Hypophosphatemia

Hypophosphatemia is secondary to decreased intestinal absorption (such as in Vit D deficiency), increased urinary excretion (such as in hyperparathyroidism), or shift into the cells (such as in refeeding syndrome).

Symptomatic hypophosphatemia occur when serum phosphate concentration reaches 0.64 mmol/L. Worrisome symptoms of hypophosphatemia are related to ATP depletion, causing metabolic encephalopathy, impaired myocardial contractility, respiratory failure due to weakness of the diaphragm, a proximal myopathy, Rhabdomyolysis, dysphagia, ileus, and hematologic abnormalities.

Hypophosphatemia should be replaced aggressively even if the patient is not overtly symptomatic, since develop myopathy and weakness.

IV phosphate is potentially dangerous, since it can precipitate with calcium causing hypocalcemia, renal failure due to calcium phosphate precipitation in the kidneys, and possibly fatal arrhythmias. So, if IV therapy is necessary in the patient with severe symptomatic hypophosphatemia, it should be given by slow infusions (over a long period of 4-12hrs).