Higher Rate of AKI with Restrictive Fluid Policy for Abdominal Surgery

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In patients undergoing major abdominal surgery, a restrictive fluid policy leads to an increased rate of acute kidney injury compared to liberal fluid therapy, while other outcomes are similar between groups, reports a study in The New England Journal of Medicine.

The “Restrictive versus Liberal Fluid Therapy in Major Abdominal Surgery” (RELIEF) trial included 3000 patients considered at increased risk of complications while undergoing major abdominal surgery. High-risk criteria included age 70 or older, heart disease, diabetes, renal impairment, and morbid obesity. The patients, enrolled at 47 centers in 7 countries, were randomly assigned to restrictive or liberal intravenous fluid regimens. One-year disability-free survival was compared between groups, along with a range of secondary outcomes.

Modified intention-to-treat analysis included 1490 patients assigned to the restrictive fluid strategy and 1493 to the liberal strategy. During surgery and up to 24 hours afterward, median IV fluid totals were 3.7 versus 6.1 L, respectively. There was no significant difference in disability-free survival at 1 year: 81.9% with the restrictive strategy and 82.3% with the liberal strategy.

Acute kidney injury, defined according to KDIGO criteria, was significantly more frequent in the restrictive fluid group: 8.6%, compared to 5.0% with the liberal fluid strategy. Rates of some other secondary outcomes were higher with the restrictive strategy: 2.18% versus 19.8% for septic complications or death, 16.5% versus 13.6% for surgical-site infection, and 0.9% versus 0.3% for renal replacement therapy. However, these differences were not significant after adjustment for multiple comparisons.

A restrictive intravenous fluid strategy has been recommended for enhanced recovery after abdominal surgery. However, there are questions about the evidence behind this recommendation, and concern that it could lead to impaired organ perfusion.

The pragmatic RELIEF trial shows similar disability-free survival with restrictive versus liberal fluid therapy for high-risk patients undergoing major abdominal surgery. However, the restrictive strategy is associated with a significant increase in acute kidney injury.

“[W]e found that restricting intravenous-fluid administration with the aim of zero balance increased the risk of acute kidney injury,” the researchers write. They believe their findings show that “a regimen that includes a modestly liberal administration of fluid is safer than a restrictive regimen” [Myles PS, et al. Restrictive versus liberal fluid therapy for major abdominal surgery. N Engl J Med 2018; DOI: 10.1056/NEJMoa1801601].