Asthma
Considerations
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Risk of perioperative respiratory complications:
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Bronchospasm, mucous plugging, pneumothorax, atelectasis, pneumonia
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Possible pulmonary hypertension & RV failure
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Need for preoperative optimization:
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Treatment of bronchospasm, infection, atelectasis
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Avoidance of triggers & exacerbating factors:
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Avoid general anesthesia, endotracheal intubation, histamine releasing medications, light anesthesia
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Medication management:
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Continue usual inhalers pre-operatively
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Stress dose steroids if recent high dose steroid use
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Goals & Conflicts
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Assess preoperative respiratory function for stability:
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Stable symptoms (sputum, bronchospasm), PFTs, imaging, ABG
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Assess for pulmonary hypertension, cor pulmonale
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Medical optimization: bronchodilators, glucocorticoids, antibiotics, BiPAP
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Anesthetic management principles:
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Avoid airway instrumentation
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Blunt airway reflexes: deep anesthesia, topical local anesthetics, opioids
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Bronchodilation: avoid histamine releasing medications (e.g., morphine), use ketamine, volatiles, MgSO4, salbutamol, ipratropium, epinephrine
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Permissive hypercapnia: ↓ respiratory rate, ↑ expiratory time, adequate tidal volumes
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Monitor intrinsic PEEP, presence of dynamic hyperinflation & pulmonary tamponade
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Postoperative monitoring for bronchospasm, respiratory failure
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Severe Asthma Exacerbation Treatment Options
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Salbutamol 2.5-5mg via nebulizer q20 minutes
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Ipratropium 500mcg via nebulizer q20 minutes
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Corticosteroids:
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Prednisone PO 40-60mg single dose
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Methylprednisolone 60-80mg IV q6-12h
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Epinephrine if anaphylaxis suspected or severe asthma refractory to standard therapy:
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Dose is 0.3-0.5mg IM/SC or 10-50 mcg IV bolus, followed by infusion @ 2-10 mcg/min
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Magnesium for life-threatening exacerbation: 2g IV over 20 min
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Heliox & humidified O2 (conflicting studies)
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Anesthetics:
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Ketamine
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Propofol
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Volatiles all are bronchodilators but sevoflurane is likely best choice
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Leukotriene receptor antagonists (only PO available in Canada)
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Always consider noninvasive PPV as rescue before intubation
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If intubation & ventilation:
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Use permissive hypercapnia
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Use low respiratory rates: start at 10-12 breaths/minute but may need lower rates
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Use prolonged expiratory time (e.g. I:E ratios 1:3, 1:4, or even 1:5)
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Tidal volume 6-8cc/kg
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FiO2 to achieve PaO2 >60mm Hg
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ECMO as last resort
Asthma Severity Based on Airflow Obstruction
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