Records noted that patient’s open fracture / dislocation was reduced in the ED after intubation and before transfer; reported “spike in blood pressure” during this event.’
-Patient reported memory / awareness experience-
Background:
Awareness with recall of paralysis is the recollection of sensory perceptions while under the influence of a neuromuscular blocking agent. When caring for critically ill intubated patients we tread a thin line of adequately managing analgesia and sedation without overdoing it and contributing to hypotension, or ICU delirium; all the while trying not to underdo it and leave our patients aware of paralysis, resulting in increased rates of PTSD, clinical depression, and complex phobias. (Up to 70% incidence in some studies).
What is Known:
- Previous operating room-based studies show IV anesthetic agents, and the use of long-acting neuromuscular blocking agents are associated with higher rates of awareness.
- ED studies have shown that in patients receiving longer acting neuromuscular blocking agents, there is a longer delay in the initiation of post intubation analgesia and sedation, (27 vs 15 min, [1]) and that once initiated, it is given in lower doses. (30 vs 42 mcg/kg/min [2])
- Anesthesia studies on a healthier population than is typically seen in the ED can help to provide baseline data and can help to potentially identify factors associated with awareness during anesthesia.
- The British NAP5 audit on Accidental Awareness during General Anesthesia [3] was an audit of all anesthetics provided over a 1-year timespan, with all patients surveyed after anesthesia. The NAP5 authors found an overall incidence of awareness of 1:19,600. Awareness during anesthesia when a neuromuscular blocking agent was used was 1:8200. Factors contributing to awareness during the induction phase of anesthesia were: Thiopental use, Rapid Sequence Intubation, Obesity, difficult airway management, and the use of a neuromuscular blocking agent.
- One EM relevant recommendation from NAP5: ‘These results suggest that more careful attention to dosing of induction agent is needed, along with a proper assessment that it has worked sufficiently well before neuromuscular blocking drugs are administered’. This is essentially a DSI strategy to ensure anesthesia before paralysis.
Paper:
Pappal RD 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. PMID: 33485698 [Access on Read by QxMD]
Clinical Question: What is the prevalence of awareness with paralysis among ED patients receiving mechanical ventilation?
What They Did:
- Study objective: Assess the prevalence of awareness with paralysis in ED patients receiving mechanical ventilation.
- Single center prospective cohort study from June 2019 – May 2020 at a large academic emergency department (census 90,000 patients per year)
- Separately published study protocol in BMJ open [5]
- Data:
- All medication data including sedative dosing and NMB dosing was collected
- Sedation depth was recorded using the Richmond Agitation-Sedation Scale
- Interviewers sought to purposely separate memories of ICU care while lightly sedated from memories with awareness of paralysis
- Memories were categorized as either factual / memories of feelings / delusional
- Awareness was considered to be present when a patient reported a memory of the period between losing consciousness and waking up. (Question 3 on the modified Brice questionnaire).
- Brice-Modified Questionnaire
- What was the last thing you remember before going to sleep?
- What is the first thing you remember after waking up?
- Do you remember anything between going to sleep and waking up?
- Did you dream during your procedure?
- Were your dreams disturbing to you?
- Awareness with paralysis was considered present when patients reported a memory of paralysis with concurrent documentation of a NMB having been administered.
- All patients reporting awareness of paralysis had a qualitative report of their experience.
- All reports of awareness were adjudicated by 3 experts. Awareness was confirmed when 2 out of 3 experts agreed
- Enrollment Timing: A full calendar year was selected to avoid any seasonal bias of reason for intubation (summer has increased trauma intubations, winter has increased respiratory illness related intubations)
- Sample size: Large enough to capture approximately 10 events, with likely 15% rate of death before extubation, and 30% rate of neurological impairment that prevents participation in survey
Outcomes:
- Primary: Prevalence of awareness (Awareness with Paralysis – AWS)
- Secondary: Perceived threat (mediator for development of PTSD)
Inclusion Criteria:
- ≥18 years of age
- Mechanical ventilation in ED (including transferred patients intubated at outside facilities)
Exclusion Criteria:
- Death before extubation
- Neuro injury with deficit that precluded patient from participating in awareness survey (TBI, hypoxic brain injury, CVA)
- Transfer to another facility
- Refusal to answer questionnaire
Results:
- 833 mechanically ventilated patients assessed for eligibility
- 450 excluded
- 252 acute neuro injury with residual deficit
- 131 death before extubation
- 26 transferred to another facility
- 41 attrition
- 450 excluded
- 383 mechanically ventilated patients included in final analysis
- 27 patients were assessed for reports of awareness with paralysis
- Awareness with Paralysis (AWP): 10 pts (2.6%)
- 373 patients with no awareness with paralysis
- 9.9% of the 383 patients had no definite NMB documented
- Prevalence of AWP for patients definitely receiving a NMB was 2.9% (10/345)
- Exposure to rocuronium (during intubation, or after intubation):
- AWP: 70%
- No AWP: 31.4%
- Odds ratio: 5.1 (95% CI: 1.30 – 20.1)
- Of the 7 definite AWP patients, 4 received Etomidate, and 3 received Ketamine as their induction agent.
