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The Cardiac Arrest Sonographic Assessment

(CASA) exam - A standardized approach to the use of ultrasound in PEA?

Background

Emergency physicians (EPs) have started integrating point-of-care- ultrasound (POCUS) into the evaluation of patients with cardiac arrest to identify Reversible causes of Pulseless electrical activity and it is now recommended by the AHA [1-6]. However, POCUS prolongs CPR pauses which negatively impacts survival [7-10]. While POCUS pro- tocols for cardiac arrest have been suggested, they are too complex and cumbersome [2-4,11-12]. Here we present an evidence based, three step protocol that is simple, rapid, and allows the EP to quickly and ac- curately identify reversible causes of PEA while minimizing CPR interruptions.

The CASA exam

The Cardiac Arrest Sonographic Assessment (CASA) exam consists of three, b 10 second POCUS exams to occur at Pulse checks (Fig. 1). We recommend the recorder time each pause out loud. A phased array (car- diac) transducer should be used and all images should be recorded for review. The EP should utilize the optimal cardiac window based on the patient, with the subxiphoid view often being preferable as this view can be performed during ongoing CPR. While the CASA exam is de- signed for a single provider, a second provider should perform the ultra- sound when possible, as this has been associated with shorter CPR interruptions [8]. FAST and Tension pneumothorax exams can be per- formed on a case-by-case basis during CPR.

Step one: cardiac tamponade

Pericardial effusion causing cardiac tamponade is the cause of cardi- ac arrest in 4-15% of patients [5,13-16]. Tamponade can be rapidly in- tervened upon to resolve PEA and patients with tamponade have higher survival to hospital discharge rates (15.4%) than other causes of PEA (1.3%) [5]. The examiner should assess for pericardial effusion and, if present, assess for signs of tamponade such as early diastolic Right ventricular collapse (Fig. 2). If cardiac tamponade is present, a pericardiocentesis should be strongly considered.

Step two: pulmonary embolus

Pulmonary embolism (PE) is the cause of cardiac arrest in 4.0-7.6% patients and these patients have higher Survival to hospital discharge rates (6.7%) than other patients in PEA (1.3%) [5,17-20]. Thus, it is im- portant that EPs quickly and accurately assess for PE in all cardiac arrest patients. To assess for the presence of PE, the examiner should evaluate for signs of right heart strain such as a dilated right ventricle and a com- paratively small left ventricle (Fig. 3). If signs of right heart strain are present, PE should remain a consideration as the cause of PEA.

? Funding sources/disclosures: none.

Fig. 1. The Cardiac Arrest Sonographic Assessment (CASA) exam schematic.

Fig. 2. Parasternal long view demonstrating pericardial effusion (*) causing cardiac tamponade. Note the early diastolic right ventricular collapse (RV).

Fig. 3. Apical four chamber view demonstrating right heart strain consistent with the pres- ence of PE. Note the dilated right atrium (RA) and right ventricle (RV).

730 Correspondence / American Journal of Emergency Medicine 36 (2018) 715-732

Fig. 4. US image of pneumothorax. Note the characteristic absence of Lung sliding and the bar code sign in M mode (*).

Step three: Cardiac activity

The presence or absence of cardiac activity on bedside echo provides useful prognostic information for patients in PEA [5]. The absence of car- diac activity in PEA portends worse outcomes. Patients in PEA with car- diac standstill on ultrasound have survival to hospital discharge rates ranging from 0.0% to 0.6% [5,21-22]. While low, these rates are not zero and thus Initial resuscitation should be attempted in all patients re- gardless of cardiac activity. The examiner should assess for global cardi- ac activity or fibrillations (Supplemental video 1). If cardiac activity is present, the examiner should reassess for pulses and blood pressure and consider starting continuous vasopressors. If no cardiac activity is seen, the utility of ongoing resuscitation should be reviewed in combi- nation with other poor prognostic factors, such as low end-tidal CO2, prolonged downtime, and unwitnessed arrest.

