Impact of Sedation Depth on Neurological Outcomes in Mechanically Ventilated Adult Patients: A Systematic Review and Meta-Analysis

Abstract

Aims: The objective of this systematic review and meta-analysis was to evaluate the impact of sedation depth (deep versus light) on neurological outcomes in mechanically ventilated adult patients. The primary outcome was the incidence of in-hospital delirium, and secondary outcomes included hospital mortality and long-term neurological impairment. Study Design: Systematic review and meta-analysis of randomised controlled trials (RCTs) and observational cohort studies, conducted in accordance with the PRISMA 2020 guidelines. Methods/Data Sources: A comprehensive search was performed in PubMed/MEDLINE, EMBASE, Cochrane CENTRAL, Scopus, Web of Science, and LILACS from database inception. We included studies involving adult ICU patients requiring mechanical ventilation where sedation depth was objectively assessed using validated scales (e.g., RASS, SAS). Methodology: Data were pooled using random-effects models due to expected clinical heterogeneity. The primary measure of effect was the Odds Ratio (OR) with 95% Confidence Intervals (CI). Heterogeneity was assessed using the I-squared statistic. The primary outcome was delirium incidence; secondary outcomes included hospital mortality and long-term neurological outcomes. Results: Eleven studies (N = 31,426) met the inclusion criteria and provided data for quantitative synthesis. Deep sedation was associated with a statistically significant twofold increase in the odds of in-hospital delirium compared to light sedation (OR = 2.07; 95% CI 1.58 to 2.71; p < 0.001), with moderate statistical heterogeneity (I-squared = 42.0%). Conversely, there was no significant difference in hospital mortality between deep and light sedation strategies (OR = 1.13; 95% CI 0.89 to 1.42; p = 0.32). Analysis of long-term neurological impairment showed a trend towards harm with deep sedation but did not reach statistical significance (OR = 1.53; 95% CI 0.81 to 2.91). Conclusion: Deep sedation is significantly associated with acute brain dysfunction (delirium) in mechanically ventilated adults. However, current evidence suggests that sedation depth alone does not appear to drive short-term mortality in the modern ICU setting. These findings support clinical guidelines advocating light sedation to minimise delirium, while highlighting the need for further research on long-term cognitive trajectories.