In Response

To reiterate, we showed that phenylephrine induced somewhat opposite changes in stroke volume measured by the third-generation Vigileo FloTrac (Edwards Lifesciences, Irvine, CA) and by the Esophageal Doppler (CardioQ, Deltex Medical, Chichester, UK).1 According to McGee et al., our conclusion was incorrect because we used the esophageal Doppler for measuring stroke volume and we considered it as a standard in the present study.2 I agree that the effects of phenylephrine on stroke volume are not clear.3,4 Phenylephrine may increase stroke volume by increasing right ventricular preload, but it may also decrease stroke volume by increasing left ventricular afterload. In our study, phenlyephrine induced a 67% increase in stroke volume measured using the Vigileo FloTrac monitor, and it induced an 11% decrease in stroke volume measured using the esophageal Doppler monitor. Even if the effects of phenylephrine on stroke volume are, again, not clear, it is very unlikely that phenylephrine can induce a 67% increase in stroke volume. This Vigileo FloTrac is the most widely used cardiac output monitor in the United States5 and may potentially improve outcomes.6,7 Furthermore, it is easy to use and has been demonstrated to decrease postoperative complications when coupled with an appropriate goal-directed therapy strategy. That being said, our principal point that clinicians must be careful when interpreting stroke volume values obtained using this device when vasopressors have been used will help clinicians to better understand the device that they are using, and it may help the company producing the device improve their system. Maxime Cannesson, MD, PhD Department of Anesthesiology and Perioperative Care University of California, Irvine Irvine, California [email protected]