You are called to review a 48-year-old male in the post-operative recovery unit (PACU) who has just undergone resection of a TSH-secreting pituitary adenoma via a trans-sphenoidal approach. He is febrile (38.5°C) and is hypertensive (160/50 mmHg) with tachycardia (130 beats/min) and hyper-dynamic circulation, and is hyper-reflexic.
Give the likely diagnosis. (10% marks)
List your immediate pharmacological management. (30% marks)
College answer
a) Thyroid storm
b) Propranolol 60-80mg 4-6 hourly (or other beta blocker) to control BP and HR Propylthiouracil (200mg 4hrly) or Carbimazole 20-30 mg every 4-6 hours Hydrocortisone 100mg 6hrly
Discussion
The patient clearly demonstrates many classic features of hyperthyroidism:
- Tachycardia
- Hypertension
- Hyperthermia
- Hypereflexia
The intuitive candidate will leap immediately to the conclusion that this is a TSH release mediated thyroid storm, as seen in one case report every ten years or so. How being able to identify this zebra diagnosis discriminates good intensivists from bad, one can only guess.
Pharmacological management of thyroid storm consists of the following steps:
- Prevent synthesis of T3 and T4:
- Thiouracils: propylthiouracil - blocks synthesis of T3 and T4 as well as peripheral T4-T3 conversion
- Imidazoles: carbimazole - block synthesis of T3 and T4
- Prevent T3 and T4 release:
- Inorganic iodine therapy, eg. potassium iodide (given after synthesis is blocked)
- Block peripheral T3 and T4 activity:
- β-blockade: propanolol (which also decreases T4-T3 conversion)
- Corticosteroids: also decrease T4-T3 conversion
- Other potentially useful agents include lithium and cholestyramine.
- Severe refractory disease may call for extracorporal clearance of thyroid hormone by plasma exchange or charcoal haemoperfusion.
References
Page, Kathleen, et al. "Development of thyroid storm after surgical resection of a thyrotropin-secreting pituitary adenoma." Endocrine Practice 14.6 (2008): 732-737.