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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 ...
The net result of these 4 mechanisms of salt and water retention is decreased output and decreased urinary excretion of sodium (< 20mEq/L). The increased reabsorption of Na leads to increased water and urea reabsorption from the proximal tubules of the kidney back into the blood. In contrast, creatinine is actually secreted in the proximal tubule.
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.
Urea allows the kidneys to create hyperosmotic urine (urine that has more ions in it - is "more concentrated" - than that same person's blood plasma). Preventing the loss of water in this manner is important if the person's body must save water in order to maintain a suitable blood pressure or (more likely) in order to maintain a suitable ...
A simple means of estimating renal function is to measure pH, blood urea nitrogen, creatinine, and basic electrolytes (including sodium, potassium, chloride, and bicarbonate). As the kidney is the most important organ in controlling these values, any derangement in these values could suggest renal impairment.
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 .
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 ...