MULTIMODAL ANALGESIA
Opioid-Sparing | Multiple Drug Classes | Superior Outcomes
CORE COMPONENTS OF MULTIMODAL ANALGESIA
Critical Must-Knows
- Synergistic effect of multiple analgesics acting at different pain pathways
- Opioid-sparing reduces side effects: PONV, ileus, respiratory depression, sedation
- Preemptive analgesia given before incision reduces central sensitization
- Regional anesthesia is cornerstone for major orthopaedic procedures
- Acetaminophen and NSAIDs are foundation - scheduled, not PRN dosing
Examiner's Pearls
- "Multimodal means targeting multiple pain pathways, not just multiple drugs
- "WHO ladder is outdated - modern approach uses concurrent non-opioid agents
- "Gabapentinoids effective for neuropathic pain but sedation limits use
- "IV acetaminophen no better than oral - save money, use oral when possible
Critical Multimodal Analgesia Exam Points
Mechanism of Synergy
Different targets equal additive effect. Acetaminophen (central COX inhibition), NSAIDs (peripheral COX), gabapentinoids (alpha-2-delta calcium channels), local anesthetics (sodium channels), opioids (mu receptors). Combining these produces superior analgesia with lower doses of each.
Opioid-Sparing Benefits
30-50 percent opioid reduction achievable with multimodal approach. Benefits: reduced PONV (40 percent reduction), faster return of bowel function, less sedation, lower respiratory depression risk, earlier mobilization, shorter hospital stay.
Preemptive Analgesia
Give analgesics BEFORE surgical incision to prevent central sensitization (wind-up phenomenon). Gabapentin 600-1200mg, acetaminophen 1g, celecoxib 200-400mg given 1-2 hours preoperatively. Reduces postoperative pain scores and opioid requirements.
Regional Anesthesia
Gold standard for major procedures. Peripheral nerve blocks (femoral, sciatic, interscalene) or neuraxial (epidural, spinal) provide superior analgesia compared to systemic opioids. Single-shot vs continuous catheter depends on surgery and expected pain duration.
Quick Decision Guide: Drug Classes in Multimodal Analgesia
| Drug Class | Mechanism | Timing | Key Contraindications |
|---|---|---|---|
| Acetaminophen | Central COX inhibition, serotonergic pathways | 1g every 6 hours scheduled (max 4g per day) | Severe hepatic impairment |
| NSAIDs (COX-2 selective) | Peripheral COX-2 inhibition, reduced prostaglandins | Celecoxib 200mg twice daily or etoricoxib 90-120mg daily | Active GI ulcer, severe renal impairment, CV disease |
| Gabapentinoids | Alpha-2-delta calcium channel, reduces glutamate release | Gabapentin 300-1200mg preop, then 300mg three times daily | Severe renal impairment (dose adjustment needed) |
| Ketamine | NMDA receptor antagonist, prevents central sensitization | Low dose 0.1-0.5 mg/kg/hr intraop, 0.1 mg/kg bolus | Psychosis, uncontrolled hypertension, raised ICP |
| Local anesthetics | Sodium channel blockade, prevents action potentials | Nerve blocks, local infiltration, wound catheters | Allergy, local infection at injection site |
MULTIMODALPrinciples of Multimodal Analgesia
Memory Hook:MULTIMODAL reminds you that pain management needs multiple approaches, not just morphine!
PANGCore Drug Classes (Foundation)
Memory Hook:PANG is the foundation - these four should be in every multimodal protocol!
SPINERegional Anesthesia Options
Memory Hook:Think SPINE for regional techniques - they're the backbone of multimodal analgesia!
Overview
Definition
Multimodal analgesia (also called balanced analgesia) is the concurrent use of multiple analgesic agents with different mechanisms of action to target different pain pathways. The goal is to achieve superior pain relief with fewer side effects compared to single-agent therapy, particularly reducing opioid consumption and opioid-related adverse events.
