Fahad Hawas

LONG-TERM INTRAVENOUS CALCITRIOL IN SECONDARY HYPERPARATHYROIDISM: THE ROLE OF TECHNETIUM-99M-MIBI SCINTIGRAPHY IN PREDICTING THE RESPONSE TO TREATMENT

Background: Despite the effectiveness of intravenous calcitriol in suppressing parathyroid hormone secretion in patients with uremic hyperparathyroidism, 50% of the patients remain refractory to this treatment. There are conflicting reports regarding the factors that can predict the response to treatment. Technetium-99m-MIBI scintigraphy was found to be correlated with functional activity of the parathyroid gland. Methods: We, retrospectively, evaluated 16 chronic hemodialysis patients, who were maintained on i.v. calcitriol for 36 months or longer, and who had MIBI scan either at the start of, or within the first 6 months of starting calcitriol. Nine patients had a positive uptake (+ve group), and 7 patients had a negative uptake (−ve group). All patients had an elevated iPTH (iPTH>300 pg/ml) at the start of treatment. Results: The percentage reduction of iPTH in the (−ve) and the (+ve) groups was 65% versus 45% at 12 months, and 65% versus 10% at 36 months respectively. In long-term follow-up of 36 months, all the patients in the (−ve) group responded to calcitriol; while 8 of the 9 patients (89%) in the (+ve) group didn’t respond. The difference in response between the 2 groups was statistically significant (p ≤ 0.001). Conclusion: We conclude that MIBI scan is a reliable technique in predicting the response to treatment with i.v. calcitriol in patients with secondary hyperparathyroidism.

A New Treatment forInterdialytic Hyperkalemia – The Use of Fosinopril Sodium

Fosinopril sodium is the first of the phosphinic acid class of angiotensin-converting enzyme inhibitors (ACEI). It is used as an antihypertensive agent, but differs from other ACEI in its dual routes of excretion (liver and kidney), and less incidence of hyperkalemia and cough. We conducted a study in known chronic hemodialysis patients who developed interdialytic hyperkalemia in spite of other treatments to control hyperkalemia. We used fosinopril in this group of patients to assess the effect of fosinopril on serum potassium (K) levels. Twenty-four patients were given fosinopril 10 mg at 18:00 h daily for 8 weeks. K levels were measured before and after each dialysis treatment. Interdialytic weight gains were recorded. The average pretrial potassium level was 6.57 mmol/l (± 0.47), and the posttrial level was 5.34 (± 0.76); p ≤ 0.0001. No statistically significant interdialytic weight gain or reduction occurred. No first dose hypertensive effect or cough were reported. We have found the use of fosinopril to be successful in lowering predialysis serum K levels in hyperkalemic dialysis patients.

Serum Parathyroid Hormone Suppression by Intravenous 1,25-Dihydroxyvitamin D3 in Patients on Maintenance Haemodialysis

Secondary hyperparathyroidism in patients with end-stage renal disease is characterised by elevated circulating levels of parathyroid hormone, due to inadequate synthesis of calcitriol, the active metabolite of vitamin D. Recent studies suggest that administration of calcitriol may directly suppress parathyroid (PTH) secretion independent of changes in serum calcium. We have studied the effect of intravenous calcitriol administration on the PTH level in 14 patients on maintenance haemodialysis with serum PTH levels above 2,000 pmol/l over a 16-week period. There was a significant reduction in the PTH level (65%) and a rise of serum calcium to the normal range. There was a significant reduction in serum PTH levels before the serum calcium concentrations increased, suggesting that calcitriol directly inhibits PTH release. In conclusion, intravenous treatment with calcitriol is of clinical importance, because it suppresses hypersecretion of PTH in uraemic patients, with minimal side effects.