Desired PTH, hypophosphatemia & low-normal calcium
Patient Scenario: Desired PTH, hypophosphatemia & low-normal calcium
Assessing the Clinical and Laboratory Parameters
A patient who falls into this category has optimal management based on current knowledge. It is important to note that patients values tend to vary from month to month particularly with serum phosphate. Therefore, ongoing counseling is indicated.
Less than 1% of all patients are in this category.
Dialysis Prescription
Dialysis Prescription
The calcium content of the dialysis bath could be raised. This would not be expected to affect phosphate control, but might result in suppression of PTH. The most frequent dialysate calcium is 1.25 mmol/L but this could be raised to 1.50 or even 1.75 mmol/L.
Correction of hypophosphatemia may also be attempted by adding phosphate to the dialysate. A common goal is 0.5 or 1.0 mmol/L of phosphate.
KDIGO Guideline 4.1.3 in patients with CKD stage 5D we suggest using a dialysate calcium concentration between 1.25 and 1.5 mmol/L (2.5 and 3.0 mEq/L)(2D).
Phosphate and Calcium Management
Phosphate and Calcium Management
Phosphate is low in this patient. Ongoing counseling about phosphate in the diet and the timing of binders with respect to meals is required. Chronically low phosphate levels have been associated with osteomalacia in dialysis patients. Some liberalization of the diet may be considered, but lowering binder therapy should allow the phosphate to rise. The dose of calcium containing phosphate binder in this patient needs to be reassessed given the hypophosphatemia. The dose of calcium binder would need to be decreased. This would be expected to allow the phosphate level to rise, but would also provide a stimulus for the PTH level to rise. If the calcium level is low, supplemental calcium could be given at a time away from the ingestion of meals.
Given this constellation of parameters, it is unlikely that this patient is receiving vitamin D sterols. However, introduction of vitamin D sterols, or an increase in the dose if the patient is, indeed, receiving them, should raise both the calcium and the phosphate. If the calcium is at the upper end of the normal range, than a reduction in the dose of calcium containing binder may be all that is required, but this could be coupled with the introduction of a vitamin D sterol. The introduction of a vitamin D sterol may reduce the PTH level, so close attention is required if the PTH is at the lower end of the target. In patients with low calcium and low phosphate, consideration should be given to measuring 25(OH)D levels which are frequently low in dialysis patients. Supplementation of 25(OH)D may raise both the calcium and the phosphate
PTH Management
PTH Management
Vitamin D sterols
The PTH is at target in this patient, and the low calcium and phosphate is a feature of some patients receiving calcimimetic therapy. Dietary liberalization may correct the hypophosphatemia if the calcium is normal, or a reduction in the dose of calcium-containing binder may help. If the calcium is low, the introduction of a vitamin D sterol may raise both the calcium and the phosphate and allow the dose of the calcimimetic to be reduced. There would be no indication to initiate calcimimetic therapy in this situation.
Other Options of Controversies in Management
Other Options of Controversies in Management
If malnutrition is a factor, diabetic counseling should be carried out. Intradialytic parenteral nutrition may be considered if patient is receiving at least 60% of his/her recommended daily caloric intake.
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