Historical Context
Evolution of pain management:
- 1980s: WHO analgesic ladder (step-wise escalation from non-opioids to strong opioids)
- 1990s: Recognition of opioid side effects and development of multimodal concept
- 2000s: ERAS (Enhanced Recovery After Surgery) protocols incorporating multimodal analgesia
- 2010s: Opioid crisis drives emphasis on opioid-sparing techniques
- 2020s: Standardized multimodal protocols, regional anesthesia expansion, personalized pain medicine
WHO Ladder is Outdated
The traditional WHO analgesic ladder suggests sequential escalation (paracetamol, then weak opioid, then strong opioid). Modern multimodal analgesia uses concurrent administration of multiple non-opioid agents, reserving opioids for breakthrough pain only. This paradigm shift has reduced opioid consumption by 30-50 percent in major surgery.
Rationale for Multimodal Approach
Synergistic mechanisms:
- Additive or synergistic effect - drugs acting at different sites produce greater pain relief than sum of individual effects
- Opioid-sparing - reduced opioid requirements decrease side effects (PONV, sedation, respiratory depression, ileus, addiction risk)
- Reduced individual drug doses - lower doses of each agent minimize dose-dependent toxicity
- Comprehensive coverage - addresses nociceptive, inflammatory, and neuropathic pain components
- Prevention of central sensitization - preemptive analgesia reduces wind-up phenomenon
Pathophysiology
Nociceptive Processing
Four-step pain pathway:
- Transduction (peripheral) - noxious stimulus converted to electrical signal at nociceptors
- Transmission (peripheral and spinal) - signal conducted via A-delta and C fibers to dorsal horn
- Modulation (spinal) - signal amplification or suppression at dorsal horn synapses
- Perception (supraspinal) - conscious awareness of pain in thalamus and cortex
Peripheral Targets
Transduction and transmission:
- NSAIDs - reduce prostaglandin synthesis, decrease nociceptor sensitization
- Local anesthetics - block sodium channels, prevent action potential propagation
- Opioids - peripheral mu receptors reduce nociceptor excitability
- Corticosteroids - reduce inflammatory mediator release
Central Targets
Modulation and perception:
- Acetaminophen - central COX inhibition, serotonergic pathways
- Gabapentinoids - reduce excitatory neurotransmitter release in dorsal horn
- Ketamine - NMDA receptor antagonism prevents central sensitization
- Opioids - spinal and supraspinal mu receptor activation
- Alpha-2 agonists - enhance descending inhibitory pathways
Central Sensitization (Wind-Up)
Mechanism:
- Repeated C-fiber stimulation causes progressive amplification of dorsal horn neuron responses
- NMDA receptor activation by glutamate leads to increased excitability
- Results in hyperalgesia (increased pain to noxious stimuli) and allodynia (pain from non-noxious stimuli)
- Persists beyond tissue healing - contributes to chronic pain
Prevention strategies:
- Preemptive analgesia - administer analgesics before surgical incision
- NMDA antagonists - low-dose ketamine during surgery
- Gabapentinoids - reduce glutamate release
- Adequate regional anesthesia - complete afferent blockade prevents sensitization
Preemptive vs Preventive Analgesia
Preemptive equals given before incision. Preventive equals given before incision AND continued postoperatively. Evidence suggests preventive (extended duration) is more effective than single preoperative dose. The key is preventing central sensitization throughout the entire nociceptive period.
Drug Classes and Mechanisms
Acetaminophen (Paracetamol)
Mechanism of action:
- Central COX inhibition - reduces prostaglandin synthesis in CNS
- Serotonergic pathway activation - enhances descending pain inhibition
- Cannabinoid system - possible indirect activation of CB1 receptors
- NO-mediated pathways - may involve nitric oxide signaling
Dosing:
- Adult: 1g PO/IV every 6 hours (maximum 4g per day)
- Elderly or low body weight (less than 50kg): 500-750mg every 6 hours
- Hepatic impairment: reduce dose or extend interval
Evidence:
- NNT for 50 percent pain relief: 4-5 (single 1g dose)
- Opioid-sparing: 20-30 percent reduction in morphine consumption
- Combination with NSAIDs: additive effect, superior to either alone
- IV vs oral: no significant efficacy difference in patients able to take oral
IV Paracetamol: Worth the Cost?
