Anesthesia and Hyperthryoidism
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Graves' disease
toxic multinodular goiter
thyroiditis
TSH-secreting pituitary tumor
functioning thyroid adenoma
overdose of thyroid replacement hormone
- weight loss
- heat intolerance
- muscle weakness
- diarrhea
- hyperactive reflexes
- nervousness
- Graves' disease: fine tremor, exophthalmos or goiter
- tachycardia, atrial fibrillation, congestive heart failure
- elevated serum total thyroxine, triiodothyronine and/or free thyroxine
- T4
- elevated in 90% of hyperthyoroid patients
- low in 85% of hypothyroid patients
- T3 elevation helps confirm hyperthyroidism
- T3 falsely low (decreased peripheral conversion from T4) in
- hepatic cirrhosis
- uremia
- malnutrition
- TSH
- elevation (plus low T4, T3) confirms primary hypothyroidism
- low TSH and T4 indicates secondary hypothyroidism
- thyroid scan shows normally functioning thyroid tissue
- ultrasound differentiates cystic from solid masses
- antibodies to thyroid components elevated in Hashimoto's thyroiditis
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Inhibit hormone synthesis (propylthiouracil, methimazole)
Prevent hormone release (potassium, sodium iodine)
Mask signs of adrenergic overactivity (propranolol)
Destroy thyroid cell function (radioactive iodine)
Anesthetic Considerations
Preoperative
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Postpone elective surgery until patient euthyroid
Normal thyroid function studies
Resting heart rate < 85
Continue antithyroid medications and beta-blockers through day of surgery
Emergency case: control hyperdynamic circulation with esmolol infusion
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Closely monitor
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Cardiovascular function
Temperature
Eyes (exophthalmos of Graves' disease)
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Elevation of head of bed 10-20 degrees
Armoured endotracheal tube passed beyond goiter
Thiopental good induction agent (antithyroid activity at high doses)
Beware chronic hypovolemia -> induction hypotension
Accelerated drug biotransformation
No change in MAC
Increased incidence of myopathies and myasthenia gravis
-
thyroid storm
- consider evaluating vocal cord movement immediately post extubation (e.g. fiberoptically)
- may require reintubation, re-exploration
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hyperpyrexia
tachycardia
agitation, delirium, coma
hypotension
may occur intraop, but usually 6-24 hours postop
treatment
-
hydration
cooling
beta-blockade
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esmolol infusion or
propranolol 0.5 mg increments until heart rate < 100
sodium iodide 1 Gm IV over 12 hours
correct any precipitating stimulus (e.g. infection)
cortisol 100-200 mg Q8H (possible coexisting adrenal gland suppression)
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recurrent laryngeal nerve palsy
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unilateral -> hoarseness
bilateral -> aphonia and stridor
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may cause airway compromise
Rx: open wound, evacuate clot
may require reintubation
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acute hypocalcemia within 24-72 hours