Measurement of glomerular filtration rate in ICU patients using 99mTc-DTPA and inulin

Improved and reliable methods for assessing glomerular filtration rate (GFR) in intensive care patients are needed in light of known deficiencies using creatinine clearance. We compared simultaneous two-hour clearances of inulin (CIn), creatinine (CCr), and 99mTc-diethylenetriaminepentaacetic acid (CDTPA) in 18 medical or surgical intensive care patients (range, 49 to 92 years old) with blood urea nitrogen (BUN) levels greater than 17.9 mmol/liter (0.5 mg/ml), serum creatinine levels greater than 150 mumol/liter (0.02 mg/ml), or estimated Cockcroft clearance less than 60 ml/min. Patients had severe renal dysfunction with average GFR of 35 ml/min (range, 2 to 69 ml/min). CDTPA and CCr correlated significantly with CIn, although CDTPA tended to provide a closer approximation. Cockcroft clearance (32 +/- 4 ml/min) was grossly similar to CDTPA and CIn and correlated significantly, especially when weight was calculated using actual as opposed to ideal body weight. In a subset of 13 patients with CIn less than 30 ml/min, only CDTPA was significantly correlated with CIn. In patients in the intensive care unit, CDTPA provides a rapid, accurate, and inexpensive clinical assessment of GFR, even at very low GFRs.