IV acetaminophen costs 10-20 times more than oral with no proven superiority in analgesia when oral route available. Reserve IV for patients who are NBM, have GI dysfunction, or require immediate effect. Switch to oral as soon as feasible.
Contraindications and cautions:
- Severe hepatic impairment (Child-Pugh C) - contraindicated
- Chronic alcohol use - reduce maximum daily dose to 2-3g
- Glutathione depletion states - malnutrition, HIV, chronic illness
Non-Steroidal Anti-Inflammatory Drugs (NSAIDs)
Mechanism of action:
- COX enzyme inhibition - reduces prostaglandin synthesis
- COX-1 (constitutive) - gastric protection, platelet function, renal blood flow
- COX-2 (inducible) - inflammation, pain, fever
- Peripheral and central effects - reduce inflammatory sensitization
Classification:
NSAID Selectivity
| Agent | COX Selectivity | Dosing | Key Advantage |
|---|---|---|---|
| Ibuprofen | Non-selective | 400mg every 6-8 hours (max 2.4g/day) | Short half-life, rapid onset, low cost |
| Diclofenac | Preferential COX-2 | 50mg every 8 hours or 75mg every 12 hours | Potent analgesia, good toleration |
| Celecoxib | Selective COX-2 | 200mg twice daily or 400mg preop | Reduced GI bleeding risk, no platelet effect |
| Etoricoxib | Highly selective COX-2 | 90-120mg daily | Once-daily dosing, potent |
| Ketorolac | Non-selective (IV) | 10-30mg every 6 hours (max 5 days) | IV/IM option for NBM patients |
Evidence:
- Opioid-sparing: 30-40 percent reduction in morphine consumption
- Combination with acetaminophen: synergistic effect
- COX-2 selective vs non-selective: similar analgesia, reduced GI bleeding with COX-2 (BUT increased CV risk at high doses)
Contraindications:
- Active peptic ulcer disease - absolute contraindication for non-selective NSAIDs
- Severe renal impairment (eGFR less than 30 mL/min) - avoid or use cautiously
- History of GI bleeding - use COX-2 selective with PPI
- Cardiovascular disease - avoid high-dose COX-2 inhibitors
- Bleeding risk - non-selective NSAIDs impair platelet function (avoid perioperatively if concern)
- Third trimester pregnancy - risk of premature ductus arteriosus closure
- Aspirin-sensitive asthma - cross-reactivity possible
NSAIDs in Orthopaedic Surgery: The Fracture Controversy
Concern: NSAIDs may impair fracture healing and spinal fusion. Evidence: Animal studies show delayed healing. Human studies are conflicting - short-term use (less than 2 weeks) appears safe. Current consensus: Avoid NSAIDs in high-risk fractures (scaphoid, femoral neck stress fracture) and spinal fusions. Safe for short-term use in routine arthroplasty and stable fractures.
Gabapentinoids
Drugs:
- Gabapentin - requires dose escalation, three times daily dosing
- Pregabalin - higher bioavailability, twice daily dosing, faster onset
Mechanism of action:
- Alpha-2-delta subunit of voltage-gated calcium channels in dorsal horn
- Reduces calcium influx into presynaptic terminals
- Decreases excitatory neurotransmitter release (glutamate, substance P)
- Prevents central sensitization
Dosing:
Gabapentin:
- Preoperative: 600-1200mg single dose 1-2 hours before surgery
- Postoperative: 300mg three times daily, titrate to 300-600mg three times daily
- Renal adjustment: reduce dose if CrCl less than 60 mL/min
Pregabalin:
- Preoperative: 150-300mg single dose 1-2 hours before surgery
- Postoperative: 75mg twice daily, titrate to 150mg twice daily
- Renal adjustment: reduce dose if CrCl less than 60 mL/min
Evidence:
- Opioid-sparing: 25-30 percent reduction in 24-hour morphine consumption
- Neuropathic pain: particularly effective for nerve injury, complex regional pain syndrome
- Chronic pain prevention: some evidence for reduced persistent postsurgical pain
- NNT for 50 percent pain relief: 7-8 (moderate effect size)
Side effects:
- Sedation (20-30 percent) - dose-limiting, avoid in elderly
- Dizziness (15-20 percent)
- Visual disturbances (blurred vision)
- Peripheral edema
- Cognitive impairment (especially elderly or cognitively impaired)
Gabapentinoids: When to Use?
