Aminoglycoside clearance is a good estimate of creatinine clearance in intensive care unit patients.

The aim of this study was to determine whether creatinine clearance can be estimated as well by clearance of gentamicin/tobramycin as by routine, non-invasive estimates in the intensive care unit. The volume of distribution and clearance values for gentamicin/tobramycin were obtained using first order kinetics and an estimate of creatinine clearance derived. Seven estimates of renal function (Cockroft-Gault, MDRD4 and MDRD6 equations, two- and 24-hour urine estimates, two equations utilising Cystatin C concentrations) were compared to the gentamicin/tobramycin clearance estimate in 100 intensive care unit patients. The gentamicin clearance estimate was at least as reliable as other estimates. The two-hour was less reliable than the 24-hour urine estimate. The Cockroft-Gault appeared to out-perform the MDRD equation estimates. The MDRD4 was not as reliable as the MDRD6 estimate. Cystatin C estimates appeared not as reliable as the gentamicin estimate of renal function. The gentamicin/tobramycin estimate is at least as good as other estimates and it is available sooner than most others. It should be used in all patients who are prescribed gentamicin. The two-hour urine and MDRD4 estimates should not be used in the intensive care unit.