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Camden, NJ
Dr. Trzeciak is Assistant Professor, Division of Cardiovascular Disease and Critical Care Medicine and the Department of Emergency Medicine, and Dr. Chansky is Chairman of the Department of Emergency Medicine, UMDNJ-Robert Wood Johnson Medical School at Camden, Cooper University Hospital.
Correspondence to: Stephen Trzeciak, MD, MPH, UMDNJ-Robert Wood Johnson Medical School at Camden, Cooper University Hospital, One Cooper Plaza, D363, Camden, NJ 08103; e-mail: trzeciak-stephen{at}cooperhealth.edu
Imagine this: You are evaluating a 65-year-old woman who presents to the emergency department (ED) with dizziness. On arrival, her blood pressure (BP) is 80/42 mm Hg. Immediately you administer IV fluids, to which the BP promptly responds and rises to a normal range. You quietly breathe a sigh of relief, and you go about your usual diagnostic evaluation. An hour later after your workup is complete, the diagnosis for your patient remains unclear and you plan to admit her for observation. However, the nurse soon informs you that while your patient has been waiting for a bed upstairs her BP has been intermittently reading "on the low side." You query the data recorded in the ED central monitoring station and you see that 3 of the last 10 recorded values for systolic BP (SBP) in the past hour have been < 100 mm Hg, including the most recent reading (88/46 mm Hg). In your mind you quickly run through a checklist of other clinical signs of potential tissue hypoperfusion, but the only "red flag" you can identify at this point is the arterial pressure. You ask the nurse to administer some more crystalloid, and you go back to the bedside. You are now reassured because the repeat BP is 109/64 mm Hg, and you find that the SBP remains > 100 mm Hg on all subsequent values that you obtain while the patient is in the ED. You think to yourself that perhaps those initially low values were spurious. Besides, you are a seasoned clinician, and in your judgment the patient "looks good." How concerned should you be? Do these numbers change how you risk-stratify your patient for an adverse outcome? What you really want to know is: "what are the odds that the patient will go up to the floor and have a bad outcome or, even worse, die suddenly?" In the practice of acute care, whether you are an ED-based clinician or a consultant seeing a patient in the ED, this clinical scenario is not uncommon. Against this backdrop, Dr. Alan Jones and coworkers have made an important contribution to the literature in this issue of CHEST (see page 941).1
The earliest measurement of arterial pressure has been attributed to cannulation of the carotid artery of a horse by Reverend Stephen Hales in 1733. With the development of the sphygmomanometer for noninvasive measurement in the late 1800s, Korotkoff (1905) first described the characteristic sounds that we use to estimate systolic and diastolic pressures. Use of arterial pressure measurement as a "vital sign," however, was not universally accepted until much later.2 In fact, when the sphygmomanometer was first introduced into clinical practice, an editorial published in the British Medical Journal warned that reliance on measurement of BP in clinical assessment could "pauperize our senses and weaken clinical acuity."3 Now, in 2006, the Jones et al1 data have made important new observations based on an old bedside technique.
This was a single-center, prospective cohort study that aimed to quantify the prevalence and prognostic significance of arterial hypotension (defined as a SBP value < 100 mm Hg) among nontrauma patients in the ED. With an unbiased sample (n = 4,790), the authors identified that 19% of patients had ED hypotension. Patients with hypotension had a threefold-higher risk of in-hospital death, and a 10-fold–increased risk of sudden, unexpected in-hospital death. Both the depth of the nadir for SBP and the duration of the hypotension were predictive of death. It is particularly notable that nonsustained hypotension characterized as either transient (defined as one isolated SBP reading < 100 mm Hg with all other values 
100 mm Hg) or episodic were associated with an increased risk of death (transient hypotension: odds ratio 2.0 [95% confidence interval, 1.2 to 3.2]; episodic hypotension: odds ratio, 3.2 [95% confidence interval, 1.9 to 5.1]). The presence of a SBP < 100 mm Hg proved to be an independent predictor for in-hospital death in multivariate analysis. This is the first clinical investigation that has quantified the strength of the relationship between hypotension and mortality risk in the ED setting.
Most contemporary clinical investigations aimed at mortality prediction in acute care would likely employ some sort of new cutting-edge technology (eg, a new severity of illness scoring system, or perhaps a novel serum biomarker or similar new type of measurement); however, this study focused on a technique, arterial pressure measurement, that has not only been available at the bedside for more than a century, but is also one of the first parameters measured on arrival to every ED. In contrast to complex multivariable severity scores that may be cumbersome for practical use at the bedside (and were not developed or validated for use in the ED), the measurement of BP can serve as a simple and rapid discriminator that is immediately available to every clinician that sees patients in the ED setting. The simplicity of this study is one of its greatest strengths.
One potential appraisal of the impact of this study might claim that the results of Jones et al1 should be obvious or perhaps intuitive. But we would disagree on the following grounds: (1) although all clinicians would view sustained hypotension as an indicator of high severity, these data are unique in that they have quantified the magnitude of the effect in what is essentially a dose-response relationship; and (2) the prognostic significance of transient or episodic hypotension in the ED had not been previously described and could be underappreciated in practice. While arterial pressure almost always serves as an essential component of an acute care clinician’s overall bedside assessment, these data from Jones et al1 tell us that regardless of other clinical signs or symptoms that may suggest a benign process, the presence of any hypotension warrants some degree of caution.
Now back to your patient. You observe her for another 30 min in the ED, and she has no additional hypotensive episodes. Although the etiology of your patient’s initial and episodic hypotension is not yet clear, you think that the perturbation of this vital sign may be telling you something. Fortunately, you recently read the article by Jones et al1 in the latest issue of CHEST, and so you fully recognize the magnitude with which these low readings might influence her hospital course. But despite the strength of the observational data in this study, there is still one all-important question that will require additional research and remains as-of-yet unanswered: "now what should you DO?"
Footnotes
The authors have no conflicts of interest to disclose.
References
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