Endocrine Abstracts

Introduction: Myxedema coma is a medical emergency and can be associated with respiratory failure. Intubated patients have been known to require persistent efforts in ventilator weaning, with one case reported to take 7 months before success.

Case report: A 77-year-old gentleman with known primary hypothyroidism presented with chest infection. He had defaulted thyroxine for the past 6 months, relying instead on complementary health products. Thyroid function test: free T₄<2 pmol/l (RI: 8–21), TSH >100 mIU/l (RI: 0.34–5.60). He was administered both thyroxine and liothyronine promptly and covered with i.v. antibiotics but continued to deteriorate into myxedematous coma and required mechanical ventilation. Despite optimisation of thyroid medications and normalisation of thyroid function (fT₄ 15 pmol/l), ventilator weaning was repeatedly unsuccessful for over 2 months. Electromyography and Nerve conduction test suggested critical illness polyneuropathy. Patient eventually made a competent decision (E4VTM6) for terminal extubation and passed on a day after extubation.

Conclusion: Our case report supports the observation in the literature regarding difficult ventilator weaning in myxedematous patients. Persistent respiratory failure may be due to a decreased respiratory drive, respiratory muscle myopathy and phrenic nerve neuropathy causing diaphragmatic dysfunction. Inefficient gas exchange from alveolar hypoventilation and concomitant pleural effusions may also contribute to respiratory failure. Underlying hypothyroidism is postulated to be an aggravating factor as well. In preventing hypothyroidism from progressing to myxedema coma, education to reinforce compliance is especially important in the elderly Asian population as they may remain wary of western medication and tend to rely on complementary health supplements. Clinicians should be cognisant that ventilator weaning in myxedematous patients may require prolonged efforts. Compliance to medications needs continuous reinforcement.