or Neuropathic

5. 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!

6. Why Treat Pain?

7. 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

8. 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

9. “… 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

10. Pain Assessment

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

12. 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

13. Pain Assessment
Visual Analogue Scale

14. 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 / PMH
Renal disease → avoid morphine, NSAID’s
Vomiting → avoid oral forms of medication
Short gut/high output stomas → avoid CR formulations

15. 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!

16. Methods to Treat Pain

17. 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

18. WHO Analgesic Ladder

19. 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. 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

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

22. 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?

23. Opioids
Dilaudid 1-4mg PO/IM/IV/SC Q3H PRN
Any concerns?

24. 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

25. Opioids
Side Effects
Nausea / Vomiting
Sedation
Respiratory Depression
Pruritus
Constipation
Urinary Retention
Ileus
Tolerance

26. 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)

27. 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)

28. 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

29. 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

30. 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

31. Opioids – PCA

32. 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

33. 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

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

35. Regional Anesthesia

36. 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

37. 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

38. Regional Anesthesia
Neuraxial Techniques
Spinal (subarachnoid) anesthesia
Epidural anesthesia (lumbar and thoracic)

39. 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

40. 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?

41. 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

42. Management of
Opioid Overdose

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

44. 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

45. Opioid Overdose
Management
Ddx:
Seizure, stroke
Hypoxia, Hypercarbia
Hypotension
Other medication effect
Severe electrolyte or acid base abnormalities
MI
Sepsis
…..etc.

46. 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

47. 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

48. 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