Regarding the treatment of thyrotoxic crisis, which ONE of the following statementsis TRUE?
Answers: B: Beta-blockers (IV propranolol or esmolol) reduce cardiovascular effects by antagonizing effects of thyroid hormones, reducing sensitivity to catecholamines, and inhibiting peripheral conversion of T4 to T3 .
In thyrotoxic crisis, propylthiouracil is given to reduce the synthesis of new hormone in the thyroid gland. It also inhibits the peripheral conversion of T4 to T3 , but does not inhibit the release of stored hormone from the thyroid. At least 1 hour after PTU is given, iodine (e.g. Lugol’s iodine, potassium iodide) can be given to stop the release of stored hormone. It decreases iodide transport and oxidation in the follicular cells.
Glucocorticoids (hydrocortisone or dexamethasone) should be given to prevent the peripheral conversion of T4 to T3 , and also to manage the risk of relative adrenal insufficiency. Salicylates are contraindicated because they displace T4 peripherally, exacerbating the crisis.
References:
In a patient who presents to the ED with a high suspicion for having a thyroid storm, which ONE of the following conditions is LEAST likely to be considered in the differential diagnosis?
Answer: C: In a patient with previously diagnosed hyperthyroidism, thyroid storm is a clinical diagnosis. A patient presenting to the ED without this background diagnosis but with highly suspicious clinical features of thyroid storm should be given careful consideration for a number of important differential diagnoses. These include:
In acute salicylate overdose, the clinical features depend mainly on the dose of ingestion. The typical presentation is with tinnitus, hearing loss, sweating, nausea and vomiting and these occur with mild toxicity. In severe toxicity, altered level of consciousness, tachypnoea, hyperpyrexia and seizures may occur but the overall clinical picture may be different to thyroid storm.
Regarding elderly patients with clinical suspicion of myxoedema crisis (myxoedema coma), which ONE of the following statements is TRUE?
Answer: A: Myxoedema crisis is a clinical diagnosis and is precipitated mainly in elderly patients with previously untreated hypothyroidism. Precipitating conditions include underlying infection or sepsis, acute myocardial infarction, heart failure, cerebrovascular accident (CVA), seasonal exposure to cold environments, post-surgery or multi-trauma. Sedative and anaesthetic use may precipitate the condition as well. The main clinical features are due to reduced metabolic rate:
Up to 75% of patients with myxoedema crisis present with hypothermia, and if their temperature is normal, an underlying infection may be contributory to the normal temperature. Due to hypoventilation and respiratory failure, CO2 narcosis may occur. Due to fluid retention and oedema, hyponatraemia is a common finding.
Regarding ED management of a patient with myxoedema crisis (myxoedema coma), which ONE of the following is the LEAST appropriate management step?
Answer: D: Myxoedema coma is a severe manifestation of hypothyroidism, with all of the typical features of hypothyroidism plus those of a reduced metabolic rate. Patients are often elderly and frail, and may have associated comorbidities. For these reasons, the patient must be intensively monitored.
Supportive care includes:
These should be performed along with careful hormone replacement therapy. The treatment should be started after blood collection for thyroid function tests and serum cortisol levels and it should not be delayed until confirmation of the diagnosis. It has been suggested that active rewarming may provoke further cooling of core temperature due to an increased return of cool peripheral circulation. Due to peripheral vasodilatation active rewarming may cause hypotension. Rewarming should be carried out passively using blankets. Intravenous hydrocortisone is recommended because acute adrenal insufficiency is commonly associated with myxoedema crisis. This is especially important if the patient is hypotensive. A hypotensive patient in severe crisis may not respond to vasopressors without steroid support and thyroid hormone replacement. Thyroid hormone replacement can be initiated with intravenous T4 (levothyroxine) alone or a combination of T4 and T3 or T3 (liothyronine) alone.
In the management of an elderly patient with hypothyroidism, which ONE of the following statements is TRUE?
Answer: A: Rapid correction of thyroid hormone deficiency can precipitate cardiac arrhythmias and myocardial ischaemia due to a sudden increase in myocardial oxygen consumption. Therefore, in an elderly hypothyroid patient thyroid hormone replacement should be commenced with no more than half the recommended dose. T4 (levothyroxine) is given in a single daily dose, starting low (e.g. 25 mcg). T4 may be less prone than T3 to precipitate cardiac arrhythmias. It is reasonable to avoid T3 in elderly patients. When treating hypothyroidism it is not essential to initiate treatment intravenously and it is preferred to initiate via the oral route. However, in myxoedema crisis the oral absorption is often affected by gastric stasis and paralytic ileus, so intravenous hormone replacement should be continued until the patient is alert and able to tolerate oral therapy.
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