Your hospital system is interested in developing a perioperative fluid administration protocol for adults undergoing noncardiac surgery. According to a recent large study, which of the following is MOST likely true regarding postoperative complications?
□ (A) Complications were least likely in patients receiving moderate volumes of fluid.
□ (B) Acute kidney injury (stage II or III) was most likely in patients receiving the lowest volume of fluids.
□ (C) The likelihood of respiratory complications was not associated with the volume of fluids.
Postoperative complications have major negative effects on overall patient outcomes and costs. Perioperative fluid management is a potentially modifiable factor for reducing postoperative complications, as both hypervolemia and hypovolemia may have adverse effects. Many studies have examined the association between perioperative fluid volumes and patient outcomes, but most have been limited in scope, focusing on specific patient populations, organ systems, or single institutions.
The authors of a recent retrospective study hypothesized that patients receiving high or low volumes of fluid may experience worse clinical outcomes than patients receiving moderate fluid volumes in the perioperative period. The study included 35,736 adults who underwent noncardiac surgery at 119 hospitals from January 1, 2012, to December 31, 2017. Patients were included if they received a minimum of 500 mL of intravenous fluid from six hours preoperatively to 24 hours postoperatively and remained in the hospital for at least 24 hours after surgery. The patients were divided into five equal quintiles (Q) based on total fluid volume from six hours before surgery to 24 hours after surgery. Volumes included both crystalloids and colloids:
Q1: 500-1,191 mL
Q2: 1,191-1,775 mL
Q3: 1,775-2,333 mL
Q4: 2,333-3,216 mL
Q5: 3,216-7,932 mL
The primary outcome was a composite of at least one complication during the hospital stay plus a postoperative hospital length of stay (LOS) of seven days or longer. Secondary outcomes included in-hospital mortality, postoperative respiratory complications, and postoperative acute kidney injury. The moderate volume quintile (Q3) was used as the reference for analysis.
For the entire study population, the mean (SD) volume of perioperative fluids was 2,290 (1,283) mL. The primary outcome occurred in 4,047 patients (11.3%). Rates for the individual categories of complications were as follows:
Gastrointestinal: 1,871 patients (5.2%)
Respiratory: 1,863 patients (5.2%)
Cardiovascular: 1,857 patients (5.2%)
Infection: 1,817 patients (5.1%)
Renal: 1,363 patients (3.8%)
Q3 had the lowest rate of complications overall.
During multivariable analysis, the authors found a U-shaped association between perioperative fluid volumes and complications, with the highest odds of complications at the extremes of volume and the lowest odds of complications with a moderate volume of fluid. The odds of the primary outcome (≥ 1 complication plus hospital LOS ≥ 7 days) was higher in Q1, Q4, and Q5, compared with Q3. The odds of stage II or III acute kidney injury were higher in Q5 and Q4 than in Q3 (when analyzing patients without chronic kidney disease), and the odds of respiratory complications were also higher in Q5 than in Q3. No association was found between perioperative fluid volumes and the odds of in-hospital mortality.
In summary, a moderate volume of perioperative fluids was associated with the lowest odds of complications after noncardiac surgery in this large multicenter study. Both low and high fluid volumes were associated with an increased odds of at least one complication (of any type), whereas only high volumes were associated with an increased odds of respiratory complications and acute kidney injury.
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