SAT-266 PHOSPHATE KINETICS IN TWICE PER WEEK HEMODIALYSIS SESSIONS IN INDIAN PATIENTS WITH ENDSTAGE RENAL DISEASE

Abstract

In patients with endstage renal disease, control of serum phosphorus levels is primarily achieved by a combination of oral phosphate binders and removal by hemodialysis. In India, a majority of patients receive twice per week hemodialysis and previous data on dietary phosphorus intake in Indian dialysis patients is lacking. This study examines phosphate kinetics during twice a week hemodialysis alongwith an assessment of dietary energy, protein and phosphorus intake in an Indian hemodialysis population. The study was conducted at a tertiary care teaching and referral hospital in northern India, and 28 consecutive stable patients (interim analysis of trial CTRI/2019/05/019383) on maintenance hemodialysis for more than 3 months were recruited by August 31, 2019. All the hemodialysis sessions were performed using F7 dialyzers on the Fresenius 4008S ARRT Plus machines (Fresenius Medical Care, Germany), with a dialysate flow rate of 500 ml/minute and a duration of 4 hours, on the first dialysis session of that week (the session preceded by a four day gap). Dietary energy, protein and phosphorus intakes were assessed using 2-day food diary and a validated food frequency questionnaire. Compliance and dosage of phosphate binder therapy was assessed by entries made in the patient-filled diary. Serum phosphorus levels were measured prior to and at hourly intervals till one hour after hemodialysis. Dialytic phosphorus removal was assessed by collection of spent dialysate by partial dialysate collection method. All the data were represented as medians with interquartile range and analysed using SPSS software (v16, IBM Corp, USA). Of the 28 patients, 20 were male, 6 were diabetic and equally from urban and rural areas. Nearly all the patients consumed diets with energy-adjusted phosphorus intake of > 1 g/day. Hyperphosphatemia (serum phosphorus levels were > 5.5 mg/dl) was seen in 32% and secondary hyperparathyroidism (iPTH > 500 pg/ml) was seen in 36% of the study population. Patients with hyperphosphatemia had higher body mass index, mid-arm circumference and dietary protein intake than those with normal serum phosphorus levels (p= 0.02,0.03,0.03 respectively)(Table 1). Hyperphosphatemia was associated with secondary hyperparathyroidism and higher intake of phosphate binders and calcitriol (p= 0.007, 0.01, 0.05, respectively). The median dialytic phosphorus removal during a single session of hemodialysis was 1116 mg/session in the group with hyperphosphatemia and 615 mg/session in those with serum phosphorus < 5.5 mg/dl (p=0.002). In patients with hyperphosphatemia, 76% of fall in serum phosphorus levels occurred in the first one hour of starting hemodialysis, whereas in patients with serum phosphorus<5.5 mg/dl, nearly 100% of fall to post-dialytic levels occurred within the first hour(p=0.002).View Large Image Figure ViewerDownload Hi-res image Download (PPT) Inspite of an overall high phosphorus intake, hyperphosphatemia and secondary hyperparathyroidism were seen in only upto one-third of the study population, possibly due to poorly absorbed vegetarian sources. Higher protein intake, still under 1.2 g/kg body weight contributed to hyperphosphatemia in this setting of twice per week dialysis. As a steep fall in serum phosphorus took place in the first hour, we postulate that increasing the frequency of dialysis would result in better control of serum phosphorus than increasing individual session length.