Pathophysiology and clinical implications of peroperative fluid management in elective surgery

The purpose of this thesis was to describe pathophysiological aspects of perioperative fluid administration and create a rational background for future, clinical outcome studies. In laparoscopic cholecystectomy, we have found "liberal" crystalloid administration ( approximately 3 liters) to improve perioperative physiology and clinical outcome, which has implication for fluid management in other laparoscopic procedures such as laparoscopic fundoplication, laparoscopic repair of ventral hernia, hysterectomy etc., where 2-3 liters crystalloid should be administered based on the present evidence. That equal amounts of fluid caused adverse physiologic effects in healthy volunteers indicates that addition of the surgical trauma per se increases fluid requirements. Volume kinetic analysis applied 4 hours postoperatively was not able to detect the presence of either overhydration or hypovolemia regardless of the administered fluid volume intraoperatively. In knee arthroplasty a approximately 4 vs. approximately 2 liters crystalloid-based fluid regimen lead to significant hypercoagulability (although with unknown clinical implications), but no over-all differences in functional recovery. Dehydration caused by bowel preparation leads to functional hypovolemia and the deficits should be corrected, in particular in elderly patients, where preoperative intravenous fluid substitution of approximately 2-3 liters crystalloid is recommended. We did not find thoracic epidural anesthesia to be accompanied by intravascular fluid mobilization. In major (colonic) surgery with a standardized multimodal rehabilitation regimen, over-all functional recovery was not affected with a "liberal" ( approximately 5 liters) vs. "restrictive" 1.5 liter crystalloid-based regimen, however based on three anastomotic leakages in the "restrictive" group, it may be hypothesized that a too "restrictive" fluid administration strategy could be detrimental in patients with anastomoses and need further evaluation. A systematic review concluded that present evidence does not allow final recommendations on which type of fluid to administer in elective surgery. Based on the current evidence, administration of < 5 liters intravenous fluid without specific indication in major surgical procedures should be avoided, while administration of < 1.5 liters in patients with anastomoses may not be recommended, an issue needing clarification in large-scale clinical studies. Finally, we have demonstrated that the conduction of double-blinded randomized trials on fluid management with postoperative outcomes is feasible.