(Reuters Health) – In a discovery that goes against emerging surgical wisdom, a new study suggests that restricting intravenous fluids before major abdominal surgery not only fails to make the operation safer for higher-risk patients, it may cause short-term kidney injury.
The rate of acute renal injury was 8.6% among 1,490 volunteers with a restricted fluid regimen versus 5.0% in a group of 1,493 getting a liberal IV-fluid regimen (P<0.001).
The risk of septic complications or death within 30 days was similar in the two groups – as high as 21.8% in the restrictive fluid group – but the research team, reporting online May 10 in The New England Journal of Medicine, also saw modestly significant increases in the rates of surgical-site infection and the need for renal-replacement therapy when fluids were restricted to replacement only.
“Our results are really quite surprising,” chief author Paul Myles of Monash University in Australia told Reuters Health in a telephone interview. “We could not identify any benefits of restrictive fluids, which is the technique experts have been using recently. In fact, we found more harm.”
But the team stressed in their paper that the findings “should not be used to support excessive administration of intravenous fluid. Rather, they show that a regimen that includes a modestly liberal administration of fluid is safer than a restrictive regimen.”
“There’s been no debate that if you give too much or too little fluid, it causes harm,” Dr. Myles said by phone. “But we didn’t know where the sweet spot was, and that was the purpose of this study. We now know where the sweet spot is, and that really is going to change practice around the world.”
“The result may surprise many surgeons and anesthesiologists, who no doubt expected that the outcome would favor the restrictive fluid group,” said Birgitte Brandstrup of Holbaek Hospital, Denmark, in a Journal editorial.
Conventional fluid administration can add 3 to 6 kilograms to a patient’s weight, and some small studies have suggested that restricting the amounts might reduce complications.
In the new pragmatic international study, known as RELIEF, patients in the restricted fluid group were only given enough fluid to replace what they were losing.
Their median intake was 3.7 liters during and up to 24 hours after surgery versus 6.1 liters in the liberal intake group.
All of the study participants were at higher risk for complications based on several criteria, such as being at least 70 years old, being morbidly obese or having heart disease, renal impairment or diabetes.
The odds of disability-free survival at one year showed no benefit for the restrictive-fluid regimen, with rates of 81.9% and 82.3% respectively (P=0.61).
Surgical-site infection rates were 16.5% with restricted intake and 13.6% without. Renal-replacement therapy was provided to 0.9% of volunteers on restricted fluids, three times higher than the rate among patients receiving unrestricted fluids (P=0.48).
The study, which was not blinded and included a range of abdominal surgeries, was done at 47 centers in seven countries.
Dr. Brandstrup said there may be several reasons why earlier research suggested a benefit to restricted fluids while the RELIEF study does not. For example, the older tests were done when surgery was more invasive, producing more stress that leads to fluid retention.
N Engl J Med 2018.