Pediatric emergency medicine trisk 475

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 <100 mOsm/kg usually
excludes the diagnosis)
Urinary Na+ concentration that is excessive in comparison to the degree of hyponatremia
(usually >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


Consider the diagnosis of hyperparathyroidism in a critically ill infant who presents
with hypercalcemia.
May present in adolescence with nonspecific symptoms including nausea and
constipation. The patient will have hypercalcemia.
Family history is important as hyperparathyroidism is associated with MEN I, II and
being an infant born to a mother with hypoparathyroidism.

Current Evidence
The parathyroid glands are derived from the third and fourth pharyngeal pouch and are usually
embedded in the posterior aspect of the thyroid gland. Occasionally, a gland may be found in
the anterior mediastinum. Parathyroid hormone (PTH) is the primary hormone produced by the
parathyroid glands. PTH is synthesized and released constitutively; its secretion is stimulated
by low, and suppressed by high, serum ionized calcium concentration. Prolonged
hypocalcemia, most commonly in the setting of renal failure, may lead to hypertrophy of the
parathyroid glands and secondary hyperparathyroidism. PTH acts on the kidney to decrease
the excretion of calcium, magnesium, and hydrogen, while increasing the excretion of
phosphate, sodium, and bicarbonate. Many of the effects are mediated by cyclic adenosine
monophosphate (cAMP), and an increased quantity of cAMP is present in the urine of patients
with hyperparathyroidism. PTH also increases the formation of 1,25-dihydroxyvitamin D in
the kidneys. PTH may increase intestinal absorption of calcium, although this effect is
primarily mediated by 1,25-(OH)2 D. Both PTH and 1,25-(OH)2 D affect bone mineralization.
PTH acts on bone to increase the release of calcium by increasing the number and activity of
the osteoclasts, whereas vitamin D decreases calcium use in bone formation by decreasing the
number of osteoblasts. The net effect of the actions of PTH and vitamin D is to increase serum
calcium by decreasing renal calcium excretion, decreasing new bone formation, increasing

bone resorption, and increasing intestinal absorption of calcium.

Clinical Considerations
Clinical Recognition
Hyperparathyroidism has two common presentations in children. The first presentation is the
critically ill infant who is found to have severe hypercalcemia during the course of diagnostic
investigations. The serum calcium level may be extremely high. The second presentation is a
child in the early- to mid-teens with nonspecific symptoms including nausea, constipation,
unexplained weight loss, personality changes, and headaches. Diffuse bone pain or renal colic
may be reported, although these symptoms are less common in children than in adults.
Triage
Consider hyperparathyroidism as a potential diagnosis in the critically ill neonate.
Initial Assessment/H&P
The physical findings of hypercalcemia are hypotonia, weakness, listlessness, anorexia,
constipation, and vomiting, and in the neonate, respiratory distress and apnea. There may be
hypertension, shortened QTc interval on ECG, polyuria (due to renal unresponsiveness to


ADH), and rarely, encephalopathy with seizures. A palpable mass may occasionally be located
in the parathyroid region. Certain characteristic features have been associated with idiopathic
hypercalcemia in infancy, including hypertelorism, broad forehead, epicanthal folds,
prominent upper lip, an underdeveloped nasal bridge, and a small mandible. Not surprisingly,
these same features have been noted in infants with hyperparathyroidism. A family history
may be helpful because hyperparathyroidism has been associated with both multiple endocrine
neoplasia types I and II, which are inherited as autosomal-dominant conditions.
Hyperparathyroidism may also occur in infants of hypoparathyroid mothers.
Management/Diagnostic Testing
Radiologic findings consistent with hyperparathyroidism include evidence of demineralization
and bone resorption ( Figs. 89.2 and 89.3 ). Osteitis fibrosa cystica, although highly suggestive
of the diagnosis, is unusual in children. Hypercalcemia is usually present but may be subtle or

intermittent in mild cases. The serum inorganic phosphate level is usually low but may be
normal, especially in patients with decreased renal function. Mild hyperchloremic acidosis
may be present. Alkaline phosphatase level and urinary hydroxyproline excretion may be
elevated secondary to increased osteoclast activity. Because PTH causes a significant increase
in cAMP in the kidney tubule, the presence of excess cAMP in the urine is strongly suggestive
of excess PTH production. The determination of PTH levels is critical for diagnostic purposes,
and elevated levels of PTH, when the patient is hypercalcemic, are a definitive laboratory
finding. Acute management of hyperparathyroidism is essentially the same as management of
hypercalcemia (see Chapter 100 Renal and Electrolyte Emergencies ). The specific
management of hyperparathyroidism depends on the level of calcium and on the presence of
signs and symptoms.
Clinical Indications for Discharge or Admission
In the asymptomatic patient with serum calcium of less than 12 mg/dL, careful follow-up with
close attention to both bone mass and renal function is recommended. Young infants with
feeding difficulty or irritability may need low calcium formula and diuretic therapy. If the
child is persistently hypercalcemic, parathyroid surgery is the preferred treatment. In the case
of hyperplasia, the common reason for hyperparathyroidism in the infant, subtotal
parathyroidectomy is indicated. If an adenoma is present, as is usually the case in the older
child, simple removal of the involved parathyroid gland is adequate.


FIGURE 89.2 Primary hyperparathyroidism in a 3-day-old girl. Roentgenogram of the chest shows profound
demineralization of the skeleton with loss of a well-defined cortical margin. Cystic changes in rib and
subperiosteal bone resorption in humerus are seen. (Courtesy of Soroosh Mahboubi, MD, The Children’s
Hospital of Philadelphia.)