What are the perioperative management recommendations for a patient on chronic furosemide (Lasix) undergoing anesthesia, including timing of drug discontinuation, fluid and electrolyte replacement, and postoperative resumption?

Perioperative Management of Furosemide (Lasix) in Anesthesia

Continue furosemide on the day of surgery in most patients undergoing elective noncardiac surgery, as withholding it does not reduce intraoperative hypotension and may worsen heart failure outcomes.

Key Management Principles

Preoperative Period

Do not routinely discontinue furosemide before elective surgery. The highest quality randomized controlled trial directly addressing this question found no significant difference in intraoperative hypotension risk between patients who continued furosemide (49%) versus those who received placebo (51.9%) on the day of surgery 1. This challenges the traditional practice of withholding diuretics perioperatively.

Specific exceptions requiring consideration for temporary discontinuation:

• Heart failure patients on SGLT2 inhibitors: These should be withheld 3-4 days before surgery to reduce perioperative metabolic acidosis risk, but furosemide itself should continue 2
• Patients with compensated heart failure: Continue guideline-directed medical therapy (GDMT) including furosemide perioperatively unless contraindicated 2
• Severe cirrhosis (Child-Pugh B/C): Use diuretics cautiously intraoperatively to maintain low portal pressure, but balance against tissue perfusion needs 3

Critical Preoperative Assessment

Check electrolytes within 24-48 hours before surgery, particularly:

• Potassium (hypokalemia risk with chronic furosemide use)
• Sodium (hyponatremia common in heart failure patients)
• Creatinine/BUN (assess volume status and renal function)
• Magnesium and calcium 4

Correct significant electrolyte abnormalities preoperatively as the FDA label explicitly warns that electrolyte depletion occurs especially in patients receiving higher doses with restricted salt intake 4.

Intraoperative Management

Maintain normovolemia using goal-directed fluid therapy (GDFT) when appropriate:

• Target mean arterial pressure ≥60-65 mmHg 3, 2
• Use balanced crystalloids (Hartmann's/Plasmalyte) over 0.9% saline 5, 6, 7
• Administer fluid boluses (200-250 mL) only for objective hypovolemia (>10% fall in stroke volume) 6
• Background crystalloid infusion: 1-4 mL/kg/h 6

Avoid excessive intravenous fluid administration as this is particularly important in patients on chronic diuretics who may have underlying heart failure or cirrhosis. Fluid restriction helps maintain lower portal pressure in cirrhotic patients 3 and prevents postoperative pulmonary complications 7.

Use vasopressors (norepinephrine) for hypotension in normovolemic patients rather than excessive fluid boluses, especially in those with epidural anesthesia 5. The FDA label notes that furosemide may decrease arterial responsiveness to norepinephrine, but it can still be used effectively 4.

Postoperative Management

Resume furosemide as soon as clinically appropriate:

• Restart oral medications when patient can tolerate oral intake
• Propensity-matched studies show delaying resumption of chronic medications increases 30-day mortality risk 2
• Do not intensify diuretic therapy at discharge unless clinically indicated, as this increases readmission risk 2

Minimize postoperative IV fluids:

• Transition to enteral route as early as possible (preferably morning after surgery) 5, 6
• Aim for zero fluid balance postoperatively 6
• Stop IV fluids once adequate oral intake established 6

Monitor closely for:

• Volume overload (especially in heart failure patients)
• Electrolyte disturbances (particularly hypokalemia, hyponatremia)
• Acute kidney injury (furosemide does not prevent AKI and may worsen it in hypovolemic states) 7
• Signs of hypovolemia: oliguria, prolonged capillary refill, tachycardia, hypotension 4

Special Populations

Heart Failure Patients

Continue furosemide perioperatively unless patient has volume overload requiring adjustment 8. Collaboration with anesthesia and surgery teams is essential to limit intraoperative fluid administration 8. Monitor in step-down or ICU setting for up to 48 hours postoperatively 8.

Cirrhotic Patients

Use diuretics strategically intraoperatively to maintain low circulating volume and portal pressure, but ensure mean arterial pressure ≥60-65 mmHg with vasoconstrictors 3. Avoid rapid correction of hyponatremia (risk of neurological complications) 3.

Patients at High Risk for Radiocontrast Nephropathy

Furosemide increases risk of renal deterioration compared to IV hydration alone in this population 4. Consider withholding if contrast administration planned perioperatively.

Common Pitfalls to Avoid

1. Do not assume furosemide causes intraoperative hypotension - Level 1 evidence shows it does not 1
2. Do not give excessive IV fluids to "compensate" for diuretic effect - this causes postoperative complications 7
3. Do not use furosemide to prevent or treat established AKI - it is ineffective and potentially harmful 7
4. Do not forget drug interactions: Furosemide potentiates succinylcholine, antagonizes tubocurarine, and increases lithium toxicity 4
5. Do not combine with aminoglycosides or ethacrynic acid due to severe ototoxicity risk 4

Practical Algorithm

Day of Surgery:

• Give morning furosemide dose with sip of water (unless specific contraindication)
• Verify recent electrolytes available
• Plan for balanced crystalloid use intraoperatively
• Prepare vasopressors for blood pressure management

Intraoperatively:

• Maintain normovolemia with GDFT principles
• Use vasopressors for hypotension in normovolemic patients
• Limit total fluid administration

Postoperatively:

• Resume furosemide when oral intake tolerated
• Discontinue IV fluids early
• Monitor electrolytes and renal function
• Do not increase home furosemide dose without clear indication