Morning Report: 6/11/2013

Thanks to Dr. Bradby for today’s Morning Report!

Myxedema Coma or Crisis

Definition: Severe (decompensated) hypothyroidism leading to decreased mental status, hypothermia, and other symptoms related to slowing of function in multiple organs.

Epidemiology:

– Mortality rate if not promptly diagnosed and treated: approx. 50% or more

Even with prompt treatment, mortality rates of up to 25% have been observed

– 4-8x more common in women

– Incidence increased with age, myxedema coma occurs primarily in the elderly

Pathophysiology:

– Thyroid hormones are critical in cell metabolism and organ function

– Decrease T3/T4 –> decrease in production of myocyte contractile proteins and enzymes including NA⁺/K⁺ ATPase

– Decreased plasma volume

– Increased systemic vascular resistance

– Respiratory muscle dysfunction, depressed resp drive, fluid accumulation

– Hyponatremia due to decreased Na reabsorption from reduced levels of Na⁺/K⁺ ATPase

– Decreased intestinal motility

– Summary: Everything slows DOWN.

Clinical Presentation:

– Neuro: lethargy, stupor, coma, altered mental status

– Cardio: bradycardia, decreased myocardial contractility, low cardiac output, hypotension, pericardial effusion à all reversed with thyroid hormone therapy.

– GI: decreased bowel sounds, distention secondary to ileus

– Lung: Hypoventilation, rales (pleural effusions)

– Skin: Edema, macroglossia, coarse/thinning hair

– GU: Bladder distention

– Hyponatremia (seizures), Hypoglycemia

– Hypothermia

Diagnosis:

– Based on hx, px, and exclusion of other causes of coma

Ex: poorly responsive patient with a thyroidectomy scar or a history of I-131 therapy or hypothyroidism
Ask about: recent infections, trauma, burns, CVA symptoms, GI Bleeding, CHF, drugs (tranquilizers, sedatives, anesthetics, amiodarone, rifampin) – Basically anything that could cause the body any stress.

– Send TFTs, cortisol

– Tx should NOT wait for test results to come back –> ENDOCRINE EMERGENCY

Treatment:

– Mechanical ventilation if needed (acidosis, hypercapnia, inability to protect airway, hypoxia)

– Immediate thyroid hormone replacement

Give IV – GI absorption is compromised
IV loading dose: 200-400mcg of levothyroxine with T3 dose of 5-20mcg
Daily dose: 50-100mcg of levothyroxine IV until patient is PO tolerant, with T3 dosing 2.5 to 10 mcg q8h. T3 can be discontinued when patient has clinical improvement and becomes stable.
Know that full-dose T4 therapy can worsen myocardial ischemia by increased myocardial oxygen consumption, so use caution.

– Stress hormone replacement (after cortisol level sent)

– Passive rewarming (active rewarming increases risk of vasodilation and worsening hypotension)

– Antibiotics if there is signs of infection, as well as pan culture

– Correct electrolyte derangements

Reference:

Ross, DS. Myxedema Coma. In: UpToDate, Rose, BD (Ed), UpToDate, Waltham, MA, 2013.