COMMENTARY

Amal Mattu -- Top 3 Articles in Emergency Medicine

Amal Mattu, MD

Disclosures

January 29, 2020

At the beginning of 2020, I would like to make sure you didn't miss the top three "must-read" emergency medicine articles of the past year. They were practice-changing, reminding or teaching us about critically important, potentially life-saving clinical pearls.

All three articles are excellent reads with take-home points. Following are my summaries; I hope all acute care physicians take time to read the articles in full.

Avoiding Misdiagnosis in Patients With Posterior Circulation Ischemia

Posterior circulation strokes represent approximately 20% of all ischemic strokes and can be associated with devastating complications, especially when delays in diagnosis or misdiagnoses occur. Unfortunately,

These delays and misdiagnoses happen much more frequently with posterior than anterior circulation strokes and are attributed to the nonspecific symptoms with which they present: nausea and vomiting, dizziness, blurry vision, headaches or neck pain, and vague sensory symptoms. Many other, more classic stroke symptoms manifest early as well, such as ataxia or focal weakness, though these are less likely to result in misdiagnosis.

In a paper published in Academic Emergency Medicine, Gurley and Edlow review the presenting symptoms and focus the reader's attention on those nonspecific symptoms that are often associated with misdiagnosis. They provide a framework for evaluating patients with these symptoms and also provide some clues that help to distinguish posterior stroke from benign conditions.

An example is their rational approach to the evaluation of the "dizzy" patient, including a discussion of abruptness of onset and triggerable versus nontriggerable dizziness, evaluation of key associated symptoms found in posterior stroke (dysarthria, diplopia, ataxia) that are typically absent in benign conditions, and discussion of headache/neck pain, which is often found in patients with cerebellar strokes and vertebral artery dissection.

The article is chock-full of additional pearls that will help the reader minimize the likelihood of inadvertently discharging one of these patients with a resulting terrible outcome.

Difficultly Intubating a Patient

The traditional mantra of emergency medicine is "Airway-Breath Sounds-Circulation." It's no wonder that airway gets top priority: Loss of a patient's airway results in rapid loss of life.

Therefore, it is incumbent on every acute care physician to be an expert in airway management. The first step in managing a patient's airway is the ability to assess the difficulty of intubation.

Detsky and colleagues reviewed 62 studies that evaluated clinical predictors of difficult intubation. They found that the single best predictor of a difficult intubation was a score of class III during the "upper lip bite test," in which the patient's lower incisors are unable to reach the upper lip. This test had a positive likelihood ratio of 14. The authors note that this finding raises the probability of a difficult intubation from 10% to greater than 60%.

Other findings that are far more commonly taught, such as short hyomental distance, small mandible size, impaired neck mobility, and Mallampati score, had much lower likelihood ratios for predicting a difficult intubation.

The upper lip bite test is a simple clinical finding that I had never heard of before, but it is certainly one that I will add to my pre-intubation checklist for all awake patients.

Using High-Sensitivity Troponins to Rule Out Acute Coronary Syndrome

High-sensitivity cardiac troponins (hsTNs) were approved for use in the United States in 2017. Since then, dozens of articles have been published about their incorporation into emergency department (ED) practice, and it seems that every author who has published on this topic has a different approach on how to use the test.

The result is that there is tremendous confusion about this test. What does the test mean, what values are diagnostic, and how should hsTN be used? For any readers who share this confusion, Potomac and Diercks have published my pick for the best comprehensive review on hsTNs and how to incorporate them into the ED chest pain evaluation process.

By definition, hsTN assays will detect cardiac troponin (at the lowest level of detection) in at least 50% of healthy, asymptomatic patients. With this increased sensitivity comes a lower specificity. In fact, approximately 2% of patients in the general population may have hsTN elevations above the 99th percentile of the upper reference limit, and this number is probably even higher in a typical ED population.

Therefore, the diagnosis of acute myocardial infarction (AMI) will often require serial changes of hsTN levels. Acute care providers should be aware of the numerous non-AMI causes of elevated hsTNs, including tachy- and brady-dysrhythmias, coronary or aortic dissection, congestive heart failure, chronic kidney disease, pulmonary embolism, shock, stroke, and many other causes of oxygen supply-demand mismatch or causes of myocardial dysfunction.

Because of its very high sensitivity, hsTN allows for rapid rule-outs of AMI with a very high negative predictive value. For example, a single hsTN below the level of detection in a patient whose chest pain began more than 3 hours prior to arrival and with a nonischemic ECG can exclude AMI. In addition, when hsTNs are used as part of an accelerated diagnostic protocol such as the HEART score, a repeat hsTN can be sent within 1-2 hours rather than waiting 3 hours.

This excellent review covers much more information than we can describe here, and readers who are going to be adopting hsTN into their practices in 2020 are strongly encouraged to read the full review.

Those are my top three must-read articles of 2019. Please share your thoughts, especially your own top picks. Thanks for reading, and best wishes to everyone for a safe and successful 2020.

Amal Mattu, MD, is a professor, vice chair of education, and co-director of the emergency cardiology fellowship in the department of emergency medicine at the University of Maryland School of Medicine in Baltimore.

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