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

Table of Contents

 

1. Abstract
2. Practice Recommendations (key points from the issue)
3. Case Presentations
4. Critical Appraisal Of The Literature
5. Epidemiology, Etiology, And Pathophysiology
   1. Epidemiology
   2. Definitions And Etiology
   3. Pathophysiology
6. Differential Diagnosis
7. Prehospital Care
8. ED Evaluation
   1. Initial Approach
   2. Important Historical Questions (From Patient, Medics, Witnesses, Family, And Other People)
   3. Important Physical Findings
9. Diagnostic Studies
   1. TSH, T4, T3
   2. Other Diagnostic Tests
   3. Electrocardiogram
   4. Chest Radiography
   5. Echocardiography
   6. Computerized Tomography Head
   7. Lumbar Puncture
10. Treatment
    1. Myxedema Coma
    2. Thyroid Storm
11. Special Circumstances
    1. Respiratory Failure
    2. Pediatrics
    3. Neonatal Hypothyroidism
    4. Neonatal Thyrotoxicosis
    5. Pregnancy
12. Controversies/Cutting Edge
    1. Cardiovascular Collapse
    2. Radiation Emergencies
    3. Screening
13. Disposition
14. Summary
15. Cost- And Time-Effective Strategies
16. Risk Management Pitfalls For Thyroid Emergencies
17. Case Conclusion
18. Clinical Pathway For Treatment Of Myxedema Coma
19. Clinical Pathway For Treatment Of Thyroid Storm
20. Tables And Figures
    1. Differential Diagnosis In Thyroid Storm
    2. Differential Diagnosis In Myxedema Coma
    3. Field Diagnostic & Therapeutic Interventions In Thyroid Crises
    4. Historical Questions In The Evaluation Of Thyroid Storm
    5. Historical Questions In The Evaluation Of Myxedema Coma
    6. Thyroid Laboratory Tests In Thyroid Disease
    7. Three-Step Treatment of Thyroid Storm
21. References

Abstract

Although thyroid-related medical conditions are relatively common in the general population, the acute life-threatening thyroid emergency rarely presents. Both hyper- and hypothyroidism can contribute to the etiology of a number of critical ED presentations, ranging from acute psychosis to frank coma. With reported mortality rates ranging from 20% to 80% for the life-threatening, decompensated forms of hypo- and hyperthyroidism, myxedema and thyroid storm, respectively, it remains crucial that the emergency clinician be versed in their diagnosis and treatment.^1,2

This issue of Emergency Medicine Practice reviews the fundamental principles of the management of thyroid emergencies using a focused, evidence-based approach to the literature. Although thyroid disorders constitute a wide-ranging clinical spectrum, this review will focus on the common final pathway of acutely decompensated hyper- and hypothyroidism, myxedema, and thyroid storm. Accurate diagnosis and the application of proven emergent treatments are critical in reducing the profound mortality rates related to both conditions.

Practice Recommendations (key points from the issue)

Click here to download a PDF of the Evidence-Based Practice Recommendations for this issue.

Case Presentations

Case #1: A 65-year-old woman is brought to the emergency department (ED) with altered level of consciousness and hypotension. Her neighbor found her on the kitchen floor. He checked on her because he hadn't seen her for 3 days. The patient is unable to provide any verbal history. Her vital signs are respiratory rate of 10 respirations per min, blood pressure of 90/60 mm Hg, temperature 35°C (95°F), and heart rate 50 beats per min. On physical examination, you see an obtunded woman in no apparent distress. You note a well-healed surgical scar on her anterior neck and that her left leg is shortened and externally rotated. The differential diagnosis of the presentation is long and complex, and you keep wondering if that scar on the neck has a bearing on her management.

Case #2: A 50-year-old man presents with complaints of a fever and "feeling anxious." The patient has had a productive cough, subjective fever, and myalgias for 7 days. Yesterday, he began to "feel anxious" and like his "heart was racing." His pas medical history is significant for a goiter that is still being evaluated. His vital signs are respiratory rate of 18 respirations per min, blood pressure of 160/80 mm Hg, temperature 38°C (100.4°F), and heart rate 140 beats per min. On physical examination, you note that the patient appears nontoxic. He has a tender goiter, a fine tremor of his hands, and an irregular heart rhythm. On his lung examination, there are left midfield rales. You suspect community-acquired pneumonia, but the tender goiter introduces management concerns.

Critical Appraisal Of The Literature

We performed a literature review through Ovid MEDLINE and PubMed using the terms hyperthyroidism, thyrotoxicosis, thyroid storm, hypothyroidism, and myxedema. We then performed a manual search of the resulting articles to find further relevant articles. The Endocrine Society has published an excellent clinical management guideline for hyperthyroidism and hypothyroidism as well as for the pregnant and postpartum population, but this does not address emergent intervention.³ Recent meta-analyses and randomized control trials tend to focus on the ideal pharmacological, radiotherapeutic, or surgical regimens for long-term therapy of hyperthyroidism, all of which are of limited importance to the emergency clinician. A number of case reports and case reviews exist as well for the more esoteric presentations associated with thyroid disorders.

