Clinical paperC.A.U.S.E.: Cardiac arrest ultra-sound exam—A better approach to managing patients in primary non-arrhythmogenic cardiac arrest☆
Introduction
Cardiac arrest is a condition frequently encountered by physicians in the hospital setting including the Emergency Department, Intensive Care Unit and medical/surgical wards. Since the implementation of preventative health policy and ACLS, deaths from ventricular fibrillation and ventricular tachycardia have decreased significantly, however the prevalence of pulseless electrical activity (PEA) and asystole have increased.1 Unlike ventricular fibrillation and pulseless ventricular tachycardia where the pattern/rhythm of electrical activity is the focus of treatment rather than the underlying cause, PEA and asystole are corrected by addressing the underlying cause.2 The importance of identifying a reversible underlying cause in these forms of cardiac arrest is of such importance that almost half of the ACLS for experienced practitioners manual is dedicated to this topic and its practical application.2 Hughes et al. provided a list of the etiologies of PEA in the order of frequency and ease of reversal.3 He lists the top five conditions as hypoxia, hypovolemia, tension pneumothorax, pericardial tamponade, and pulmonary emboli. These conditions are potentially reversible, but the treatment is often invasive and may be deadly if mistakenly applied to the wrong etiology.4 For this reason accurate and timely diagnosis of the underlying cause is crucial. Currently the AHA recommends using physical signs and the patient's history to guide the management of PEA and asystole.2 However, physical examination can be unreliable and many physicians may withhold therapy for a fear of causing harm if uncertain of the cause of cardiac arrest.4
Ultrasound is a diagnostic tool with increasing applications and use in emergency situations.5 Levitt et al. have observed that emergency physicians had increased confidence in clinical decision-making when presented with diagnostic ultrasonographic images of medical conditions versus clinical impression and physical examination alone.6 Ultrasound examination has the potential to bring increased diagnostic clarity to clinical decision-making and aid in the identification of a reversible cause for PEA or asystole. Recently many studies and case reports have examined the application of emergency ultrasound to cardiac arrest.6, 7, 8, 9, 10, 11, 12, 13, 14, 15 Niendorff et al. observed that it was feasible for trained emergency sonographers to obtain diagnostic images during resuscitation of cardiac arrest patients and that obtaining sonographic images did not interfere with the resuscitation process.15 Other investigators have also made this observation.7, 14, 15 Many of these investigators have studied the application of ultrasound to one, or a few, causes of PEA and cardiac arrest; however a protocol that addresses the most common cardiac and pulmonary causes of PEA has not been developed.6, 7, 8, 9, 10, 11, 12, 13, 14, 15
There remains a need for an organized and structured approach to non-arrhythmogenic cardiac arrest with sufficient diagnostic accuracy to justify appropriate aggressive life-saving therapy. An effective protocol for emergency ultrasound evaluation in cardiac arrest patients would address the most likely and reversible causes; severe hypovolemia, tension pneumothorax, cardiac tamponade, and pulmonary embolus. There is a body of literature supporting the use of ultrasound as an accurate diagnostic aid in the four above-mentioned conditions. The purpose of this paper is twofold; first, to review the literature involving ultrasound and resuscitative conditions. Second, to propose a goal oriented approach to the cardiac arrest patient that incorporates the use of ultrasound to address the most common reversible causes of non-arrhythmia cardiac arrest. The name of this new test is C.A.U.S.E., an acronym for cardiac arrest ultra sound examination, and whose name has the added benefit of reminding the practitioner that the primary goal of their effort in PEA or asystole should be to identify and address the underlying cause. The protocol also serves to organize a process that can at times be chaotic and disorganized. Past studies have shown that increased organization during resuscitation increases the likelihood of survival.16, 17 A similar organizational protocol has been used for the treatment of ventricular arrhythmias using three-lead electrocardiogram as a diagnostic tool with great success.1, 2
Section snippets
Sonographic applications for cardiac arrest
Ultrasound has been used as an effective diagnostic tool during cardiac arrest and has identified causes of PEA. These include cardiac tamponade, severe hypovolemia, pulmonary embolus, tension pneumothorax, and true asystole.
Conclusion
Ultrasound is currently the only radiographic modality with the potential to guide management in real time, at the bedside, during cardiac arrest without interfering with resuscitation. This literature review justifies the need for further study of ultrasound in the setting of cardiac arrest and also demonstrates that implementation of sonography into patient-care provides substantial potential benefits to patients and clinicians alike. As technology and training improve it will become easier
Conflict of interest
None.
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A Spanish translated version of the summary of this article appears as Appendix in the final online version at 10.1016/j.resuscitation.2007.06.033.