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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 ...
So the ratio of K × t / V is a so-called "dimensionless ratio" and can be thought of as a multiple of the volume of plasma cleared of urea divided by the distribution volume of urea. When Kt/V = 1.0, a volume of blood equal to the distribution volume of urea has been completely cleared of urea.
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°.
The next line to the right (in light blue) shows the effects of urea generation during a typical 3-4 hour treatment. Urea generation during such a session results in a slightly lower URR (by about 0.10) than expected as a result of urea clearance, due to the fact that urea is being added to the body by generation during the dialysis session.
Solvent drag, also known as bulk transport, refers to solutes in the ultrafiltrate that are transported back from the renal tubule by the flow of water rather than specifically by ion pumps or other membrane transport proteins. [1] This is a phenomenon primarily in renal physiology, but it also occurs in gastrointestinal physiology.
Kt/V is a ratio of the pre- and post-dialysis urea concentrations. Standardized Kt/V is an equivalent clearance defined by the initial urea concentration (compare equation 8 and equation 10 ). Kt/V is defined as (see article on Kt/V for derivation):
Urea is usually excreted as a waste product from the kidneys. However, when plasma blood volume is low and ADH is released the aquaporins that are opened are also permeable to urea. This allows urea to leave the collecting duct into the medulla, creating a hyperosmotic solution that "attracts" water.
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 ...