bjectives: Acute respiratory distress syndrome (ARDS) is a frequent complication seen in patients after aneurysmal subarachnoid hemorrhage (aSAH), but its prevalence, timing, and influence on neurological outcome is unclear. We aimed to investigate the prevalence, timing, risk factors, and outcome of ARDS in patients with aSAH.

Methods: PubMed and four other databases (Embase, Cochrane Library, Web of Science Core Collection, and Scopus) from inception to July 6, 2020. We included all randomized controlled trials (RCTs) and observational studies of patients older than 18 years old. Two independent reviewers extracted the data. Study quality was assessed by the Cochrane Risk of Bias tool for RCTs, the Newcastle-Ottawa Scale for cohort and case-control studies. High-grade aSAH was defined as admission Glasgow coma scale 3-5 and/or modified fisher scale>=3 and/or Hunt Hess grade>=3. Good neurological outcome was defined as Glasgow Outcome Scale ≥ 4. Random-effects meta-analyses were conducted to estimate pooled outcome prevalence and their 95% confidence intervals (CI).

Results: Nine observational studies (n=2,039) met the inclusion criteria, with the median age of 55 years (range=50-61, 28% male) and 71% patients suffered high-grade aSAH. Overall, 16% patients (95% CI=0.05-0.28, I2=94%) had ARDS after aSAH. The median time from SAH to ARDS was 3 days (range=2-6 days). Overall survival at discharge was 79% (95% CI=0.71-0.87; I2=95%) and good neurological outcome at any time was achieved in 65% of aSAH patients (95%CI=0.61-0.69; I2= 0.02%). aSAH cohort without ARDS had higher proportion of survival compared to those with ARDS (79% vs. 49%, p=0.028). Male sex, patients with high-grade aSAH, patients who developed pneumonia and systemic inflammatory response syndrome during hospital admission were at higher risk of developing ARDS.

Conclusions: In this meta-analysis, approximately one in six patients developed ARDS after aSAH with the median time of 3 days from initial presentation and is associated with increased mortality. Further research to better understand the prevention and treatment strategy is necessary.