Hypothyroidism is a clinical syndrome in which the deficiency or absence of thyroid hormone slows bodily metabolic processes. Symptoms can manifest in all organ systems and range in severity based on the degree of hormone deficiency. The disease typically progresses over months to years but can occur quickly following cessation of thyroid replacement medication or surgical removal of the thyroid gland.
The term myxedema refers to the thickened, nonpitting edematous changes to the soft tissues of patients in a markedly hypothyroid state. Myxedema coma, a rare, life-threatening condition, occurs late in the progression of hypothyroidism. The condition is seen typically in elderly women and is often precipitated by infection, medication, environmental exposure, or other metabolic-related stresses. Since rapid confirmatory laboratory tests are often unavailable, the diagnosis may be made on clinical grounds with treatment started promptly.
Treatment of myxedema coma requires potentially toxic doses of thyroid hormone, and mortality rates exceeding 20% have been reported even with optimum therapy.
History: The symptoms characteristic of hypothyroidism are numerous yet often vague and subtle, especially in early stages of the disease.
Lethargy
Generalized weakness
Brittle or thinning hair
Menstrual irregularity
Menorrhagia
Forgetfulness
Fullness in throat
Deep, husky voice secondary to mucopolysaccharide infiltration of the vocal cords
Cold intolerance
Weight gain
Muscle/joint pain or weakness
Inability to concentrate
Headaches
Constipation
Emotional lability
Depression
Blurred vision
Dry hair
Physical:
Pseudomyotonic reflexes - Prolonged relaxation phase, usually at least twice as long as the contraction phase
Hypothermia (especially in myxedema coma)
Skin changes - Dry, cool, coarse, and thickened with a yellowish appearance
Subcutaneous tissues - Nonpitting, waxy, dry edema, secondary to accumulation of polysaccharides
Loss of axillary and pubic hair
Pallor
Loss of outer one third of eyebrows
Abdominal distention
Goiter
Unsteady gait/ataxia
Pericardial effusion
Dull facial expression
Coarsening or huskiness of voice
Periorbital edema
Bradycardia, narrow pulse pressure
Macroglossia
Thyroidectomy scar - In patients with altered mental status, suggests myxedema coma as a potential cause
Prehospital Care: Stabilize acute life-threatening conditions, and initiate supportive therapy.
Emergency Department Care: Patients with myxedema coma may present in extremis; implement initial resuscitative measures, including intravenous (IV) access, cardiac monitoring, and oxygen therapy, as indicated. Mechanical ventilation is indicated for patients with diminished respiratory drive or obtundation.
Evaluate for life-threatening causes of altered mental status (eg, bedside glucose, pulse oximetry).
If myxedema coma is suspected on clinical impression, start IV thyroid hormone treatment.
Confirmatory tests often are not available to an ED physician.
With a diagnosis of myxedema coma, initiate hormonal therapy.
Investigate immediately for inciting events such as infection.
Treat respiratory failure with appropriate ventilatory support.
The condition often requires mechanical ventilation.
Treat underlying pulmonary infection.
Hypotension may respond to crystalloid infusion.
Occasionally, vasopressive agents are required.
In refractory cases, hypotension may resolve with thyroid hormone replacement.
Treat hypothermia.
Most patients with myxedema coma respond to passive rewarming measures such as blankets and removal of cold or wet clothing; aggressive rewarming may lead to peripheral vasodilatation and hypotension. However, hemodynamically unstable patients with profound hypothermia require active rewarming measures.
Treat hyponatremia initially with water restriction; however, if sodium levels are less than 120 mEq/L or any seizures occur, hypertonic saline is indicated.
Avoid medications such as sedatives, narcotics, and anesthetics. Metabolism of these agents may be slowed significantly, causing prolonged effects.
Consultations:
For patients with myxedema coma, consult a critical care intensivist regarding admission to an ICU and optimization treatment.
An endocrinologist should be consulted to help confirm the diagnosis and assist in patient management after admission.
