One discussion this week included restrictive vs liberal perioperative fluid management on the development of perioperative acute kidney injury.

References: Brandstrup B, et al. Effects of intravenous fluid restriction on postoperative complications: comparison of two perioperative fluid regimens: a randomized assessor-blinded multicenter trial. Annals of Surgery. 2003 Nov;238(5):641-648.

Myles PS, et al. Restrictive versus liberal fluid therapy for major abdominal surgery. NEJM. 2018 Jun 14;378:2263-2274. doi:10.1056/NEJMoa1801601

Summary: Traditional intravenous-fluid regimens administered during abdominal surgery deliver up to 7 liters of fluid on the day of surgery. Some small trials have shown that a more restrictive fluid regimen led to fewer complications and a shorter hospital stay. However, the evidence for fluid restriction during and immediately after abdominal surgery is inconclusive. Fluid restriction could increase the risk of hypotension and decrease perfusion in the kidney and other vital organs, leading to organ dysfunction, but excessive intravenous-fluid infusion may increase the risk of pulmonary complications, acute kidney injury, sepsis, and poor wound healing (Myles 2018).

Each of the RCTs below compare restrictive vs liberal fluid management, with conflicting conclusions.

BRANDSTRUB ET AL (2003)

This multicenter RCT involved 172 patients allocated to either a restricted or a standard intraoperative and postoperative intravenous fluid regimen. The restricted regimen aimed at maintaining preoperative body weight; the standard regimen resembled everyday practice. The primary outcome measures were complications; the secondary measures were death and adverse effects.

Results: The restricted intravenous fluid regimen significantly reduced postoperative complications both by intention-to-treat (33% versus 51%, P = 0.013) and per-protocol (30% versus 56%, P = 0.003) analyses. The numbers of both cardiopulmonary (7% versus 24%, P = 0.007) and tissue-healing complications (16% versus 31%, P = 0.04) were significantly reduced. No patients died in the restricted group compared with 4 deaths in the standard group (0% versus 4.7%, P = 0.12). No harmful adverse effects were observed.

Conclusion: The restricted perioperative intravenous fluid regimen aiming at unchanged body weight reduces complications after elective colorectal resection.

MYLES ET AL (2018)

This international trial randomly assigned 3000 patients who had an increased risk of complications while undergoing major abdominal surgery to receive a restrictive or liberal intravenous-fluid regimen during and up to 24 hours after surgery. The primary outcome was disability-free survival at 1 year. Key secondary outcomes were acute kidney injury at 30 days, renal-replacement therapy at 90 days, and a composite of septic complications, surgical-site infection, or death.

Results: Up to 24 hours after surgery, 1490 patients in the restrictive fluid group had a median intravenous-fluid intake of 3.7 liters, as compared with 6.1 liters in 1493 patients in the liberal fluid group. The rate of disability-free survival at 1 year was 81.9% in the restrictive fluid group and 82.3% in the liberal fluid group. The rate of AKI was 8.6% in the restrictive fluid group and 5.0% in the liberal fluid group. The rate of septic complications or death was 21.8% in the restrictive fluid group and 19.8% in the liberal fluid group; rates of surgical-site infection (16.5% vs. 13.6%) and renal-replacement therapy (0.9% vs. 0.3%) were higher in the restrictive fluid group, but the between-group difference was not significant after adjustment for multiple testing.

Conclusion: Among patients at increased risk for complications during major abdominal surgery, a restrictive fluid regimen was not associated with a higher rate of disability-free survival than a liberal fluid regimen and was associated with a higher rate of acute kidney injury.

Additional Reading: Romagnoli S, Ricci Z, Ronco C. Perioperative acute kidney injury: prevention, early recognition, and supportive measures. Nephron. 2018;140(2):105-110.

Salmasi V, et al. Relationship between intraoperative hypotension, defined by either reduction from baseline or absolute thresholds, and acute kidney and myocardial injury after noncardiac surgery: a retrospective cohort analysis. Anesthesiology. 2017;126:47-65. doi:10.1097/ALN.0000000000001432

OpenAnesthesia. Encyclopedia: Fluid Management. OpenAnesthesia. 2019. International Anesthesia Research Society. Retrieved from: http://www.openanesthesia.org/fluid-management/