The Predictive Value of Bedside Ultrasound to Restore Spontaneous Circulation in Patients with PEA: A Systematic Review and Meta-Analysis

Background

Cardiac arrest remains one of the leading causes of death in the United States and is frequently encountered in the emergency department (ED). It is defined as cessation of cardiac function and lack of circulation. Cardiopulmonary resuscitation (CPR) improves outcomes especially if it is performed within minutes of cardiac arrest. According to recent American Heart Association (AHA) statistics, approximately,  10.6% of patients who experience cardiac arrest survive to hospital discharge [1]. On the other hand, pulseless electrical activity (PEA) is a form of cardiac arrest in which patients continue to have organized cardiac electrical activity without a palpable pulse. This patient population's overall survival is much lower with 2.4% of patients surviving to hospital discharge [2]. Until recently, there has been an incomplete understanding of the the term PEA and what this means physiologically. With the advent of ultrasound (US), there has now been elucidation of two forms of PEA. True-PEA (tPEA) which lacks cardiac activity on US, has poor survival rates, while pseudo-PEA (pPEA) which demonstrates some cardiac activity on US,  shows improved survival,  potentially due to altering standard ACLS protocol driven management. The following study specifically looks at the data evaluating the predictive value of US in patients presenting in cardiac arrest with PEA.

The predictive value of bedside ultrasound to restore spontaneous circulation in patients with pulseless electrical activity: A systematic review and meta-analysis.

Clinical Question

Does bedside US predict the restoration of spontaneous circulation in patients with pulseless electrical activity?

Methods & Study Design

  • Design
    • Systematic review and meta-analysis
    • Data from MEDLINE, EMBASE, Cochrane library databases (inception to June 2017)
    • Statistical analysis
      • Review Manager 5.4 and Stata 12
      • I2 statistics to assess heterogeneity
      • Random effects model for all polled outcome measures
      • Begg’s test for publication bias
  • Study Eligibility Criteria
    • Adults with PEA
    • Cardiac US was used to detect cardiac activity
    • ROSC defined as primary outcome
    • Prospective/ observational studies
    • Written in English
    • 2x2 contingency table can be formed from data

Results

Included Studies

    • 11 studies with 777 patients with PEA included
    • 230 patients had ROSC
    • 42/343 "true-PEA" patients had ROSC
    • 188/434 "pseudo-PEA" patients had ROSC
    • Patients with pPEA were 4.35x more likely to experience ROSC than those tPEA (Risk ratio 4.35, confidence interval 2.20-8.63, p<0.00001, significant statistical heterogeneity I2= 60%)

Limitations

    • Significant heterogeneity amongst the 11 studies
      • 4 studies enrolled both trauma and non-trauma patients
      • In 3 studies, US evaluation occurred in the pre-hospital setting
    • Large confidence interval
    • Small pooled sample size
    • Varying protocols and US views used in different studies to determine cardiac activity
    • Varying definition of ROSC between studies

Authors Conclusion

 

"In cardiac arrest patients who present with PEA, bedside US has an important value in predicting ROSC. The presence of cardiac activity in PEA patients may encourage more aggressive resuscitation. Alternatively, the absence of cardiac activity under US could be promoted as a way of confirming a poor prognosis and used to support the decision to terminate resuscitative efforts."

Our Conclusion

This study found that patients in cardiac arrest with pPEA (i.e. cardiac motion on ultrasound) have higher ROSC than those with tPEA (i.e. no cardiac motion on ultrasound). The exact risk ratio for ROSC quoted in their results should be interpreted with caution since this meta-analysis included studies with vastly different characteristics. The 11 studies included took place in 9 different countries over the span of 15 years, included different US views (subxiphoid, parasternal), varied settings (pre-hospital and in-hospital US studies), varied patient populations (some studies included traumatic cardiac arrest) and had varying US operator experience. Additionally, other factors such as time to initiation of CPR, length of CPR, and the previous health of the patient were not accounted for. These limitations can affect the accuracy of the risk ratio presented in this study.  That being said, even with significant heterogeneity in this study, resulting in a very wide confidence interval, the lower limit of the risk ratio (2.20) still finds statistical significance for higher rate of ROSC in patients with pPEA compared to patients with tPEA.

This study essentially confirms what is already known from previous data (specifically the Gaspari study which represents the majority of patients in this meta-analysis) but fails to address the big question of "Does US guided resuscitation provide a mortality benefit in the management of cardiac arrest?" This is a complex question that takes into account multiple other questions including the debate over US increasing interruptions in chest compressions, the use of US to identify immediately reversible causes of cardiac arrest (i.e. tamponade, massive PE) , the true definition of cardiac standstill (which calls the results of all cardiac arrest studies thus far into questions), and ultimately, can US be used to determine if further resuscitation is futile? As with all advances in technology, finding the right niche to benefit the patient is of upmost importance and at this point in time, the utility of US in cardiac arrest remains to be determined.

