Peritoneal vascular reserve characterization through nitroprusside-induced modification of peritoneal mass transfer coefficients.

The transport of solutes across the peritoneum may be increased by the topical administration of nitroprusside; the effects of the drug seem to be due to an increase in the number of perfused capillaries and/or in their permeability. We have compared the peritoneal mass transfer coefficients (MTC) for urea, creatinine and parathormone (PTH) under basal conditions and after administration of nitroprusside (4.5 mg/l dialysate) in 15 patients under CAPD therapy. The mean increments of the MTC were 48.8% for urea, 77.5% for creatinine and 323% for PTH. The relative MTC increments for the three molecules (taken in pairs) were: MTCPTH/urea' 2.53 times (mean), MTCPTH/creatinine' 1.7 times, and MTCcreatinine/urea' 0.73-times, with very variable ranges. The overall mean increment (OMI) for all three ratios ranged from -1.25 and +6 times. In six patients, some of the relative increments (and in three of them the OMI) were negative but the epidemiological features of these patients revealed no clear data. The OMI shows a direct correlation with the body surface area and an inverse correlation with the the duration of CAPD and ESRD and with the number of peritonitis episodes, albeit without statistical significance. We conclude that the peritoneal vascular reserve has individual characteristics, and that perhaps the OMI or some other similar index might serve to quantify and characterise it, if our findings are confirmed.