Background: There are few data describing the relationship between amount of perioperative fluid and organ function. In this study we investigated the effects of two levels of intravascular fluid administration ("liberal" versus "restrictive") in knee arthroplasty on physiological recovery as the primary outcome variable.

Methods: In a double-blind study, 48 ASA I-III patients undergoing fast-track elective knee arthroplasty were randomized to restrictive or liberal perioperative intravascular fluid administration. Patients received a fixed rate infusion of Ringer's lactate solution with a standardized volume of colloid. All other aspects of perioperative management (including anesthesia, preoperative fluid status, and postoperative management) were standardized. Primary outcome variables included pulmonary function (spirometry), exercise capacity ("timed up and go" test), coagulation (Thrombelastograph), postoperative hypoxemia (nocturnal pulse oximetry), postoperative ileus (defecation), and subjective patient recovery (visual analog scales). Hospital stay and complications were also noted.

Results: Fluid guidelines were followed strictly in all patients. Liberal (median 4250 mL, range 3150-5200 mL) compared with restrictive (median 1740 mL, range 1100-2165 mL) intravascular fluid administration led to improved pulmonary function 6 h postoperatively, significant hypercoagulability 24-48 h postoperatively, and reduced incidence of vomiting. There were no overall differences in the other assessed perioperative physiological recovery variables (postoperative hypoxemia, exercise capacity or subjective patient recovery variables). No difference was found in hospital stay (median 4 days in both groups, not significant).

Conclusion: A liberal compared to a restrictive intravascular fluid regimen may lead to significant hypercoagulability and a reduction in vomiting, but without differences in other recovery variables or hospital stay after fast-track knee arthroplasty.