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Anaesthetic Management of Poorly Controlled Bronchial Asthma for Emergency Laparotomy / Cystoscopy

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1. PRE-OPERATIVE ASSESSMENT (Emergency - Time-Limited)

• Severity, frequency of attacks; hospitalizations/ICU admissions
• Current medications: inhalers (SABA, LABA, ICS), oral steroids, theophylline
• Recent exacerbations; steroid use within last 6 months
• Allergies (NSAIDs, aspirin, latex, antibiotics)
• Last attack and current symptom status

• Auscultation - wheeze, prolonged expiration, silent chest (ominous)
• RR, SpO2, pulsus paradoxus (>10 mmHg = severe)
• Signs of impending respiratory failure: rising PaCO2, right ventricular strain on ECG

• ABG - hypoxemia + hypocapnia (early); normal or raised PaCO2 = severe/impending failure
• PFT (bedside PEFR if possible) - FEV1, FEV1/FVC
• CXR - hyperinflation (flat diaphragm, small heart, hyperlucent fields), rule out pneumothorax
• ECG - right axis deviation, RBBB, ST changes with severe disease
• Routine labs: CBC, electrolytes, RFT

Key point: PaCO2 normalization in an acutely wheezing patient is a danger sign - they are tiring out.

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2. PRE-OPERATIVE OPTIMIZATION (Do Before Surgery if Even Briefly Possible)

• Continue all existing bronchodilators up to the time of surgery
• Glucocorticoids take hours to work - give early
• If on chronic steroids (>5 mg/day prednisone or equivalent), give stress dose steroids: hydrocortisone 50-100 mg IV q8h perioperatively

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3. CHOICE OF ANAESTHESIA

Cystoscopy (Shorter, Peripheral Procedure - Preferred Option)

• Regional anaesthesia preferred - spinal (T10 level adequate for cystoscopy) avoids airway instrumentation
• Avoids the most hazardous moment: laryngoscopy and intubation
• Caution: High spinal/epidural (T1-T4) can block sympathetic supply to bronchi → unopposed parasympathetic activity → bronchoconstriction
• If GA required: LMA preferred over ETT (avoids tracheal stimulation) - use only if airway protection not needed

Emergency Laparotomy (Full GA + ETT Usually Required)

• Full stomach risk → RSI required
• Regional (epidural/spinal) alone is inadequate; consider GA with regional as adjunct for postoperative analgesia

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4. PRE-MEDICATION

• Avoid: Morphine, pethidine (meperidine) - histamine releasers
• Prefer: Fentanyl/sufentanil for opioid premedication
• Avoid H2-blockers (e.g., ranitidine) as monotherapy - H2 blockade leaves H1-mediated bronchoconstriction unopposed if histamine is released
• Benzodiazepine for anxiolysis (anxiety can trigger bronchospasm); use cautiously if respiratory function is poor
• Anticholinergic (glycopyrrolate/atropine) - not routinely given; use if ketamine is the induction agent (to dry secretions) or if copious secretions are present
• Salbutamol inhaler 2 puffs 15-20 min before induction

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5. INDUCTION

• Bronchodilator via sympathomimetic (catecholamine release) action
• Dose: 1-2 mg/kg IV
• Advantage: maintains hemodynamic stability - ideal if patient is also hemodynamically compromised
• Disadvantage: increases secretions (give glycopyrrolate 0.2 mg IV with it), causes emergence delirium (give midazolam 0.03 mg/kg)

• Propofol (1.5-2.5 mg/kg) - suppresses airway reflexes, mild bronchodilation; best for normotensive patients
• Etomidate (0.3 mg/kg) - hemodynamically neutral; no bronchodilation but does not cause histamine release; suitable for hemodynamically unstable patients

• Thiopentone (sodium thiopental) - triggers bronchospasm via histamine release and reduced cAMP

• 1-2 mg/kg IV, 2-3 min before laryngoscopy - blunts reflex bronchospasm
• Intratracheal lidocaine can paradoxically worsen bronchospasm if anaesthesia depth is inadequate

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6. AIRWAY MANAGEMENT & INTUBATION

