The effect of crystalloid infusion on body water content and intra-abdominal pressure in patients undergoing orthopedic surgery under spinal anesthesia

Background. Crystalloids are frequently used for the correction of spinal anesthesia-induced hypotension, intraoperative bleeding, or vaporisation from surgical wounds. Objectives. The aim of this study was to observe the effect of perioperative crystalloid infusion on intra-abdominal pressure (IAP), volume excess (VE), total body water (TBW), and extracellular body water (ECW) in patients undergoing elective orthopedic surgery under spinal anesthesia. Material and methods. Adult patients undergoing hip or knee replacement were studied. Changes in VE, TBW, ECW, and IAP were observed in patients who received restrictive fluid therapy (group R) and in patients who received liberal fluid therapy (group L). IAP was measured in the urinary bladder. All para-meters were measured at 4 points in time: just before anesthesia (baseline value, A); just after surgery (B); 3 h after surgery (C); and on the morning of postoperative day 1 (D). Additionally, IAP was measured after anesthesia, just before surgery (A1). Results. The mean baseline values of IAP, ECW, TBW, and VE were comparable between groups L and R. The induction of anesthesia reduced IAP in both groups (p < 0.001). IAP and VE increased in both groups after surgery. Significantly higher values of IAP, however, were noted in group L at time points B, C, and D. TBW and ECW increased after surgery in group L. In group R, ECW slightly increased only at time point C. IAP strongly correlated with ECW in group L (p < 0.001, r = 0.62). Conclusions. Spinal anesthesia reduces IAP. A perioperative increase in body water content and IAP mainly depends on the volume of the infused crystalloids.