A “triple threat” of low dialytic removal of phosphate, high intestinal absorption, and low binder efficacy can make phosphate control challenging for some hemodialysis (HD) patients with hyperphosphatemia, according to a new editorial published in the American Journal of Kidney Diseases.
Richard A. Sherman, MD, of Rutgers Robert Wood Johnson Medical School in New Brunswick, NJ, suggested these factors may be responsible for individual variation in phosphate balance. Non-adherence to dietary changes and treatment regimens is not always to blame.
A single dialysis session is believed to remove 800 to 1,000 mg of phosphate, but differences do exist, he explained. Plasma refilling from intracellular phosphate stores varies by patient. A patient’s pre-dialysis serum phosphate levels also influences results. For those with lower dialytic removal of phosphate, binding requirements may be higher than estimated.
With regard to diet, enteral absorption of phosphate from foods can vary. Although a 60% rate of absorption is often cited, it is only an average; the actual range appears wide. Paradoxically, a low phosphate diet and activated vitamin D also may end up increasing phosphate absorption in some patients.
Phosphate binder efficacy likewise differs by patient. For some, even high doses of the medication may be insufficient to control hyperphosphatemia.
“There is every reason to believe that many or most patients with controlled phosphate levels are simply luckier than their fellow hyperphosphatemic patients as a result of having more rapid dialytic phosphate flux, less baseline enteral absorption, and/or better binder efficacy,” Dr. Sherman stated.
Clinicians also need to consider other factors such as residual kidney function and inorganic phosphate in food additives and prescription medications.
A “flexible sequential approach to treatment may result in greater success than more traditional approaches,” Dr. Sherman concluded.