Standard Kt/V: comparison of calculation methods

Standard Kt/V (stdKt/V) makes possible the comparison of the dialytic efficiency of different therapies, with different frequencies, whether intermittent, continuous or a mixture of both. To determine stdKt/V, the clearance of urea, a function of urea generation and blood concentration, is calculated over a period of one week and is normalized to total body water. For continuous processes, clearance per se is used. For intermittent therapy, two different equations have been developed by Gotch and by Leypoldt. Both equations allow the calculation of stdKt/V from the single-pool Kt/V (spKt/V). Gotch's method requires spKt/V and six other variables. Leypoldt's equation is simpler and limited to spKt/V plus two variables. The present study compared the nomograms created from both equations to determine their equivalence. The nomograms were superimposed for comparison. It also compared the stdKt/V obtained from random simulated patients with each method and the theoretic efficiency of continuous and intermittent clearances. The graphic comparison of the numeric values obtained appeared very similar in both methods, suggesting that either can be useful in clinical practice. A significant theoretic advantage was noted for continuous therapies over intermittent modalities. These results further support the use of frequent, daily, and continuous renal replacement therapies.