• Deepen anaesthesia before laryngoscopy - allow 2-3 MAC volatile agent for 5 min if inhalation induction, or a top-up dose of IV agent
• Use RSI for emergency laparotomy (full stomach):
  • Succinylcholine 1.5 mg/kg - generally safe; rarely causes histamine release
  • Rocuronium 1.2 mg/kg (with sugammadex backup) - acceptable alternative
• Use the largest ETT that passes easily to minimize airway resistance
• After intubation, confirm placement by capnography (chest auscultation unreliable in severe bronchospasm)

• Rocuronium, vecuronium, cisatracurium
• Avoid: Atracurium, mivacurium (histamine releasers)

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7. MAINTENANCE OF ANAESTHESIA

• Volatile agents of choice: Sevoflurane (smoothest bronchodilation, least airway irritation)
• Isoflurane - bronchodilator but can cause more cough/laryngospasm on induction; acceptable for maintenance
• Avoid desflurane - most airway-irritant volatile; increases airway resistance especially in asthmatics and children
• Supplement with IV opioid (fentanyl) for analgesia
• Use warmed, humidified gases throughout
• TIVA (propofol infusion) is an acceptable alternative, especially if avoiding volatile agents

• Low tidal volume: 6 mL/kg
• Prolonged expiratory time: I:E ratio 1:3 or 1:4 (prevents air trapping/auto-PEEP)
• Permissive hypercapnia: acceptable unless contraindicated (raised ICP, CVS disease)
• Monitor peak airway pressure; capnograph waveform (shark-fin/obstructive pattern = expiratory obstruction)
• Avoid PEEP if auto-PEEP is already developing
• Low respiratory rate (8-10/min) to allow complete exhalation

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8. INTRAOPERATIVE BRONCHOSPASM - RECOGNITION & MANAGEMENT

• Rising peak airway pressure (plateau pressure unchanged) - pure bronchospasm
• Wheeze on auscultation
• Decreasing exhaled tidal volumes
• Shark-fin capnograph (slowly rising ETCO2 waveform)
• Decreasing SpO2

• D - Displacement of ETT (endobronchial intubation)
• O - Obstruction (kinked tube, secretions, biting on tube)
• P - Pneumothorax
• E - Equipment failure
• S - Stacking/auto-PEEP, or true bronchospasm/anaphylaxis

1. 100% FiO2
2. Deepen anaesthesia - increase volatile agent (sevoflurane/isoflurane)
3. Nebulized salbutamol via circuit (5-10 puffs MDI via T-piece)
4. IV salbutamol 0.25 mg slow IV if severe
5. IV hydrocortisone 200 mg
6. IV magnesium sulfate 2 g over 20 min
7. IV epinephrine (adrenaline) 0.1-0.5 mg SC/IM, or 10-100 mcg IV boluses for severe/anaphylactic bronchospasm
8. Aminophylline 5 mg/kg loading (if not on theophylline) - second line
9. If anaphylaxis suspected: epinephrine + antihistamine + steroids

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9. EXTUBATION

• Extubate DEEP (under adequate anaesthesia) if surgically safe - avoids cough and reflex bronchospasm on extubation
• If awake extubation needed (full stomach/difficult airway): give IV lidocaine 1 mg/kg 2-3 min before extubation
• Pre-extubation salbutamol nebulization
• Suction gently - excessive suctioning can trigger bronchospasm
• Have airway equipment ready for re-intubation
• Avoid neostigmine if possible (muscarinic effect → bronchoconstriction); if reversal needed, combine with glycopyrrolate 0.01 mg/kg or use sugammadex (preferred for rocuronium)

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10. POST-OPERATIVE MANAGEMENT

• HDU/ICU monitoring - SpO2, RR, ETCO2 if ventilated
• Continue bronchodilators (nebulized + IV)
• Continue stress-dose steroids and taper over 24-48 hours
• Adequate analgesia (avoid NSAIDs, aspirin - can precipitate aspirin-exacerbated respiratory disease)
• Use paracetamol + regional techniques (neuraxial/wound infiltration) for analgesia
• Thoracic epidural provides excellent post-laparotomy analgesia and reduces splinting/atelectasis
• Watch for: pneumothorax, pneumomediastinum (barotrauma), delayed extubation

