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Acute severe asthma

Management guidelines

Introduction

These guidelines are prepared from those published by the British Thoracic Society, and are based on the best available evidence. Acute severe asthma is a frequent cause of hospital admission, and rarely of death in young adults. Effective management depends upon a rapid but thorough assessment of initial severity, and of subsequent response to treatment. In difficult cases there should be a low threshold for contacting the chest physician on-call.

Initial assessment & management

A calm and reassuring manner is worth several doses of bronchodilator. The following are important:

• Assess for life threatening features: SaO₂ <92% or PaO₂ <8kPa, normal PaCO₂ (4.6-6.0kPa), cyanosis, confusion/coma, PEFR <33% predicted/best, absent breath sounds, hypotension, bradycardia/dysrhythmia; or
  • Severe features: respiratory rate >25/min, pulse rate>110/min, PEFR 33-50% predicted/best, inability to speak in sentences
• Try rapidly to obtain information about time course of symptoms, normal PEFR (or use nomogram) and medication
• Administer high-concentration oxygen and 5mg salbutamol or 10mg terbutaline via oxygen-driven nebuliser on arrival
• Give prednisolone 40mg p.o. Intravenous hydrocortisone is not required or beneficial unless the patient is unconscious or unable to swallow
• If life-threatening features or severe, unresponsive to initial therapy, add ipratropium bromide 500 micrograms nebulized, and start i.v. magnesium sulphate infusion (1.2-2g infusion over 20 min).
• Get a CXR to exclude pneumothorax
• Measure arterial blood gasses (ABG) if SaO₂ <92% on oxygen, or any severe/life-threatening features.

Monitoring progress

• Monitor vital signs, PEFR, SaO₂ every 15-30 min while severely breathless, and administer further doses of nebulised salbutamol and ipratroprium if not improving
• Repeat ABG if initial PaO₂ <8.0, initial PaCO₂ normal or high, or patient's condition deteriorates
• Seek intensive care opinion if falling SaO₂, rising PaCO₂, drowsiness/exhaustion, coma, or respiratory arrest
• Consider adding infusion of aminophylline 0.5-0.7 mg/kg/hr if poor response to above therapy
• Inform Chest Unit about any patient with severe acute asthma; admission to the Chest Unit may be appropriate if patient is safe for transfer away from JR site without need for ITU, and a Chest Unit bed is available

Stepping down treatment

• Consider discharge if no life-threatening features and PEFR >75% predicted/best 1 hr after initial treatment
• Continue prednisolone 40mg daily until 5 days post discharge
• Continue nebulised salbutamol until PEFR is >75% predicted/best
• All patients should have inhaler technique checked before discharge (respiratory nurse specialist can advise)
• Arrange GP follow-up within 1 week of discharge.

The full BTS guideline is available here.