Case Report

Severe angioedema in Myxedema coma: a difficult airway in a rare Endocrine emergency

Abstract

Myxedema coma is the most lethal manifestation of hypothyroidism. It is a true medical emergency and can result in profound hemodynamic instability and airway compromise. Myxedema coma currently remains a diag- nostic challenge due to the rarity of cases seen today, and failure to promptly initiate therapy with replacement thyroid hormone can be fatal. As thyroid hormone therapy can take days or weeks to reverse the manifestations of myxedema coma, interim supportive therapy is critical while awaiting clinical improvement. Some patients will require endotra- cheal intubation in the emergency department (ED), and physicians should be aware that unanticipated posterior pharyngeal edema in myxedema coma could severely complicate airway management. Although mechanical ventilation is a well-described adjunctive therapy for myxedema coma, reports of the potential difficulty in securing a definitive airway in these patients are rare. We describe a case of an unidentified woman who presented to the ED with myxedema coma requiring urgent endotracheal intubation and was found to have extensive posterior pharyngeal angioedema inconsistent with her relatively benign external examination. This case highlights the typical features of myxedema coma and discusses our necessity for a Rescue device in definitive endotracheal tube placement. Emergency physicians should anticipate a potentially difficult airway in all myxedema coma patients regardless of the degree of external facial edema present.

A 55-year-old woman presented to the emergency depart- ment (ED) for altered mental status. The patient stated that she was “weak” but was unable to provide further details. On examination, the patient appeared disheveled without external signs of trauma. Vital signs were as follows: blood pressure, 100/63; heart rate, 40/min; respirations, 12/min; temperature,

34.4?C (rectal); and oxygen saturation, 100% on room air. Her examination was notable for mild bilateral periorbital edema, dry mucous membranes, and delayed deep tendon reflexes. She was Neurologically intact other than global amnesia.

Passive rewarming was initiated. An electrocardiogram showed Sinus bradycardia. A chest x-ray and noncontrast head computed tomography were unremarkable. thyroid function tests confirmed our diagnosis of myxedema coma as follows: thyroid-stimulating hormone, 49.5 uU/mL; total thyroxine (T4), 1.2 ng/dL; and free thyroxine, 0.2 ng/dL.

In the ED, the patient became increasingly agitated and confused. An arterial blood gas showed respiratory acidosis, and concerns for airway protection prompted rapid sequence intubation. Upon laryngoscopy, a significant amount of posterior pharyngeal edema obscured direct visualization of the vocal cords. endotracheal tube placement was unsuc- cessful on several attempts necessitating periodic oxygena- tion with bag-valve-mask ventilation and administration of atropine. After several failed intubation attempts, a bougie catheter was used as a rescue device. Once the catheter was inserted through her vocal cords, a 6.0-mm endotracheal tube was successfully placed with Seldinger technique. A bedside echocardiogram did not reveal signs of cardiac tamponade, although a moderate pericardial effusion was present. rewarming techniques were continued, and broad-spectrum antibiotics were empirically initiated.

We administered 300 ug of levothyroxine, 100 ug of thyroxine (T4), 20 ug of triiodothyronine (T3), and 100 mg of hydrocortisone. Our patient ultimately did well and was successfully extubated on hospital day 3. There were no postextubation airway difficulties or complications, and her amnesia completely resolved. The patient’s family and primary care physician were contacted, and she was discharged home on hospital day 7 with daily levothyroxine. Myxedema coma is a life-threatening condition man- ifesting as the most lethal form of hypothyroidism. It is a true medical emergency, and documented mortality rates have widely ranged from 20% to 60% [1,2]. This condition is rarely seen today due to improved outpatient treatment of hypothyroidism. However, given its high mortality and potential for airway compromise, myxedema coma should be readily recognized for prompt initiation

of treatment.

Myxedema coma occurs in patients with long-standing hypothyroidism and is most commonly seen in women older than 60 years during the winter [3]. The acute decompensa- tion seen in myxedema coma is typically precipitated by

0735-6757/$ – see front matter (C) 2009

1021.e2 Case Report

environmental cold exposure, infection, or medications such as amiodarone and lithium [4,5].

Clinical findings include altered mental status, hypother- mia, hypotension, bradycardia, nonPitting edema, and delayed deep tendon reflexes. electrocardiographic findings include sinus bradycardia and QT prolongation. Pericardial effusions can also occur. The most specific laboratory test for myxedema coma is an elevated thyroid-stimulating hor- mone, as well as decreased total and free T4 and T3.

Thyroid hormone replacement is the definitive treatment of myxedema coma. However, controversy exists regarding the administration, dosage, and frequency of therapy [6-12]. Many endocrinologists prefer to administer T4 at 200 to 500 ug as an initial bolus, followed by 50 to 100 ug daily [13]. Some endocrinologists advocate adding T3 (10-25 ug every 8 hours). Caution should be used in rapid thyroid replacement, as increased levels of levothyroxine can precipitate myocardial infarction.

Thyroid hormone replacement therapy can take days, if not weeks, to improve a patient’s clinical status [14]. Therefore, supportive treatment is critical to optimize a patient’s survival. Airway is always paramount. The relatively mild degree of periorbital edema in our patient did not reflect the extensive degree of edema present in her posterior pharynx. To our knowledge, there is no discussion in the literature regarding airway angioedema in myxedema coma. A high index of suspicion for a difficult airway should be maintained regardless of the degree of facial edema present.

In hypothermic myxedema coma patients, passive rewarming is required. The risk of Cardiovascular collapse secondary to peripheral vasodilation necessitates simulta- neous intravenous fluid repletion, and vasopressor support may also be required. It is prudent to assume Adrenal insufficiency, as the possibility of Schmidt syndrome is increased in hypothyroid patients who have an underlying polyendocrine deficiency. The initiation of hydrocortisone before the administration of thyroid replacement is warranted. Infection is also a common precipitant in myxedema coma, and the traditional signs of infection may be masked. Historically, fatal cases of myxedema coma often had an unrecognized source of infection [15]. Broad-spectrum

antibiotic coverage is warranted.

Our patient ultimately survived with Complete recovery. Although we were able to initiate thyroid replacement in the ED, supportive measures such as rapid sequence intubation, corticosteroids, and vasopressors were critical interventions for her survival. This case suggests that patients with this rare

endocrine emergency may present with significant phar- yngeal edema necessitating the use of ancillary intubation equipment to secure a definitive airway.

Christopher H. Lee MD Section of Emergency Medicine Yale-New Haven Hospital

New Haven, CT 06519, USA E-mail address: [email protected]

Charles R. Wira MD Section of Emergency Medicine Yale-New Haven Hospital

New Haven, CT 06519, USA

doi:10.1016/j.ajem.2008.12.027

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