Best for: Neuropathic pain component (spine surgery, limb amputation, nerve injury). Avoid: Elderly patients, pre-existing cognitive impairment, patients requiring high alertness postoperatively. Alternative: Use lower doses (gabapentin 300mg twice daily) or omit if sedation is concern.
Contraindications:
- Severe renal impairment - dose reduction required (renally cleared)
- Respiratory depression risk - caution when combined with opioids (synergistic respiratory depression)
- Myasthenia gravis - may worsen muscle weakness
Ketamine
Mechanism of action:
- NMDA receptor antagonist - prevents glutamate-mediated excitation
- Prevents central sensitization and wind-up
- Opioid receptor interactions - may reverse opioid-induced hyperalgesia
- Anti-inflammatory effects - modulates cytokine release
Dosing:
Low-dose (sub-anesthetic):
- Intraoperative infusion: 0.1-0.5 mg/kg/hr (typical 0.2 mg/kg/hr)
- Bolus: 0.1-0.25 mg/kg IV at induction
- Postoperative infusion: 0.05-0.2 mg/kg/hr for 24-48 hours
Evidence:
- Opioid-sparing: 15-30 percent reduction in morphine consumption
- Most effective in: opioid-tolerant patients, procedures with high pain intensity
- Persistent pain reduction: possible benefit in preventing chronic postsurgical pain
Side effects:
- Psychomimetic effects - dysphoria, hallucinations, nightmares (dose-dependent)
- Nausea - less common than with opioids
- Hypertension and tachycardia - sympathomimetic effects
- Respiratory depression - minimal at low doses
Contraindications:
- Psychotic disorders - may precipitate psychosis
- Uncontrolled hypertension - sympathomimetic effects
- Raised intracranial pressure - increases cerebral blood flow and ICP
- Ischemic heart disease - caution due to increased myocardial oxygen demand
Ketamine Dosing: Low is the Key
Psychomimetic effects occur at doses greater than 1 mg/kg. Analgesia occurs at much lower doses (0.1-0.5 mg/kg/hr infusion). Always use low-dose protocols for postoperative analgesia. Consider benzodiazepine (midazolam 1-2mg) if emergence phenomena occur.
Local Anesthetics
Mechanism of action:
- Sodium channel blockade - prevents action potential generation and propagation
- Differential blockade - smaller fibers (pain, autonomic) blocked before motor fibers
- Reversible nerve conduction block
Agents:
Local Anesthetic Comparison
| Agent | Onset | Duration | Maximum Dose |
|---|---|---|---|
| Lidocaine | Fast (5-10 min) | Short (60-120 min) | 4.5 mg/kg plain, 7 mg/kg with epinephrine |
| Bupivacaine | Slow (15-20 min) | Long (4-8 hours) | 2 mg/kg plain, 3 mg/kg with epinephrine |
| Ropivacaine | Moderate (10-15 min) | Long (4-8 hours) | 3 mg/kg |
| Levobupivacaine | Slow (15-20 min) | Long (4-8 hours) | 2.5 mg/kg |
Applications in multimodal analgesia:
- Peripheral nerve blocks - femoral, sciatic, interscalene, adductor canal, TAP block
- Neuraxial techniques - spinal, epidural analgesia
- Local infiltration - wound infiltration, intra-articular injection
- Continuous catheters - peripheral nerve catheters, wound catheters
Toxicity:
- CNS toxicity - tinnitus, metallic taste, perioral numbness, seizures
- Cardiovascular toxicity - arrhythmias, cardiac arrest (bupivacaine most cardiotoxic)
- Treatment: lipid emulsion (Intralipid 20 percent) 1.5 mL/kg bolus, then infusion
Local Anesthetic Systemic Toxicity (LAST)
Prevention: Aspiration before injection, incremental dosing, stay below maximum dose. Recognition: CNS symptoms (tinnitus, seizures) precede cardiovascular collapse. Treatment: Stop injection, call for help, manage airway/seizures, give Intralipid 20 percent 1.5 mL/kg bolus (repeat if needed), start CPR if arrest occurs.
