The standard peritoneal permeability analysis in the rabbit: a longitudinal model for peritoneal dialysis

The development of an experimental peritoneal dialysis (PD) model in rabbits to investigate peritoneal transport characteristics during a longitudinal follow-up and to assess normal values of these peritoneal transport parameters.

Peritoneal transport parameters were determined in conscious, unrestrained rabbits by standard peritoneal permeability analysis adjusted for rabbits (SPAR). In this test a 1-hour dwell with 3.86% glucose dialysate is used. Dextran 70 (1g/L) was added to the dialysate to allow calculation of fluid kinetics. Dialysate samples were taken before, 10, and 40 minutes after instillation and at the end of the dwell. Blood was drawn at the end of the dwell.

Eighteen female New Zealand White rabbits (2565 g) were included for catheter implantation. SPARs were performed in 15 animals; the other 3 were excluded due to complications.

The mass transfer area coefficients (MTACs) of the low molecular weight solutes urea (MTAC(urea)) and creatinine (MTACcr) were calculated. The clearances of albumin (CIalb) and IgG (CI(IgG)), glucose absorption, and fluid transport were computed. Coefficients of intraindividual variation (Vc) were calculated for these parameters.

The main complications were catheter obstruction and/or dislocation. Five rabbits underwent uncomplicated PD during a 4-week period. Fifteen SPARs in 15 stable rabbits were performed and analyzed to obtain normal values. Means and standard deviations of the transport parameters were as follows: MTAC(urea) 2.24+/-0.57 mL/min, MTACcr 1.61+/-0.30 mU/min, CI(alb) 52.9+/-17.2 microL/min, CI(IgG) 44.5+/-22.9 UL/min. The transcapillary ultrafiltration rate was 0.66+/-0.13 mL/min and the lymphatic absorption rate 0.47+/-0.26 mL/min. The parameters of solute transport were upscaled to those in humans using two different methods. MTACs of low molecular weight solutes in rabbits and patients were of the same order of magnitude, but the clearance of albumin was approximately four times higher in rabbits than in patients, and that of IgG eight times. In all rabbits sieving of sodium was observed. The dialysate/plasma (D/P) of sodium decreased to a minimum at 40 min (p<0.003 vs the initial value), followed by a rise to 60 min. The minimal value was 0.884+/-0.002. The coefficients of variation calculated on 7 rabbits that underwent two or more SPARs were similar to those assessed from the patient data. This indicates stability of the model and reproducibility of the SPAR.

The conscious rabbit model for PD can be used for repeated studies on peritoneal transport.