Management of Diuretic-Induced Hyponatremia in an 84-Year-Old with Heart Failure and CKD Stage 3b
Continue holding both furosemide and metolazone until sodium normalizes above 135 mEq/L, maintain fluid restriction and high-protein diet, and when diuresis is eventually needed, restart furosemide alone at a reduced dose (40 mg daily or twice daily) while permanently discontinuing metolazone. 1, 2
Immediate Management: Continue Current Approach
Your current management is appropriate and should be continued:
Hold all diuretics (both furosemide and metolazone) until sodium normalizes above 135 mEq/L, as the patient has clear diuretic-induced hyponatremia from excessive self-administration (120 mg furosemide daily plus metolazone). 1, 2
Continue fluid restriction and high-protein diet as these are first-line interventions for hypervolemic hyponatremia in heart failure patients. 1
Monitor sodium every 24-48 hours until stable and normalized, which aligns with your current BMP monitoring schedule. 2
The patient is not volume overloaded on exam (no pulmonary edema on CXR, normal oxygen saturation, diminished but not congested breath sounds), so aggressive diuresis is not indicated. 1
Critical Context: CKD Stage 3b Considerations
This patient's renal function significantly impacts diuretic management:
With CKD stage 3b (eGFR 33, creatinine 1.54), loop diuretics like furosemide remain effective, but thiazide-type diuretics (metolazone/Zaroxolyn) lose effectiveness at creatinine clearance <40 mL/min and increase risk of electrolyte abnormalities. 2
Metolazone should be permanently discontinued in this patient given her CKD stage 3b and propensity for severe hyponatremia. 2
The combination of loop diuretic plus metolazone markedly enhances risk of electrolyte depletion, which clearly occurred here. 1
When to Restart Diuretics
Restart furosemide only when:
Sodium is ≥135 mEq/L (currently trending up from 120→122→124→125→127, so continue monitoring). 2
Clinical evidence of volume overload develops (pulmonary edema, significant peripheral edema, worsening dyspnea with hypoxia). 1
Dosing strategy when restarting:
Start with furosemide 40 mg once or twice daily (significantly lower than her self-administered 120 mg daily), not the previous home dose of 40 mg BID plus metolazone. 2
Never restart metolazone given her CKD stage 3b and severe hyponatremia episode. 2
Check electrolytes and renal function within 2-4 days of restarting diuretics. 2
Addressing the Underlying Trigger
The patient's COVID-19 infection likely triggered:
Increased fluid intake or decreased oral intake leading to relative volume changes. 3, 4
Her self-medication with triple-dose furosemide (120 mg daily) plus metolazone was inappropriate and caused the hyponatremia, not actual volume overload. 5
Guideline-Directed Medical Therapy (GDMT) Continuation
Continue her current heart failure medications (sacubitril-valsartan/Entresto, apixaban) as she is hemodynamically stable:
Blood pressure 115-130/61-78 mmHg is acceptable and not contraindicated for GDMT. 1
Sertraline was appropriately held as SSRIs can contribute to hyponatremia. 5
Do not hold Entresto unless she becomes hypotensive (<90 mmHg systolic) or develops acute kidney injury. 1, 6
Vasopressin Antagonists: Not Indicated
While the 2013 ACC/AHA guidelines mention vasopressin antagonists (tolvaptan, conivaptan) for persistent severe hyponatremia:
This patient is asymptomatic (no cognitive symptoms, confusion, or seizures). 1
Her sodium is improving with conservative management (fluid restriction, holding diuretics). 1
Vasopressin antagonists are Class IIb (may be considered) only for persistent severe hyponatremia with cognitive symptoms despite water restriction. 1
They did not improve mortality in heart failure patients and have unknown long-term safety. 1
Monitoring Plan Going Forward
Check BMP every 24-48 hours until sodium >135 mEq/L. 2
Once stable, monitor electrolytes and renal function every 3-6 months. 2
Patient and family education is critical: she must not self-adjust diuretic doses, and should contact her provider if she feels volume overloaded. 5
Consider nephrology consultation if sodium fails to improve or if complex diuretic management is needed given her CKD stage 3b. 2, 6
Key Pitfalls to Avoid
Do not restart metolazone in this patient with CKD stage 3b—it is ineffective and dangerous at her level of renal function. 2
Do not restart diuretics at previous doses—she was overdosed at 120 mg furosemide daily plus metolazone. 1, 2
Do not use vasopressin antagonists in asymptomatic patients with improving sodium on conservative management. 1
Do not hold Entresto unnecessarily—continue GDMT unless hemodynamically unstable. 1, 6