Regional Anesthesia Integration
Peripheral Nerve Blocks
Lower limb procedures:
Indications: TKA, femoral shaft fracture, anterior thigh procedures
Advantages: excellent quadriceps analgesia
Disadvantage: quadriceps weakness (fall risk)
Alternative: adductor canal block (motor-sparing)
Femoral nerve blocks provide excellent analgesia but cause motor weakness.
Neuraxial Analgesia
Epidural analgesia:
Indications:
- Major spine surgery (multi-level fusion)
- Lower limb surgery with expected severe pain (revision arthroplasty)
- Bilateral lower limb procedures
Technique:
- Catheter placement: thoracic (T8-L1) or lumbar (L2-L4) depending on surgical level
- Infusion: bupivacaine 0.125-0.25 percent plus fentanyl 2-4 mcg/mL at 4-10 mL/hr
- Duration: 48-72 hours postoperatively
Advantages:
- Superior analgesia compared to systemic opioids
- Bilateral coverage
- Opioid-sparing (60-80 percent reduction)
- Facilitates mobilization and physiotherapy
Disadvantages:
- Hypotension - sympathetic blockade (manage with fluids, vasopressors)
- Motor blockade - delays mobilization if concentration too high
- Urinary retention - catheter required
- Rare complications: epidural hematoma (1 in 10,000), abscess, permanent neurological injury
Epidural Hematoma Risk
High-risk scenarios: traumatic placement, anticoagulation (therapeutic or prophylactic), coagulopathy, spinal abnormalities. Timing: Stop LMWH 12 hours before neuraxial procedure, restart 6-8 hours after catheter removal. Monitoring: check motor/sensory function every 2-4 hours, remove catheter before restarting therapeutic anticoagulation.
Procedure-Specific Protocols
Total Knee Arthroplasty (TKA)
Preoperative:
- Gabapentin 600mg
- Acetaminophen 1g
- Celecoxib 400mg
- All given 1-2 hours before surgery
Intraoperative:
- Spinal anesthesia with intrathecal morphine 100-200 mcg OR
- Adductor canal block (motor-sparing, preferred over femoral block)
- Local infiltration analgesia (LIA) - 100 mL ropivacaine 0.2 percent periarticular injection
- Dexamethasone 8mg IV
Postoperative:
- Acetaminophen 1g every 6 hours
- Celecoxib 200mg twice daily (or ibuprofen 400mg three times daily)
- Gabapentin 300mg three times daily
- Oxycodone 5-10mg PO every 4 hours PRN (goal less than 30mg per 24 hours)
- Early mobilization (day 0-1)
Expected outcomes:
- Pain scores 3-4 out of 10 at rest, 5-6 with physiotherapy
- Opioid consumption 20-40 mg oral morphine equivalents in first 24 hours
- Mobilization day 0-1
- Discharge day 1-2
Total Hip Arthroplasty (THA)
Preoperative:
- Gabapentin 600mg
- Acetaminophen 1g
- Celecoxib 200mg
Intraoperative:
- Spinal anesthesia with intrathecal morphine 100 mcg OR
- Lumbar plexus block or fascia iliaca block
- Local infiltration around acetabulum and femoral canal
- Dexamethasone 4-8mg IV
Postoperative:
- Acetaminophen 1g every 6 hours
- Ibuprofen 400mg every 8 hours
- Oxycodone 5mg PO every 6 hours PRN (goal less than 20mg per 24 hours)
- Mobilization day 0
Expected outcomes:
- Pain scores 2-3 out of 10 (THA generally less painful than TKA)
- Minimal opioid requirement (10-20 mg oral morphine equivalents)
- Mobilization day 0
- Discharge day 1
Evidence Base
Multimodal Analgesia in Total Joint Arthroplasty
- Multimodal analgesia reduced opioid consumption by 45 percent (95 percent CI 38-52 percent) in first 24 hours
- Pain scores reduced by 1.2 points on 10-point scale
- PONV reduced by 38 percent compared to opioid-based analgesia
