SAT-351 - Multifactorial Myxedema Coma Complicated by Hypercapnic Respiratory Failure and Septic Shock in an Elderly Patient with Prior Thyroid Surgery

Background: Myxedema coma is a rare endocrine emergency with reported mortality of 25-60%, requiring early recognition and coordinated management. This case highlights diagnostic and therapeutic challenges in a complex, multifactorial presentation.


Case Presentation: A 79-year-old female with prior right lobectomy and isthmusectomy presented unresponsive and required intubation. Initial evaluation revealed profound hypothyroidism (TSH 110.75 mIU/L, free T4 < 0.40 ng/dL) and multifactorial acute encephalopathy due to myxedema coma, CO2 narcosis, and septic shock. She developed hemodynamic instability requiring vasopressor support and recurrent hypotension with hypersomnolence despite initial therapy.

Management: Intravenous levothyroxine was administered (100 mcg day 1; 100 mcg twice daily day 2; followed by 50 mcg IV on days 4-5, total 400 mcg IV) then transitioned to oral levothyroxine 125 mcg daily. Empiric corticosteroids included methylprednisolone 80 mg once on day 1 followed by 20 mg every 8 hours, hydrocortisone 50 mg IV once on day 6, and a prednisone taper. Free T4 improved to 0.62 ng/dL by day 7. The hospital course was complicated by atrial fibrillation managed with digoxin (anticoagulation deferred due to psoas hematoma), HFpEF, AKI on CKD, anemia, and hypercapnic respiratory failure requiring BiPAP.

Key Learning Points:

Initial Thyroid Hormone Dosing: Guideline-recommended IV levothyroxine loading doses (200-400 mcg) were appropriately used, with dose consideration for age and cardiac risk.

Corticosteroid Coverage: Stress-dose hydrocortisone should be administered before or concurrent with levothyroxine; delayed and inconsistent steroid coverage can lead to a potential management gap.

Role of Liothyronine: In severe cases with impaired peripheral T4-to-T3 conversion, adjunctive IV liothyronine may be considered to hasten clinical recovery.

Respiratory Failure Recognition: CO2 retention from impaired ventilatory drive is common in myxedema coma; earlier noninvasive ventilation may prevent clinical deterioration.


Conclusion: This case highlights the importance of guideline-adherent thyroid hormone replacement, early empiric stress-dose corticosteroids, consideration of combination T4/T3 therapy in severe disease, and recognition of multifactorial contributors to deterioration. Aggressive supportive care and vigilance for complications are essential to improving outcomes in myxedema coma.

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