54-year old male who called 911 for dyspnea. He states he has felt tired and short of breath for the last 2 weeks. His symptoms are constant, made worse with ambulation or doing things around the house, and has noticed bilateral lower extremity swelling within the same period. Endorses subjective chills, but no chest pain, abdominal pain, or nausea.
VS: P105, BP 160/90, Sp02 94% on RA, Temp 100.4F Your physical exam reveals an alert male of stated age with moderate increase in work of breathing, scattered crackles bilaterally on lung auscultation, 1+ bilateral lower extremity pitting edema. No other notable findings.
Which POC ultrasound (POCUS) studies would be helpful in the assessment of this patient?
The evaluation of the patient with dyspnea is complex due to the many different organ systems that can be involved in the primary pathophysiology of their disease. Many of these patients are in some degree of respiratory distress, further adding to the urgency that a working diagnosis be made so appropriate treatment can be started. Although we have traditionally relied on history and a good physical exam to do so, POCUS can augment our diagnostic power of the aforementioned techniques. Pre-hospital providers should be focused on obtaining several key studies when performing POCUS on these patients including the cardiac, lung, and IVC studies. Cardiac views can give you an adequate assessment of LV/RV size and function, the presence of pericardial effusion/tamponade, assess for wall-motion abnormalities, and even sometimes catch proximal aortic dissections in the most able ultrasonographers. A view of the IVC and its associated size and collapsibility will give you a quick approximation of a patient’s intravascular fluid status and/or RV function. Lung views give us a very sensitive way to diagnose a pneumothorax, pleural effusion, and the presence/absence of interstitial fluid which can lead to differentiating between pulmonary edema vs. pneumonia.
What findings would you expect to see on POCUS for each of the disease processes in your differential?
- CHF: LV reduced ejection fraction with dilatation or LV preserved ejection fraction with wall thickening (seen in diastolic CHF aka HFpEF), bilateral B-lines seen most commonly in the lung base, and IVC dilatation with <50% inspiratory collapse.
- STEMI: mostly normal cardiac/pulmonary/IVC exams in many patients. In those that have progressed to later or more severe stages of their MI, regional wall-motion abnormalities may be seen. These patients can also decompensate into acute cardiogenic shock, and findings would be similar to those seen for CHF.
- Pulmonary Embolism: most patients have normal cardiac/lung/IVC exams except for the most severe cases in which RV strain can be seen with RV dilatation, reduced EF, and septal flattening.
- Pneumonia: focal unilateral B-lines signifying pulmonary edema/consolidation in one area. A small subset of patients can have multiple areas of B-lines in both lungs due to multifocal pneumonia, but these are generally seen in immunocompromised patients.
- Pneumothorax: Absence of lung-sliding +/- lung point (a point in which the transition between the absence and presence of lung sliding can be seen). In a supine patient, the most sensitive areas for the diagnosis of pneumothoraxes are along the parasternal borders.
- Pericardial effusion/tamponade: hypo-echoic collection of fluid within the pericardium mostly within the dependent portions of the heart. In a supine patient, this collection can be best seen in a subcostal view surrounding the RV. Take note that the amount of effusion does not necessarily correlate with the presence or severity of tamponade; in fact, the patients with the largest effusions are most commonly the most stable and at lowest risk for hemodynamic collapse, as their hearts and pericardium have had time to accommodate to the decreased preload state. Tamponade can be seen by diastolic collapse of the RA/RV when correlated with hemodynamic compromise.
Several views of the POCUS done for the patient are shown below:
What is the most likely diagnosis, and how would you use this to augment your treatment of this patient?
The views provided to you show a hyper-echoic mass within the RA and IVC, most likely correlating with severe thromboembolic disease. Although we cannot directly visualize the pulmonary vessels, it can be safely assumed that our patient with respiratory distress, tachycardia, and hypoxia likely has a pulmonary embolism. These ultrasound studies help guide our treatment by giving us a better understanding of the primary pathophysiology of the patient. Before performing the study, it would not be unreasonable to have diagnoses such as CHF exacerbation or pneumonia on our differential given the respiratory distress, hypoxia, crackles on auscultation, and bilateral lower extremity edema found on physical exam. Patients with these disease processes might benefit from supplemental oxygen and non-invasive positive pressure ventilation (NIPPV, e.g. BiPAP/CPAP) if their respiratory distress progresses. However, NIPPV would be detrimental to the hemodynamic status of our current patient with a likely pulmonary embolism, as they are very dependent on venous return and cardiac preload and any increase in intra-thoracic pressure from NIPPV would likely cause them to decompensate further. Our current patient would likely be better treated with increasing amounts of FiO2 via a nasal cannula or non-rebreather, and early vasopressors if hemodynamic collapse is imminent.
Joshua Fan, MD
Department of Emergency Medicine
University of Texas, Houston