Rapid Ultrasonography in Shock: Is this really useful?
Caring for patients with undifferentiated hypotension, causes anxiety for most health care providers. This is natural. Fear, however, must not lead to hesitation or poor decision-making. Therapies chosen early in shock disproportionately impact mortality. For example, giving fluids to a patient in cardiogenic shock may worsen the outcome, but aggressively giving fluids to a patient in septic shock has proven to be lifesaving. Being able to properly classify a patient’s shock is critical, but patients are often too unstable to wait for confirmatory lab tests or undergo diagnostic imaging such as CT scans. Point of care ultrasound allows physicians to expand diagnostic capabilities at the bedside, and in real time, collect information that will favorably affect outcomes.
The Rapid Ultrasonography in Shock (RUSH) exam, was developed to give providers a framework for managing hypotensive medical patients. In brief, the exam focuses on three physiologic parameters, the pump, the tank and the pipes. Examining the heart (pump) from four basic positions, identifies the presence of pericardial fluid, abnormal left ventricular contractility and acute right ventricular strain. Measuring the diameter and respiratory change of the inferior vena cava (tank), provides an estimate of volume status-and more importantly volume responsiveness. Assessment of the abdominal aorta (pipe), identifies dissection or aneurysmal dilatation, and finally compressing the deep veins of the legs (more pipes), detects deep vein thromboses. See the original article on RUSH by Dr. Perera for details on how these exams are completed.1
Are we as emergency providers capable of learning the RUSH exam?
A significant body of evidence supports the proficiency of emergency medicine and hospital medicine providers in using point of care ultrasound to complete the various parts of the RUSH exam. For example, compared to cardiologists reading formal echocardiograms, emergency physicians with 2 days of training accurately predicted ejection fraction as normal, moderately depressed or severely depressed 84% of the time. 2 Calculation of the IVC distensibility index ((largest IVC diameter-smallest IVC diameter)/smallest IVC diameter) accurately predicts fluid responsiveness in critically ill patients. A distensibility index greater than 18% predicted a rise in cardiac index of greater than 15% with greater than 90% sensitivity and specificity.3 In a study evaluating accuracy of aortic diameter measurements, 3rd year emergency medicine residents had near perfect correlation with formal ultrasonography. 4 Finally, emergency physicians with one hour of training were able to exclude DVT with 95% negative predictive value using compression venography. Each physician performed five supervised exams in training prior to participating in the study. 5
How will this change what I do in the ED?
Recently, a 58 year-old woman from out of town came to our ER with substernal chest pain. The EKG showed left bundle branch block. With no comparison EKGs to review, we performed a limited bedside echo and saw septal hypokinesis. This information influenced the cardiologist to take the patient for cardiac catheterization despite negative cardiac enzymes. A 90% lesion of the left anterior descending artery was discovered. A 73 year-old woman hospitalized a week earlier with a UTI, had syncope during physical therapy. She was profoundly hypotensive, and with bedside ultrasound had a large right ventricle, a septum bowing to the left, a full IVC and an uncompressible common femoral vein. She was given thrombolytics and her shock resolved within 30 minutes. A 48 year-old cirrhotic patient had a cardiac arrest on arrival to the emergency department. After resuscitation, his bedside ultrasound showed a hyperdynamic heart, a flat IVC and large amount of peritoneal fluid. On peritoneal aspiration, the fluid was bloody not ascitic. The patient was rushed to the OR and found to have a bleeding mesenteric varix.
Rapid Ultrasonography in Shock is a bedside physiologic assessment using point of care ultrasound. The exam can be performed competently with limited training and practice, and provides invaluable information in managing the sickest patients in the emergency department.
1. Perera, et al. The RUSH Exam: Rapid Ultrasound in Shock in the Evaluation of the Critically Ill, Emerg Med Clin N Am 28 (2010) 29-56.
2. Moore, MD et al. Determination of Left Ventricular Function by Emergency Physician Echocardiography of Hypotensive Patients, Acad Emerg Med, March 2002, Vol 9, No 3.
3. Barbier, et al. Respiratory changes in inferior vena cava diameter are helpful in predicting fluid responsiveness in ventilated septic patients. Inten Care Med (2004) 30:1740-1746.
4. Costantino TG, et al. Accuracy of Emergency Medicine Ultrasound in the Evaluation of Abdominal Aortic Aneurysm. J of Emerg Med. Vol. 29, 2005. No 4;455-460.
5. Frazee, et al. Emergency Department Compression Ultrasound to Diagnose Deep Vein Thrombosis, J Emerg Med, 2001 Feb:20 (2):107-12.