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Relationship between fill volume, intraperitoneal pressure, body size, and subjective discomfort perception in CAPD
M de Jesús Ventura1, D Amato, R Correa-Rotter
1Unidad de Investigación Médica en Enfermedades Nefrológicas, Hospital de Especialidades, Mexico City, Mexico.
Objective:
To determine changes in intraperitoneal pressure (IPP) when dialysate fill volume is increased from 2.0 L to 2.5 L to 3.0 L per exchange, and to evaluate the relationship with subjective discomfort perception.
Design:
Cross-sectional survey.
Setting:
Seven Mexican hospital-based dialysis centers.
Patients:
Eighty-one adult patients on continuous ambulatory peritoneal dialysis (CAPD) without restriction criteria for age, gender, or time on dialysis, were studied. Patients seropositive for HIV or hepatitis B, and those with cancer or receiving immunosuppressive drugs were excluded. Participants were studied as outpatients.
Main Measures:
Blindly and in random order, 2.0-, 2.5-, and 3.0-L volumes of dialysate were infused consecutively. Body surface area (BSA) was calculated from patient height and weight. IPP was assessed with the patient lying supine, measuring the height of the dialysate column inside the peritoneal dialysis bag tubing. Blood pressure and subjective discomfort perception (using a visual analog scale of 0-100 mm) were also evaluated and registered after each of the three exchanges.
Results:
The IPP rose with each increase of dialysate volume and was higher in males than in females for each fill volume level. For males IPP was 18.9 +/- 6.9, 20.8 +/- 7.1, and 22.9 +/- 7.5 cm H2O; and for females it was 16.5 +/- 5.7, 18.4 +/- 5.5, and 19.7 +/- 6.2 cm H2O for 2.0-, 2.5-, and 3.0-L fill volumes respectively (p < 0.01 among fill volumes and between genders). Intraperitoneal pressure showed significant negative correlation with the fill volume corrected for patient body size as reflected by the dialysate volume/ BSA ratio (r= -0.393, p < 0.01; r= 0.319, p < 0.01; and r= -0.274, p < 0.02 for 2.0-, 2.5-, and 3.0-L fill volumes respectively). Discomfort score rose as fill volume rose, with a median of 0, 2.5, and 13.0 for 2.0-, 2.5-, and 3.0-L fill volumes respectively (p< 0.001). It is interesting, however, that with 2.5-L and 3.0-L dialysate infusion volumes, 64% and 44% of the patients, respectively, had no discomfort at all.
Conclusion:
Dialysate volume increase is associated with higher IPP, which is modulated by the gender and body size of the patients. Although the mean discomfort score was higher with larger dialysate volumes, there was no significant correlation between discomfort and IPP or the dialysate volume/BSA ratio. Many patients had no discomfort with 2.5-L or even with 3.0-L dialysate infusions; theoretically, they can be treated with larger volumes.