The underlying cause of SIADH, such as meningitis or pneumonia, should be treated when possible; successful treatment is usually accompanied by remission of inappropriate water retention TABLE 89.9 CRITERIA FOR DIAGNOSIS OF SYNDROME OF INAPPROPRIATE ANTIDIURETIC HORMONE SECRETION Hyponatremia, reduced serum osmolality Urine osmolality inappropriately elevated (a urine osmolality 18 mmol/L) Normal renal, adrenal, and thyroid function Absence of volume depletion (euvolemic to hypervolemic state) Asymptomatic or Mildly Symptomatic Children Asymptomatic or mildly symptomatic children are best treated by rigorous fluid restriction Fluid input should be sharply limited, often below insensible loss (to 800 cc/m2), until the [Na+ ] and osmolality begin to rise If the initial [Na+ ] is less than 125 mEq/L, all fluids must be withheld Frequent measurements of plasma electrolytes, glucose, and osmolality, as well as close monitoring of fluid input and output, are essential As the serum [Na+ ] rises and urine osmolality falls, the rate of fluid administration can be gradually increased The child with chronic or recurrent episodes of SIADH may require treatment with a drug in the “vaptan” class (tolvaptan, conivaptan), which blocks vasopressin binding to its receptor Pediatric dosing parameters have not yet been formally established Consultation with a pediatric endocrinologist should be conducted to guide dosing Clinical Indications for Discharge or Admission Admission is indicated for children who are symptomatic, or are newly diagnosed with hyponatremia, until a reassuring trajectory has been established HYPERPARATHYROIDISM Goal of Treatment The major ED treatment goal is to address clinical effects of severe hypercalcemia and hypophosphatemia while trying to correct these electrolytes CLINICAL PEARLS AND PITFALLS