- Length of stay reduced by 0.8 days (95 percent CI 0.5-1.1 days)
Preemptive Gabapentin for Postoperative Pain
- Single preoperative dose gabapentin 600mg reduced morphine consumption by 28 percent
- Pain scores reduced by 0.8 points at 24 hours
- Improved early mobilization outcomes
- Sedation occurred in 18 percent vs 8 percent in placebo group (not statistically significant)
NSAIDs and Fracture Healing
- Animal studies show delayed fracture healing with NSAIDs (high doses, prolonged duration)
- Human studies are conflicting - no clear evidence of delayed healing with short-term use (less than 2 weeks)
- High-risk fractures (scaphoid, femoral neck stress fractures): avoid NSAIDs as precaution
- Routine fractures and arthroplasty: short-term NSAIDs (5-7 days) appear safe
Adductor Canal vs Femoral Nerve Block for TKA
- Adductor canal block provides non-inferior analgesia compared to femoral nerve block
- Quadriceps strength preserved with adductor canal block (88 percent vs 62 percent at 6 hours)
- Fall risk reduced by 40 percent with adductor canal block
- No difference in opioid consumption or pain scores at 24 hours
Exam Viva Scenarios
Practice these scenarios to excel in your viva examination
Scenario 1: Multimodal Protocol for Total Knee Arthroplasty
"You are planning anesthesia for a 68-year-old woman undergoing primary total knee arthroplasty. She has well-controlled hypertension and takes aspirin for cardiovascular prophylaxis. Describe your multimodal analgesia plan."
Scenario 2: Opioid-Sparing for Opioid-Tolerant Patient
"A 45-year-old man with chronic low back pain on long-term opioids (oxycodone 40mg twice daily) requires lumbar spinal fusion L4-S1. How would you manage his perioperative analgesia?"
Scenario 3: NSAID Controversy in Orthopaedic Surgery
"The orthopaedic surgeon asks you not to use NSAIDs in a patient undergoing open reduction and internal fixation of a scaphoid nonunion as he is concerned about fracture healing. What is your response?"
MCQ Practice Points
Exam Pearl
Q: What is the primary mechanism of analgesia achieved by preoperative paracetamol administration?
A: Central COX-2 inhibition in the spinal cord and descending serotonergic pathways. Paracetamol is NOT peripherally anti-inflammatory but provides central analgesia by inhibiting prostaglandin synthesis in the CNS. Maximum dose 4g/day (reduce to 3g/day if liver disease or weight under 50kg). Can be given IV or oral with equal efficacy.
Exam Pearl
Q: Which injectable NSAID is commonly used perioperatively in Australian orthopaedic practice and what are its key contraindications?
A: Parecoxib (Dynastat) 40mg IV is a COX-2 selective inhibitor. Key contraindications: sulfonamide allergy, cardiovascular disease (MI, stroke risk), renal impairment (GFR under 60), GI ulceration, aspirin-sensitive asthma. Avoid in patients on anticoagulation. Risk of bone healing impairment remains controversial - short-term use (under 14 days) appears safe.
Exam Pearl
Q: What is the opioid-sparing effect of a well-designed multimodal analgesia protocol?
A: 30-50% reduction in opioid consumption. A typical ERAS multimodal protocol includes: preoperative paracetamol 1g + gabapentin 300mg, intraoperative local infiltration analgesia (LIA), postoperative regular paracetamol + NSAID + low-dose opioid PRN. The synergistic effect of targeting multiple pain pathways reduces opioid requirements and associated complications (nausea, constipation, respiratory depression).