The Bottom Line

Bedside ultrasound can be used to determine pPEA from tPEA in patients with cardiac arrest. This may help guide resuscitation efforts as patients with pPEA have increased rates of ROSC.

Authors

This post was written by Tina Vajdi, MS4 at UCSD. Review and further commentary was provided by Michael Macias, MD, Ultrasound Fellow at UCSD.

References

    1. Mozaffarian D, Benjamin EJ, Go AS, Arnett DK, Blaha MJ, Cushman M et al. Heart Disease and Stroke Statistics-2016 Update: A Report From the American Heart Association. Circulation 2016; 133(4):e38– e360. https://doi.org/10.1161/CIR.0000000000000350 PMID: 26673558
    2. Engdahl J, Bang A, Lindqvist J, Herlitz J. Factors affecting short- and long-term prognosis among 1069 patients with out-of-hospital cardiac arrest and pulseless electrical activity. Resuscitation 2001; 51 (1):17–25. PMID: 11719169
    3. Gaspari R, e. (2018). Emergency department point-of-care ultrasound in out-of-hospital and in-ED cardiac arrest. - PubMed - NCBI . Ncbi.nlm.nih.gov. Retrieved 20 April 2018, from https://www.ncbi.nlm.nih.gov/pubmed/27693280

Variability in Interpretation of Cardiac Standstill Among Physician Sonographers

Background

The use of point-of-care echocardiography to inform termination or continuation of cardiopulmonary resuscitative efforts remains controversial [1,2]. Current understanding of its utility in prognostication is limited by varying definitions of cardiac activity. Definitions of cardiac standstill range from absence of “organized contractile activity (nonfibrillating) with a decrease in chamber size” to absence of “any visible movement of the myocardium, excluding movement of blood within the cardiac chambers or isolated valve movement” to absence of “any detected atrial, valvular, or ventricular motion within the heart” [3-5]. Without a consistent definition of cardiac standstill, it is difficult to interpret studies reporting conflicting resuscitation outcomes in cardiac arrest.

Variability in Interpretation of Cardiac Standstill Among Physician Sonographers

Clinical Question

What is the interrater reliability among providers in classification of cardiac standstill in point-of-care echocardiography?

Methods & Study Design

  • Design
    • Cross-sectional convenience sample survey
  • Population
    • Eligible: Residents, fellows, and faculty practicing in emergency medicine, critical care, or cardiology in attendance at one of six weekly emergency medicine (EM) conferences held at the following locations:
      • Icahn School of Medicine at Mount Sinai
      • Beth Israel Medical Center
      • St. Luke’s-Roosevelt Hospital
  • Exclusion criteria
    • Providers who had previously participated at a prior conference
  • Intervention
    • Participants were presented with the following clinical scenario: “55-year-old man in cardiac arrest who remains pulseless after 20 minutes of CPR”
    • Participants were shown 15 clips (6 seconds each, looped for 20 seconds total) presenting a variety of sonographic features
    • Asked to identify presence or absence of cardiac activity
    • Responses transmitted via remote polling devices
    • No definition of cardiac activity was provided
  • Outcomes
    • Primary: interrater reliability in interpreting cardiac standstill (Krippendorff’s alpha coefficient)
    • Secondary: subgroup analyses by specialty, training level, and self-described point of care (POC) ultrasound experience

Results

    • 127 participants (majority EM residents with basic ultrasound skills)
    • Overall moderate agreement with respect to identifying cardiac standstill (alpha 0.47)
    • Clips with stronger agreement:
      • No myocardial contraction
      • Myocardial contraction
      • Strong myocardial contraction
    • Clips with poorer agreement:
      • Valve flutter
      • Mechanical ventilation
      • Weak myocardial contraction
    • Moderate agreement across all training levels and self-reported ultrasonographic skill levels

Strengths & Limitations

  • Strengths
    • All participants saw the same clips
    • Response time limited (similar to clinical practice)
  • Limitations
    • Bias: recruitment from academic conferences
    • Majority with no or basic self-reported ultrasonographic skill level
    • Reported discussion among participants throughout survey

Author's Conclusions

“Our results support the possibility that previous studies have been subject to variability in the interpretation of cardiac standstill.”

