Do volatile anaesthetics depress urine output?

Abstract

Urine output is markedly reduced by isoflurane, but it is unclear whether the decrease is a specific effect of volatile anaesthetics. Therefore, this study compared the diuretic response to crystalloid volume loading during surgical procedures performed with volatile anaesthetics or intravenous anaesthesia. Data from two clinical trials in which patients were randomized between isoflurane and propofol anaesthesia (open thyroid surgery, n = 29) and between sevoflurane and propofol anaesthesia (open hysterectomy; n = 25) were analysed. Urine volume was measured and the diuretic response to volume loading with 1.7-1.8 L of Ringer's solution over 30 min was studied by population volume kinetic analysis. The kinetic method used 631 measurements of plasma dilution based on blood haemoglobin and plasma albumin and 138 measurements of urine output to quantify the diuretic response to volume loading in the four study groups. The urine output after 150 min of thyroid surgery was 132 (77-231) mL in the propofol group and 218 (80-394) mL in the isoflurane group ( P = 0.50; median and interquartile range). The corresponding volumes were 50 (45-65) mL for propofol and 60 (34-71) mL for sevoflurane at 90 min in the hysterectomy patients ( P = 0.81). The kinetic analysis, which corrected for differences in infused volume, body weight, and plasma volume expansion, did not reveal any statistically significant differences in diuretic response to volume loading between the two inhaled anaesthetics and intravenous anaesthesia. Isoflurane and sevoflurane did not affect urine output more strongly than propofol.