Aside from the relatively recent development of intravenous thyroxine, the management of myxedema and thyroid storm has changed little since the mid twentieth century. Perhaps the most relevant papers to the practicing emergency clinician are the focused clinical reviews available on subtopics within the thyroid disease literature, including neonates, children, the elderly, antithyroid drugs, and mechanical ventilation principles.

Risk Management Pitfalls For Thyroid Emergencies

1. "I thought she was hypothermic because it was cold outside." The vast majority of cases of myxedema coma occur in the winter. The differential diagnosis of hypothermia includes myxedema coma. Do not dismiss all hypothermia to environmental causes.
2. "I didn't want to start thyroxine until I had laboratory test confirmation of her thyroid status." The use of IV thyroxine has not been shown to be harmful in euthyroid patients. Many facilities batch test their thyroid panels, and results may not be available for several days. If the clinical suspicion exists for myxedema coma, start treatment early. Delays in treatment result in increased mortality.
3. "She was hypotensive, so I started norepinephrine." Patients with myxedema coma tend to be hypotensive. The first therapy is fluid resuscitation, as these patients are hypovolemic. If patients remain hypotensive after fluid resuscitation, evaluate perfusion. If the patient is perfusing the end organs, continue supportive therapy. Evidence of impaired perfusion indicates the need for vasopressors. The vasopressor of choice is one with low a-adrenergic activity, such as dopamine. a-adrenergic vasopressors, such as norepinephrine and phenylephrine, can precipitate cardiovascular collapse in myxedema coma.
4. "She had altered mental status because she was septic." Although this is true in many cases, an ED physician should remember to consider the presence of decompensated thyroid conditions in patients with systemic illness. The diagnoses of myxedema coma and thyroid storm are clinical diagnoses. Therefore, the physician must suspect them to diagnose them.
5. "I sent a TSH. If it's low, I will treat him for thyroid storm." The acute decompensation of thyroid storm is not reflected in the laboratory tests for many hours after the onset of the clinical syndrome. Thyroid storm is a clinical diagnosis. The physician must diagnose thyroid storm based on history and physical examination findings.
6. "She's confused because she's old and sick." Systemic illness can cause decompensation in a geriatric patient's mental status. The ED physician should always consider the complicating factor of an underlying thyroid disorder in confused patients. This is especially true in geriatric women.
7. "I treated the patient as though she was septic because she had fever, tachycardia, hypertension, and altered mental status." This clinical picture is consistent with both thyroid storm and sepsis. Hypertension can be present in early sepsis, but hypotension is the hallmark of late sepsis. As the conditions can coincide, the ED physician should always consider the role of the thyroid in systemically ill patients.
8. "I gave the patient T3 for presumed myxedema coma because it works faster than T4." The onset of action is faster with T3 than T4. However, T3 has a higher risk of complications, including cardiac arrhythmias. The standard of care in myxedema coma is to administer T4 intravenously. If the physician only has access to T3, this can be administered.
9. "The patient has atrial fibrillation and congestive heart failure from thyroid storm. I gave the patient a diuretic for the heart failure and a calcium channel blocker for the heart rate." Patients with a fast heart rate and signs of heart failure may have high output heart failure, which means the heart rate is too fast for the heart to fill in diastole. So, the cardiac output is decreased. The left ventricle may have normal function or may be depressed in these instances. The treatment is to slow the heart rate and reassess the patient. In this sense, the calcium channel blocker is a good choice. However, a b-blocker is the preferred agent in thyroid storm, as it also treats the patient's symptoms of agitation and anxiety and other peripheral effects of thyroid hormone. Patients with thyroid storm are hypovolemic, even if they have pulmonary edema. The administration of a diuretic should be avoided if possible, as this worsens the dehydration and also worsens the cardiac output. When the heart rate has slowed, reassess the patient's oxygenation and ventilation status before administering a diuretic. In patients with underlying cardiac dysfunction complicating the case, the physician must use clinical judgment as to which agent to administer first.
10. "The patient has thyroid storm, so I gave iodine immediately to stop the production of thyroid hormone." Iodine is an important therapy in thyroid storm, but it must be given 2 h after an antithyroid medication (methimazole or PTU). If given before these medications, iodine will worsen the clinical picture by stimulating the release of increased amounts of thyroid hormone. A patient may not be in the ED long enough for the ED physician to administer this medication.

Tables And Figures

References

Evidence-based medicine requires a critical appraisal of the literature based upon study methodology and number of subjects. Not all references are equally robust. The findings of a large, prospective, randomized, and blinded trial should carry more weight than a case report.

To help the reader judge the strength of each reference, pertinent information about the study, such as the type of study and the number of patients in the study, will be included in bold type following the reference, where available. In addition, the most informative references cited in this paper, as determined by the authors, will be noted by an asterisk (*) next to the number of the reference.

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