Acute asthma exacerbation: severity assessment and emergency management

Causes and risk

To identify patients at risk of asthma-related death is the first step of the general approach. A history of near fatal asthma with intubation and mechanical ventilation is the strongest predictor. The other risk factors for potentially fatal asthma are hospitalization in the previous year, frequent emergency visit in the past year of more than 2, being on oral steroids or having recently stopped them as a marker of event severity, not being on inhaled steroids, overdependence on SABA with more than 1 canister of salbutamol per month, psychiatric disease or psychosocial problems, and poor adherence to treatment or to the action plan.

How it presents

Severity is read off the physical examination in four bands.

• Mild: breathless on walking, can lie down, usually not agitated, speech in sentences, moderate end expiratory wheeze, heart rate below 100, no pulsus paradoxus.
• Moderate: breathless on talking, prefers sitting, may be agitated, speech in phrases, accessory muscles commonly used, loud wheeze throughout exhalation, heart rate 100-120, pulsus paradoxus of 12-20 mmHg may be present.
• Severe: breathless at rest, hunched forward, usually agitated, speech in words, accessory muscle use with suprasternal retraction, loud wheeze on inhalation and exhalation, respiratory rate above 30, heart rate above 120, pulsus paradoxus often above 25 mmHg.

Pulsus paradoxus is the drop in systolic BP with inspiration. Imminent respiratory arrest is a different picture: drowsy or confused, paradoxical thoracoabdominal movement, absent wheeze and bradycardia. Absence of pulsus paradoxus there suggests respiratory muscle fatigue.