Ancillary steps: tension pneumothorax and FAST

Tension pneumothorax is an exceedingly rare cause of non-traumat- ic cardiac arrest and can often be diagnosed clinically [18]. During ongoing CPR, the EP should examine the bilateral anterior chest for the absence of lung sliding indicating pneumothorax (Fig. 4). If a pneu- mothorax is detected, needle decompression or thoracostomy may be considered. Small, clinically insignificant pneumothoraces can occur from rib fractures during CPR and clinicians should be aware that these injuries may not need acute intervention.

Also during ongoing CPR, the EP, if the clinical scenario indicates, can assess for a ruptured Abdominal aortic aneurysm (AAA) or ectopic preg- nancy by performing a FAST exam looking for evidence of free fluid [23]. Evaluation of the IVC and hypovolemia was intentionally excluded from the CASA exam as intravenous fluids are traditionally given empir- ically in cardiac arrest and we expect the IVC to be distended in most

cardiac arrest as there is severely limited forward flow.

Discussion

POCUS is a powerful tool for assessing reversible causes of cardiac ar- rest. However, it must be utilized in a protocolized, efficient manner so as to not do harm. The CASA exam assesses for the highest yield revers- ible causes of PEA that can be visualized with ultrasound, while limiting POCUS’s negative impact. It is our hope that the utilization of the CASA exam will limit prolonged CPR pauses and improve diagnostic accuracy. Supplementary data to this article can be found online at http://dx.

doi.org/10.1016/j.ajem.2017.08.052.

Kevin F. Gardner, MD* Eben J. Clattenburg, MD, MPH

Peter Wroe, MD Amandeep Singh, MD Daniel Mantuani, MD

Department of Emergency Medicine, Highland Hospital—Alameda Health

System, Oakland, CA, United States

*Corresponding author at: Highland Hospital, Department of Emergency Medicine, 1411 East 31st St., Oakland, CA 94602,

United States.

E-mail address:[email protected] (K.F. Gardner).

Arun Nagdev, MD

Department of Emergency Medicine, Highland Hospital—Alameda Health

System, Oakland, CA, United States School of Medicine, University of California, San Francisco, CA, United States

19 August 2017

http://dx.doi.org/10.1016/j.ajem.2017.08.052

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    Soft tissue oxygen saturation to predict admission

    We thank the authors for their interest in our paper, “Soft tissue ox- ygen saturation to predict admission from the emergency department: A prospective observational study” [1]. We agree that it is important to consider whether soft tissue oxygen saturation offers prognos- tic utility in addition to that provided by pulse oximetry (SpO2) as a rou- tine component of triage vital signs. The authors note that we did not include pulse oximetry in our original logistic regression analysis. In adding pulse oximetry to the model, we chose a cutoff value of <= 95% similar to Mower et al. to reflect a level of hypoxia likely to affect clinical decision making [2]. The odds ratio of Sto2 b 76% for predicting admis- sion in the original analysis was 1.54 (95% confidence interval (CI)

    1.19 to 1.98). Upon adding SpO2 <= 95% as a predictor variable to the lo- gistic regression model, the odds ratio remained significant for Sto2 b 76% (OR 1.51, 95% CI 1.17 to 1.93). The odds ratio for SpO2 <= 95% is

    1.38 (95% CI 1.03 to 1.84). Most patients with SpO2 <= 95% were assigned to more urgent emergency severity index levels (see Table 1) which likely explains these findings [3].

    The authors highlight the value of describing the patients within our

    study population who had a low Sto2 but were not identified by pulse oximetry. Three hundred twenty-three patients in our study had Sto2 b 76% and SpO2 N 95%. Given the volume of data required to address this request, we will look to provide a future brief report describing the characteristics of these patients. Our intent is that this will lay the foundation for future studies of the impact of routine Sto2 triage mea- surements on ED patient management and Disposition decisions. Much in the way Mower et al. conducted impact studies of pulse oxim- etry use in the 1990s which have now culminated in the routine mea- surement of pulse oximetry in most ED settings [2,4,5], we encourage

    future prospective investigations seeking to establish whether Sto2 data lead to significant changes in ED provider Treatment decisions. Un- fortunately, because we blinded providers in our study to the Sto2 re- sults, our current dataset cannot provide insight into the impact of Sto2 on clinical decision making.

