UBP 3.7 (Short Form): Endocrine – Thyroidectomy

Question 1

What are your concerns with this patient?

(A 21-year-old female is scheduled for total thyroidectomy to treat a multinodular goiter. She states she has had progressive dyspnea and dysphagia over the last 2 weeks, and stridor is noted during an initial physical exam. Her past medical history is significant for gastroesophageal reflux (GERD), irritable bowel syndrome, and bipolar disorder. Her current medications include lithium, olanzapine, propylthiouracil (PTU), omeprazole, and oral birth control pills. Vital Signs: HR = 122, BP = 158/88 mmHg, RR = 22, Hgb = 13 mg/dL.)

Answer 1

I have several concerns in providing care for this patient.

First, her thyroid mass combined with progressive dyspnea, dysphagia, and inspiratory stridor is consistent with tracheal compression, which significantly increases the risk and difficulty of airway management.

Second, I am concerned about her GERD, which potentially increases the risk of aspiration.

Third, the presence of tachycardia and hypertension in this patient being treated for hyperthyroidism (propylthiouracil) is concerning, since it may represent inadequate treatment, placing her at increased risk of experiencing a hyperdynamic circulation, cardiac arrhythmias, and/or thyroid storm in the perioperative period (on the other hand, her tachycardia and hypertension may simply represent the patient’s reaction to respiratory distress and/or impending surgery).

Finally, given this patient’s bipolar disorder, I am concerned about patient cooperation and the potential complications associated with lithium treatment and lithium toxicity, such as – polyuria, skeletal muscle weakness, ataxia, cognitive changes, widening of the QRS, atrioventricular block, hypotension, and seizures.

Question 2

How would your anesthetic management be different for a patient taking lithium?

(A 21-year-old female is scheduled for total thyroidectomy to treat a multinodular goiter. She states she has had progressive dyspnea and dysphagia over the last 2 weeks, and stridor is noted during an initial physical exam. Her past medical history is significant for gastroesophageal reflux (GERD), irritable bowel syndrome, and bipolar disorder. Her current medications include lithium, olanzapine, propylthiouracil (PTU), omeprazole, and oral birth control pills. Vital Signs: HR = 122, BP = 158/88 mmHg, RR = 22, Hgb = 13 mg/dL.)

Answer 2

Given the detrimental side effects of lithium toxicity, I would evaluate the patient for signs of toxicity such as –

• skeletal muscle weakness,
• cognitive changes (sedation),
• ataxia,
• widening QRS,
• atrioventricular heart block,
• hypotension, and
• seizures.

In addition to this examination, I would –

• check the patient’s most recent lithium level and/or order lab work to check her current level.

Finally, I would –

• avoid any drugs that may lead to toxicity (i.e. thiazide diuretics, NSAIDs, ACE inhibitors),
• administer sodium containing fluids to prevent excessive renal reabsorption of lithium (reabsorption occurs in the proximal tubule in exchange for sodium),
• watch the ECG for lithium-induced atrioventricular blockade or dysrhythmias, and
• closely monitor both anesthetic depth and neuromuscular blockade throughout the case (lithium has the potential to reduce anesthetic requirements and prolong the effects of both depolarizing and nondepolarizing muscle relaxants).

Question 3

How would you evaluate her for possible airway obstruction?

Would you order flow-volume loops?

(A 21-year-old female is scheduled for total thyroidectomy to treat a multinodular goiter. She states she has had progressive dyspnea and dysphagia over the last 2 weeks, and stridor is noted during an initial physical exam. Her past medical history is significant for gastroesophageal reflux (GERD), irritable bowel syndrome, and bipolar disorder. Her current medications include lithium, olanzapine, propylthiouracil (PTU), omeprazole, and oral birth control pills. Vital Signs: HR = 122, BP = 158/88 mmHg, RR = 22, Hgb = 13 mg/dL.)

Answer 3

Assuming she was adequately oxygenating,

I would perform a focused history and physical to determine the severity and onset of her respiratory symptoms,

identify any aggravating factors, and note the effects of positioning, if any, on her respiratory function (supine vs. prone vs. upright).

I would also review or order airway films and/or CT scan of the neck to identify the location of the mass and assess the extent of airway compression.

Finally, I would consider pulmonary function testing to more accurately evaluate her pulmonary function.

Flow volume loops may be beneficial in determining the effects of positioning on the airway, whether the obstruction is fixed or variable, and whether the mass is intrathoracic or extrathoracic.

However, I would NOT necessarily order flow-volume loops since a CT scan combined with a careful history and physical in which the patient is observed in both the sitting, supine, and prone positions may provide the needed information, such as –

• tumor location (substernal extension increases the risk of worsening tracheal compression with the loss of respiratory muscle tone),
• the degree of tracheal compression, and
• the effects of positioning on mass compression of the trachea.

Question 4

What type of flow-volume loop pattern would you expect to find with this patient?

(A 21-year-old female is scheduled for total thyroidectomy to treat a multinodular goiter. She states she has had progressive dyspnea and dysphagia over the last 2 weeks, and stridor is noted during an initial physical exam. Her past medical history is significant for gastroesophageal reflux (GERD), irritable bowel syndrome, and bipolar disorder. Her current medications include lithium, olanzapine, propylthiouracil (PTU), omeprazole, and oral birth control pills. Vital Signs: HR = 122, BP = 158/88 mmHg, RR = 22, Hgb = 13 mg/dL.)

Answer 4

Patients with large thyroid masses usually have a fixed obstruction that may be intrathoracic or extrathoracic in location.

Airway flow with this type of obstruction is limited during both inspiration and expiration, with subsequent flattening of both limbs of the flow-volume loop (regardless of whether the obstruction is intrathoracic or extrathoracic).

