Anestesia e Pesquisa Clínica
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Fluid Retention is Alleviated by Crystalloid but Not by Colloid Fluid after Induction of General Anesthesia: An Open-Labeled Clinical Trial

Robert G Hahn, Yuhong Li and Rui He

Background: Renal fluid conservation, which is possible to quantify by urine analysis, is often caused by dehydration. The present study aimed to determine whether such fluid retention could be reversed by crystalloid and/or colloid fluid during surgery. Methods: Urine colour, specific weight, osmolality and creatinine concentration were used to calculate a “fluid retention index” (FRI) in 108 patients undergoing major abdominal surgery. Urine was collected at baseline and after flow-guided fluid volume optimisation with hydroxyethyl starch 130/0.4 (n=86) or Ringer's lactate (n=22). The third sample was taken after one hour of surgery. Results: The mean preoperative FRI was 3.4 (SD 1.1) and did not change during the volume optimization. The FRI was unchanged from starch during the first hour of surgery, whereas it decreased from 3.6 to 2.9 in response to Ringer´s lactate (P<0.01). The urine became more concentrated when the urinary excretion was below 100 ml/hour. Preoperative fluid retention (FRI ≥ 4.0), which is cut-off for renal fluid conservation consistent with a body fluid deficit amounting to 3% of the body weight, was present in 32% of the patients. Such retention increased the risk of a minor postoperative increase in serum creatinine (n=15, odds ratio 6.4) despite a higher creatinine clearance during the surgery (155 versus 80 ml/min; P<0.02). Conclusions: Ringer´s lactate, but not hydroxyethyl starch, decreased the urinary markers of fluid retention in the perioperative setting. Fluid retention increased the risk of a postoperative increase in serum creatinine.