Should I make any other medication changes or continue the current regimen for a diabetic patient with hyponatremia (serum sodium 131 mmol/L) on lisinopril 20 mg daily after stopping citalopram and reducing the lisinopril dose, who is scheduled for surgery?

Continue Current Regimen and Optimize Perioperatively

Continue lisinopril 20 mg daily through surgery without further dose reduction, ensure sodium is ≥135 mmol/L before proceeding, and maintain close perioperative monitoring. The patient's sodium has improved from 127 to 131 mmol/L after stopping citalopram and reducing lisinopril, indicating the primary culprit was likely citalopram, not lisinopril alone.

Rationale for Continuing Lisinopril

The improvement in sodium after stopping citalopram strongly suggests SSRI-induced SIADH was the primary driver of hyponatremia 1, 2. Citalopram causes hyponatremia in 16.5% of patients, with onset typically 6-20 days after initiation or dose escalation 1, 2. While lisinopril can rarely cause SIADH through central angiotensin II-mediated ADH release 3, 4, the temporal relationship and improvement after citalopram discontinuation points to the SSRI as the main offender.

ACE inhibitors should generally be continued perioperatively in patients with cardiovascular indications unless specific contraindications arise 5. For a diabetic patient, maintaining cardiovascular medications through surgery reduces perioperative MACE risk. The 2024 AHA/ACC perioperative guidelines emphasize continuing chronic cardiovascular medications through the hospital stay unless clear contraindications develop 5.

Preoperative Optimization Strategy

Sodium Management

• Target sodium ≥135 mmol/L before elective surgery 6, 7
• Current sodium of 131 mmol/L requires further correction
• Implement adequate solute intake (increased dietary salt and protein) with initial fluid restriction of 500 mL/day 7
• Monitor sodium every 2-3 days until normalized
• If sodium doesn't improve with conservative measures, consider oral urea as second-line therapy 7

Lisinopril Dosing Considerations

The FDA label recommends 2.5 mg once daily as the starting dose for heart failure patients with hyponatremia (sodium <130 mEq/L) 8. However, your patient:

• Has improved to 131 mmol/L (above the 130 threshold)
• Is on lisinopril for hypertension, not heart failure
• Has already tolerated dose reduction to 20 mg daily

Continue 20 mg daily rather than further reduction, as additional lowering may compromise blood pressure control perioperatively without clear benefit given the sodium improvement.

Perioperative Diabetes Management

Critical Preoperative Actions

• Discontinue any SGLT2 inhibitors 3-4 days before surgery to prevent perioperative metabolic acidosis 5
• Check HbA1c if not done within 3 months 5
• Continue metformin perioperatively if used, stopping only the night before surgery and restarting after 48 hours for major surgery with confirmed adequate renal function 9

Day of Surgery

• Hold lisinopril morning of surgery only if patient develops hypotension (SBP <100 mmHg) 8
• Resume lisinopril postoperatively once hemodynamically stable and taking oral intake
• Monitor sodium closely in immediate postoperative period

Key Monitoring Parameters

Preoperatively:

• Sodium levels every 2-3 days until ≥135 mmol/L
• Blood pressure to ensure adequate control on current lisinopril dose
• Renal function (creatinine clearance should be >30 mL/min for standard lisinopril dosing) 8

Perioperatively:

• Sodium levels daily for first 3 postoperative days
• Blood pressure and volume status
• Renal function before restarting metformin if applicable

Common Pitfalls to Avoid

1. Do not restart citalopram postoperatively - the hyponatremia risk remains high, especially with concurrent ACE inhibitor use 1, 2
2. Do not over-restrict fluids - aim for 500 mL/day restriction initially, adjusting based on sodium response 7
3. Do not delay surgery for mild asymptomatic hyponatremia - sodium of 131-134 mmol/L can be managed with conservative measures while proceeding with necessary surgery 7
4. Avoid thiazide diuretics - these significantly increase hyponatremia risk (HR 1.141) 1

The evidence strongly supports that stopping citalopram was the correct intervention and continuing lisinopril at the current dose through surgery is appropriate for this diabetic patient with improving hyponatremia.