How to manage hypophosphatemia in patients undergoing dialysis?

From the Guidelines

Managing hypophosphatemia in patients undergoing dialysis requires increasing dialysis time, specifically more than 24 hours per week, distributed over at least 3 treatments per week, to effectively control phosphorus levels. This approach is supported by the Tassin experience, where patients receiving 8 hours of dialysis per week, 3 times a week, showed improved phosphorus control, with approximately one third of patients no longer requiring phosphate binders 1.

To manage hypophosphatemia, the following steps can be taken:

• Identify the cause of low phosphate levels, which may include inadequate dietary intake, intradialytic phosphate removal, or use of phosphate binders
• Provide phosphate supplementation, typically with oral phosphate salts such as potassium phosphate or sodium phosphate at doses of 250-500 mg elemental phosphorus 2-3 times daily, adjusted based on serum phosphate levels
• For severe hypophosphatemia (< 1.0 mg/dL) or in patients unable to take oral supplements, consider intravenous phosphate at 0.08-0.16 mmol/kg over 4-6 hours, with close monitoring
• Encourage phosphate-rich foods like dairy products, nuts, and whole grains through dietary counseling
• Temporarily reduce or discontinue phosphate binders
• Regularly monitor serum phosphate levels, aiming for a target range of 3.5-5.5 mg/dL
• Time phosphate supplements after dialysis sessions, as dialysis removes phosphate, to prevent recurrence by balancing dietary intake, medication adjustments, and dialysis parameters 1.

It is essential to note that increasing dialysis time, as mentioned earlier, can effectively control phosphorus levels and may eliminate the need for phosphate binders in some patients, thereby reducing the risk of hypophosphatemia 1.

From the FDA Drug Label

The ability of sevelamer hydrochloride to lower serum phosphorus in CKD patients on dialysis was demonstrated in six clinical trials: one double-blind placebo-controlled 2-week study (sevelamer hydrochloride N=24); two open-label uncontrolled 8-week studies (sevelamer hydrochloride N=220) and three active-controlled open-label studies with treatment durations of 8 to 52 weeks (sevelamer hydrochloride N=256). Eighty-four CKD patients on hemodialysis who were hyperphosphatemic (serum phosphorus >6 mg/dL) following a two-week phosphate binder washout period received sevelamer hydrochloride and active-control for eight weeks each in random order. Both treatments significantly decreased mean serum phosphorus by about 2 mg/dL

To manage hypophosphatemia in patients undergoing dialysis, the use of sevelamer hydrochloride is not the answer as it is used to lower serum phosphorus in CKD patients on dialysis, which is the opposite of what is needed for hypophosphatemia.

• Key points:
  • Sevelamer hydrochloride is used to treat hyperphosphatemia, not hypophosphatemia.
  • The drug label does not provide information on managing hypophosphatemia.
  • Therefore, sevelamer hydrochloride is not the appropriate treatment for hypophosphatemia in dialysis patients. 2

From the Research

Managing Hypophosphatemia in Dialysis Patients

• Hypophosphatemia is a condition that can occur in patients undergoing dialysis, and it is essential to manage it properly to prevent complications 3.
• The management of hypophosphatemia in dialysis patients involves a combination of dietary changes, phosphate binders, and dialysis techniques 4, 5.
• Dietary changes include restricting phosphate intake, choosing foods with a low phosphate-to-protein ratio, and preferring boiling as a cooking method to reduce phosphate content 4.
• Phosphate binders are used to reduce phosphate absorption in the gut, but their efficacy is limited, and dietary restriction is necessary to achieve optimal phosphate control 4, 5.
• Dialysis techniques, such as mixed diffusive-convective hemodialysis, can enhance phosphate removal, but dialytic removal does not equal the high phosphate intake linked to high dietary protein requirements 4.

Causes of Hypophosphatemia in Dialysis Patients

• Low-protein diet and alcoholism can cause hypophosphatemia in dialysis patients 3.
• Decreased dietary intake due to non-digestive problems or digestive problems, plus antacids, phosphate binders, and dietary phosphorus restriction, can also lead to hypophosphatemia 3.
• Secondary hyperparathyroidism can be a cause of hypophosphatemia in some patients 3.

Treatment of Hypophosphatemia in Dialysis Patients

• Treatment of hypophosphatemia involves oral supplementation with diet and changes in oral calcium salts 3.
• Intravenous supplementation may be required in acute cases to raise serum phosphate levels 3.
• Vitamin D supplementation may be necessary in patients with low vitamin D concentrations 3.

Adherence to Phosphate-Control Strategies

• Adherence to phosphate-control strategies, including phosphate binder medication, low-phosphorus diet, and dialysis, is crucial for managing hyperphosphatemia in dialysis patients 5.
• Patient, provider, and phosphorus-control strategy-related factors can influence adherence rates, which are often suboptimal 5.
• Multicomponent strategies that address therapy-related factors, patient factors, and provider factors may improve adherence and long-term control of phosphorus levels 5.