Acute Perioperative Pain Management

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

Introduction

Classification of Pain– Acute or Chronic– Nociceptive or Neuropathic

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!

Why Treat Pain?

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– 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

“… 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

Pain Assessment

Pain Assessment

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

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

Pain Assessment Visual Analogue Scale

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

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!

Methods to Treat Pain

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

WHO Analgesic Ladder

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

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

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).

• 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

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

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– High cardiac risk – COXII inhibitors– Asthma– Allergy

• ?Avoid celecoxib if allergic to Sulpha

Concern for anastomotic leaks?

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

Side Effects– 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)

• 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)

• 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

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

Hydromorphone

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

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

Opioids – PCA

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

Management of Side Effects

• Nausea / Vomiting– Ondansetron (Zofran)– Dimenhydrinate (Gravol)– Metoclopramide (Maxeran)– Changing medication(s) / ↓ dose

• Pruritus– Diphenhydramine (Benadryl)– Changing medication(s) / ↓ dose

Regional Anesthesia

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

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

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

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

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?

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

Management of Opioid Overdose

Management of Opioid Overdose

• For ↓LOC, somnolent patient:– Stimulate patient – Vitals/Monitors/Lines– Airway – Breathing– Circulation – CODE BLUE? CCRT? ICU? APS

• 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

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

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

Thank you