Figure 415

Diagnosis of early ultrafiltration failure. The dialysate to plasma ratio (D/P) curve of sodium, during the unabridged peritoneal equilibrium test (2.5% dextrose dialysis solution), typically shows an initial decrease owing to the high ultrafiltration rate. Because of sodium sieving, the ultrafiltrate is low in sodium. Consequently, the dialysate sodium is lowered, resulting in a lower D/P ratio of sodium. Later, during the dwell when ultrafiltration ceases, dialysate sodium tends to equilibrate with that of capillary blood, returning the D/P ratio of sodium to baseline. Absence of the initial decrease of the D/P of sodium is an indication of ultrafiltration failure and is typically seen in the early phase of sclerosing encapsulating peritonitis. (From Dobbie and coworkers [17]; with permission.)

where C = clearance in mL/min:

DxV = dialysate solute removed per minute; D = dialysate solute concentration; V = volume of dialysate in mL/min; and P = plasma solute concentration or

clearance in mL/exchange at time t; solute equilibrium rate at time t; and volume of dialysate at time t where C = D/P =

Kt/V

where K = urea clearance in mL/min; t = minutes of therapy; and V = volume of urea distribution or total body water

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