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Dynamic Indices: Use With Caution in Spontaneously Breathing Patients

Bloomstone, Joshua A. MD, MSc, CSSGB; Nathanson, Brian H. PhD, DSHS; McGee, William T. MD, MHA

doi: 10.1213/ANE.0000000000003550
Letters to the Editor: Letter to the Editor

Envision Physician Services, Plantation, Florida,

OptiStatim, LLC, Longmeadow, Massachusetts

University of Massachusetts Medical School, Baystate Medical Center, Springfield, Massachusetts

Conflicts of Interest: J. A. Bloomstone and W. T. McGee are in the Speaker’s Bureau of Edwards Lifesciences, Irvine, CA. The remaining author declares no conflicts of interest.

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To the Editor

It is with great pride for our specialty and with clinical intrigue that we read the narrative review by Moitra et al1 and McEvoy et al2 focused on the evidence-based management of intraoperative cardiac arrest. Indeed, the authors of both associated reviews are to be congratulated for distilling what is a large and complex body of literature into a useful, pragmatic, and clinically relevant set of publications. We would like to clarify a few points that we believe are of particular import to the practicing anesthesiologist.

First, hypovolemia is the most common cause of postoperative hemodynamic compromise.3 As such, methodologies to accurately determine volume responsiveness should be applied by practitioners before volume administration to assure that patients who require volume receive it, and those who do not, don’t. The authors suggest that a “growing literature” exists supporting the use of dynamic indices to predict volume responsiveness in spontaneously breathing patients. The 2 cited articles in Moitra et al,1 authored by Zollei et al4 and Hong et al,5 included patients who were spontaneously breathing under highly specific conditions that may not be readily accomplished in the general surgical population: forced inspiratory breathing and trained patterned breathing. While the methodology of both cited studies is valid, the strength of the conclusions based on study size is questionable and is remindful of Professor John Ioannidis’ first corollary, “the smaller the studies conducted in a scientific field, the less likely the research findings are to be true.”6,7

Second, while we agree that the presence of acute right ventricular (RV) shock often yields elevated dynamic indices that are generally false-positive, patients with RV failure may also be volume responsive, and dynamic indices may be predictive in this setting; however, further evaluation is required. Indeed, Mahjoub et al8 prospectively demonstrated that tissue Doppler assessment of peak systolic velocity of tricuspid annular motion can discriminate patients with true-positive and false-positive dynamic indices in the setting of RV failure.

Third, relative to the use of dynamic indices for predicting volume responsiveness, we completely agree with the authors that the interpretive pitfalls are legion, and that fluid should only be administered after other assessments of volume responsiveness such as stroke volume change to a fluid bolus or a passive leg raise confirm the existence of volume responsiveness. However, to our knowledge, there are no studies validating the use of either dynamic indices or a passive leg raise test to predict volume responsiveness in the immediate postcardiac arrest period.

Joshua A. Bloomstone, MD, MSc, CSSGB
Envision Physician Services
Plantation, Florida

Brian H. Nathanson, PhD, DSHS
OptiStatim, LLC
Longmeadow, Massachusetts

William T. McGee, MD, MHA
University of Massachusetts Medical School
Baystate Medical Center
Springfield, Massachusetts

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1. Moitra VK, Einav S, Thies KC, et al. Cardiac arrest in the operating room: resuscitation and management for the anesthesiologist: part 1. Anesth Analg. 2018;126:876–888.
2. McEvoy MD, Thies K-C, Einav S, et al. Cardiac arrest in the operating room: part 2 – special situations in the perioperative period. Anesth Analg. 2018;126:889–903.
3. Saclarides TJ, Myers JA, Millikan KW. Common Surgical Diseases: An Algorithmic Approach to Problem Solving. 2015.2nd ed. New York, NY: Springer
4. Zollei E, Bertalan V, Nemeth A, et al. Non-invasive detection of hypovolemia or fluid responsiveness in spontaneously breathing subjects. BMC Anesthesiol. 2013;13:40.
5. Hong DM, Lee JM, Seo JH, Min JJ, Jeon Y, Bahk JH. Pulse pressure variation to predict fluid responsiveness in spontaneously breathing patients: tidal vs forced inspiratory breathing. Anaesthesia. 2014;69:717–722.
6. Bloomstone JA, Nathanson BH, McGee WT. Applying dynamic parameters to predict hemodynamic response to volume expansion in spontaneously breathing patients with septic shock: the eye cannot see what the mind does not know. Shock. 2013;39:461–462.
7. Ioannidis JP. Why most published research findings are false. PLoS Med. 2005;2:e124.
8. Mahjoub Y, Pila C, Friggeri A, et al. Assessing fluid responsiveness in critically ill patients: false-positive pulse pressure variation is detected by Doppler echocardiographic evaluation of the right ventricle. Crit Care Med. 2009;37:2570–2575.
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