Dehydration before Major Urological Surgery and the Perioperative Pattern of Plasma Creatinine: A Prospective Cohort Series

Abstract

Preoperative dehydration is usually found in 30-50% of surgical patients, but the incidence is unknown in the urologic population. We determined the prevalence of preoperative dehydration in major elective urological surgery and studied its association with postoperative outcome, with special attention to plasma creatinine changes. We recruited 187 patients scheduled for major abdominal urological surgery to participate in a single-center study that used the fluid retention index (FRI), which is a composite index of four urinary biomarkers that correlate with renal water conservation, to assess the presence of dehydration. Secondary outcomes were postoperative nausea and vomiting (PONV), return of gastrointestinal function, in-hospital complications, quality of recovery, and plasma creatinine. The proportion of dehydrated patients at surgery was 20.4%. Dehydration did not correlate with quality of recovery, PONV, or other complications, but dehydrated patients showed later defecation (p = 0.02) and significant elevations of plasma creatinine after surgery. The elevations were also greater when plasma creatinine had increased rather than decreased during the 24 h prior to surgery (p < 0.001). Overall, the increase in plasma creatinine at 6 h after surgery correlated well with elevations on postoperative days one and two. In conclusion, we found preoperative dehydration in one-fifth of the patients. Dehydration was associated with delayed defecation and elevated postoperative plasma creatinine. The preoperative plasma creatinine pattern could independently forecast more pronounced increases during the early postoperative period.

Keywords: dehydration; gastrointestinal function; major urologic surgery; perioperative plasma creatinine pattern.

Figure 1

Linear correlations between changes in plasma creatinine; (A) the preoperative change vs. the change from the day before surgery to 6 h after surgery; (B) the further change to the first postoperative day (POD1).

Figure 2

Perioperative trajectory of plasma creatinine based on whether the final postoperative value represented a decrease in plasma creatinine values (green), a moderate increase (0–50%; red) or a substantial increase (>50%, blue) as compared to the concentration measured on the day before surgery. A statistically significant difference between these groups had occurred already before surgery was initiated, i.e., from the day before the surgery to the onset of surgery.

Figure 3

Change in plasma creatinine (as a percentage) from the day before surgery to the first day after surgery, depending on whether patients were dehydrated and/or showed an increase in plasma creatinine from the day before surgery to just before the surgery started. The box shows the 25th, 50th, and 75th percentiles and the error bars indicate the 10th and 90th percentiles.