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Parathyroid Gland Dysfunction

Excela Health School of Anesthesia

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Parathyroids

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Parathyroid Hormone

Released into circulation by negative feedback PTH release stimulated by hypocalcemia PTH maintains normal serum calcium levels

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Hyperparathyroidism

PTH level elevated Serum calcium levels may be increased,

decreased, or unchanged Classified as primary, secondary, or ectopic

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Primary Hyperparathyroidism

Excessive secretion PTH from benign parathyroid adenoma, carcinoma of parathyroid, or hyperplasia of parathyroid glands

Benign adenoma responsible for 90% primary; carcinoma for 5%

Hyperplasia usually involves all 4 parathyroids

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Primary Hyperparathyroidism

Diagnosis:

~serum calcium >5.5 mEq/L & ionized calcium

concentration >2.5 mEq/L Measurement of serum parathyroid hormone

concentration is not always sufficiently reliable to confirm the diagnosis of primary hyperparathyroidism

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Primary Hyperparathyroidism

Signs & Symptoms:

~early: sedation, vomiting

~others: skeletal muscle weakness, hypotonia that may mimic myasthenia gravis

~persistent increases in plasma calcium concentration can interfere with urine concentrating ability with resulting polyuria

~Oliguric renal failure in advanced cases of hypercalcemia (see handout)

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Primary Hyperparathyroidism

Treatment: Initially by medical means followed by surgical removal of diseased area(s)

Medical: Saline infusion (150ml/hour) for pts. with symptomatic hypercalcemia

~Loop diuretics (furosemide 40-80mg IV q 2-4 hours

~Do not administer thiazide diuretics for hypercalcemia

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Primary Hyperparathyroidism

Medical Treatment for Life Threatening Hypercalcemia: Use of Bisphosphonates such as disodium etidronate

~binds to hydroxyapetite and acts as potent inhibitor of osteoclastic bone reabsorption

~Hemodialysis can also be considered

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Primary Hyperparathyroidism

Surgical Management: Normalization of serum calcium levels within 3-4 days

~postoperative: potential complication is hypocalcemic tetany

~a hypomagnesemia may occur postop that will aggravate the hypocalcemia and may render it refractory to treatment

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Primary Hyperparathyroidism

Anesthetic Management: No specific drugs or techniques

~Maintain hydration and urinary output

~If somnolent preop anesthestic requirements decreased

~If coexisting renal dysfunction use of sevoflurane is questionable

~Careful use of muscle relaxants and monitoring

~Careful positioning

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Secondary Hyperparathyroidism

A disease process produces hypocalcemia and parathyroids compensate by secreting more parathyroid hormone (ex. Chronic renal disease)

Since secondary hyperparathyroidism is adaptive, rather than autonomous, it seldom produces hypercalcemia

Treatment: Treat underlying disease

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Ectopic Hyperparathyroidism

Due to secretion of parathyroid hormone by tissues other than the parathyroid glands

(ex. Humoral hpercalcemia of malignancy, cancer of lung, breast, pancreas, kidney)

Likely to be associated with anemia

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Hypoparathyroidism

PTH absent or deficient, or peripheral tissues are resistant to the effects of PTH

Absence or deficiency of PTH almost always iatrogenic (inadvertent removal)

Diagnosis: Measurement of serum calcium concentrations and the ionized fractions of calcium is best indicator

Signs & Symptoms: Depend of the rapidity of the onset of hypocalcemia

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Acute Hypocalcemia

Can occur after accidental removal Likely to manifest as perioral paresthesias,

restlessness, neuromuscular irritability, as evidenced by a positive Chvostek’s sign or Trousseau’s sign

Treatment: Infusion of calcium (10 ml of 10% calcium gluconate IV) until signs of neuromuscular irritability disapper

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Chronic Hypocalcemia

Associated with complaints of fatigue and skeletal muscle cramps

Prolonged QT Neurological: lethargy, cerebration deficits,

personality changes CRF is most common cause of chronic

hypocalcemia

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Anesthesia Management

Management of anesthesia in presence of hypocalcemia is designed to treat any further decreases in serum calcium and to treat adverse effects of hypocalcemia on the heart; so… ~avoid iatrogenic hyperventilation

~rapid infusions of blood (500 ml q 5-10 min) as during CPB or liver transplantation can decrease ionized calcium concentration

~when metabolism or elimination of citrate is impaired as with hypothermia, cirrhosis, renal dysfunction