Our Conclusions

We agree with the authors’ conclusions that there appears to be substantial variability in the interpretation of cardiac standstill. This study highlights a weakness in the current literature examining the utility of POC echocardiography used during resuscitation futility assessment. While this study does not provide data on clinical outcomes of standstill misclassification, it identifies a potential weakness in the available research. It is difficult to interpret studies reporting outcomes after standstill (such as meaningful survival) when the predictor is not consistently identified.

As a follow-up study, it would perhaps be interesting to see how the interrater reliability changes when participants are provided with a clear definition of cardiac standstill. Does the variability persist even with a uniform definition? If this improves interrater reliability it would provide additional support for the need for a consensus definition across future studies.

The Bottom Line

There is significant variability in classification of cardiac standstill among providers. A uniform definition of standstill may reduce this variability and aid in the interpretation of studies reporting conflicting outcomes after cardiac arrest.

Authors

This post was written by Carly Dougher, MS4 at UCSD. It was reviewed by Michael Macias, MD, Ultrasound Fellow at UCSD.

References

    1. Blyth, L., Atkinson, P., Gadd, K. & Lang, E. Bedside Focused Echocardiography as Predictor of Survival in Cardiac Arrest Patients: A Systematic Review: Echocardiography in Cardiac Arrest. Acad. Emerg. Med. 19, 1119–1126 (2012).
    2. Cohn, B. Does the Absence of Cardiac Activity on Ultrasonography Predict Failed Resuscitation in Cardiac Arrest? Ann. Emerg. Med. 62, 180–181 (2013).
    3. Schuster, K. M. et al. Pulseless Electrical Activity, Focused Abdominal Sonography for Trauma, and Cardiac Contractile Activity as Predictors of Survival After Trauma: J. Trauma Inj. Infect. Crit. Care 67, 1154–1157 (2009).
    4. Gaspari, R. et al. Emergency department point-of-care ultrasound in out-of-hospital and in-ED cardiac arrest. Resuscitation 109, 33–39 (2016).
    5. Kim, H. B., Suh, J. Y., Choi, J. H. & Cho, Y. S. Can serial focussed echocardiographic evaluation in life support (FEEL) predict resuscitation outcome or termination of resuscitation (TOR)? A pilot study. Resuscitation 101, 21–26 (2016).

Ultrasound use during cardiopulmonary resuscitation is associated with delays in chest compressions

Background

Point-of-care ultrasound (POCUS) has quickly become a core adjunct used in the emergency department (ED) during cardiopulmonary resuscitation (CPR). Specifically, it is now frequently used to evaluate for reversible causes of cardiac arrest (i.e. cardiac tamponade, pulmonary embolism), guide resuscitation, and prognosticate on patient outcomes based on presenting cardiac activity [1]. However at this time, the benefits of the use of POCUS during CPR are not yet clear in terms of patient centered outcomes. What is known to have an effect on patient outcomes is providing high quality CPR, with minimal interruptions, and early defibrillation [2]. POCUS during CPR is often performed during pulse checks and it can take ample time to obtain sufficient views for proper interpretation. One concern is that this can result in unnecessary delays in resuming chest compressions during CPR, leading to harmful effects on patient outcomes.

Ultrasound use during cardiopulmonary resuscitation is associated with delays in chest compressions

 

Clinical Question

Does use of point-of-care ultrasound (POCUS) in cardiopulmonary resuscitation lengthen the duration of pulse checks beyond the guideline recommendation of 10 seconds?

Methods & Study Design

  • Design
    • Prospective cohort study
  • Population
    • This was a single center study performed at an adult, urban, tertiary care, academic medical center
    • All patients, 18 years of age or older, who presented to the emergency department (ED) in cardiac arrest or in whom cardiac arrest occurred while in the ED were eligible for enrollment
  • Exclusion criteria 
    • No documentation of a pulse check
    • Not placed in one of three designated resuscitation rooms with continuous video monitoring capability
    • Video monitoring obtained was not available or image quality was too poor for extraction of data
  • Intervention
    • All cardiac arrest resuscitations were recorded by video camera
      • Researchers recorded the duration of pulse checks (in milliseconds) and whether POCUS was used
  • Outcomes
    • Duration of pulse checks with the use of POCUS

Results

    • 23 patients enrolled
    • 123 individual rhythm checks
    • The use of POCUS significantly increased the pulse-check duration by 8.4 seconds (95% CI, 6.7-10.0 [p<0.0001])
    • Age and BMI did not affect the duration of pulse checks or CPR interruptions
    • No findings on any of the POCUS images prompted a procedure
    • Survival to ED discharge/hospital admission: 35% (8/23)
    • Survival to hospital discharge: 4% (1/23)
    • Survival at 30 days: 4% (1/23)

