Postoperative anesthesia complications

🥊 The Recovery Room Rumble

• Hypoxemia (SpO₂ <90%): Most common cause is atelectasis. Others: airway obstruction (tongue), residual neuromuscular blockade (NMB), opioid depression, aspiration, pulmonary edema.
• Hypotension: Due to hypovolemia (bleeding, dehydration), vasodilation (residual anesthetics), or cardiac dysfunction (MI, arrhythmia).
• Hypertension: Often from pain, anxiety, bladder distension, or underlying hypoxia/hypercarbia.
• Shivering: Dramatically ↑O₂ consumption by ~400%. Treat with forced-air warming; low-dose meperidine is effective.
• Emergence Delirium: Always rule out hypoxia first. Common in children and the elderly.

⭐ Postoperative atelectasis is the most common cause of fever in the first 48 hours post-op, often termed "wind."

🤒 Common Post-Op Problems

• Fever: 📌 Mnemonic: The 5 W's. See timeline.
• Hypoxia ($PaO_2$ < 60 mmHg):
  • Immediate: Airway obstruction, residual anesthetic effect.
  • Early (0-48h): Atelectasis (most common), aspiration, pulmonary edema.
  • Late (>48h): Hospital-acquired pneumonia, PE.
• Hypotension:
  • Causes: Hypovolemia (bleeding, third-spacing), ↓cardiac output (MI, arrhythmia), ↓SVR (sepsis, anaphylaxis, epidural).
• Post-Op Nausea & Vomiting (PONV):
  • Risks: Female, non-smoker, Hx of PONV, opioids.
• Urinary Retention:
  • Common with spinal/epidural, anticholinergics, opioids. Bladder scan is diagnostic.

⭐ Atelectasis is the most common cause of fever in the first 48 hours post-op. It's typically low-grade and resolves with pulmonary toilet (incentive spirometry, deep breathing).

🩺 The "5 Ws" Workup

📌 Mnemonic for postoperative fever: Wind, Water, Wound, Walking, Wonder drugs.

• Wind (POD 1-2): Atelectasis.
  • Path: Bronchial obstruction from secretions.
  • Dx: CXR (linear opacification), ↓ breath sounds.
  • Tx: Incentive spirometry.
• Water (POD 3-5): UTI.
  • Risk: Foley catheter.
  • Dx: Urinalysis, culture (E. coli).
• Wound (POD 5-7): Surgical Site Infection (SSI).
  • Dx: Erythema, purulent drainage. Culture (S. aureus).
• Walking (POD >7): DVT/PE.
  • Dx: Doppler US (DVT), CT Angiogram (PE).
• Wonder Drugs (Anytime): Drug fever.
  • Diagnosis of exclusion. Common culprits: anesthetics, antibiotics.

⭐ Atelectasis is the most common cause of early postoperative fever (first 48 hours), often resolving with pulmonary toilet. It is not a true infection.

🛠️ Management - Taming the Complications

• Post-Op Nausea/Vomiting (PONV):
  • Prophylaxis/Tx: Ondansetron (5-HT3 antagonist), Dexamethasone, Scopolamine patch.
• Hypothermia & Shivering:
  • Primary: Forced-air warming (e.g., Bair Hugger).
  • Pharmacologic for severe shivering: Meperidine (acts on κ-opioid receptors).
• Pain Management (Multimodal Approach):
  • Foundation: Scheduled NSAIDs, Acetaminophen.
  • Moderate-Severe: Opioids (PCA, IV).
  • Adjuncts: Regional anesthesia (epidural, nerve blocks), low-dose Ketamine.
• Respiratory Depression:
  • Support airway (ABC's first!).
  • See flowchart for specific reversal agents.
• Hypotension:
  • IV fluid bolus, vasopressors (e.g., phenylephrine) if refractory.

⭐ Naloxone's half-life (30-60 min) is shorter than most opioids (e.g., morphine). Always monitor for recurrent respiratory depression ("re-narcanization") and consider a continuous infusion if necessary.

⚡ High-Yield Points - Biggest Takeaways

• Post-op fever follows the "5 Ws": Wind (atelectasis), Water (UTI), Wound (infection), Walking (DVT/PE), and Wonder drugs.
• Atelectasis is the most common cause of hypoxemia and fever in the first 48 hours; prevent with incentive spirometry.
• Malignant hyperthermia (fever, rigidity, ↑ETCO₂) requires immediate dantrolene.
• Post-op urinary retention is common after spinal anesthesia. Diagnose with a bladder scan and catheterize.
• In elderly post-op delirium, first rule out reversible causes like hypoxia.