Exam Pearl
Q: What is the mechanism of gabapentin in multimodal analgesia and what is the optimal dosing strategy?
A: Gabapentin inhibits alpha-2-delta voltage-gated calcium channels, reducing central sensitization and hyperalgesia. For perioperative use: single preoperative dose of 300-600mg given 1-2 hours before surgery. Reduces acute postoperative pain scores and opioid requirements by approximately 30%. Avoid high doses (over 600mg) due to sedation, especially in elderly. Contraindicated in renal impairment.
Exam Pearl
Q: What are the key components of local infiltration analgesia (LIA) used in total knee arthroplasty?
A: Typical LIA cocktail contains ropivacaine 200mg (or bupivacaine 100mg) + ketorolac 30mg + adrenaline 0.3mg in saline 100-150mL. Injected into the posterior capsule, collateral ligaments, quadriceps, and subcutaneous tissues before closure. Provides 12-24 hours analgesia. Adductor canal block provides additional analgesia while preserving quadriceps strength for early mobilization (preferred over femoral nerve block).
Australian Context
Australian Epidemiology and Practice
Multimodal Analgesia in Australian Orthopaedic Practice:
- ERAS (Enhanced Recovery After Surgery) protocols incorporating multimodal analgesia are now standard of care across Australian orthopaedic units
- The Australian and New Zealand College of Anaesthetists (ANZCA) provides guidelines on acute pain management that emphasise multimodal approaches
- Opioid stewardship initiatives have driven adoption of opioid-sparing multimodal protocols across Australian hospitals
- State-wide real-time prescription monitoring (SafeScript in Victoria, Electronic Recording and Reporting of Controlled Drugs in NSW) track perioperative opioid prescribing
RACS Orthopaedic Training Relevance:
- Multimodal analgesia is a core topic in the FRACS Orthopaedic examination syllabus, particularly for perioperative care
- Viva scenarios commonly test understanding of drug classes, mechanisms, contraindications, and procedure-specific protocols
- Key examination focus: opioid-sparing rationale, preemptive analgesia concept, regional anesthesia options for common orthopaedic procedures
- Candidates should understand the NSAID and bone healing controversy and when to avoid NSAIDs
eTG (Therapeutic Guidelines) Recommendations:
- eTG Analgesic guidelines recommend multimodal analgesia as first-line approach for acute postoperative pain
- Paracetamol 1g every 6 hours (maximum 4g/day) is foundation - consider reduced dosing in elderly or hepatic impairment
- COX-2 selective NSAIDs (celecoxib) preferred over non-selective for reduced GI bleeding risk
- Gabapentinoids recommended for procedures with neuropathic pain component (spine surgery, amputation)
- Opioids recommended as breakthrough analgesia only, with patient counseling on risks and expected duration
PBS (Pharmaceutical Benefits Scheme) Considerations:
- Gabapentin and pregabalin are PBS-listed for chronic neuropathic pain but have specific authority requirements
- Parecoxib (IV COX-2 inhibitor) is hospital-restricted in Australia
- Tramadol and tapentadol are S8 medications with prescribing restrictions
- Post-discharge opioid prescribing subject to state regulations and quantity limits
Regional Anesthesia in Australian Practice:
- Ultrasound-guided regional anesthesia is standard practice in Australian hospitals
- Adductor canal block has largely replaced femoral nerve block for TKA in major Australian centres
- Interscalene block remains gold standard for shoulder surgery with appropriate patient selection
- Peripheral nerve catheter services available in major metropolitan hospitals for extended analgesia
ANZCA Acute Pain Management Guidelines:
