Preoperative Orders for Hypothyroid Patients on Levothyroxine
Continue levothyroxine on the morning of surgery without interruption, including the day of the procedure. 1
Medication Management
Levothyroxine Administration
- Administer levothyroxine on the morning of surgery with a small sip of water, as thyroid hormone levels must remain stable to prevent perioperative complications 1
- Continue the patient's usual daily dose without modification 1
- No stress-dose adjustment is required for levothyroxine, unlike glucocorticoids 2
- Levothyroxine does not increase bleeding risk or interfere with anesthesia, making it safe to continue perioperatively 1
Rationale for Continuation
The National Comprehensive Cancer Network explicitly recommends continuing levothyroxine through the surgical period 1. Interrupting therapy risks destabilizing thyroid hormone levels, which can worsen perioperative outcomes including heart failure, gastrointestinal complications, and prolonged ventilation requirements 2.
Preoperative Assessment
Thyroid Status Optimization
- Delay elective surgery until euthyroidism is achieved whenever feasible 2
- Verify thyroid function tests (TSH, free T4) are within target range preoperatively 3
- Document euthyroid status by measuring serum TSH as part of preoperative evaluation 3
Risk Stratification
Hypothyroid patients undergoing surgery face specific complications 4:
- Increased risk of heart failure (29% vs 6% in cardiac surgery) 5
- Higher incidence of gastrointestinal complications (19% vs 1%) 5
- Neuropsychiatric complications (38% vs 18%) 5
- Intraoperative hypotension (61% vs 30% in noncardiac surgery) 5
- Increased risk of postoperative atrial fibrillation, particularly with TSH ≥10 mIU/L 4
Special Consideration: Coronary Artery Disease
For patients with angina or coronary artery disease requiring revascularization, address coronary blood flow first before initiating or adjusting thyroid hormone therapy, as preoperative levothyroxine could tax ischemic myocardium 3.
Critical Preoperative Orders
Adrenal Function Assessment
- Rule out adrenal insufficiency before surgery 2
- Hypothyroidism treatment is contraindicated until adrenal insufficiency is corrected, as thyroid hormone accelerates cortisol clearance and can precipitate adrenal crisis 2
- If adrenal insufficiency is present, treat with replacement glucocorticoids prior to initiating or continuing levothyroxine 6
Anesthetic Considerations
- Avoid etomidate for induction when possible, as it suppresses cortisol production 2
- Maintain high clinical suspicion for relative adrenal insufficiency throughout the perioperative period 2
- Anticipate and preemptively manage intraoperative hypotension 5
Postoperative Management
Monitoring
- Monitor for signs of severe hypothyroidism including lethargy, prolonged ventilation requirements, and hypotension 4
- Watch for gastrointestinal and neuropsychiatric complications 5
- Note that hypothyroid patients less frequently manifest fever with infection (35% vs 79%), which can mask postoperative infections 5
Medication Continuation
- Resume oral levothyroxine as soon as the patient can tolerate oral intake 6
- Administer as a single dose, preferably on an empty stomach, one-half to one hour before breakfast with a full glass of water 6
- Separate levothyroxine administration by at least 4 hours from iron, calcium supplements, and antacids that decrease absorption 6
Common Pitfalls to Avoid
Do not hold levothyroxine perioperatively - this is the most critical error, as interruption destabilizes thyroid status and worsens surgical outcomes 1
Do not confuse hypothyroidism with euthyroid sick syndrome - low thyroid hormones in acutely ill surgical patients may represent nonthyroidal illness rather than true hypothyroidism, and thyroid hormone replacement in euthyroid sick syndrome may be harmful 3
Do not use oral thyroid hormone to treat myxedema coma - this rare but severe complication requires intravenous therapy, not oral formulations 6
Do not overlook subclinical hypothyroidism - even patients with TSH between 4.5-10 mIU/L face increased perioperative risks, particularly cardiovascular complications 4