Introduction: The renal clearance of infused crystalloid fluid is very low during anaesthesia and surgery, but\r\nexperiments in conscious sheep indicate that the renal fluid clearance might approach a normal rate when the\r\nadrenergic balance is modified.\r\nMethods: Sixty females (mean age, 32 years) undergoing laparoscopic gynecological surgery were randomized to\r\ncontrol group and received only the conventional anesthetic drugs and 20 ml/kg of lactated Ringerâ��s over 30 mins.\r\nThe others were also given an infusion of 50 �µg/kg/min of esmolol (beta1-receptor blocker) or 0.01 �µg/kg/min of\r\nphenylephrine (alpha1-adrenergic agonist) over 3 hours. The distribution and elimination of infused fluid were\r\nstudied by volume kinetic analysis based on urinary excretion and blood hemoglobin level.\r\nResults: Both drugs significantly increased urinary excretion while heart rate and arterial pressure remained largely\r\nunaffected. The urine flows during non-surgery were 43, 147, and 176 ml in the control, esmolol, and\r\nphenylephrine groups, respectively (medians, P < 0.03). When surgery had started the corresponding values were\r\n34, 65 and 61 ml (P < 0.04). At 3 hours, averages of 9%, 20%, and 25% of the infused volume had been excreted in\r\nthe three groups (P < 0.01). The kinetic analyses indicated that both treatments slowed down the distribution of\r\nfluid from the plasma to the interstitial fluid space, thereby preventing hypovolemia.\r\nConclusions: Esmolol doubled and phenylephrine almost tripled urinary excretion during anesthesia-induced\r\ndepression of renal fluid clearance
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