Extra Topic 1.4 -- Thyrotoxicosis

Question 1

Is this patient ready for surgery?

(A 32-year-old female presents for elective laparoscopic cholecystectomy. She has a thyroid nodule and is taking propylthiouracil. VS: BP = 162/98 mmHg, HR = 119, hematocrit = 29%.)

Answer 1

(Per online UBP – you could demonstrate a lot of knowledge here. You could talk about the next 2-3 questions in 5-10 seconds … and save the examiner from asking them. Give the examiner the impression that you know a lot about thyrotoxicosis.)

–

Possibly, but as for any elective surgery, I would make that determination based on a thorough history and physical examination, including pertinent laboratory findings.

Specifically, I am concerned about –

• her anemia,
• history of hyperthyroidism,
• hypertension, and
• resting tachycardia.

Therefore, I would perform a history and physical to identify signs and symptoms of thyroid dysfunction and consider ordering lab tests based on my findings.

Question 2

What are ths signs and symptoms of thyrotoxicosis?

(A 32-year-old female presents for elective laparoscopic cholecystectomy. She has a thyroid nodule and is taking propylthiouracil. VS: BP = 162/98 mmHg, HR = 119, hematocrit = 29%.)

Answer 2

Cardiac manifestations (due to direct effects of T3 on the myocardium and the peripheral vasculature) include –

• tachycardia, arrhythmias, cardiomegaly, increased stroke volume and cardiac output, and decreased systemic and pulmonary vascular resistance.

Neurologic symptoms include –

• anxiety, agitation, tremors, insomnia, and muscle weakness.

There are also nonspecific signs and symptoms, such as –

• sweating, heat intolerance, weakness, and weight loss.

Question 3

What laboratory tests would you order to assess thyroid function?

(A 32-year-old female presents for elective laparoscopic cholecystectomy. She has a thyroid nodule and is taking propylthiouracil. VS: BP = 162/98 mmHg, HR = 119, hematocrit = 29%.)

Answer 3

I would order –

• a TSH,
• free T3, and
• free T4,

recognizing that a hyperthyroid patient would likely present with –

• a low TSH (due to negative feedback) and
• elevated levels of both free T3 (more active than T4) and free T4.

While I would not necessarily order them, other tests to evaluate thyroid function include –

• Total T4,
• Total T3,
• T4 resin uptake,
• T3 resin uptake, and
• radioactive iodine uptake.

Question 4

How would you prepare this patient for emergent surgery if her thyroid hormone levels were elevated?

(A 32-year-old female presents for elective laparoscopic cholecystectomy. She has a thyroid nodule and is taking propylthiouracil. VS: BP = 162/98 mmHg, HR = 119, hematocrit = 29%.)

Answer 4

All elective procedures should be postponed until the patient has been treated medically and rendered euthyroid.

However, in the case of emergent surgery where a delay is unacceptable, preoperative treatment should focus on minimizing the risk of hemodynamic instability, cardiac arrhythmias, and thyroid storm.

Therefore, I would:

1. consult an endocrinologist;
2. continue her PTU,
   
   • which inhibits the organification of iodide, the synthesis of thyroid hormone, and the peripheral conversion of T4 to T3;
3. administer a –
   
   1. B-blocker
      
      • (to achieve a normal heart range, some sources say to achieve a heart rate < 90 beats per minute),
   2. glucocorticoids
      
      • (to reduce thyroid hormone secretion and the peripheral conversion of T4 to T3), and
   3. iopanoic acid
      
      • (an iodine containing compound that inhibits thyroid hormone release and the peripheral conversion of T4 to T3;
      • can reduce T3 levels by 50-75% in 6-12 hours);
4. ensure adequate hydration and a normal electrolyte balance; and
5. consider a small dose of benzodiazepine to relieve anxiety.