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Is Intraoperative Hypotension Truly a Too Simple Problem for Useful Decision Support?

Kappen, Teus H. MD, PhD; Wanderer, Jonathan P. MD, MPhil; Ehrenfeld, Jesse M. MD, MPH; Weinger, Matthew B. MD

doi: 10.1213/ANE.0000000000001364
Letters to the Editor: Letter to the Editor

Department of Anesthesiology, Vanderbilt University Medical Center, Nashville, Tennessee,

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To the Editor:

We read with great interest the randomized trial by Panjasawatwong et al1 on automated alerts for intraoperative hypotension (IOH). The authors conclude that the decision support may only be useful in more complicated decision situations. It appears this conclusion presumes that IOH is a simple problem, which should be easy to solve; hence, IOH decision support is an unnecessary intervention. However, this conclusion is unsubstantiated by their findings.

In multiple studies, IOH is associated with postoperative adverse events.2–4 In the study by Panjasawatwong et al, anesthesiologists typically noticed and corrected IOH within minutes. Has the IOH problem been solved so quickly? In the study by Panjasawatwong et al, average blood pressures (BPs) appear to be similar to BPs in previous studies by the same authors (Figure).1,4 If IOH occurrence has not changed, then the risks of adverse events also remain the same. IOH remains a complex problem remaining to be addressed.



Furthermore, the results do not prove that IOH decision support does not work. The random allocation of patients may have caused study group contamination because of a learning effect. When anesthesiologists receive IOH alerts in their first cases, their BP management of all subsequent cases may also be affected, regardless of patient random allocation status. In contrast to the assertion by Panjasawatwong et al in their discussion, cluster random allocation of providers or time-series designs (before versus after) could be superior to patient-randomized trials in such contamination situations. We do not know if contamination occurred in this study, but such a confound would be a viable alternative explanation for their results.

In conclusion, without further exploration and additional studies, possibly using alternative experimental designs, it is premature to assert that decision support cannot be an effective tool to combat the risks of IOH.

Teus H. Kappen, MD, PhDJonathan P. Wanderer, MD, MPhilJesse M. Ehrenfeld, MD, MPHMatthew B. Weinger, MDDepartment of AnesthesiologyVanderbilt University Medical CenterNashville,

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1. Panjasawatwong K, Sessler DI, Stapelfeldt WH, Mayers DB, Mascha EJ, Yang D, Kurz A. A randomized trial of a supplemental alarm for critically low systolic blood pressure. Anesth Analg 2015;121:15007.
2. Sessler DI, Sigl JC, Kelley SD, Chamoun NG, Manberg PJ, Saager L, Kurz A, Greenwald S. Hospital stay and mortality are increased in patients having a “triple low” of low blood pressure, low bispectral index, and low minimum alveolar concentration of volatile anesthesia. Anesthesiology 2012;116:1195203.
3. Walsh M, Devereaux PJ, Garg AX, Kurz A, Turan A, Rodseth RN, Cywinski J, Thabane L, Sessler DI. Relationship between intraoperative mean arterial pressure and clinical outcomes after noncardiac surgery: toward an empirical definition of hypotension. Anesthesiology 2013;119:50715.
4. Mascha EJ, Yang D, Weiss S, Sessler DI. Intraoperative mean arterial pressure variability and 30-day mortality in patients having noncardiac surgery. Anesthesiology 2015;123:7991.
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