Figure 20-9 Creatinine clearance: 2- versus 22-hour values. There is a close and significant correlation in creatinine clearance estimates from a 2-hour and 22-hour urine collection. CC02, 2-hour urine collection; CC22, 22-hour urine collection. (From Sladen RN, Endo E, Harrison T: Two-hour versus 22-hour creatinine clearance in critically ill patients. Anesthesiology 67:1013–1016, 1987.)