Clinical predictors of postoperative hemoglobin drift

Background The decision to transfuse red blood cells in surgical patients should be based on multiple clinical variables, rather than on isolated hemoglobin (Hb) measurements alone. An important but often unrecognized clinical variable is the postoperative downward drift in Hb concentration (Hb drift), but the etiology, predictors, and time course of Hb drift are not well understood. Study Design and Methods Data were retrospectively collected for patients who did not receive postoperative transfusion. Initially, 11 common surgical procedures from one institution (n=3179) were compared to assess clinical predictors of Hb drift. Data were analyzed in detail for two procedures associated with a large Hb drift (Whipple [n=82] and lumbar spinal fusion [n=74]), to determine the clinical predictors and temporal pattern of postoperative Hb drift. Results Surgical procedures with greater intraoperative intravenous (IV) fluid and blood requirements had greater postoperative Hb drift. The maximum Hb drifts after the Whipple and spinal fusion procedures were -2.5±1.1g/dL (occurring on Day4, p<0.0001) and -1.8±1.2g/dL (on Day3, p<0.0001), respectively. After the nadir, a 0.6g/dL upward Hb drift (p<0.0001) occurred after both procedures, resulting in a total drift after Whipple and spinal fusion of -1.9±1.2g/dL (p<0.0001) and -1.3±1.2g/dL (p<0.0001), respectively. Type of surgery (p=0.03), intraoperative blood loss (p=0.003), and a positive perioperative fluid balance (p=0.0008) were independent predictors of Hb drift. Conclusions Postoperative Hb drift was greater after surgical procedures with greater intraoperative IV fluid and blood requirements. Recognition of Hb drift may be an important facet of perioperative patient blood management.