Rapid decline of serum creatinine and a challenge of aminoglycoside dosing: a case of post bilateral lung transplantation cystic fibrosis patient
Abstrakt
Serum or plasma creatinine level determination has been serving for decades as the most commonly used marker of renal function. However, creatinine levels are affected by a number of other factors not related to renal function, particularly age, gender, muscle mass, starvation, wasting diseases, post surgical states, and activity or exertion.
Alternatives for the assessment of renal function or glomerular filtration rate (GFR), through measurement of the clearance of exogenous substances like, inulin, 51Cr- ethylendiaminotetraacetate (51Cr-EDTA), 99mTc- diethylenetriaminepentaacetic acid or iohexol are more accurate, but too complex, laborious, and not suitable for routine clinical use. Therefore, serum creatinine measurement yet remains the most common method to estimate renal function in routine clinical practice.
In the presented case study, nearly 50% decline in serum creatinine level as measured by enzymatic colorimetry method according to the manufacture's recommendation is described. Relatively rapid serum creatinine concentration decline from 67 μ/L baseline value to 30 μmol/L within 4 days in a CF patient post bilateral lung transplantation, who, was on courses of essential immunosuppressive, antimycotic, and antibacterial drugs including an aminoglycoside (amikacin) was observed.
The change in serum creatinine level within four consecutive days after bilateral lung transplantation (mean difference, -49.25 % μmol/L; with 95% confidence interval, -29 to -37 μmol/L) was significant. Herein, the event is not essentially reflecting better renal function, since amikacin trough level was unacceptably high (20 mg/L) at the same time, rather explaining probably low production of creatinine as a result of underlying pathology in cystic fibrosis.
Patient related explanations and existing methodological challenges have also been discussed.