Asthma: acute exacerbation: mechanically-ventilated patients were at risk of barotrauma.

Clinical bottom line (level 4)

  1. Deaths were uncommon in patients with acute severe asthma who were sent to ITU.
  2. Patients who were mechanically ventilated were at increased risk of pulmonary barotrauma, hypotension and cardiac arrhythmias.
Williams et al: American Review of Respiratory Diseases 1992; 146: 607-615
Expires November 2002

The study

Case series with ?objective ?blinded outcomes, not adjusted for confounding factors, not validated in an independent set of patients.

Setting: intensive care unit, acute hospital, Australia over 5 years

73 patients (aged mean 40 years, 51% female) admitted 88 times with severe asthma to ITU. 51 were ventilated. Admission criteria were:
  • unremitting dyspnoea
  • pO2 < 8 kPa
  • pCO2 > 6 kPa
  • clinical deterioration despite initial treatment
  • intubated and ventilated mechanically

All patients had salbutamol and ipratropium nebulisers, aminophylline iv, steroids iv, and oxygen to keep SaO2 > 95%.


Outcomes studied:
  • death
  • barotrauma pneumothorax, pneumomediastinum, and/or subcutaneous emphysema on CXR
  • hypotension systolic bp < 100 mmHg on at least 2 occasions or < 90 mmHg on one occasion
  • cardiac arrhythmias sinus tachycardia > 160, ventricular premature beats > 1:5, atrial or ventricular tachyarrhythmias

    • The evidence

    outcome time to outcome number of patients/total number %
    (95% CI)
    death ? 0/88 0.0%
    (0.0% to 3.4%)
    barotrauma ? 18/88 21%
    (12% to 29%)
    hypotension ? 12/88 14%
    (6.5% to 21%)
    cardiac arrhythmias ? 8/88 9.1%
    (3.1% to 15%)

    • All complications occurred in ventilated patients.
    • Other ventilation strategies, such as noninvasive positive pressure ventilation may reduce these hyperinflation related complications

    Citation

    1. Williams IJ, Tuxen DV, Scheinkestel CD, et al: Risk factors for morbidity in mechanically ventilated patients in acute severe asthma. American Review of Respiratory Diseases 1992; 146: 607-615
    Search Terms: reference from asthma chapter in Lee, Hsu, Stasior: Quick-consult manual to evidence-based medicine: publ. Lippincott-Raven 1997
    Contributor: Chris Ball and Clare Wotton, February 1999
    Reviewer:

    Clinical Question.
    Patient asthma
    Intervention or Exposure mechanical ventilation
    Outcome complications