Fluids, Electrolytes, Acid-Base Disorders, and Nutrition Support
iii.
Calcitonin 4 units/kg intramuscularly or subcutaneously every 12 hours; can be increased to
a maximum of 8 units/kg every 8 hours. Calcitonin inhibits bone reabsorption and promotes
the renal excretion of calcium by decreasing tubular reabsorption. The onset of action is rapid
(within hours); however, tachyphylaxis can occur because of down-regulation of calcitonin
limited to 24–72 hours. Calcitonin is most useful in patients with symptomatic hypercalcemia
in combination with rehydration.
iv.
Bisphosphonates.
| (a) | Pamidronate |
|---|---|
| (1) | 30 mg intravenously daily × 3 days if the cause is immobilization or chronic critical |
illness–associated metabolic bone disease
| (2) | 90 mg intravenously × 1 for other causes |
|---|---|
| (b) | Zoledronic acid is an option; however, evidence in chronic critical illness–associated |
metabolic bone disease is lacking.
| (c) | Onset of action for hypercalcemia is typically at least 48 hours. |
|---|---|
| (d) | Use caution in renal impairment. |
| (e) | Redosing bisphosphonates may be considered, but the frequency of such varies depending |
on etiology (Chest. 2000;118(3):761-766).
Denosumab is preferred in patients with bisphosphonate-refractory hypercalcemia or those
the degree of kidney impairment that warrants the use of denosumab over other options for
hypercalcemia is not clearly established. Further, the presence of kidney dysfunction increases
the risk of hypocalcemia from denosumab; therefore, a single dose of 60 mg or 0.3 mg/kg
subcutaneously may be used in patients with kidney disease or in bishphosphonate-naive
patients with moderate hypercalcemia. Otherwise, doses up to 120 mg once weekly for 3
weeks can be used. If the etiology of hypercalcemia persists, then 120 mg can continue to be
administered every 4 weeks starting 2 weeks after the initial 3 weekly doses.
vi.
Parathyroidectomy for patients with primary hyperparathyroidism. If surgery is not an
option, cinacalcet may be used for patients with severe, chronic hypercalcemia from
vii.
Prednisone 40 mg/day and greater for 10 days for patients with granulomatous diseases (e.g.,
sarcoidosis, tuberculosis)
viii.
Hemodialysis may be necessary for severe hypercalcemia (serum calcium greater than 3
mmol/L).
Disorders of Phosphorus Homeostasis
Phosphorus homeostasis overview
99% intracellular, of which 85% is bound to bone
Extracellular pool of phosphorus: Around 600 mg (about 20 mmol), 10% protein bound
Normal serum concentration: 2.5–4.5 mg/dL
| d. | Serum concentration can be influenced by parathyroid hormone (increased parathyroid hormone |
|---|
leads to increased urinary excretion of phosphorus), and alkalemia can decrease serum phosphorus
concentration.
Average daily requirement: Around 20 mg/kg/day
Kidney is primary route of elimination.
Definition: Serum phosphorus less than 2.5–3 mg/dL; severe hypophosphatemia less than
1 mg/dL