Ep 131: A 55-Year-Old with Differing Causes of Shortness of Breath
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This is Katarina Heidhausen, Executive Editor of Harrison's Principles of Internal Medicine. Harrison's Pod Class is brought to you by McGraw-Hill's Access Medicine, the online medical resource that delivers the latest content from the best minds in medicine. And now, on to the episode. Hi, everyone. Welcome back to Harrison's Pod Class. We're your co-hosts. I'm Dr. Kathy Handy. And I'm Dr. Charlie Wiener, and we're joining you from the Johns Hopkins School of Medicine.

Welcome to episode 131 of 55-year-olds with differing causes of shortness of breath. Okay, well, Kathy, today we're going a little bit different, and we're going to talk about how we can use technology to assist with our physical diagnosis of the bedside. What are you referring to? Well, we're talking about point-of-care ultrasound, or POCUS.

I really liked it as now becoming more of a routine part of the physical examination, especially in the hospital. It can really improve care, and I love that it's another way to get clinicians away from the computer screens and back to the bedside. So before we start, why don't you just give us a little background on POCUS, since you're part of the younger generation.

So POCUS is defined as the acquisition, interpretation, and clinical integration of ultrasonographic views by a treating clinician in real time at the patient's bedside. So it's distinct from consultative ultrasound, and it's not meant to replace the imaging specialist, but rather to improve diagnostic and therapeutic decisions made by the treating clinician at the bedside.

POCUS started as an aid to emergency trauma care in the 1980s and is now spread to ambulatory and inpatient locations. The technology has progressed dramatically, right, in that period of time? Yeah, initially portable ultrasound machines were cart-based, but now there are highly accurate handheld devices with wired or even wireless probes connected to a tablet or even your phone.

This is making me feel old, Kathy. Me too. We were not using this as routinely when I was in training. Okay, well, let's get to the question now. It's asking, POCUS can be used as a diagnostic modality in all of the following patients except option A is a 55-year-old woman with a long history of poorly controlled asthma who reports six hours of shortness of breath and wheezing.

Option B is also a 55-year-old woman, but she has long-standing cirrhosis, and she presents with shortness of breath, abdominal pain, and a distended abdomen. Option C is also a 55-year-old woman, but she has a history of metastatic breast cancer. She presents with shortness of breath and hypotension, and on examination, her neck veins are elevated, and she has a 20-millimeter pulsus paradoxus.

Option D, also a 55-year-old woman, has a history of heart failure with reduced ejection fraction, and she reports dyspnea. On exam, she has dullness to percussion over the right lung and diffuse crackles. Option E, our only man, is also 55. He presents with three days of worsening lower abdominal pain, shallow breathing, and new kidney injury. Okay, interesting. I think I know where you're going with this, but frankly, POCUS can be helpful for all of these patients. Yes.

The key to the question is what POCUS can see and what it can't. Okay, I'm listening. Why don't you just explain my organ system?

All right, let's start with the heart since that's really where ultrasound first became widely used. And I think it's relevant to two of our patients. Cardiac POCUS exams can help characterize shock states, qualitatively assess left ventricular systolic function, assess for acute right ventricular failure, and cardiac tamponade from a large pericardial effusion and even gross valvular abnormalities.

Great. That certainly can add to your physical examination. It's better than auscultation in some cases. What about the lung? Well, as part of your lung examination, POCUS can be useful in finding pneumothorax, pleural effusions, pulmonary edema, or even pneumonia. Ultrasound is superior to chest x-ray for detection of pneumothorax, early interstitial processes, and small pleural effusions. And it's superior to chest CT for characterization of pleural effusion complexity.

Normal air-filled lung tissue reflects sound waves, thereby preventing visualization of aerated lung parenchyma and airways. And finally, what about the abdomen?

Evaluation of peritoneal free fluid is a common abdominal POCUS application. It can't specify the type of fluid, so it can't really tell the difference between ascites, blood, urine, bile, but it can detect as little as 100 to 500 milliliters of peritoneal free fluid. When ascites is present, POCUS can identify a safe site for paracentesis, improving procedural success and complication rates compared to landmark-based techniques.

Also, POCUS can be used in the initial evaluation of acute kidney injury and decreased urine output. Bladder ultrasound can rapidly identify the presence or absence of urine and saline-filled urinary catheter balloons in the bladder, confirming appropriate placement and function of a urinary catheter. Great. Well, not relevant to today's question, we can also add that POCUS can add to the physical examination of the lower extremities, the skin, and the soft tissues. And don't forget that it's also helpful for vascular access.

Okay, well, let's get back to our patients. All of these patients present with some respiratory symptoms, but from different potential etiologies. For patient B, the woman with cirrhosis, POCUS will clearly tell us if there is tappable ascites. For patient C, the woman with metastatic breast cancer and an elevated pulsus paradoxus, I'm worried that she has pericardial tamponade, so I would definitely get a POCUS probe on her.

Sounds like patient D has pulmonary edema, and that can be from cardiomyopathy. So using POCUS to assess the LV function, look for pulmonary edema, and a pleural effusion would be helpful. And patient E sounds like he may have urinary obstruction causing an acute kidney injury. So POCUS would settle that issue pretty quickly. Okay, well, you left out patient A.

Yes, and that's the best answer for this question because POCUS can't visualize the airways, so really doesn't help directly for a patient in whom you suspect has asthma or vocal cord dysfunction. Now, that being said, since it is part of the routine physical examination, I would make sure she doesn't have pulmonary edema, pneumothorax, or right ventricular dysfunction since PE is always in the diagnosis or the differential diagnosis of a patient with acute dyspnea.

Great. So today's teaching points are that point-of-care ultrasound, or POCUS, has or should become part of your routine physical examination. It can help optimize your diagnostic evaluation and direct therapy. And you can find this question and other questions like it in the Harrison Self-Review Book. And if you want to learn more, you can check out the Harrison's chapter on POCUS.

Visit the show notes for links to helpful resources, including related chapters and review questions from Harrisons. And thank you so much for listening. If you enjoyed this episode, please leave us a review so we can reach more listeners just like you.