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<< Identifying And Treating Thyroid Storm And Myxedema Coma In The Emergency Department

Special Circumstances

Respiratory Failure

Airway assessment and protection comprise the basis of ED stabilization. Emergently intubate patients with respiratory failure, those unable to protect their own airway, and those for whom the predicted clinical course is poor.

Large goiters and a hyperdynamic state present special considerations in the patient with hyperthyroidism. Upper airway edema and a large anterior neck mass causing direct tracheal compression inhibit direct laryngoscopy and passage of the endotracheal tube.115-117 One literature review cites that approximately 80% of substernal goiters cause tracheal deviation and tracheal compression on preoperative radiographs.118

Once the patient has been successfully intubated, special considerations apply in managing the ventilator.58 Decreased ventilation has been written about but rarely studied in the patient with myxedema. One study of 17 patients with hypothyroidism on a ventilator concluded that the patients had depressed hypoxic ventilatory response. The study concluded that the hypercapnic ventilatory drive was not clinically significant.119 Be aware that hypothyroidism also affects the neuromuscular system, which results in direct diaphragmatic muscle weakness and delayed conduction velocity within the phrenic nerve and causes skeletal muscle atrophy.

Pediatrics

The majority of pediatric patients with hyperthyroidism have autoimmune thyroid disease; Graves' disease encompasses 95% of this patient population.120 The incidence of thyrotoxicosis ranges from 0.1 per 100,000 in young children to 3 per 100,000 in adolescents.120 The preponderance of patients is women, and incidence increases in relation to other autoimmune conditions. The diagnosis of hyperthyroid disease, unless discovered during neonatal screening, is typically delayed.121 Nontoxic prepubertal hyperthyroidism presents with long-standing complaints of weight loss and diarrhea. Pubertal children may present with irritability, heat intolerance, and neck swelling.122 Children are typically tall but not necessarily thin.123 Eye signs may be present in 25% to 63% of pediatric patients.124,125 Patients with known hyperthyroidism are typically on regimens similar to adults, beta-blockers for symptom control, and thioamides for thyroid hormone control.

Thyroid storm is rare in the pediatric population. As with thyroid storm in adults, precipitants include surgery, infection, radioiodine therapy, and nonadherence with antithyroid medications.126,127 Physical findings include fever, diaphoresis, widened pulse pressure, and hypertension. Tachycardia may progress to high-output cardiac failure. Management principles are the same: treat symptoms, resuscitate, diagnose, and manage precipitating factors.

Neonatal Hypothyroidism

In the preterm infant and in the fetus of similar gestational age, the thyroid axis is immature, resulting ultimately in a physiological hypothyroid state.85,89 T4 levels in the premature infant are low, correlating with gestational age and birth weight, whereas TSH and T3 levels are low to normal.85,90 The more premature the infant, the more pronounced is the hypothyroidism. Although the reasons for hypothyroidism are multifactorial, the loss of maternal T4 contribution, immaturity of the hypothalamicpituitary axis, responsiveness of the thyroid gland to TSH, and immaturity of peripheral tissue deiodination contribute significantly.85 Ultimately, the importance of the hypothyroid state lies in its relation to increased in-perinatal mortality and morbidity, prolonged supplemental oxygen demand, mechanical ventilation, longer hospital stay, and increased occurrence of intraventricular hemorrhage.91-94 Despite the serious short- and long-term morbidity and mortality related to neonatal hypothyroidism, the evidence to date does not support the routine use of supplemental thyroid hormone in this population.95-100 In the rare instance of a hypothyroid neonatal patient presenting to the ED, emergency clinicians should not be concerned with emergent intervention or diagnosis of hypothyroidism. It would not be feasible for this diagnosis to be made in the ED. The emergency clinician's responsibility is to provide supportive care for the neonate as indicated by presentation. Diagnosis and definitive treatment of neonatal hypothyroidism is the purview of the neonatal service.

Neonatal Thyrotoxicosis

Neonatal thyrotoxicosis presents rarely but carries a high mortality rate. Maternal severity of the disease directly relates to the occurrence of thyrotoxicosis in infants as well as infant morbidity and mortality due to thyrotoxicosis. In mothers with Graves' disease, the incidence of neonatal hyperthyroidism ranges from 1% to 12.5%. In women requiring treatment with antithyroid drugs to term, the incidence is as high as 22% of children affected.101-108 Mortality rates range from 12% to 20% in overt neonatal thyrotoxicosis. Mortality typically results from heart failure, tracheal compression, infectious complication, and thrombocytopenia.109-112 Clinical signs and symptoms of neonatal thyrotoxicosis are similar to those in adults and may present at birth or be delayed up to 10 days. The delay is related to the effects of maternal antithyroid drugs or the effect of coexistent blocking antibodies.113,114 Neonates typically present with goiter, irritability, exophthalmos, tachycardia, arrhythmias, hypertension, voracious appetite, weight loss, and diarrhea. The diagnosis in the ED is presumptive and based predominately on history of hyperthyroidism in the mother and physical examination findings in the infant.

Management goals in the thyrotoxic neonate are identical to goals in all other patients: symptomatic control and control of thyroid function. beta-blockers effectively control symptoms and inhibit deiodination of T4 to T3, as they do in adults. There are no studies comparing the efficacy of different beta-blockers in the neonatal population. Propranolol has been traditionally used in doses of 0.27 to 0.75 mg/kg orally every 8 h. There is a risk of hypoglycemia and cardiovascular collapse with bradycardia and hypotension. Intravenous dosing should be discussed with the neonatologist. The thioamides, PTU and carbimazole, block further thyroid synthesis and in the case of PTU, inhibit peripheral conversion of T4 to T3. Start PTU at 5 to 10 mg/kg/day orally divided q8 or methimazole at 0.4 to 0.7 mg/kg/day orally divided q8. Consider adding iodine solution, as there may be a delayed clinical response to the thioamides until intrinsic thyroid hormone stores are depleted. Also consider the use of prednisolone at a dose of 2 mg/ kg/day orally in the severely thyrotoxic neonate. Prednisolone suppresses deiodination of T4 to T3 and replaces endogenous glucocorticoids lost in the hypercatabolic state induced by T3 and T4.85 Sedatives may be necessary to manage irritability and restlessness. All critically ill patients require admission to an intensive care unit (ICU). Consult with a neonatologist or pediatric intensivist.

Pregnancy

Myxedema coma is exceedingly rare in the pregnant population. Hypothyroidism is generally related to low fertility rates and high rates of first trimester fetal loss. Fewer than 40 cases in the literature have been reported since 1897.129 Untreated hypothy roidism in pregnancy is related to a multitude of maternal and fetal complications, with a literature review showing 44% of pregnant women with untreated hypothyroidism progress to preeclampsia and increased incidence of placental abruption, fetal demise, and perinatal mortality.130

Symptoms and signs of hypothyroidism in pregnancy are similar to those of nonpregnant women. Management goals in the pregnant patient presenting in myxedema coma are similar to those in nonpregnant adults. Obstetric guidelines recommend aggressive replacement of thyroid hormone in hypothyroid pregnant women, regardless of the degree of thyroid function, to minimize the time the fetus is exposed to a hypothyroid environment.131 These recommendations are based on expert opinion.

Hyperthyroidism can be a challenging diagnosis in pregnant women. Low TSH levels with high FT4 levels is diagnostic of hyperthyroidism. However, approximately 15% of pregnant women who are euthyroid have a low TSH in the first trimester.132, 137

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Last Modified: 03/27/2017
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