Thank you for allowing us the opportunity to respond to the letter by Horowitz and Kumar. In our study, 1we investigated whether goal-directed intraoperative plasma volume expansion guided by the esophageal Doppler monitor would shorten the length of hospital stay and improve postoperative outcomes. The control and protocol groups consisted of patients undergoing similar procedures. The general anesthetic for both groups was standardized. We did not regiment the type of fluid to be administered in the control group, because we wanted this group to receive, as closely as possible, a routine standard of care. The protocol group received 6% hetastarch in saline to a maximum of 20 ml/kg, based on a fluid challenge algorithm. Patients in the protocol group received, on average, 500 ml more colloid than the control group. Hence, we could not completely rule out that additional colloid may have contributed to the findings of our study. This was stated in the discussion of the original manuscript. Goal-directed fluid administration is a strategy. Using the fluid challenge algorithm with esophageal Doppler monitoring minimizes the risk of over-resuscitation, because stroke volume is reassessed before each additional fluid bolus.
A number of confounding factors in this study must be addressed in future studies. First is the timing of fluid administration. A significantly greater volume of intravenous fluid was administered toward the beginning of the surgical procedure in the protocol group than in the control group. It may be that the earlier administration of fluid resulted in better perfusion of the gastrointestinal tract and, hence, earlier resumption of gastrointestinal motility and return to normal diet.
The type of fluid administered may also be important in postoperative patient outcome. In a recent study, 2we found an improvement in the quality of recovery in patients receiving a combination of colloid (6% hetastarch) and crystalloid (lactated Ringer's) versus crystalloid alone. Specifically, the colloid/crystalloid patients had a lower incidence of postoperative nausea and vomiting, severe pain, and peripheral edema. Further investigations are therefore needed to study the contribution of these factors.