Letters to the Editor: Letter to the Editor
To the Editor
We thank Dr Bloomstone et al1 for their comments on our review article and for their thoughtful analysis of fluid responsiveness during the perioperative period. We agree that the generalizability of hemodynamic studies should be considered in the context of the conditions of the investigation and that larger studies are needed to validate previous findings.2,3 While there are no studies that demonstrate that dynamic indices predict fluid responsiveness after a cardiac arrest, El Hadouti et al4 recently found that the passive leg raise predicts fluid responsiveness in postoperative spontaneously breathing patients who had signs of hypovolemia. Additionally, predicting fluid responsiveness in right ventricular failure is challenging. For experts in advanced echocardiography, measurement of peak systolic velocity of tricuspid annular motion via tissue Doppler offers a potential parameter to identify false positives of fluid responsiveness in patients who have right ventricular dysfunction.5
We thank Dr Whitaker and O’Sullivan6 who correctly note that a sudden loss of end-tidal carbon dioxide (Etco2) with a flat trace of 0 mm Hg should prompt the clinician to consider esophageal intubation.7 The mental model of a flat trace of 0 in esophageal intubation contrasts with the reduction of Etco2 to the low levels of Etco2 observed during a cardiac arrest. Low levels of Etco2 can also occur in the setting of bronchospasm, endotracheal tube obstruction, and an air leak.8 The characteristics of carbon dioxide accumulation in the periarrest state are poorly studied in humans. Ongoing reviews by the European Society of Anesthesiologists, the American Society of Anesthesiologist, and the European Resuscitation Council may help inform our understanding of the issue and point to new opportunities for research.
Vivek K. Moitra, MD, FCCM
New York, New York
Sharon Einav, MD
Shaare Zedek Medical Center
Karl-Christian Thies, MD
University Medical Center Greifswald
Mark E. Nunnally, MD
New York University
New York, New York
Andrea Gabrielli, MD
University of Pennsylvania
Gerald A. Maccioli, MD
Guy Weinberg, MD
The University of Illinois at Chicago
Arna Bannerjee, MD
Kurt Ruetzler, MD
Gregory Dobson, MD
Nova Scotia, Canada
Matthew McEvoy, MD
Michael F. O’Connor, MD, FCCM
University of Chicago
1. Bloomstone JA, Nathanson BH, McGee WT. Dynamic indices: use with caution in spontaneously breathing patients. Anesth Analg. 2018;127:e47–48.
2. Zöllei E, Bertalan V, Németh A, et al. Non-invasive detection of hypovolemia or fluid responsiveness in spontaneously breathing subjects. BMC Anesthesiol. 2013;13:40.
3. 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.
4. El Hadouti Y, Valencia L, Becerra A, Rodríguez-Pérez A, Vincent JL. Echocardiography and passive leg raising in the postoperative period: a prospective observational study. Eur J Anaesthesiol. 2017;34:748–754.
5. 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.
6. Whitaker DK, O’Sullivan EP. Capnography, esophageal intubation, and capnomanaging cardiac arrests in the operating room. Anesth Analg. 2018;127:e48–49.
7. Cook TM, Woodall N, Frerk C; Fourth National Audit Project. Major complications of airway management in the UK: results of the Fourth National Audit Project of the Royal College of Anaesthetists and the Difficult Airway Society. Part 1: anaesthesia. Br J Anaesth. 2011;106:617–631.
8. Link MS, Berkow LC, Kudenchuk PJ, et al. Part 7: Adult Advanced Cardiovascular Life Support: 2015 American Heart Association Guidelines Update for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Circulation. 2015;132:S444–S464.