- Patient reported memory / awareness experience vignettes are documented in table 2 of the article and make for some sobering reading that should encourage all clinicians to confirm adequate sedation / analgesia prior to intubation / painful procedures.
- 27 patients were assessed for reports of awareness with paralysis
Strengths:
- Largest study of its kind in ED population
- Prospectively enrolled population
- Rigorous questionnaire
- Separates awareness of intubation from awareness during paralysis
- Enrollment of large, diverse ED population increases external validity of results
Limitations:
- Small sample size, single center study: Hypothesis generating study only
- Possible that an event was missed. (Unlikely given previous OR rates with iv anesthesia, and increased risk of awareness in ED population)
- Hawthorne effect amongst treating clinicians: If they know awareness is being watched for, their sedation and analgesia practices may be better than usual.
- Surveying for awareness could induce false memories. The associated higher perceived threat in patients with awareness suggests the patients’ experiences were real.
- Patients with definite, and possible awareness were included. This could inflate the event rate.
- 1.8% rate of definite awareness with paralysis is still a concerning result
Discussion:
- In the ED there appears to be a pattern of delayed intravenous sedation along with frequent administration of longer-acting neuromuscular blocking agents
- Solution: Order analgesia/sedation prior to intubation so that it is ready once patient is intubated
- Although a 2.6% rate of awareness with paralysis seems low, this was a small number of patients from a single institution. Extrapolated to multiple Emergency Departments across the globe this could equate to several thousand patients who are aware during paralysis
- The use of Rocuronium is a significant risk factor or awareness with paralysis. All patients with awareness with paralysis in the post-intubation phase of care had a longer-acting neuromuscular blocking agent
- Awareness with paralysis can result in psychological sequelae including PTSD, depression, and complex phobias, as stated before. In this trial patients with awareness with paralysis had a higher degree of perceived threats (i.e. perceived vulnerability during the hospital stay and after discharge)
Authors Conclusion:
“Awareness with paralysis occurs in a significant minority of ED patients who receive mechanical ventilation. Potential associations of awareness with paralysis with ED care and increased perceived threat warrant further evaluation.”
Bottom Line:
- When faced with the dual challenge of not adding to the risk of ICU delirium from oversedation, and not inflicting psychological trauma from patient’s awareness during paralysis, a reasonable strategy is to ensure moderate / deep sedation for the full duration of paralysis in the ED. This could be up to 90 min after a 1.5 mg/kg dose of Rocuronium.
- In patients in shock receiving a reduced dose of sedative, consider a DSI strategy to ensure sedation prior to paralysis
- Awareness with paralysis had a prevalence of 2.6% in this cohort of ED patients receiving mechanical ventilation and was associated with Rocuronium exposure
- These results should be considered exploratory and hypothesis generating
- Further studies are warranted to further quantify the risk of awareness with paralysis in the ED and should explore targeted interventions to reduce this risk
References:
- Watt JM et al. Effect of Paralytic Type on Time to Post-Intubation Sedative Use in the Emergency Department. Emerg Med J 2013. PMID: 23139098
- Korinek JD et al. Comparison of Rocuronium and Succinylcholine on Post-intubation Sedative and Analgesic Dosing in the Emergency Department. Eur J Emerg Med 2014. PMID: 23510899
- Pandit JJ et al. 5th National Audit Project (NAP5) on Accidental Awareness During General Anaesthesia: Summary of Main Findings and Risk Factors. Br J Anaesth 2014. PMID: 25204697
- Pappal RD 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. PMID: 33485698 [Access on Read by QxMD]
- Pappal RD et al. Protocol for a Prospective, Observational Cohort Study of Awareness in Mechanically Ventilated Patients Admitted From the Emergency Department: The ED-AWARENESS Study. BMJ Open 2019. PMID: 31594905
For More on This Topic Checkout:
Post Peer Reviewed By: Salim R. Rezaie, MD (Twitter: @srrezaie)
The post The ED-AWARENESS Study: Awareness with Paralysis appeared first on REBEL EM - Emergency Medicine Blog.