Prediction of glomerular filtration rate using aminoglycoside clearance in critically ill medical patients.
OBJECTIVE
The aim of this preliminary investigation was to evaluate the use of aminoglycoside serum concentrations as a surrogate measure of the glomerular filtration rate (GFR) in comparison with other measured and empiric methods against inulin, the criterion standard measure of GFR.


METHODS
A consecutive sample of all eligible patients.


METHODS
An eight-bed medical intensive care unit in a university-affiliated tertiary-care teaching hospital.


METHODS
Ten critically ill medical patients receiving gentamicin or tobramycin for presumed or documented gram-negative bacillary infection were enrolled in the study. The patients were mechanically ventilated and had underlying organ system dysfunction. All ten patients completed the study.


METHODS
Patients underwent renal functional assessment by measured inulin (Cl(in)) and 24-hour urinary creatinine clearance (Clcr). Aminoglycoside serum concentrations were used to estimate GFR and were compared with the two measured methods and a creatinine clearance calculated with the Cockcroft-Gault method (ClCG). All evaluations were performed the same day.


RESULTS
Cl(in) averaged 51.6 +/- 35.0 mL/min and serum creatinine ranged from 0.3 to 5.4 mg/dL (26.5 to 477.3 mumol/L). Steady-state peak and trough aminoglycoside concentrations were 6.1 +/- 1.4 and 1.3 +/- 0.9 micrograms/mL, respectively. There were no statistically significant differences between the various methods, although the aminoglycoside-calculated GFR (Cl(amg)) 95 percent confidence intervals were smaller than Clcr and ClCG compared with Cl(in). Mean absolute errors were smaller with Cl(amg) than with Clcr and ClCG. Regression results indicated that only Cl(amg) and ClCG demonstrated agreement with Cl(in) (lines not different from y = x). However, the Cl(amg) showed closer agreement, with a mean square error almost half that of ClCG (9.6 vs. 18.1).


CONCLUSIONS
Cl(amg) can be used routinely as an estimate of GFR in critically ill patients, with less error than empiric methods.
Zarowitz
B J
BJ
Department of Pharmacy Services, Henry Ford Hospital, Detroit, MI 48202.
Robert
S
S
Peterson
E L
EL
D000328:Adult; D000368:Aged; D000617:Aminoglycosides; D000900:Anti-Bacterial Agents / Q000493:pharmacokinetics*; D003404:Creatinine / Q000097:blood / Q000652:urine; D003422:Critical Care; D005260:Female; D005919:Glomerular Filtration Rate; D016905:Gram-Negative Bacterial Infections / Q000188:drug therapy; D006785:Hospitals, University; D006801:Humans; D007444:Inulin / Q000493:pharmacokinetics; D008297:Male; D008657:Metabolic Clearance Rate; D008875:Middle Aged; D011014:Pneumonia / Q000188:drug therapy; D011237:Predictive Value of Tests
D000617:Aminoglycosides; D000900:Anti-Bacterial Agents; D007444:Inulin; D003404:Creatinine