• Hai Bin Zhu, Xiaozhu Zheng, Han Jian Chen, and Liang Shao.
• Department of Anesthesiology, First Affiliated Hospital, College of Medicine, Zhejiang University, 79 Qingchun Road, 310003 Hangzhou, China.
• Crit Care. 2012 Jan 1;16(1):R18.

IntroductionThe renal clearance of infused crystalloid fluid is very low during anaesthesia and surgery, but experiments in conscious sheep indicate that the renal fluid clearance might approach a normal rate when the adrenergic balance is modified.MethodsSixty females (mean age, 32 years) undergoing laparoscopic gynecological surgery were randomized to control group and received only the conventional anesthetic drugs and 20 ml/kg of lactated Ringer's over 30 mins. The others were also given an infusion of 50 μg/kg/min of esmolol (beta1-receptor blocker) or 0.01 μg/kg/min of phenylephrine (alpha1-adrenergic agonist) over 3 hours. The distribution and elimination of infused fluid were studied by volume kinetic analysis based on urinary excretion and blood hemoglobin level.ResultsBoth drugs significantly increased urinary excretion while heart rate and arterial pressure remained largely unaffected. The urine flows during non-surgery were 43, 147, and 176 ml in the control, esmolol, and phenylephrine groups, respectively (medians, P<0.03). When surgery had started the corresponding values were 34, 65 and 61 ml (P<0.04). At 3 hours, averages of 9%, 20%, and 25% of the infused volume had been excreted in the three groups (P<0.01). The kinetic analyses indicated that both treatments slowed down the distribution of fluid from the plasma to the interstitial fluid space, thereby preventing hypovolemia.ConclusionsEsmolol doubled and phenylephrine almost tripled urinary excretion during anesthesia-induced depression of renal fluid clearance.

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