ARTICLE: Driver BE, Prekker ME, Wagner E, et al. Recall of Awareness During Paralysis Among ED Patients Undergoing Tracheal Intubation. CHEST. 2022;S0012-3692(22)03708-4.
OBJECTIVE: To determine the prevalence of recalled awareness during paralysis in patients who underwent tracheal intubation and what clinical variables are associated with awareness.
Awareness of paralysis is a feared complication for patients undergoing endotracheal intubation using neuromuscular blocking agents (NMBA). The memory of paralysis has been associated with adverse patient outcomes such as PTSD, depression, or phobias. This event has been advocated to be defined as a never event.1 The frequency has previously been studied in anesthesia OR studies, but there is limited data in the emergency department.2 A recent study of ED studies has suggested the frequency may be significantly higher in the ED vs the OR setting (approximately 3% vs 0.1%).3 Clinically, awareness has been hypothesized to occur due to many possible variables, including the type, timing, and quantity of induction agent or post-intubation sedation. The issue is further complicated in the ED as emergent hemodynamic parameters often affect the choice of sedation.
This study tracks the frequency in a high volume, urban, county ED setting following intubation. In addition, it looks at the clinical variables that may be associated with awareness, including the type of sedation, type of NMBA, level of preintubation consciousness, RSI drug order, shock index, and drug given following intubation.
This study was a single-center, prospective observational study conducted from July 2018 – January 2021 (interrupted by COVID-19 from March-September 2020). The study occurred at an urban, level 1 adult and pediatric trauma center with >100,000 visits/year. EM physicians had procedural responsibility and chose medications for induction and post-sedation based on the clinical scenario.
Data was collected and physician adjudicators reviewed eligible participants' data to determine if there had been awareness during paralysis. In addition, a modified Brice questionnaire was completed by participants and used to evaluate memories. This questionnaire is a well-accepted tool for evaluating patient memories and has been used in previous similar studies.4
To meet the criteria for further evaluation of awareness during paralysis, patients needed a memory of wakeful paralysis. To undergo further evaluation for memory of the intubation procedure, the patient had to report memory of a breathing tube being placed.
For patient meeting criteria, three trained independent expert physicians reviewed responses and surrounding clinical information. These reviewers labeled each event as definite, possible, or no plausible awareness of paralysis or memory of intubation. When two or more reviewers were in agreement with definite or possible, the patient was labeled as experiencing that outcome. Agreement among adjudicators was statistically assessed with a two-way random effects intraclass correlation coefficient.
To determine clinical variables associated with study outcomes, logistic regression models were constructed for both the primary and secondary outcomes.
Patients ≥ 18 years undergoing orotracheal intubation who received a NMBA for intubation in the ED during the 30-month study period
- Patients who did not have data collected prospectively
- Patients who did not receive a NMBA
- Patients unwilling or unable to complete the pre- and post-memory interviews
Awareness of paralysis in the ED, defined as when 2 out of 3 expert adjudicators agreed on an event being definite or possible
Memory of the intubation procedure, defined as when 2 out of 3 expert adjudicators agreed on an event being definite or possible. Additional sensitivity studies were performed and can be found in table E1-E2 of the article.
The final cohort consisted of 886 patients. The two outcomes occurred in 79 unique patients.
66 patients (7.4%) were deemed to possibly (n=61) or definitely (n=5) have awareness of paralysis. A total of 80 patients (9.0%) of the cohort underwent adjudication for potential awareness of paralysis.
34 patients (3.8%) were deemed to possibly (n=15) or definitely (n=19) have memory of the endotracheal intubation; 37 patients (94.2%) of the cohort underwent adjudication for memory of endotracheal intubation.
Clinical Variables for Primary Outcomes
Data presented as OR (95% CI)
- Rocuronium vs. succinylcholine:22 (0.73-2.05), no statistically significant difference
- Ketamine vs. etomidate:11 (0.69-6.52), no statistically significant difference
- Mental status prior to intubation: unconscious or responsive only to pain vs other: 0.39 (0.22-0.69), statistically significant
- Shock index: for every increase of 0.1 beats per min/mm HG: 1.01 (0.97-1.07), no statistically significant difference
- Ketamine vs. propofol given in the ED following intubation: 5.37 (0.72-40.1), no statistically significant difference
Clinical Variables for Secondary Outcomes
Data presented as OR (95% CI)
- Rocuronium vs. succinylcholine:87 (0.84-4.17), no statistically significant difference
- Ketamine vs. etomidate:96 (0.43-8.96), no statistically significant difference
- Mental status prior to intubation: unconscious or responsive only to pain vs other: 0.58 (0.26-1.30), no statistically significant difference
- RSI drug order: NBMA first vs sedative first: 0.49 (0.23-1.04), no statistically significant difference
- Adjudicating recall of awareness is inherently subjective. The final determinations cannot be taken as certainties.
- Patients’ memories can be uncertain and difficult to assess. It is possible to feel paralysis from non-NMBA factors. Patients may also have trouble discerning the intubation procedure itself from the presence of the tube.
- The study did not address the perception of awareness of paralysis for those who did not receive NMBAs.
- A considerable portion of patients were discharged prior to being able to get data. These likely represented shorter extubation times and might have had higher levels of awareness.
- The study only questioned patients during hospitalization. Patients may recall awareness of paralysis at later times.5
- The study may be underpowered to detect differences based on risk factors due to the low number of events.
- Data regarding the exact minute of post-intubation sedation was not available, which could provide insight into the relationship between timing and memories.
This topic has not been heavily explored in the emergent setting, and additional clinical factors may influence awareness levels. But key points include:
- An appreciable number of patients report awareness during paralysis following endotracheal intubation in the ED and ICU.
- This study found patients with near-normal levels of consciousness prior to intubation were more likely to be aware during paralysis.
- It is imperative that effective sedation is given during neuromuscular blockade to avoid awareness of paralysis.
- Goettlieb M, Carlson JN. Speechless: Awareness With Recall of Paralysis in the Emergency Department Setting. Ann Emerg Med. 2021;77(5):545-546.
- Fuller BM, Pappal RD, Mohr NM, et al. Awareness with Paralysis among Critically Ill Emergency Department Patients: A Prospective Cohort Study∗. Crit Care Med. 2022;50(10):1449-1460.
- Pappal RD, Roberts BW, Mohr NM, et al. The ED-AWARENESS Study: A Prospective, Observational Cohort Study of Awareness With Paralysis in Mechanically Ventilated Patients Admitted From the Emergency Department. Ann Emerg Med. 2021;77(5):532-544.
- Brice DD, Hetherington RR, Utting JE. A simple study of awareness and dreaming during anaesthesia. Br J Anaesth. 1970;42(6):535-542.
- Ghoneim MM, Block RI, Haffarnan M, Mathews MJ. Awareness during anesthesia: Risk factors, causes and sequelae: A review of reported cases in the literature. Anesth Analg. 2009;108(2):527-535.