What Is Enough Dialysis?
The Kt/V is a popular equation that helps doctors define dialysis adequacy. It can be useful in patients on hemodialysis, home hemodialysis and PD. Residual kidney function can also be expressed in terms of Kt/V. Adequacy of kidney function is calculated by adding the weekly Kt/V determined by dialysis measurements and the Kt/V measured from blood and urine. This helps doctors assess the total minimum amount of dialysis and native kidney function necessary for an adequate treatment. The most recent guidelines from the International Society of Peritoneal Dialysis (ISPD), the National Kidney Foundation’s K/DOQI Workgroup, European Practice Guidelines (EPG) and Caring for Australians with Renal Impairment (CARI) have independently determined a Kt/V of 1.7 per week was equally effective as a Kt/V of 2.0. The rationale for this was a careful review of two
clinical trials comparing patients on both doses of therapy. Nevertheless, it is essential patients receive this minimum amount of therapy. If a patient is not doing well with a Kt/V of 1.7, the PD prescription should be increased.
Adequate PD is measured by how much of a patient’s body’s waste products carried in their blood are removed during one week. The amount of waste produced by the patient’s body depends on how active he/she is and how much protein he/she eats. Urea is a waste product of protein. How well it is removed indicates how well other waste products are being removed. Therefore, urea removal is used as a marker of adequate dialysis. Urea removal in PD is measured by calculating the weekly Kt/V, which shows how effective dialysis treatments are. (In hemodialysis Kt/V is calculated per
single treatment, rather than per week). The Kt (“K” stands for clearance and “t” stands for time) refers to the weekly clearance (removal) in liters of urea provided by the PD plus any remaining clearance of urea provided by the kidneys. This total urea clearance (Kt) in liters is divided by the volume (V) in liters of the total space taken up by water in the body. V, the total body water space, is calculated from a formula using height and weight. Currently, the desirable PD dose for patients is a total weekly Kt/V of 1.7 or more based upon several
clinical studies and guideline group recommendations.
Adequate dialysis treatments replace only a small part (less than 15 percent) of normal kidney function. If a patient does not get enough dialysis (i.e. being under-dialyzed or receiving inadequate dialysis), his/her body will retain waste products causing him/her to always feel tired and sick. Under-dialysis
may cause many of the following symptoms: weakness and tiredness, weight (muscle) loss, poor appetite, disturbed sleep, nausea and a bad taste in
your mouth. The patient may also be at a higher risk for infections and prolonged bleeding. Under-dialysis also places patients at risk for eliminating toxic minerals such as acid and electrolytes. Many under-dialyzed patients may overlook or deny these symptoms and may not experience the more severe
complications of uremia (infections, prolonged bleeding, vomiting, extreme loss of strength, inability to think clearly, etc.). In addition, continuing weight loss or failure to re-gain weight should cause serious worry. Failure to remove water weight during dialysis may mask true weight loss. The patient will know this is happening when his/her blood pressure seems to be higher than it used to be, he/she tire more easily when walking or climbing, he/she easily become short of breath, and he/she may get water in his/her lungs (pulmonary edema) as the water accumulates in the body. If a patient experiences any
of these symptoms, bring it to the attention of the doctor and dialysis staff. They will decide if any of the symptoms are due to inadequate dialysis or another illness. On the other hand, patients who are well dialyzed will experience a sense of feeling well, and can enjoy a good
appetite. A well dialyzed patient should be able to look ahead to doing many of the things which were planned before renal disease began.
http://www.aakp.org/brochures/pd-advisory/enough-dialysis/index.cfm