Changes in plasma volume before and after major abdominal surgery following stroke volume variation-guided fluid therapy: a randomized controlled trial

The aim of intraoperative fluid therapy is to avoid both hypovolemia and hypervolemia; however, the patient's exact volume status is difficult to determine during surgery. Fluid optimization guided by stroke volume variation (SVV) has been widely used in patients undergoing major open abdominal surgery. The aim of this study was to evaluate the changes in plasma volume before and after surgery following SVV-guided fluid therapy.Patients were randomly allocated into one of two groups according to the SVV criteria for fluid administration during surgery. In the fixed SVV fluid strategy group, fluid was administered to maintain the SVV below 13%. In the individual SVV group, individual SVV values of each patient were maintained until the end of surgery. Plasma volume, body weight, and extracellular water (ECW) were measured before and after surgery. Plasma volume was estimated using the indocyanine green dilution technique.A total of 118 patients were included. Median (25-75%) plasma volumes in the preoperative and postoperative period were 2.46 (2.20-2.88) L and 2.69 (2.33-3.12) L for the fixed SVV group (N.=57, P=0.133), respectively, and 2.56 (2.23-2.90) L and 2.89 (2.48-3.19) L for the individual SVV group (N.=61, P<0.001), respectively.Fluid administration during surgery to maintain SVV below 13% was effective for maintaining the preoperative plasma volume until the end of surgery in patients undergoing major open stomach or colorectal surgery. This result supports the validity of SVV-guided fluid therapy, which maintains the SVV value below 13%, in terms of maintaining patient volume status.