Myxoedema Coma
OVERVIEW
- extreme form of hypothyroidism
- high mortality
CLINICAL FEATURES
- stupor
- hypothermia
- respiratory failure
- confusion
- coma
- dry skin
- sparse hair
- hoarse voice
- periorbital oedema
- CVS: non-pitting oedema of hands and feet, bradycardia, hypotension refractory to vasopressors, reduced contractility, pericardial effusion
- RESP: respiratory depression, impaired respiratory muscle function, hypoxia and hypercapnia
- RENAL: bladder atony, urinary retention, urinary Na+ normal or high
- ELECTROLYTES: hyponatraemia from increased H2O reabsorption from high levels of ADH
- GI: macroglossia, anorexia, abdominal pain, constipation, ileus
- CNS: delayed tendon reflexes, slow mentation, depression -> psychosis, seizures
Risk or Precipitating Factors
- hypothermia
- CVA
- CHF
- infections
- drugs: anaesthetics, sedatives, narcotics, amiodarone, lithium
- GIH
- trauma
- electrolytes: hypoglycaemia, hyponatraemia
- acidosis
- hypoxaemia
- hypercapnia
INVESTIGATIONS
- TSH: markedly elevated in 95% of cases, 5% are caused by central TSH failure
- low free T4
- low T3
- hyponatraemia
- hypoglycaemia
- anaemia
- hypercholesterolaemia
- high LDH
- high CK
MANAGEMENT
Resuscitate
- admit to ICU because if high mortality and multi-faceted therapy
- may require intubation for various reasons (respiratory failure, airway obstruction from macroglossia, coma)
- ventilation may be required for several days -> weeks
- IV fluid resuscitation and vasoactive agents until thyroid hormone action begins
- warm patient and pre-empt vasodilation and hypotension
Acid-base and Electrolytes
- supportive care
- glucose
- hyponatraemia: cautious correction over time (<10mmol/L day)
Specific Therapy
- hydrocortisone 100mg Q 6hourly if adrenal or pituitary insufficiency suspected
- replacement of thyroid hormones (T4 or T3 is controversial):
(1) T4 – loading dose = 500mcg IV -> 50-100mcg OD IV or orally
(2) T3 – loading dose = 10mcg IV -> 10mcg Q4 hrly for 24 hours then every 6 hours
Underlying Cause
- treat precipitant (withdraw drugs, treat infection…)
Critical Care
Compendium
Chris is an Intensivist and ECMO specialist at the Alfred ICU in Melbourne. He is also a Clinical Adjunct Associate Professor at Monash University. He is a co-founder of the Australia and New Zealand Clinician Educator Network (ANZCEN) and is the Lead for the ANZCEN Clinician Educator Incubator programme. He is on the Board of Directors for the Intensive Care Foundation and is a First Part Examiner for the College of Intensive Care Medicine. He is an internationally recognised Clinician Educator with a passion for helping clinicians learn and for improving the clinical performance of individuals and collectives.
After finishing his medical degree at the University of Auckland, he continued post-graduate training in New Zealand as well as Australia’s Northern Territory, Perth and Melbourne. He has completed fellowship training in both intensive care medicine and emergency medicine, as well as post-graduate training in biochemistry, clinical toxicology, clinical epidemiology, and health professional education.
He is actively involved in in using translational simulation to improve patient care and the design of processes and systems at Alfred Health. He coordinates the Alfred ICU’s education and simulation programmes and runs the unit’s education website, INTENSIVE. He created the ‘Critically Ill Airway’ course and teaches on numerous courses around the world. He is one of the founders of the FOAM movement (Free Open-Access Medical education) and is co-creator of litfl.com, the RAGE podcast, the Resuscitology course, and the SMACC conference.
His one great achievement is being the father of three amazing children.
On Twitter, he is @precordialthump.
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