The Practical Art of POCUS

15.09.2017
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The longer you practice a profession, the easier it is not to bother to learn the next new thing. We may think we’re doing just fine without that new drug, or that new piece of expensive equipment. We’ve seen how the new drug sometimes turns out to have more side effects than benefits, and how the equipment may gather dust in the corner because no one really needed it in the first place.

That isn’t going to happen with point-of-care ultrasound, or “POCUS”, I’m willing to bet. As I learned at a weekend conference on POCUS, jointly hosted by the anesthesiology departments at UCLA and Loma Linda University, the practical applications for bedside patient care are multiplying, and the technology is improving all the time. Ultrasound isn’t just for cardiologists and radiologists any more.

Armed with a portable ultrasound probe and a tablet computer, we can evaluate patients before or after surgery and provide prompt answers to vexing clinical questions. Low blood pressure in the recovery room after surgery? A quick transthoracic echo of the heart can help you determine if the patient needs volume replacement, is evolving an acute myocardial infarction, or has a failing right ventricle due to a pulmonary embolism. The scan can be completed in minutes, with no expensive consult or dangerous delay.

When to request an ultrasound consult

Many of us in mid-career or later won’t ever need to become highly expert in the tips and tricks of obtaining perfect ultrasound views. But there are plenty of reasons to learn how ultrasound techniques can help in clinical care. My husband, a cardiac anesthesiologist, always says that in anesthesia, it isn’t necessarily what you know, it’s what you can think of in time. The single most important point to remember may be that calling a colleague with the training to do a quick bedside ultrasound may help you diagnose significant risk factors prior to surgery, or save critical time if a patient develops a problem afterward.

In the preoperative area, for example, we’ve all encountered the patient with a vague diagnosis of “moderate pulmonary hypertension” mentioned in the internist’s preoperative note without any details. We’ve all seen the patient with a hip fracture who has a heart murmur but no prior cardiac evaluation in the record. A bedside transthoracic echo — painless and noninvasive — can evaluate the size and function of the heart valves and ventricles in a matter of minutes, and prevent delay or cancellation of surgery if the result is favorable.

In the post-anesthesia care unit or ICU, abdominal ultrasound can assess volume status by looking at the diameter and compressibility of the inferior vena cava, or find immediate evidence of surgical bleeding after an abdominal or pelvic procedure. If a patient develops shortness of breath or can’t get enough oxygen in the bloodstream, thoracic ultrasound can diagnose an effusion, a collapsed lung, or pulmonary edema much faster than you can get a chest X-ray.

Driving without headlights

Most of us are quite familiar with using ultrasound for vascular access. Inserting a central venous line without it would feel like driving without headlights.

But there’s another clinical use for ultrasound that may one day seem just as indispensable:  scanning the gastric antrum to evaluate how full the stomach may be. I wasn’t aware that ultrasound technology could make that determination.

Right now we depend on patients to tell us when they last ate prior to surgery, and we have NPO guidelines (nil per os, or nothing by mouth) to help make sure that a patient’s stomach is empty prior to the induction of anesthesia. As a general rule, we assume that if a patient hasn’t eaten solid food within six to eight hours, or had any clear liquids within two hours, the stomach will be reasonably empty.

The guidelines don’t always work. Years ago, I took care of a patient who needed a brief emergency operation to drain fluid out of his inflamed knee. It was an especially busy day, and the patient was forced to wait in the emergency department for 18 hours without anything to eat before the operating room could find time and staff for his case. The patient was a successful businessman and a reliable historian; he was neither overweight nor diabetic, hadn’t needed much pain medication, and had no risk factors for delayed gastric emptying.

I elected to place a laryngeal mask airway (LMA), assuming that the patient’s stomach was empty. But shortly after he went to sleep for the procedure, he began to vomit solid food in large quantities. This was a highly dangerous situation. It was a near miracle that the patient didn’t aspirate stomach contents into his lungs, and fortunately he recovered with no ill effects. His case could have ended in tragedy. But if ultrasound of the gastric antrum had been readily available then, I would have known that his stomach was full and could have averted the entire problem with a different approach to the anesthesia.

Perhaps, in the not too distant future, we will do ultrasound of the gastric antrum before any emergency procedure, or for that matter any elective procedure. That could certainly help us quantitatively assess the risk of vomiting and aspiration. We may find that we should adapt our NPO guidelines and clinical practice based on the results in thousands of patients under differing circumstances, rather than on the limited evidence that exists today.

Hands-on learning

Certainly there is a great deal of information about POCUS available online, and videos can demonstrate the basics. In my opinion, however, there’s no substitute for the immersive experience of a conference with hands-on learning opportunities in addition to lecture content. This weekend’s POCUS conference featured presentations by a team of experts, and multiple stations where attendees could practice ultrasound techniques on simulation mannequins and live models under the guidance of experienced educators.

The course co-directors were Davinder Ramsingh, MD, of Loma Linda University School of Medicine, and two UCLA faculty members, Kimberly Howard-Quijano, MD, MS, and Jacques Prince Neelankavil, MD. Department chairs Aman Mahajan, MD, PhD, and Robert Martin, MD, lent their support to the conference and participated in an opening panel discussion on the promising future of POCUS in clinical care.

Image copyright: falco/pixabay/CC0

Article last time updated on 26.09.2017.

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