Assessing accuracy of estimated dry weight in dialysis patients post transplantation: the kidney knows best

INTRODUCTION: Estimated dry weight is used to guide fluid removal during outpatient hemodialysis sessions. Errors in estimated dry weight can result in intradialytic hypotension and interdialytic fluid overload. The goal of this study was to assess the accuracy of estimated dry weight by comparing it to the two-week post-transplant weight in two cohorts of hemodialysis patients. METHODS: This observational, multi-center, retrospective cohort study included maintenance hemodialysis patients who underwent kidney transplantation at two medical centers in Massachusetts. The relationship between estimated dry weight pre-transplant and weight at week 2 post-transplant in patients with good allograft function (serum creatinine ≤ 1.5 mg/dL) was analyzed. Estimated dry weight was considered accurate if it was within ±2% of the week 2 post-transplant weight. RESULTS: Fifty seven patients with good allograft function were identified: mean age 54±14 years, 32 (58%) from deceased donors, 22 (38.6%) females. 38 were Caucasian (66.7%), 11 Hispanic (19.3%), 3 black (5.3%), and 5 others (8.8%). 2-week mean post transplantation serum creatinine was 1.2±0.2 mg/dL. Mean (SD) estimated dry weight was 71.4±15.9. Before transplantation, only 14 (24.6%) patients were within ±2% of the 2-week post-transplant weight; 23 (40.3%) were above and 20 (35.1%) were below. CONCLUSIONS: Our point of view, based on the assumption that the weight of patients with good allograft function at 2 weeks post-transplant approaches their accurate dry weight, is that a majority of maintenance hemodialysis patients (75.4%) are hypervolemic or hypovolemic prior to renal transplantation. This highlights the importance of finding novel tools to achieve euvolemia in patients undertaking dialysis. Timely feedback regarding achieved weight 2 weeks post-transplant to treating nephrologists and dialysis centers may be a starting point for assessing accuracy of dry weight.