1 Parathyroid Gland Dysfunction Excela Health School of Anesthesia

2 Parathyroids

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

4 Hyperparathyroidism PTH level elevated Serum calcium levels may be increased, decreased, or unchanged Classified as primary, secondary, or ectopic

5 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

6 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

7 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)

8 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

9 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

10 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

11 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

12 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

13 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

14 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

15 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

16 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

17 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