Introduction
============

Urine flow rate during cardiac surgery is frequently augmented with diuretics.  Recent evidence has shown that a *continuous* infusion of low dose furosemide - starting before cardiopulmonary bypass (CPB) - has detrimental effects on renal function \[[@B1]\].  It is not known, if this does also apply to a *single dose* of a diuretic. 

Methods
=======

We performed a study to determine the effects of a single dose of furosemide - given immediately before or during CPB - on urine flow (UV), fluid balance and the course of plasma creatinine as a crude measure of renal function in patients subjected to coronary artery bypass grafting (CABG) procedures with CPB.  Anesthesia charts from 1/01 to 3/01 were analysed retrospectively in alphabetical order until 24 patients had been selected that fulfilled the criteria: (a) isolated CABG procedure; (b) normal left ventricular function, and (c) no need for inotropes during surgery. 

Results
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Urine flow (UV), infused fluids and plasma creatinine values P~CREA~ (mean ± SEM) are given in Table [1](#T1){ref-type="table"}.  Three patients - all in the diuretics group - received transfusion of packed red cells.  Subgroup analysis excluding these patients revealed that relative P~CREA~ was significantly higher (*P* \< 0.05) after CPB in the diuretics group in comparison with control. 

                                                                             P~CREA~       
  --------------------------------------------- ----------- ---------------- ------------- ----------
  No diuretics (*n* = 12; control)                                                         
   Before CPB                                   1.5 ± 0.5   1458 ± 498       86 ± 12       100
   During CPB                                   7.1 ± 3.6                                  
   After CPB                                    5.7 ± 2.9   1333 ± 443       81 ± 13       95 ± 47
  Furosemide (*n* = 12), mean dose: 12 ± 9 mg                                              
   Before CPB                                   1.8 ± 1.1   1333 ± 325       74 ± 10^\*^   100
   During CPB                                   9.0 ± 5.2                                  
   After CPB                                    6.5 ± 2.5   1708 ± 541^\*^   76 ± 15       106 ± 17

^\*^*P* \< 0.05 vs control. 

Conclusions
===========

These retrospective data suggest that a single dose of furosemide during cardiac surgery does have no beneficial effects on the course of P~CREA~ and UV but conversely may lead to a greater need of fluids and to a trend to more blood transfusions and a deterioration of renal function.