Postoperative Pain Management
Introduction
Postoperative pain management is a critical aspect of patient care, aimed at reducing pain, improving recovery, minimizing complications, and enhancing overall patient satisfaction. A multimodal approach combining pharmacological and non-pharmacological interventions is the gold standard.
Physiology of Postoperative Pain
Postoperative pain is a combination of nociceptive and neuropathic pain.
• Nociceptive Pain: Results from tissue damage and inflammation.
- Neuropathic Pain: Caused by nerve injury during surgery.
Assessment of Postoperative Pain
-Pain Scales
• Numerical Rating Scale (NRS): 0–10 scale (0 = no pain, 10 = worst pain).
• Visual Analog Scale (VAS): 10 cm scale, patient marks pain intensity.
• Wong-Baker Faces Scale: Used in pediatrics.
• Critical-Care Pain Observation Tool (CPOT): Used in sedated ICU patients.
Principles of Postoperative Pain Management
1. Multimodal Analgesia: Combining different classes of analgesics for synergistic effects.
2. Preemptive Analgesia: Administering analgesics before surgical incision to reduce central sensitization.
3. Scheduled vs PRN Dosing: Scheduled dosing prevents breakthrough pain.
4. Individualized Therapy: Based on surgery type, patient factors, and pain severity.
Pharmacological Management
1. Non-Opioid Analgesics (First-Line)
–Paracetamol (Acetaminophen)-Mechanism: Inhibits COX centrally, reducing pain perception.
• Dose: 1g IV/PO every 6 hours (max 4g/day).
• Advantages: Opioid-sparing, minimal side effects.
– NSAIDs (Ibuprofen, Ketorolac, Diclofenac)
• Mechanism: Inhibit COX-1 & COX-2, reducing prostaglandin synthesis.
• Dose: Ketorolac 30 mg IV Q6H (max 120 mg/day).
• Side Effects: GI bleeding, renal impairment, platelet dysfunction.
2. Opioids (For Moderate to Severe Pain)
• Common Opioids: Morphine, Fentanyl, Oxycodone, Hydromorphone.
• Mechanism: Act on μ-opioid receptors in the CNS, inhibiting pain transmission.
• Side Effects: Respiratory depression, sedation, nausea, constipation.
• Routes of Administration: IV, PO, PCA (Patient-Controlled Analgesia).
3. Adjunctive Medications
-Gabapentinoids (Gabapentin, Pregabalin)
• Used for neuropathic pain and opioid-sparing.
• Dose: Gabapentin 300 mg preoperatively, then 300 mg BD.
• Side Effects: Dizziness, sedation.
-Ketamine (NMDA Antagonist)
• Low-dose infusion (0.2–0.5 mg/kg/h) for opioid-sparing.
• Useful in opioid-tolerant patients.
-Lidocaine Infusion
• IV infusion (1.5 mg/kg bolus, then 1–2 mg/kg/h).
• Reduces opioid requirements, used in abdominal surgery.
–Dexamethasone
• 4–8 mg IV reduces pain and PONV (postoperative nausea and vomiting).
4. Regional Anesthesia Techniques
1. Neuraxial Analgesia
-Epidural Analgesia
• Used for major abdominal, thoracic, and lower limb surgeries.
• Drugs: Local anesthetics (Bupivacaine, Ropivacaine) ± Opioids (Fentanyl).
• Advantages: Superior pain relief, reduces opioid consumption.
• Complications: Hypotension, motor block, urinary retention.
-Spinal Analgesia
• Single-shot intrathecal morphine (100–300 mcg) provides long-duration analgesia.
• Side Effects: Pruritus, respiratory depression.
2. Peripheral Nerve Blocks
• Upper Limb Blocks:Brachial Plexus Blocks (Interscalene, Supraclavicular, Axillary).
• Lower Limb Blocks: Femoral, Sciatic, Adductor Canal Block for TKA.
• Truncal Blocks: Transversus Abdominis Plane (TAP) Block for abdominal surgery. Erector Spinae Plane Block (ESP) for thoracic/abdominal pain.
5. Non-Pharmacological Management
• Psychological Interventions: Cognitive Behavioral Therapy (CBT), relaxation techniques.
• Physical Therapy: Early mobilization reduces pain and improves recovery.
• Acupuncture & TENS (Transcutaneous Electrical Nerve Stimulation): Modulates pain perception.
Complications of Poor Pain Control
• Cardiovascular: Hypertension, tachycardia, myocardial ischemia.
• Respiratory: Atelectasis, pneumonia due to reduced coughing.
• Gastrointestinal: Ileus, delayed recovery.
• Psychological: Anxiety, depression, chronic pain development.
Enhanced Recovery After Surgery (ERAS) Protocol
ERAS guidelines emphasize multimodal pain control:
1. Preoperative: Preemptive analgesia (NSAIDs, Gabapentin).
2. Intraoperative: Regional blocks, multimodal analgesia.
3. Postoperative: Scheduled non-opioid analgesics, opioid-sparing techniques.
MCQs
1. Which of the following is NOT part of multimodal analgesia?
a) NSAIDs
b) Opioids
c) Antihistamines
d) Local anesthetics
Answer: c) Antihistamines
2. Which opioid has the fastest onset of action?
a) Morphine
b) Fentanyl
c) Oxycodone
d) Hydromorphone
Answer: b) Fentanyl
3. Which nerve block is commonly used for total knee replacement?
a) Interscalene block
b) Femoral nerve block
c) Sciatic nerve block
d) Axillary block
Answer: b) Femoral nerve block
4. What is the maximum daily dose of IV Paracetamol?
a) 2g
b) 3g
c) 4g
d) 6g
Answer: c) 4g
5. Which of the following is a side effect of epidural analgesia?
a) Tachycardia
b) Hypertension
c) Urinary retention
d) Hyperreflexia
Answer: c) Urinary retention
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