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Awareness With Paralysis (AWP) During Intubation in the ICU

Updated: Aug 28, 2023

Awareness with paralysis (AWP) refers to a patient's ability to remember sensory experiences while affected by a neuromuscular blocking agent. Research on patients who have experienced this form of awareness during surgery has found that up to 70% of them face significant long-term psychological effects. These consequences can range from posttraumatic stress disorder (PTSD) and clinical depression to intricate phobias [1].


This topic has been extensively studied in the operating room environment. However, there is a relatively limited data regarding intubated patients in emergency rooms and ICUs. In this article, we will discuss the tools used to detect AWP, then, we will delve into the existing research on this subject within these specific settings, aiming to determine its prevalence, identify associated risk factors, and suggest preventive measures.

Which of the following predispose to awareness with paralysis? (Check all what apply)?

  • 0%Use of a long-acting paralytic agent (i.e. rocuronium)

  • 0%Delayed analgosedation

  • 0%Absence of sedation depth monitoring

How is AWP Detected?

The Modified Brice Questionnaire is a tool used to detect awareness with recall under general anesthesia. It is a modified version of the Brice questionnaire and consists of questions such as “What is the last thing you remember before going to sleep?”, "Do you remember anything happening during surgery", "Did you have any dreams during surgery", and "What is the first thing you remember after waking up?" [2].


For a potential AWP event to be recognized, patients needed to recall an instance of being awake yet paralyzed, either after initially becoming unconscious (e.g., awakening during paralysis) or just before losing consciousness (e.g., recalling paralysis while being intubated).

Brice Awareness Questionnaire
Brice Awareness Questionnaire

This tool underwent its main validation for assessing AWP in operating rooms. Nonetheless, it was also utilized in numerous studies that evaluated AWP in emergency departments (EDs) or intensive care units (ICUs).

What is Prevalence of AWP in ICU?

Data gathered from numerous cohort studies and randomized controlled trials indicate an incidence of awareness in about 0.1–0.2% of operating room procedures [3]. Studies of AWP in the ER and ICU have shown higher rates. A systematic review and meta-analysis of seven studies found an AWP incidence rate of 12.3% with notable variability between the studies. When grouped by study quality, good quality studies had a 3.4% AWP incidence, while poor quality ones had 18.2%. Based on the survey tool, studies using the modified Brice questionnaire had a 1.9% incidence, while others showed 21.0% [4].


The ED-AWARENESS Study is a single center observational study revealed a prevalence of awareness with paralysis of 2.6% using the modified Brice Questionnaire [5]. Another study in three academic centers revealed a rate of 3.4% in mechanically ventilated adult patients that received neuromuscular blockers [6].


A recent study from a single city-county hospital observed 886 patients, of which 66 (7.4%; 95% CI, 5.8-9.4) either likely (61 patients) or definitively (5 patients) felt awareness of paralysis [7].


What are the Risk Factors?

Factors contributing to an increased likelihood and intensity of awareness with paralysis in the operating room encompass the use of intravenous anesthetics (as opposed to inhaled ones), insufficient dosage of anesthesia, the use of longer-acting neuromuscular blocking agents, and the absence of standardized monitoring for sedation depth.


Emergency department (ED) data shows that AWP is linked with:

  1. Increased use of longer-lasting neuromuscular blocking agents.

  2. Delayed analgosedation.

  3. Absence of sedation depth monitoring.

The ED-AWARENESS Study showed that 70% of patients who experienced awareness with paralysis in the ED had been exposed to rocuronium, compared to 31.4% of the other patients. This difference is notable with an unadjusted odds ratio of 5.1 (95% confidence interval ranging from 1.30 to 20.1) [5].


In the study by Fuller [6], 12 out of 230 (5.5%) patients who received rocuronium developed AWP, compared to only 1 out of 158 (0.6%) patients with another paralytic agent. The odds ratio stands at 8.64 with a 95% confidence interval of 1.11 to 67.15.


A logistic regression analysis in the study by Driver [7] showed that a lower consciousness level before intubation was linked to reduced chances of awareness (adjusted OR, 0.39; 95% CI, 0.22-0.69). However, factors like the type of neuromuscular blocking agent, sedative used, preintubation shock index, and postintubation sedation didn't significantly affect the recall of this outcome.

What are the Consequences of AWP?