Strengths & Limitations

  • Strengths
    • Data collected directly from video which removes any bias on recall of events that occurred during cardiopulmonary resuscitation
  • Limitations
    • Small number of patients included in the study
    • Single center study reduces its external validity
    • No information of level of training of US operators
    • No commentary on the impact of POCUS on mortality or neurologic outcomes

Author's Conclusions

"The use of POCUS during cardiac arrest resuscitation was associated with an increase in the duration of pulse checks by 8.4 seconds, causing interruptions in high-quality chest compressions nearly double the 10-second duration recommended by current international cardiopulmonary resuscitation guidelines. It is critical for acute care providers to pay close attention to the duration of CPR interruptions when using POCUS during cardiac arrest resuscitation."

Our Conclusions

With the introduction of novel indications for POCUS, we need to be aware of both the benefits and harms. This is an important study that identifies a potential harm of POCUS during CPR. There is no doubt from this data that POCUS did result in prolonged pulse checks above the guideline recommended 10 seconds. While this study does not directly tell us that POCUS increases mortality in cardiac arrest (as it is much too small), there is clear evidence that increased interruptions in chest compressions during CPR leads to worse outcomes.

The utility of this study is that it identifies a problem with POCUS in which there are clear solutions. With this new evidence, we must take a thoughtful approach to use of POCUS during CPR. Some proposed solutions to address this problem include:

    • Identifying personnel during CPR who can verbalize the time spent during pulse check to make providers acutely aware of when CPR should be resumed ("10, 9, 8, 7...")
    • Recording a POCUS clip for 5 seconds, then reviewing the stored images while CPR is resumed
    • Having a care provider ready to perform POCUS exam with probe on chest just before chest compressions are withheld
    • Use of transesophageal (TEE) POCUS which allows for image acquisition during ongoing CPR

The findings of this paper are definitely not the end of POCUS in CPR, as I find that there are numerous reasons that it is useful (i.e. monitoring of proper chest compression location, identification of reversible etiology of cardiac arrest, prognostication, closure for health care providers during end of resuscitations...), however I would like to see larger studies on this topic as well as quality improvement and awareness of this potential harm of prolonged pulse checks secondary to POCUS utilization.

The Bottom Line

The use of POCUS during CPR may increase the duration of pulse checks beyond the recommended 10 seconds. Care providers should be aware of this potential harm and measures should be taken to prevent unnecessary delays in chest compressions.

Authors

This post was written by Michael Macias, MD, Ultrasound Fellow at UCSD.

References

    1. Gaspari R, e. (2017). Emergency department point-of-care ultrasound in out-of-hospital and in-ED cardiac arrest. - PubMed - NCBI . Ncbi.nlm.nih.gov. Retrieved 8 September 2017, from https://www.ncbi.nlm.nih.gov/pubmed/27693280
    2. Link MS et al. Part 7: Adult Advanced Cardiovascular Life Support: 2015 American Heart Association Guidelines Update for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Circulation. 2015 Nov 3;132(18 Suppl 2):S444-64.

    3. Huis In 't Veld MA, e. (2017). Ultrasound use during cardiopulmonary resuscitation is associated with delays in chest compressions. - PubMed - NCBI . Ncbi.nlm.nih.gov. Retrieved 8 September 2017, from https://www.ncbi.nlm.nih.gov/pubmed/28754527

FAST Ultrasound Examination as a Predictor of Outcomes After Resuscitative Thoracotomy

Background

The emergency resuscitative thoracotomy (RT), aka The ED Thoracotomy, is a procedure performed as a last-ditch effort during resuscitation of a patient in traumatic arrest or impending traumatic arrest. Unfortunately despite physicians’ best efforts, outcomes for this procedure are generally poor. The largest review of outcomes after RT performed in the emergency department found an overall survival of 7.4% (8.8% for penetrating injury, 1.4% for blunt injury), with good neurological outcomes present in 92.4% of surviving patients [2]. Furthermore, given the lack of high quality evidence on this procedure, there are no universal guidelines that exist to determine optimal candidates [3,4]. Point-of-care ultrasound has become a core adjunct in evaluation of the trauma patient, however there is minimal data evaluating its utility in determining which trauma patients may benefit from RT [5].

FAST Ultrasound Examination as a Predictor of Outcomes After Resuscitative Thoracotomy: A Prospective Evaluation

Clinical Question

Can the Focused Assessment Using Sonography for Trauma (FAST) predict survival after a RT in patients presenting to the emergency department in traumatic cardiac arrest?

