The presence of an enlarged right ventricle (RV) in the patient with PEA can prove difficult to interpret. We recognize that the presence of an enlarged RV may indicate chronic RV disease, lack of forward cardiac flow in cardiac arrest, and other pathologies not from PE. The presence of an enlarged hypodynamic RV in the presence of a hyperdynamic left ventricle may be a more specific finding, but it can be difficult to interpret in the brief interval during active chest compressions.
Overall, we recommend that if signs of right heart strain are present, PE should remain a consideration, and the underlying goal of the active resuscitation should be to attain ROSC, followed by a more detailed POCUS or computed tomography imaging. The decision to administer thrombolytics remains controversial, and current AHA guidelines recommend confirming the diagnosis of PE prior to fibrinolysis.14
Step 3: Cardiac Activity
The presence or absence of cardiac activity provides useful prognostic information for patients in PEA. Patients in PEA with cardiac standstill on ultrasound have survival to hospital discharge rates ranging from 0.0 to 0.6 percent.5 We have intentionally placed the detection of cardiac activity at the end of the CASA exam for two primary reasons. First, as detailed above, there is variability in physician interpretation of cardiac activity.15 Second, after several rounds of cardiac compressions, a persistent inactive heart will be more clear to the provider, and in conjunction with clinical data (ie, potassium, pH, total down time, and comorbidities) and end-tidal CO2 readings, determination of when to end resuscitative measures can be more definitive.
Ancillary Steps: Pneumothorax and FAST
Evaluating for pneumothorax and the focused assessment with sonography in trauma (FAST) examination are ancillary steps of the CASA exam because these can occur during any time of the resuscitation and need not occur during a pulse check. Tension pneumothorax is a rare cause of nontraumatic cardiac arrest and can often be diagnosed clinically.11 During ongoing CPR, examine the anterior chest for the absence of lung sliding indicating pneumothorax. If you detect a pneumothorax, consider needle decompression or thoracostomy. Small, clinically insignificant pneumothoraces can occur from rib fractures during CPR, and clinicians should know these injuries may not require acute intervention.
Also, during ongoing CPR, if the clinical scenario indicates, the physician can assess for a ruptured abdominal aortic aneurysm or ectopic pregnancy by performing a FAST exam looking for evidence of free fluid. We intentionally excluded evaluation of the inferior vena cava (IVC) and hypovolemia from the CASA exam because intravenous fluids are traditionally given empirically in cardiac arrest and we expect the IVC to be distended in most cardiac arrests because there is severely limited forward flow.
POCUS is a powerful tool for assessing reversible causes of cardiac arrest. However, it must be utilized in a protocolized, efficient manner to reduce error and minimize CPR interruptions. The CASA exam provides a framework for clinicians to maintain high-quality CPR while also assessing for the highest-yield reversible causes of PEA that can be visualized with ultrasound.