Study designs of evaluations included in the review
All articles of any study design were eligible for inclusion in the review.
Specific interventions included in the review
Ketamine therapy comprised 0.75 mg/kg intravenous (i.v.) bolus, then 0.75 mg/kg i.v. over 10 minutes followed by 0.15 mg/kg/hour infusion for 1 to 8 hours; 2.5 mg/kg/hour infusion for 26 hours; 20 mg i.v. then 5 microg/kg/minute for 18 hours; or three i.v. bolus over 75 minutes. In the one included controlled trial, ketamine 0.2 mg/kg i.v. bolus and an infusion of 0.5 mg/kg/hour for 3 hours was added to conventional asthma therapy and compared with placebo added to the same conventional asthma therapy. Conventional asthma therapy included oxygenation, nebulised albuterol (0.5 mg every 20 minutes), and intravenous sodium succinate (125 mg) followed by continuous nebulised albuterol (10 mg/hour).
Participants included in the review
Adults aged 18 to 65 years with severe acute exacerbation of asthma were included in the controlled trial. Acute asthma exacerbation was defined as a peak expiratory flow rate (PEFR) of less than 40% of the predicted value after 3 courses of therapy with nebulised albuterol, 0.5 mg in 2.5 mL saline solution. Patients with chronic obstructive disease, emergency intubation, hypertension, coronary artery disease, hyperthyroidism, pregnancy, psychiatric disorders, inability to perform bedside spirometry, or allergy to ketamine were excluded from the study. The case reports included patients with the following: acute severe asthma unresponsive to conventional therapy; respiratory arrest; refractory severe asthma complicated by acute myocardial infarction; and severe asthma. Articles discussing ketamine administered for analgesia, sedation, rapid-sequence intubation, and non-asthma-related bronchospasm were excluded.
Outcomes assessed in the review
The clinical end points included spirometry testing (forced expiratory volume in 1 second, i.e. FEV1, and PEFR), oxygen saturation, arterial blood gases (pH, partial arterial oxygen pressure and partial arterial carbon dioxide pressure), length of stay, hospital admission where applicable, and adverse effects.
How were decisions on the relevance of primary studies made?
The authors do not state how the papers were selected for the review, or how many of the reviewers performed the selection.