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Pearls & Pitfalls for Ultrasound of Hypotensive Patients
1. Start with the heart. Parasternal images tend to give the most information, but the subxyphoid view may be easier in some patients. Look for effusions, chamber dilation, and wall motion abnormalities (advanced).
2. Use the curvilinear probe or the phased array transducer. Start in the 4th intercostal space and position the probe between the ribs. If you do not get a good image try moving up or down one rib space and redirecting the angle of your probe. Remember to direct the beams of your probe through the long axis of the heart. If you need to decrease the distance between the patient’s heart and the ultrasound beams, have the patient roll over onto their left side and bring their heart closer to their chest wall.
3. Take the time to adjust your depth and gain to maximize image quality. Make sure you have enough depth to look behind the heart for a pericardial effusion. You should always try to see the cross-sectional descending aorta coursing behind the left ventricle.
4. In the setting of hypotension, pericardial fluid, especially when accompanied by right ventricular collapse, may signify tamponade, a condition which is best treated by immediate pericardiocentesis. Pleural effusions may mimic pericardial effusions in certain instances. If you are unsure, find the retrocardiac aorta. If the fluid is between the heart and aorta, it is pericardial. If it is on the opposite side of the aorta from the heart, it is pleural.
5. A hyperdynamic rapidly beating heart usually signifies hypovolemia. Look at the IVC to assess if the patient is indeed intravascularly depleted. Many studies have correlated IVC diameter to Swan Ganz RA pressures. If the heart is hyperdynamic and the IVC is compressed, the aggressive administration of fluids or blood products may be life-saving. Consider a search for the source of bleeding. Look for melena, hemoperitoneum, or an aortic aneurysm.
6. A dilated right ventricle should raise your suspicion for a massive pulmonary embolism. In such cases, tPA should be considered. Remember that CHF or pulmonary hypertension can also cause a dilated RV, although these chronic conditions will show a dilated RV with hypertrophy of the RV walls. A dilated RV with thin walls prompt consideration of the diagnosis of an acute massive PE.
7. Scanning further south may also help find the cause. Image the abdomen for evidence of retro-peritoneal bleeding from a ruptured AAA, or intraperitoneal bleeding from occult trauma, or ruptured ectopic pregnancy or spleen. Ultrasound of the legs may show DVT.
8. Ultrasound may be useful for more than just establishing a diagnosis. It can also help with procedures such as central line placement and pericardiocentesis during the resuscitation.
9. Consider the CORE Scan (Concentrated Overview of Resuscitative Efforts) in all undifferentiated hypotensive patients: https://apps.acep.org/WorkArea/DownloadAsset.aspx?id=42470
Brady Pregerson manages a free online EM Ultrasound Image Library and is the author of the Tarascon Emergency Department Quick Reference Guide. For more info visit EMResource.org.
Teresa S. Wu is the Assoc. Residency Director and Director of Ultrasound and Simulation Based Training for the Maricopa EM Program in Phoenix.