Management of myxedema coma and severe thyrotoxicosis in the intensive care unit

Abstract

Hypothyroidism and hyperthyroidism, generally benign conditions, may result in severe features leading to patient admission to the intensive care unit (ICU). Myxedema coma, generally related to the non-compliance with replacement therapy in a patient with chronic hypothyroidism, is characterized by coma associated with hypothermia, bradycardia, and respiratory failure. Thyroid hormone measurement allows the diagnosis. Protocols with rapid intravenous administration of high doses of thyroid hormones, together with warming and mechanical ventilation, have improved the prognosis which remains severe with 50% mortality rate. Nowadays, severe forms of thyrotoxicosis admitted to the ICU are more frequently amiodaroneassociated thyrotoxicosis (whose severity is related to the presence of underlying cardiac diseases) than classic thyroid storms. Treatment of thyroid storm with antithyroid drugs, corticoids, and beta-blockers is generally effective and allows avoiding the need for plasma exchange or emergency thyroidectomy. Prognosis of thyroid storm has improved but remains severe with 20% mortality rate. Diagnosis of the mechanism of amiodarone-induced thyrotoxicosis (type 1 versus type 2) is crucial for treatment. In type 1 (latent preexisting hyperthyroidism worsened by iodine excess), treatment is similar to the one proposed for thyroid storm; in type 2 (thyrotoxicosis related to amiodarone-induced destructive thyroditis), antithyroid drugs are ineffective and treatment relies on corticoids at high doses. However, in these cases, interruption of amiodarone may not be mandatory.