From the FDA Drug Label
Because methimazole may cause hypoprothrombinemia and bleeding, prothrombin time should be monitored during therapy with the drug, especially before surgical procedures. Thyroid function tests should be monitored periodically during therapy Once clinical evidence of hyperthyroidism has resolved, the finding of a rising serum TSH indicates that a lower maintenance dose of methimazole should be employed. Because propylthiouracil may cause hypoprothrombinemia and bleeding, monitoring of prothrombin time should be considered during therapy with the drug, especially before surgical procedures. Thyroid function tests should be monitored periodically during therapy Once clinical evidence of hyperthyroidism has resolved, the finding of an elevated serum TSH indicates that a lower maintenance dose of propylthiouracil should be employed.
The preoperative management targets and checklist for patients with hyperthyroidism undergoing surgery include:
- Monitoring prothrombin time before surgical procedures due to the potential for hypoprothrombinemia and bleeding caused by methimazole or propylthiouracil 1 2
- Monitoring thyroid function tests periodically during therapy to assess the resolution of hyperthyroidism and adjust the maintenance dose of methimazole or propylthiouracil accordingly 1 2
- Adjusting the dose of methimazole or propylthiouracil based on the findings of rising serum TSH or elevated serum TSH to ensure a sufficient but not excessive dose is given during therapy 1 2
- Considering the potential interactions between antithyroid drugs and other medications, such as anticoagulants, beta-adrenergic blocking agents, digitalis glycosides, and theophylline 1 2 Key points to consider:
- Thyroid function: Monitor thyroid function tests periodically to assess the resolution of hyperthyroidism.
- Bleeding risk: Monitor prothrombin time before surgical procedures to minimize the risk of bleeding.
- Medication interactions: Consider potential interactions between antithyroid drugs and other medications.
- Dose adjustment: Adjust the dose of methimazole or propylthiouracil based on the findings of thyroid function tests and clinical evidence of hyperthyroidism.
From the Research
Thyroidectomy can be safely performed in hyperthyroid patients without achieving euthyroidism before surgery, as long as the patient's overall condition and comorbidities are evaluated and managed by a multidisciplinary team. The primary targets for preoperative management include controlling heart rate and addressing symptoms, rather than solely focusing on achieving euthyroidism 3. Patients should be started on beta-blockers such as propranolol (20-40 mg every 6 hours) or atenolol (25-50 mg daily) to maintain heart rate below 90 beats per minute and control adrenergic symptoms.
Some key points to consider in the preoperative management of hyperthyroid patients include:
- Controlling heart rate and addressing symptoms with beta-blockers
- Evaluating and managing the patient's overall condition and comorbidities, particularly cardiovascular stability
- Considering the use of antithyroid medications, iodine, and other treatments as needed, but not necessarily requiring euthyroidism before surgery
- Assessing the patient's airway, electrolyte balance, and cardiac function as part of the preoperative evaluation
The preoperative checklist should include:
- Verification of heart rate control
- Evaluation of electrolyte balance (particularly calcium and potassium)
- Airway assessment for goiter-related compression
- Cardiac evaluation if indicated
- Assessment of the patient's overall condition and comorbidities
According to a recent study, thyroidectomy can be safely performed in hyperthyroid patients without increasing the risk of thyroid storm or perioperative complications, even if the patient is not euthyroid at the time of surgery 4. Another study found that patients who were unable to tolerate antithyroid drugs and underwent thyroidectomy without being euthyroid had similar outcomes to those who were euthyroid at the time of surgery 5.
Overall, the goal of preoperative management in hyperthyroid patients is to optimize the patient's condition and minimize the risk of perioperative complications, rather than necessarily achieving euthyroidism before surgery. This approach should be individualized to each patient's needs and circumstances, and should involve a multidisciplinary team of healthcare providers 3, 4, 5.