Studies from anesthesia literature shows that long-term psychological consequences of AWP are common and include depression, anxiety, post-traumatic stress disorder (PTSD), and debilitating phobias [8].


In the ED-AWARNESS study, patients with AWP had higher average threat perception scores (A scale that measures fear for one's safety and well-being during illness) than those without such awareness, signifying a more pronounced sense of threat and predisposition for PTSD. The scores were 13.4 (SD 7.7) versus 8.5 (SD 6.2), a mean difference of 4.9, with a 95% confidence interval of 0.94 to 8.8 [5].


Similarly, in the study by Muller, patients experiencing AWP had a higher mean (standard deviation) threat perception scale score, compared to patients without AWP [15.6 (5.8) vs. 7.7 (6.0), p < 0.01] [6].


How to Prevent AWP?

Based on the above studies and discussions, here are recommendations to prevent AWP in the ICU:


Based on the above studies and discussion, here are recommendations to prevent AWP in intubated patients with paralysis in the ICU:

  1. Use succinylcholine as a paralytic agent during rapid sequence intubation whenever possible. Ensure that the patient has no contraindication to its use.

  2. Administer sedation early and appropriately for the duration of paralysis and minimize any delays.

  3. Implement standardized monitoring for sedation depth and ensure deep level of sedation in patients on paralysis. Use objective measures, preferably Bispectral index (BIS)

  4. Use paralysis for the shortest possible duration.


Conclusion

Awareness with paralysis is more frequent in the ICU than in the operating room, potentially reaching 12%. Contributing factors encompass the usage of long-acting paralytic agents, delayed analgesia, and insufficient sedation depth. Significant psychological effects like depression and PTSD can result. Preventive measures include appropriate selection of paralytic agent, prompt sedation, monitoring, and limiting paralysis duration.

REFERENCES:

  1. Cook TM, Andrade J, Bogod DG, Hitchman JM, Jonker WR, Lucas N, Mackay JH, Nimmo AF, O'Connor K, O'Sullivan EP, Paul RG, Palmer JH, Plaat F, Radcliffe JJ, Sury MR, Torevell HE, Wang M, Hainsworth J, Pandit JJ; Royal College of Anaesthetists; Association of Anaesthetists of Great Britain and Ireland. 5th National Audit Project (NAP5) on accidental awareness during general anaesthesia: patient experiences, human factors, sedation, consent, and medicolegal issues. Br J Anaesth. 2014 Oct;113(4):560-74. [PubMed].

  2. Brice DD, Hetherington RR, Utting JE. A simple study of awareness and dreaming during anaesthesia. Br J Anaesth. 1970;42:535–42. [PubMed].

  3. Sebel PS, Bowdle TA, Ghoneim MM, et al.: The incidence of awareness during anesthesia: a multicenter United States study. Anesth Analg 2004; 99(3):833–839 [PubMed].

  4. Pappal RD, Roberts BW, Winkler W, Yaegar LH, Stephens RJ, Fuller BM. 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. [PubMed].

  5. Pappal RD, Roberts BW, Mohr NM, Ablordeppey E, Wessman BT, Drewry AM, Winkler W, Yan Y, Kollef MH, Avidan MS, Fuller BM. 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 May;77(5):532-544 [PubMed].

  6. Fuller BM, Pappal RD, Mohr NM, Roberts BW, Faine B, Yeary J, Sewatsky T, Johnson NJ, Driver BE, Ablordeppey E, Drewry AM, Wessman BT, Yan Y, Kollef MH, Carpenter CR, Avidan MS. Awareness With Paralysis Among Critically Ill Emergency Department Patients: A Prospective Cohort Study. Crit Care Med. 2022 Oct 1;50(10):1449-1460 [PubMed].

  7. Driver BE, Prekker ME, Wagner E, Cole JB, Puskarich MA, Stang J, DeVries P, Maruggi E, Miner JR. Recall of Awareness During Paralysis Among ED Patients Undergoing Tracheal Intubation. Chest. 2023 Feb;163(2):313-323. doi: 10.1016/j.chest.2022.08.2232 [PubMed].

  8. Leslie K, Chan MT, Myles PS, Forbes A, McCulloch TJ. Posttraumatic stress disorder in aware patients from the B-aware trial. Anesthesia & Analgesia 2010, 110(3):823–828. [PubMed]




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