Although serum creatinine and urine output are usually easily measured, several limitations in their interpretation in patients suspected of having sepsis and AKI are worth emphasizing1.
First, there is an inherent lag of hours between a drop in glomerular filtration rate (GFR) and a rise in serum creatinine concentration. Second, in critically ill hypotensive patients with sepsis receiving aggressive fluid resuscitation, hemodilution may mask serum creatinine rise and delay the diagnosis of AKI by a day. Third, sepsis itself may reduce muscular production of creatinine, even in the absence of weight loss, as demonstrated in animal studies2. Fourth, patients receiving diuretics may fail to meet criteria for AKI diagnosis based on reduced urine output alone because of increased urine output.
Lastly, as renal function deteriorates, the half-life of serum creatinine increases from several hours to several days3, prolonging the time needed to achieve a new steady-state that may be more reflective of the concurrent GFR.
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References
- Godlin M, Murray P, Mehta. Clinical approach to the patient with AKI and sepsis. Semin Nephrol 2015;35:12-22.
- Doi K, Yuen PST, Eisner C, et al. Reduced production of creatinine limits its use as marker of kidney injury in sepsis. J Am Soc Nephrol 2009;20:1217-21.
- Chiou WL, Hsu FH. Pharmacokinetics of creatinine in man and its implications in the monitoring of renal function and in dosage regimen modifications in patients with renal insufficiency. J Clin Pharmacol. 1975; 15(5-6):427-34.
