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Myxedema is a used to described severe hypothrdoism. Myxedema is also used to describe the dermatologic changes that occur in hypothrdoisim and occasionally hyperthyroidism. In this setting, mixed refers to the deposition of mucopolysaccharide in the dermis, which results in swelling of the impacted area. When skin changes occur in hyperthyroidism, primarily Graves disease, it is called pretibial myxedema.
Myxedema coma sometimes referred to as myxedema crisis, is an uncommon, life-threatening clinical ailment that signifies severe hypothyroidism with physiological decompensation. The condition normally happens in patients who undiagnosed hypothyroidism for many years and is usually hastened by heart failure, infection, trauma, cerebrovascular disease, or drug therapy. Patients with myxedema coma are commonly seriously -ill with notable hypothermia have a depressed mental status.
A medical emergency, myxedema coma demands immediate attention. If the diagnosis is presumed, direct supervision is needed before establishing the diagnosis due to the high mortality rate associated with this condition. Patients with myxedema coma should be attended to in an intensive care unit with non-stop cardiac monitoring. The first steps in therapy include airway control, glucocorticoid therapy, thyroid hormone replacement, and supportive measures.
Myxedema coma transpires as a consequence of long-standing, undiagnosed, or undertreated hypothyroidism and is normally hastened by a systemic illness. Myxedema coma can be due to any of the causes of hypothyroidism, ordinarily chronic autoimmune thyroiditis. This can also befall patients who had thyroidectomy or experienced radioactive iodine therapy for hyperthyroidism. Rare causes may comprise subsequent hypothyroidism and medicines such as amiodarone and lithium
Given the significance of thyroid hormones in cell metabolism, long-standing hypothyroidism is connected with reduced metabolic rate and reduced oxygen consumption, which affects all body systems. This ends in hypothermia, which is a powerful predictor of mortality. Another outcome is reduced drug metabolism leading to overdosing of medications especially sedatives, hypnotics, and analgesic agents; this can accelerate myxedema coma.
Cardiac contractility is an impartment, low cardiac output volume, commencing low cardiac output, bradycardia and at times hypotension. Reduced stroke volume in critical cases may also be due to pericardial effusions triggered by the accumulation of fluid heavy in mucopolysaccharides within the pericardial sac. Congestive heart failure is rarely observed in the vacancy of preexisting cardiac disease.
Electrocardiographic conclusions can include bradycardia,low voltage, varying degrees of the block, nonspecific ST-segment changes, flattened or inverted T waves, extended Q-T interval, and ventricular or atrial arrhythmias.
The reduction of the effect of beta-adrenergic receptors leads to the pervasiveness of the effect of alpha-adrenergic receptors, increased catecholamines, and enhanced systemic vascular resistance, causing some sufferers to have diastolic hypertension and a restricted pulse pressure.
Plasma capacity is limited, and capillary permeability rises, causing fluid buildup in tissue and expanses and pericardial effusions.
Notwithstanding the term myxedema coma, many patients do not present in a coma, but manifest variable degrees of altered consciousness. Brain function is impacted by reduction in oxygen delivery and subsequent damage, lowered glucose usage and reduced cerebral blood flow. Hyponatremia can also lead to altered mental function.
The main pulmonary outcome of myxedema coma is hypoventilation, which results from central depression of ventilatory drive with reduced responsiveness to hypoxia and hypercapnia. Other participating factors to hypoventilation involve respiratory muscle instability, reflex obstruction by a large tongue, and obesity-hypoventilation syndrome. Fluid buildup may cause pleural flows and lowered diffusing capacity.
Kidney function may be compromised with reduced glomerular filtration rate because of low cardiac output and peripheral vasoconstriction or because of rhabdomyolysis. Hyponatremia is prevalent in patients with myxedema coma and is generated by increased serum antidiuretic hormone and impaired water excretion.
The gastrointestinal tract in myxedema coma can be remarked by mucopolysaccharide infiltration and edema. Also, neuropathic changes can cause malabsorption, gastric-atony, , megacolon, impaired peristalsis, and paralyticileus, Ascites may happen due to enlarged capillary permeability, heart failure, or other adjustments. Gastrointestinal bleeding secondary to an associated coagulopathy may occur.
Myxedema coma is associated with a greater risk of bleeding created by coagulopathy related to an acquired von Willebrand syndrome (type 1) and lowers factors V, VII, VIII, IX, and X. . Patients may also have microcytic anemia secondary to hemorrhage, or macrocytic anemia produced by normocytic normochromic anemia, or vitamin B12 deficiency, which can be subordinate to reduced oxygen requirement and decreased erythropoietin
Myxedema coma is a rare outcome of untreated hypothyroidism, and the exact predominance in the United States is not known.
A study from Spain showed that the incidence rate of myxedema coma is 0.22 per million per year. A study by Ono et al estimated the annual frequency of myxedema coma in Japan to be 1.08 per million people.
Myxedema coma is a medical emergency. If the ailment is not promptly diagnosed and treated, the mortality rate can be more than 50%. Even with prompt recognition and timely medical intervention, mortality rates are as high as 25%.
The most common circumstances of death are a respiratory failure, sepsis, and gastrointestinal bleeding.
