APD: clinical measurement of the maximal acceptable intraperitoneal volume

In automated peritoneal dialysis (APD) patients treated with 3-L dwell, intraperitoneal volumes can easily be increased up to 4 or 4.5 L using hypertonic solutions without objective control of their good tolerance. In 20 adult patients treated with continuous ambulatory peritoneal dialysis (CAPD) in good conditions, hydrostatic intraperitoneal pressure (IPP) and pulmonary vital capacity (VC) were measured in strict supine position, after infusing isotonic dialysate in 0.5-L increments from 2 up to 5 L as tolerated, according to intraperitoneal volumes (IPV). None of the patients had cardiac or pulmonary dysfunction. IPP was measured following a routine method previously described. In all cases, experience was stopped when IPP increased over 20 cm H2O and/or VC decreased over 25%. IPV is linearly and positively correlated with IPP (p < 0.0001), and negatively with VC (p = 0.0012), but the reliability of VC is less than that of IPP, particularly in old patients. Clinical symptomatology of bad IPV tolerance never occurred alone and was always associated with an increase in IPP over 20 cmH2O and/or a decrease in VC over 25%. The maximal acceptable IPV is better defined by an IPP less than 18 cmH2O, according with a decrease in VC of less than 20%. Routine measurement of IPP can be used to determine maximal IPV and for optimal PD prescription.