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V = 70 kg × 0.6 L of water/kg of body mass = 42 L = 42,000 mL; Therefore: Kt/V = 1.23. This means that if you dialyze a patient to a Kt/V of 1.23, and measure the postdialysis and predialysis urea nitrogen levels in the blood, then calculate the URR, then −ln(1−URR) should be about 1.23.
Kt/V, like the URR, focuses on urea as the target solute, and is based on the assumption that removal of urea is from a single space – urea distribution volume, or similar in capacity to the total body water. The urea distribution volume , although traditionally thought of as 60% of body weight, may actually be closer to 50% of the body ...
Creatinine is the product of muscle creatine catabolism. Both are relatively small molecules (60 and 113 daltons, respectively) that distribute throughout total body water. In Europe, the whole urea molecule is assayed, whereas in the United States only the nitrogen component of urea (the blood or serum urea nitrogen, i.e., BUN or SUN) is measured.
The structure of the molecule of urea is O=C(−NH 2) 2.The urea molecule is planar when in a solid crystal because of sp 2 hybridization of the N orbitals. [8] [9] It is non-planar with C 2 symmetry when in the gas phase [10] or in aqueous solution, [9] with C–N–H and H–N–H bond angles that are intermediate between the trigonal planar angle of 120° and the tetrahedral angle of 109.5°.
Phenol in the Berthelot reagent can be replaced by a variety of phenolic reagents, the most common being sodium salicylate, which is significantly less toxic. [1] This has been used for blood urea nitrogen (BUN) determinations and commonly is used to determine water and soil total and ammonia-N. Replacement of phenol by 2-phenylphenol reduces interferences by a variety of soil and water ...
Clearance of a substance is sometimes expressed as the inverse of the time constant that describes its removal rate from the body divided by its volume of distribution (or total body water). In steady-state, it is defined as the mass generation rate of a substance (which equals the mass removal rate) divided by its concentration in the blood .
The glomerular filtration rate is the flow rate of filtered fluid through the kidney. The creatinine clearance rate (C Cr or CrCl) is the volume of blood plasma that is cleared of creatinine per unit time and is a useful measure for approximating the GFR. Creatinine clearance exceeds GFR due to creatinine secretion, [1] which can be blocked by ...
The above formula only applies for GFR calculation when it is equal to the clearance rate. The normal range of GFR, adjusted for body surface area , is 100–130 average 125 (mL/min)/(1.73 m 2 ) in men and 90–120 (mL/min)/(1.73 m 2 ) in women younger than the age of 40.