Assessing the adequacy of dialysis

Abstract

A 59-year-old black man developed end-stage renal disease secondary to hypertension. Maintenance hemodialysis was initiated 9 years ago, and 3 years ago he received a cadaveric renal transplant. He experienced three rejection episodes over the following 6 months, but renal function stabilized at an adequate level. Two years ago, however, gradually worsening renal function was noted. Renal biopsy at that time showed moderately severe chronic rejection, and hemodialysis was reinstituted one month later. Because of moderate residual urine output (500—600 cc/day), he was dialyzed only 2 times weekly, 4 hours each time, at a blood flow of 200 mI/mm and dialysate flow of 500 mI/mm. Initially, the blood urea nitrogen (BUN) and serum creatinine were in the range of 62—75 mg/dl and 13—15 mg/dl, respectively; the hematocrit was stable at 25%. Over the next few months, the predialysis BUN (measured on a monthly basis) gradually rose to 90—100 mg/dl; the total CO2 decreased to 14 mM/liter, The hematocrit was approximately 20% and he required approximately two units of packed red blood cells per month to maintain this level. Kinetic modeling was performed 9 months ago. The KT/V was 0.78 (K = dialyzer clearance at the specified blood flow, T time on dialysis, V = volume of distribution of urea). The residual glomerular filtration rate was less than 2 mI/mm, and the 'time-averaged concentration of BUN (TACUI.) was 73 mg/dl. The protein catabolic rate was calculated to be 0.77 g/kg/day. Eight months ago, he complained of shortness of breath on exertion and developed paroxysmal nocturnal dyspnea; examination disclosed bilateral rales. His estimated dry weight was reduced by 2 kg during