Objectives: To evaluate enhanced renal clearance over time in patients with aneurysmal subarachnoid hemorrhage or intracerebral hemorrhage via measured creatinine clearance and to compare measured creatinine clearance to creatinine clearance calculated by the Cockcroft-Gault equation and estimated glomerular filtration rate calculated by the Modification of Diet in Renal Diseases equation.
Design: Prospective, observational study.
Setting: Neurosciences ICU in a tertiary care academic medical center.
Patients: Study participants had an admission diagnosis of aneurysmal subarachnoid hemorrhage or intracerebral hemorrhage, an expected neurosciences ICU length of stay greater than 48 hours, no evidence of renal dysfunction (admission serum creatinine < 1.5 mg/dL), and no history of chronic kidney disease.
Interventions: Eight-hour urine collections to measure creatinine clearance were collected daily as the primary method of measuring renal function. Creatinine clearance was also calculated using the Cockcroft-Gault equation and estimated glomerular filtration rate was calculated using the Modification of Diet in Renal Disease equation. Enhanced renal clearance was defined as a measured creatinine clearance greater than the calculated creatinine clearance via Cockcroft-Gault and estimated glomerular filtration rate via Modification of Diet in Renal Disease. Augmented renal clearance was defined by a measured creatinine clearance greater than or equal to 130 mL/min/1.73 m. Relevant demographic, clinical, and outcome data were recorded.
Measurements and main results: Fifty aneurysmal subarachnoid hemorrhage patients and 30 intracerebral hemorrhage patients were enrolled, contributing 590 individual measurements. Patients with aneurysmal subarachnoid hemorrhage had a higher mean measured creatinine clearance compared with the mean calculated creatinine clearance based on the Cockcroft-Gault equation (147.9 ± 50.2 vs 109.1 ± 32.7 mL/min/1.73 m; p < 0.0001) and higher mean measured creatinine clearance compared with the mean calculated estimated glomerular filtration rate based on the Modification of Diet in Renal Disease equation (147.9 ± 50.2 vs 126.0 ± 41.9 mL/min/1.73 m; p = 0.04). Ninety-four percent of participants with aneurysmal subarachnoid hemorrhage experienced augmented renal clearance on at least 1 day. In patients with intracerebral hemorrhage, there was a higher mean measured creatinine clearance over the study period compared with the mean calculated creatinine clearance (119.5 ± 57.2 vs 77.8 ± 27.6 mL/min/1.73 m; p < 0.0001) and higher mean measured creatinine clearance compared with the mean calculated estimated glomerular filtration rate based on the Modification of Diet in Renal Disease equation (119.5 ± 57.2 vs 93.0.0 ± 32.8 mL/min/1.73 m; p = 0.02). Fifty percent of participants with intracerebral hemorrhage experienced augmented renal clearance on at least 1 day.
Conclusions: A substantial group of patients with aneurysmal subarachnoid hemorrhage or intracerebral hemorrhage experienced enhanced renal clearance, which may be otherwise unknown to clinicians. Enhanced renal clearance may lead to increased renal solute elimination over what is expected, resulting in subtherapeutic renally eliminated drug concentrations. This may result in underexposure to critical medications, leading to treatment failure and other medical complications.