Myxedema coma bears a high mortality and morbidity rate. Therefore, timely identification and proper management are critical. Factors leading to a poor prognosis are older age, steadfast hypothermia, or bradycardia, lower degree of awareness by Glasgow Coma Scale, multiorgan impairment indicated by high APACHE (Acute Physiology and Chronic Health Evaluation) II score. The study above by Ono et al. reported that, as revealed through multivariable logistic regression, a higher in-hospital mortality rate was associated with older age and catecholamine use (with or without steroids).
Patients who are identified to have hypothyroidism should be advised concerning the requirement of taking daily thyroid hormone replacement and observing thyroid tests on a routine basis.
Patients with a history of thyroiditis or who have undergone thyroid irradiation or thyroid surgery should be recommended that hypothyroidism may occur in the future. They should be educated about the symptoms of hypothyroidism and should understand the importance of seeking timely medical advice for examination and testing.
Myxedema coma is a medical emergency that requires prompt attention. If the diagnosis is suspected, immediate management is needed before confirming the diagnosis due to the high linked mortality rate. Patients with myxedema coma should be administered in an intensive care unit with consistent cardiac monitoring. Initial steps in control include the elements below.
Preservation of adequate airway is crucial, since most patients have discouraged mental status along with respiratory failure. Mechanical ventilation is commonly needed during the first 36-48 hours, but some patients require prolonged respiratory support for as long as 2-3 weeks.
Thyroid hormone replacement
The ideal form of therapy and doses of thyroid hormone therapy in myxedema coma continue to be controversial due to the rarity of the condition and lack of clinical trials. Some clinicians advocate the administration of levothyroxine (T4), while others prefer a combination of T4 and liothyronine (T3) The American Thyroid Association recommends combination therapy with T4 and T3.
Because of declining gastrointestinal absorption, intravenous thyroid hormone therapy is advised.
An intravenous loading dose of 300-600 micrograms of levothyroxine (T4) is supplanted by a daily intravenous dose of 50-100 micrograms. Larger doses of T4 probably have no advantage and may be dangerous. The lower end of the dosing range is supported in senior patients, those at risk for cardiac complications such as arrhythmias, myocardial infarction and arrhythmias, and in patients with coronary artery disease, because full-dose T4 therapy may worsen myocardial ischemia by heightening myocardial oxygen consumption.
Since the rate of conversion of T4 to the active hormone T3 can be reduced in these patients, the addition of T3 along with T4 has been advised. T3 has a quicker onset of action than T4, as rises in body temperature and oxygen consumption has been stated to be faster with T3 therapy compared to T4. T3 therapy is given as a bolus of 5-20 micrograms intravenously and to be maintained at a dosage of 2.5-10 micrograms every 8 hours depending on the patient’s age and coexistent cardiac risk factors.
Intravenous levothyroxine treatment in severely hypothyroid patients normally leads to improvement in the cardiovascular, renal, pulmonary, and metabolic framework within a week. Serum T4 and T3 concentrations may advance or normalize with a similar time frame, with more progressive improvement in serum TSH. Thus, the therapeutic endpoints in myxedema coma should be enhanced mental status, improved cardiac function, and improved pulmonary function.
Analysis of thyroid hormones every 1-2 days is suggested. Failure of TSH to decrease or of thyroid hormone levels to increase suggests the need to increase doses of T4 and add T3.
The treatment is adapted to the oral form once the patient can take medications by mouth.
Patients with primary hypothyroidism may have lined primary adrenal insufficiency while patients with secondary hypothyroidism may have linked hypopituitarism and secondary adrenal insufficiency. The other reason for the treatment with corticosteroids is the possible risk of precipitating acute adrenal insufficiency caused by faster metabolism of cortisol that follows T4 therapy.
Stress doses of intravenous glucocorticoids should be given the chance of adrenal insufficiency is barred by a random serum cortisol, which is beneficial only if very low, or, better, by an ACTH stimulation test.
Hydrocortisone at a dose of 50-100 mg every 8 hours is administered. An option is a dexamethasone at a dose of 2-4 mg every 12 hours. Dexamethasone has the benefit of not impacting the serum cortisol concentration and can be used immediately without altering the results of the ACTH stimulation test, which can be implemented at any time. If the test is negative, corticosteroids can be stopped without tapering.
Treat hypothermia by passive rewarming using ordinary blankets and a warm room. Active rewarming using external tools carries a risk of vasodilatation and deteriorating hypotension and should be avoided. The use of a rectal probe helps to discover the true core temperature and to monitor rewarming.
Treat related infection. Given the severity of the condition, contamination infection should always be acknowledged, and empiric broad-spectrum of antibiotics be considered until suitable cultures are proven negative.
Correct severe hyponatremia with free water restriction saline.
Correct hypoglycemia with intravenous dextrose.
Hypotension is ordinarily corrected with thyroid hormone therapy. If blood pressure continues to be low, cautious use of intravenous fluids with normal saline is recommended. Refractory hypotension can be treated with vasopressors like dopamine. However, patients should be weaned off the vasopressor as soon as possible because of the risk of the pressor-induced ischemic event.
Patients who are awake, no longer reliant on a ventilator, and medically stable may be transported from the intensive care unit to a medical ward.