Awareness With Paralysis in Mechanically Ventilated Patients in the Emergency Department and ICU: A Systematic Review and Meta-Analysis

Crit Care Med. 2021 Mar 1;49(3):e304-e314. doi: 10.1097/CCM.0000000000004824.


Objective: Awareness with paralysis is a devastating complication for mechanically ventilated patients and can carry long-term psychologic sequelae. Hundreds of thousands of patients require mechanical ventilation in the emergency department and ICU annually, yet awareness has only been rigorously examined in the operating room (incidence ~0.1%). This report collates the global literature regarding the incidence of awareness with paralysis outside of the operating room.

Data sources: We searched OvidMedline, Embase, Scopus, Cochrane Database of Systematic Reviews, Cochrane Central Register of Controlled Trials,, conference proceedings, and reference lists.

Study selection: Randomized or nonrandomized studies (except single case studies) reporting on awareness with paralysis in the emergency department or ICU were eligible.

Data extraction: Two independent reviewers screened abstracts for eligibility.

Data synthesis: The search identified 4,454 potentially eligible studies. Seven studies (n = 941 patients) were included for analysis. A random effects meta-analysis of proportions along with multiple subgroup analyses was performed. Significant between-study heterogeneity in reporting of awareness with paralysis was noted, and the quality of the evidence was low. Analyses stratified by: 1) good-quality studies and 2) use of the modified Brice questionnaire to detect awareness revealed estimates of 3.4% (95% CI, 0-10.2%) and 1.9% (95% CI, 1.0-3.0%), respectively.

Conclusions: The incidence of awareness with paralysis in mechanically ventilated patients in the emergency department and ICU, as evaluated in a small number of qualifying studies from this comprehensive systematic review, appears much higher than that reported from the operating room. Given the clinical and statistical heterogeneity, caution is warranted in the interpretation of these findings. Further high-quality studies are needed to both define the true incidence and to target the prevention of awareness with paralysis in this vulnerable patient cohort.

Publication types

  • Meta-Analysis
  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Systematic Review

MeSH terms

  • Awareness*
  • Critical Care / statistics & numerical data*
  • Critical Illness / therapy*
  • Emergency Service, Hospital
  • Humans
  • Intensive Care Units / organization & administration*
  • Respiration, Artificial / statistics & numerical data*
  • Respiratory Paralysis / diagnosis*
  • Respiratory Paralysis / epidemiology