- ANZCA Faculty of Pain Medicine publishes guidelines on acute pain management in Australian hospitals
- Emphasise pre-procedure patient education, realistic pain expectations, and opioid minimisation
- Recommend regular pain assessment using validated tools (NRS, VAS)
- Advocate for early mobilisation and physiotherapy as part of multimodal pain management
MULTIMODAL ANALGESIA EXAM CHEAT SHEET
High-Yield Exam Summary
Definition and Principles
- •Multimodal equals concurrent use of multiple analgesics with different mechanisms targeting different pain pathways
- •Goal: superior analgesia with reduced opioid consumption and fewer side effects
- •Synergy - additive or synergistic effect greater than sum of individual agents
- •Opioid-sparing achieves 30-50 percent reduction in opioid use with improved outcomes
Core Drug Classes (Foundation)
- •Acetaminophen 1g every 6 hours - central COX inhibition, foundation of all protocols
- •NSAIDs - celecoxib 200mg twice daily or ibuprofen 400mg three times daily
- •Gabapentinoids - gabapentin 300-600mg three times daily or pregabalin 75-150mg twice daily
- •Regional anesthesia - peripheral nerve blocks or neuraxial (gold standard)
- •Opioids - rescue therapy only, NOT primary analgesic
Preemptive Analgesia
- •Give BEFORE surgical incision to prevent central sensitization (wind-up)
- •Gabapentin 600-1200mg given 1-2 hours preoperatively
- •Acetaminophen 1g and celecoxib 200-400mg preoperatively
- •Mechanism - prevents NMDA receptor activation and dorsal horn sensitization
Regional Anesthesia Options
- •TKA - adductor canal block (motor-sparing) or spinal plus intrathecal morphine
- •THA - spinal plus intrathecal morphine or fascia iliaca block
- •Shoulder - interscalene block (gold standard, but 100 percent phrenic palsy)
- •Spine fusion - ketamine infusion plus local infiltration
- •Single-shot vs catheter - single shot lasts 12-24h, catheter for 48-72h
Adjuvant Agents
- •Ketamine 0.1-0.5 mg/kg/hr intraoperatively - NMDA antagonist
- •Dexamethasone 4-8mg IV - anti-inflammatory, antiemetic
- •Local infiltration - surgeon performs periarticular injection
- •Lidocaine infusion - emerging evidence for 1 mg/kg/hr for 24h
Opioid-Sparing Benefits
- •PONV reduced by 40 percent
- •Ileus - faster return of bowel function (6-12 hours earlier)
- •Sedation reduced by 30 percent
- •Respiratory depression reduced by 50 percent
- •Length of stay reduced by 0.5-1 day
NSAID Controversy
- •Animal studies - NSAIDs delay fracture healing (high doses, prolonged use)
- •Human studies - conflicting, short-term use (less than 2 weeks) appears safe
- •Avoid in - scaphoid fractures, femoral neck stress fractures, spinal fusions
- •Safe in - arthroplasty, routine stable fractures (5-7 days duration)
Special Populations
- •Elderly - reduce doses by 25-50 percent, avoid gabapentinoids
- •Opioid-tolerant - continue baseline opioid, add ketamine, expect 50-100 percent higher needs
- •Renal impairment - avoid NSAIDs if eGFR less than 30, reduce gabapentin dose
- •Chronic pain - high-dose gabapentinoids, ketamine, early pain team involvement
TKA Protocol (Example)
- •Preop - gabapentin 600mg, acetaminophen 1g, celecoxib 400mg
- •Intraop - adductor canal block plus LIA plus dexamethasone 8mg IV
- •Postop - acetaminophen 1g every 6 hours plus celecoxib 200mg twice daily
- •Breakthrough - oxycodone 5-10mg every 4 hours PRN (goal less than 30mg in 24 hours)
High-Yield Numbers
- •Opioid reduction - 30-50 percent achievable with multimodal approach
- •PONV reduction - 40 percent compared to opioid-based analgesia
- •Acetaminophen max dose - 4g per day (reduce to 2-3g in liver disease)
- •Gabapentin preoperative - 600-1200mg
- •Ketamine low dose - 0.1-0.5 mg/kg/hr
- •Intrathecal morphine - 100-200 mcg for lower limb surgery