Tachycardia from hyperthyroidism

Epinephrine usually Is administered slowly by Intravenous (IV) Injection to relieve acute asthmatic attacks not controlled by other treatments. Intravenous Injection produces an Immediate response. Use of EPI with drugs that enhance cardiac arrhythmias (digitalis or quinidine) Is not recommended. Tricyclic antidepressants and MAO Inhibitors will potentiate the effects of EPI on the heart. Epinephrine should be used with caution In Individuals suffering from hyperthyroidism, cardiovascular disease, hypertension, or diabetes. Adverse effects Include palpitations, tachycardia, sweating, nausea and vomiting, respiratory difficulty, dizziness, tremor, apprehension, and anxiety. 

The answer is d. (Hardman, p 1401.) In patients who are suspected of having hyperthyroidism, propranolol can be administered to provide temporary relief of the peripheral manifestations of the disease while the patient is further evaluated. Propranolol suppresses adrenergic symptoms such as tremors and tachycardia it has no effect on the release of thyroid hormones from the gland. 

Excessive catecholamine action is an important aspect of the pathophysiology of hyperthyroidism, especially in relation to the heart (see Chapter 38). The 13 antagonists are beneficial in this condition. The effects presumably relate to blockade of adrenoceptors and perhaps in part to the inhibition of peripheral conversion of thyroxine to triiodothyronine. The latter action may vary from one 13 antagonist to another. Propranolol has been used extensively in patients with thyroid storm (severe hyperthyroidism) it is used cautiously in patients with this condition to control supraventricular tachycardias that often precipitate heart failure. 

---