• Clinical Note:*
• The flow-volume loop plots the inspiratory and expiratory airflow (Y-axis) against the flow volume (X-axis) during the performance of maximally forced inspiratory (total lung capacity) and expiratory (residual volume) maneuvers.

Question 5

Is this patient euthyroid?

How could you tell?

(A 21-year-old female is scheduled for total thyroidectomy to treat a multinodular goiter. She states she has had progressive dyspnea and dysphagia over the last 2 weeks, and stridor is noted during an initial physical exam. Her past medical history is significant for gastroesophageal reflux (GERD), irritable bowel syndrome, and bipolar disorder. Her current medications include lithium, olanzapine, propylthiouracil (PTU), omeprazole, and oral birth control pills. Vital Signs: HR = 122, BP = 158/88 mmHg, RR = 22, Hgb = 13 mg/dL.)

Answer 5

While her tachycardia and hypertension may be due to anxiety associated with her respiratory distress and/or upcoming surgery, these symptoms are concerning since they may represent inadequate treatment and hyperthyroidism.

Therefore, I would perform a history and physical exam to identify additional signs of inadequately treated hyperthyroidism, such as –

• diarrhea,
• warm moist skin,
• heat intolerance,
• cardiac arrhythmias,
• fatigue,
• skeletal muscle weakness,
• fine tremor of the hands, and
• hyperactive tendon reflexes.

Additionally, 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 6

Her total T4 is elevated. What do you think about this finding?

(A 21-year-old female is scheduled for total thyroidectomy to treat a multinodular goiter. She states she has had progressive dyspnea and dysphagia over the last 2 weeks, and stridor is noted during an initial physical exam. Her past medical history is significant for gastroesophageal reflux (GERD), irritable bowel syndrome, and bipolar disorder. Her current medications include lithium, olanzapine, propylthiouracil (PTU), omeprazole, and oral birth control pills. Vital Signs: HR = 122, BP = 158/88 mmHg, RR = 22, Hgb = 13 mg/dL.)

Answer 6

While an elevated T4 may indicate hyperthyroidism, this test (or a total T3) should NEVER be used alone to evaluate thyroid function, especially for this patient who is taking an oral contraceptive.

While total T4 and T3 levels are often utilized in the evaluation of thyroid function, thyroid hormone protein binding influences these concentrations.

Unfortunately, the principal binding protein, thyroxine-binding globulin (TBG), does not remain at a reliably constant level, increasing with acute liver disease, pregnancy, and estrogen containing drugs (such as oral contraceptives), and decreasing with chronic liver disease, nephrotic syndrome, and conditions associated with elevated glucocorticoids.

Therefore, total T4 and T3 levels should ALWAYS be used in conjunction with a test used to assess thyroid hormone binding, such as a T4 or T3 resin uptake test.

The information from these tests can be used to calculate the free T4 index and/or free T3 index, which are proportional to free levels of T4 and T3 respectively.

Question 7

Assuming her lab work showed an elevated free T4, would you delay surgery in order to medically treat her hyperthyroidism?

(A 21-year-old female is scheduled for total thyroidectomy to treat a multinodular goiter. She states she has had progressive dyspnea and dysphagia over the last 2 weeks, and stridor is noted during an initial physical exam. Her past medical history is significant for gastroesophageal reflux (GERD), irritable bowel syndrome, and bipolar disorder. Her current medications include lithium, olanzapine, propylthiouracil (PTU), omeprazole, and oral birth control pills. Vital Signs: HR = 122, BP = 158/88 mmHg, RR = 22, Hgb = 13 mg/dL.)

Answer 7

While I would delay any elective case to achieve a euthyroid state prior to surgery, her progressive dyspnea and dysphagia may make a significant delay in surgical intervention unacceptable.

Unfortunately, rendering this patient euthyroid may require an extended amount of time due to potentially large stores of hormones within the thyroid gland

(7-14 days with propranolol and iodides; 6-8 weeks with PTU).

Therefore, I would discuss my concerns with the surgeon and, if the case was deemed urgent or emergent, consult an endocrinologist, attempt to medically optimize this patient’s condition, and proceed to surgery;

recognizing that proceeding with surgery when the patient remains hyperthyroid places her at increased risk for perioperative complications such as – hemodynamic instability (hyperdynamic circulation), cardiac arrhythmias, and thyroid storm.

Question 8

Assuming this is an urgent case, how would you optimize this patient’s thyroid status for surgery?

(A 21-year-old female is scheduled for total thyroidectomy to treat a multinodular goiter. She states she has had progressive dyspnea and dysphagia over the last 2 weeks, and stridor is noted during an initial physical exam. Her past medical history is significant for gastroesophageal reflux (GERD), irritable bowel syndrome, and bipolar disorder. Her current medications include lithium, olanzapine, propylthiouracil (PTU), omeprazole, and oral birth control pills. Vital Signs: HR = 122, BP = 158/88 mmHg, RR = 22, Hgb = 13 mg/dL.)

Answer 8

In optimizing this patient’s thyroid status for urgent surgery, I would –

• consult an endocrinologist;
• continue her PTU, which inhibits the organification of iodide, the synthesis of thyroid hormone, and the peripheral conversion of T4 to T3; and
• administer a B-blocker (to achieve a normal heart rate),
• glucocorticoids (to reduce thyroid hormone secretion and the peripheral conversion of T4 to T3), and
• iopanoic acid (can reduce T3 levels by 50-75% in 6-12 hours).
• Additionally, I would provide adequate hydration and ensure a normal electrolyte balance.
• I would also consider a small dose of benzodiazepine to relieve anxiety, taking care to avoid respiratory depression in this patient with apparent airway obstruction.

My goal would be to minimize the risk of hemodynamic instability, cardiac arrhythmias, and thyroid storm.