Methods & Study Design

  • Population
    • All penetrating trauma patients with absent vital signs and blunt trauma patients with a loss of vital signs en route or in the resuscitation bay that underwent RT.
  • Intervention
    • A FAST exam was performed just prior to RT to assess for the presence or absence of a pericardial effusion and cardiac motion.
  • Outcomes
    • Survival to Discharge or Organ Donation
  • Design
    • Prospective, observational study performed at a single academic level-1 trauma center
  • Excluded
    • Patients who were taken directly to the OR for an emergent or urgent thoracotomy were excluded.
    • Patients who did not have a FAST exam performed prior to RT were excluded from analysis

Results

    • 223 patients underwent RT, 187 underwent analysis (36 had no FAST performed)
      • Primary Outcome
        • Survival: 3.2%
        • Organ Donation: 1.6%

Strengths & Limitations

  • Strengths
    • First large, prospective observation study on emergency RT
    • Sensitivity analysis performed to include patients who had inadequate views obtained
  • Limitations
    • Study performed at a high-volume, single academic level-1 trauma center with which may skew generalizability
    • Residents who had formal training in the FAST exam performed all ultrasound scans. Many emergency medicine physicians are not credentialed in ultrasound or FAST examination

Author's Conclusions

"In summary, for the patients that arrived to hospital and underwent a FAST examination, all survivors and organ donors had visible cardiac motion. If no cardiac motion or pericardial effusion was seen, the survival was zero. Ultrasound was, therefore, able to effectively identify those patients who had the potential to survive the RT and discriminate them from those who did not. Utilizing ultrasound would have resulted in the avoidance of a significant proportion of thoracotomies which were ultimately found to be futile.”

Our Conclusions

This is a well done study examining the utility of the FAST exam in identifying which patients will potentially benefit from emergency RT. One may look at the primary outcomes of this study and think that the very low overall survival rate (3.2%) does not jive with previously reported studies. However, it is important to note that during the study period, 21 patients who had a penetrating cardiac injury and went straight to the OR for thoracotomy, were excluded. All of these patients survived. If we were to incorporate this number into the the final analysis, survival would be ~13% which fits better with previous data. But that isn’t the point of this study. The big question that I feel is appropriately answered is which patient population can we safely avoid undertaking an emergency RT, knowing it is futile. While resource utilization for a procedure of this magnitude may be less burdensome at an academic level-1 trauma center, performing a RT in an emergency department where this is rare occurrence requires a much larger undertaking by the staff. The new data from this study, demonstrates that patients who did not have cardiac motion or a pericardial effusion on initial FAST had a zero survival rate. This is practice changing, especially for providers who rarely perform this procedure. If an experienced trauma team performing this procedure had zero survival rate in patients with no cardiac motion or pericardial effusion, it is safe to say that a provider with less experience will not perform better. Furthermore, having real time data to share with the entire resuscitation team during a traumatic arrest can provide closure to the team and a sense that performing any further heroic procedures is futile.

The Bottom Line

The FAST exam is a critical adjunct in traumatic patients and should be applied to all cases of traumatic arrest in order to determine the utility of performing an emergency RT.

References

    1. Inaba K, e. (2017). FAST ultrasound examination as a predictor of outcomes after resuscitative thoracotomy: a prospective evaluation. - PubMed - NCBI . Ncbi.nlm.nih.gov. Retrieved 4 July 2017, from https://www.ncbi.nlm.nih.gov/pubmed/26258320
    2. Rhee PM, e. (2017). Survival after emergency department thoracotomy: review of published data from the past 25 years. - PubMed - NCBI . Ncbi.nlm.nih.gov. Retrieved 4 July 2017, from https://www.ncbi.nlm.nih.gov/pubmed/10703853
    3. Seamon MJ, e. (2017). An evidence-based approach to patient selection for emergency department thoracotomy: A practice management guideline from the Eastern Association ... - PubMed - NCBI . Ncbi.nlm.nih.gov. Retrieved 4 July 2017, from https://www.ncbi.nlm.nih.gov/pubmed/26091330
    4. Burlew CC, e. (2017). Western Trauma Association critical decisions in trauma: resuscitative thoracotomy. - PubMed - NCBI . Ncbi.nlm.nih.gov. Retrieved 4 July 2017, from https://www.ncbi.nlm.nih.gov/pubmed/23188227
    5. Moore EE, e. (2017). Defining the limits of resuscitative emergency department thoracotomy: a contemporary Western Trauma Association perspective. - PubMed - NCBI . Ncbi.nlm.nih.gov. Retrieved 4 July 2017, from https://www.ncbi.nlm.nih.gov/pubmed/21307731