Measuring transport of water across the peritoneal membrane

Measuring transport of water across the peritoneal membrane.IntroductionMechanisms of water flow across the peritoneal membrane include diffusion, convection, and reabsorption.Objectves. To understand these processes more clearly we have developed a method to measure transport of water across the peritoneal membrane.MethodsAn artificial gradient of deuterated water (HDO) between blood and dialysate compartments was created in five subjects who took 0.3g per kg of body weight of D2O, which was allowed to equilibrate with total body water. During a test dwell (2L, bicarbonate:lactate buffer, 1.36% glucose to minimize convection), frequent dialysate samples were drawn to determine the abundance of deuterium and other solutes and to calculate their time constants. Dialysate deuterium abundance was measured using flowing afterglow mass spectrometry (FA-MS). The method was combined with 125iodine-labeled albumin (RISA) to enable simultaneous estimates of intraperitoneal volume and thus calculation of the mass transfer area coefficient (MTAC) for small solutes using the Garred equation.ResultsThe appearance of HDO in dialysate in four subjects is described by a single exponential fit with residuals of