Thyroid Storm

Endocrine Emergency - Thyroid Storm

The theme for the week is management of the patient with critical illness, and today in Morning Report we discussed a case of thyroid storm.  This has been blogged before on Tangent's, but I wanted to focus more on the management of this medical emergency.

We also discussed the other thyroid related emergencies that might result in a patient being admitted to the ICU, mainly myxedema coma, which is the polar opposite of thyroid storm and hypokalemic periodic paralysis which classically presents as paralysis in male patients of Asian ancestry who are hyperthyroid.

Thyroid Storm:

In terms of thyroid storm, the Burch-Wartofsky scoring system is probably the most widely utilized clinical scoring system for making a diagnosis of thyorid storm.  The key clinical features in this scoring system include thermoregulatory dysfunction, CNS effects, GI-hepatic dysfunction, and cardiovascular dysfunction (including congestive heart failure and atrial fibrillation).  There is also often a precipitant (infection, trauma, surgery) that triggers the acute thyrotoxicosis.

Clinical pearl: thyrotoxicosis + hypotension
One clinical pearl that Dr. Silver mentioned was the presence of hypotension, in the context of a patient with symptoms and signs of thyrotoxicosis, should make a clinician very worried about true thyroid storm.

Management:
The management of thyroid storm includes the following:

1. Symptomatic treatment - In terms of managing symptoms beta blockers are the key component.  But other medications that can be helpful include acetaminophen 500-1000 mg PO q6h prn, which can be given to help manage the pyrexia.  Additionally, benzodiazepenes such as lorazepam can be given if the patient is very anxious and distressed.

Beta blockers such as propranolol can be given orally or intravenously if the patient is truly unstable.  The typical oral dose in thyroid storm is 40 - 80 mg PO q 4 hourly.  Beta-blockers assist with the psychomotor agitation, tachycardia, and also reduce the peripheral conversion of T4 to the more active T3.

2. Blocking the synthesis of new hormone - Thionamide (PTU)  - This class of medication, which mainly consists of Methimazole and PTU (propylthiouracil) blocks the synthesis of new thyroid hormone.  In the acute setting as Dr. Silver mentioned, PTU which has a rapid onset of action as compared with methimazole is the drug of choice.  If the patient is truly in thyroid storm than a loading dose of PTU may be given (1000 mg PO x 1 dose), then it is typically dosed TID in the 200 -400 mg range.

3. Reducing peripheral T4 conversion - Steroids - High dose steroids are often given for a variety of purposes.  The typical doses are 100 mg of hydrocortisone IV TID, or Prednisone 60 mg PO OD.  The duration is usually only for a couple of days.  The purpose of the steroids is to treat concomitant adrenal insufficiency that can be precipitated by the increased metabolism of endogenous cortisol as a result of the thyroid hormone excess.  Also, steroids decrease the peripheral conversion of T4 to T3.

4. Blocking the release of new thyroid hormone - Iodine - Once the patient has received a thionamide to block the synthesis of thyroid hormone, Iodine can be given as this will suppress the release of thyroid hormone from the thyroid gland.  Lugol's solution can be given, and as was mentioned today in morning report, it is usually only used for a short period of time (the initial 48-72 hours).
Other treatments that can be given if iodine is unavailable include Lithium, which also blocks the release of new thyroid hormone from the gland.

5. Treat the underlying precipitant - If is an infection, than appropriate antibiotics should be prescribed.

Lastly, a patient in true thyroid storm needs close monitoring (telemetry, frequent vital signs) and should be monitored in a high acuity setting such as a step-down unit or ICU.  These are also patients where your friendly neighbourhood Endocrinologist should be awoken in the middle of the night to assist in management.

Thanks to Dr. Robert Silver and team 3 for presenting this interesting case!

Reference:
Hampton, J. Thyroid Gland Disorder Emergencies. 2013.AACN Advanced Critical Care. Volume 24. number 3. pp. 325-332.