    A final note: the positive predictive value for Sto2 b 76% predicting admission in our population was 41.1% as calculated by the authors. The positive predictive value of 50% in the manuscript was incorrect, though the 95% confidence interval of 36% to 46% was accurate. We apologize for this error.

    William T. Davis, MD Department of Emergency Medicine, San Antonio Uniformed Services Health Education Consortium, San Antonio, TX, United States Corresponding author at: San Antonio Military Medical Center, Department of Emergency Medicine, 3841 Roger Brooke Dr, Fort Sam

    Houston, TX 78234, United States.

    E-mail address: [email protected].

    Josh Lospinso, DPhil

    Portia Statistical Consulting LLC, San Antonio, TX, United States

    Robert M. Barnwell, MD John Hughes, MD

    Department of Emergency Medicine, San Antonio Uniformed Services Health Education Consortium, San Antonio, TX, United States

    Steven G. Schauer, DO

    United States Army Institute of Surgical Research, San Antonio, TX, United

    States

    Thomas B. Smith, MD Michael D. April, MD, DPhil, MSc

    Department of Emergency Medicine, San Antonio Uniformed Services Health Education Consortium, San Antonio, TX, United States

    26 July 2017

    http://dx.doi.org/10.1016/j.ajem.2017.08.059

    References

    Davis WT, Lospinso J, Barnwell RM, Hughes J, Schauer SG, Smith TB, et al. Soft tissue oxygen saturation to predict admission from the emergency department: a prospec- tive observational study. Am J Emerg Med 2017;35(8):1111-7.

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18. Tanabe P, Gimbel R, Yarnold PR, Kyriacou DN, Adams JG. Reliability and validity of scores on the emergency severity index version 3. Acad Emerg Med 2004;11(1):59-65.
19. Mower WR, Myers G, Nicklin EL, Kearin KT, Baraff LJ, Sachs C. Pulse oximetry as a fifth vital sign in emergency geriatric assessment. Acad Emerg Med 1998;5(9):858-65.
20. Mower WR, Sachs C, Nicklin EL, Baraff LJ. Pulse oximetry as a fifth pediatric vital sign. Pediatrics 1997;99(5):681-6.

    Table 1

    Number of admissions stratified by Emergency Severity Index level, soft tissue oxy- gen saturation (Sto2) and pulse oximetry (SpO2).

    ESI level Sto2 b 76% Sto2 >= 76%

    Emergency department electrocardiogram images sent through the mobile phone: Feasibility and accuracy

    In patients with cardiac symptoms, the most commonly performed Diagnostic investigation, after a history and physical examination, is 12-lead Electrocardiography . Depending on the practice setting, emergency department (ED) providers may need to confer with a cardi- ologist who is off-site. It is difficult to establish an exact diagnosis through only a verbal report of the ECG and transmittal of images by fax is time consuming. The fax process can also significantly affect the

    	SpO2 <= 95%		SpO2 N 95%		SpO2 <= 95%		SpO2 N 95%
    	N admitted/N total		N admitted/N total		N admitted/N total		N admitted/N total
    1	0/0		1/1 (100%)		2/2 (100%)		1/3 (33%)
    2	16/21 (76%)		45/69 (65%)		36/47 (77%)		164/333 (49%)
    3	19/33 (58%)		71/214 (33%)		40/131 (31%)		325/1408 (23%)
    4	0/3 (0%)		2/34 (6%)		0/18 (0%)		15/237 (6%)
    5	3/4 (75%)		1/5 (20%)		0/2 (0%)		2/23 (9%)
    All patients	38/61 (62%)		120/323 (37%)		78/200 (39%)		507/2004 (25%)