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DRUGS TO AVOID IN ASTHMA

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VIVA QUESTIONS

1. What are the pathophysiological changes in bronchial asthma relevant to anaesthesia?
   • Airway hyperreactivity, mucosal edema, bronchospasm, mucus plugging → increased airway resistance, air trapping, auto-PEEP, V/Q mismatch
2. Why is a normal PaCO2 dangerous in an acute severe asthmatic?
   • In acute asthma, hyperventilation causes hypocapnia. A normal or rising PaCO2 means the patient can no longer maintain the work of breathing - impending respiratory failure.
3. What is pulsus paradoxus and what does it indicate in asthma?
   • Exaggerated fall in systolic BP >10 mmHg during inspiration; indicates severe air trapping and high intrathoracic pressure swings - sign of severe asthma.

1. Which drugs should you continue up to the time of surgery in an asthmatic? Which should you stop?
   • Continue: all bronchodilators, inhaled and systemic steroids
   • Stop: beta-blockers, NSAIDs if prescribed
2. What is steroid stress dosing and when is it needed?
   • Patients on >5 mg/day prednisolone or high-dose ICS within 6 months may have HPA suppression → give hydrocortisone 50-100 mg IV q8h; taper within 1-2 days postoperatively
3. Why avoid H2-blockers as premedication in asthmatics?
   • H2-receptor activation normally produces bronchodilation. Blocking H2 while H1 remains active leads to unopposed H1-mediated bronchoconstriction if histamine is released.

1. Why is ketamine the induction agent of choice in asthma with hemodynamic instability?
   • Sympathomimetic effect causes catecholamine release → bronchodilation + maintains blood pressure; also does not trigger histamine release
2. Why is thiopentone avoided in asthmatics?
   • Triggers bronchospasm via histamine release and reduced airway reflex suppression at induction
3. Why prefer sevoflurane over desflurane in asthmatic patients?
   • Sevoflurane provides smooth bronchodilation and least airway irritation; desflurane is pungent, increases airway resistance, and commonly causes cough and laryngospasm
4. What is the I:E ratio you would use in a ventilated asthmatic and why?
   • 1:3 to 1:4; prolonged expiratory time allows complete exhalation, prevents air trapping and auto-PEEP (intrinsic PEEP)
5. How do you differentiate bronchospasm from endobronchial intubation intraoperatively?
   • Both raise peak airway pressure; endobronchial intubation shows unequal air entry (absent breath sounds on one side), while bronchospasm has bilateral wheeze. Confirm with capnography and direct laryngoscopy or fibreoptic check.
6. What is the DOPES mnemonic in a ventilated patient with rising airway pressures?
   • Displacement, Obstruction, Pneumothorax, Equipment failure, Stacking/bronchospasm
7. Why is regional anaesthesia not completely safe in severe asthmatics?
   • High spinal/epidural blocks T1-T4 sympathetic supply to bronchi → unopposed parasympathetic activity → bronchoconstriction
8. Why is lidocaine useful before intubation in asthmatics, and what is the risk?
   • Blunts airway reflexes; reduces reflex bronchospasm. Risk: if anaesthesia depth is inadequate, intratracheal lidocaine itself can trigger bronchospasm.
9. How would you manage intraoperative bronchospasm stepwise?
   • 100% O2 → deepen anaesthesia (sevoflurane) → nebulized/IV salbutamol → IV hydrocortisone → IV MgSO4 → IV adrenaline if severe/anaphylaxis suspected → aminophylline as last resort

1. When and how would you extubate an asthmatic patient after emergency laparotomy?
   • Deep extubation preferred (avoids cough/reflex bronchospasm); if full stomach mandates awake extubation, give IV lidocaine 1 mg/kg 2-3 min before and pre-extubation salbutamol nebulization
2. Why prefer sugammadex over neostigmine for reversal in asthmatics?
   • Neostigmine is a cholinesterase inhibitor → increased muscarinic activity → bronchoconstriction; sugammadex directly encapsulates rocuronium with no muscarinic effects
3. Why are NSAIDs avoided postoperatively in asthmatics?
   • Inhibit COX-1 → shift arachidonic acid toward lipoxygenase pathway → leukotriene production → bronchospasm (aspirin-exacerbated respiratory disease in 10-20% of asthmatics)

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