What are the medication dosages and management strategies for furosemide (Lasix) and digoxin (Digitalis) in a 3-week-old infant with mild congestive heart failure, Down syndrome, and ventricular septal defect (VSD)?

Furosemide and Digoxin Management for Dylan Banks

Furosemide Dosing and Administration

For this 3-week-old infant with mild CHF secondary to VSD, initiate furosemide at 1 mg/kg/dose orally or IV every 12-24 hours, with careful monitoring for response and electrolyte disturbances. 1, 2

Initial Dosing Strategy

• Start with 1 mg/kg/dose every 12-24 hours (Dylan weighs 3.5 kg, so approximately 3.5 mg per dose) 1, 2
• At doses ≤2 mg/kg/day, excess potassium loss generally does not occur and potassium supplementation may not be needed 1
• If inadequate diuresis occurs, increase by 1 mg/kg increments up to maximum 10 mg/kg/day 2
• For this infant with mild CHF, the lower end of dosing (1-2 mg/kg/day total) is most appropriate 1, 2

Route and Frequency Considerations

• Continuous infusion (0.1-0.2 mg/kg/hour) produces more controlled diuresis with fewer hemodynamic fluctuations compared to intermittent boluses 3, 4
• If using intermittent dosing, administer every 12 hours in full-term infants 5
• IV administration should be given over 5-30 minutes to minimize ototoxicity risk 2

Critical Safety Thresholds

• Never exceed 6 mg/kg/day for longer than 1 week due to significant ototoxicity risk 2
• Absolute maximum is 10 mg/kg/day for severe edema 2
• Cumulative doses >10 mg/kg carry a 48-fold increased risk of nephrocalcinosis 5

Digoxin Dosing and Administration

The use of digoxin in this infant with VSD and mild CHF is controversial, but may be beneficial if ventricular function is reduced; if used, initiate with maintenance dosing without loading doses. 1

Dosing Controversy in VSD

• Digoxin use in infants with VSD remains controversial because contractility is frequently normal 1
• Evidence suggests digoxin may benefit infants with large VSD who have reduced ventricular function or symptomatic heart failure despite other therapies 1
• The combination of digoxin and furosemide provides increased contractility over baseline 1

Practical Dosing Recommendations

• If digoxin is initiated, use 0.125 mg daily (or 5-10 mcg/kg/day divided twice daily for infants) 6
• Loading doses are NOT necessary for chronic heart failure management 6
• Lower doses should be used in patients with impaired renal function 6

When to Use Digoxin

• Consider digoxin if Dylan shows persistent symptoms despite furosemide therapy 1, 6
• More clearly indicated if echocardiography demonstrates reduced ventricular function 1
• Digoxin should NOT be used for acute stabilization but may be initiated after initial management 6

Side Effects and Monitoring

Furosemide Side Effects

• Hypercalciuria leading to nephrocalcinosis (especially with prolonged use) 1, 5
• Hypokalemia and metabolic alkalosis (can exacerbate CO2 retention) 1
• Transient deafness (rare, avoid with aminoglycosides) 1
• Hypovolemia and hypotension 1, 2

Digoxin Side Effects

• Toxicity commonly occurs with levels >2 ng/mL but can occur at lower levels with hypokalemia, hypomagnesemia, or hypothyroidism 6
• Bradycardia and AV block 6
• Nausea, vomiting, visual disturbances 6
• Avoid in patients with significant sinus or AV block unless pacemaker present 6

Essential Monitoring Parameters

• Fluid status and urine output (target >1 mL/kg/hour with furosemide) 2, 4
• Electrolytes (especially potassium, sodium, chloride) - monitor periodically 1, 2
• Renal function (creatinine) 2
• Blood pressure 2
• Weight (daily) 1
• Digoxin levels only if toxicity suspected (not for routine monitoring) 6
• Clinical symptoms: feeding tolerance, respiratory rate, diaphoresis 1, 7

Patient and Family Teaching

Furosemide Education

• Expect increased urination within 1-2 hours of oral dose 1
• Monitor for decreased wet diapers (paradoxically indicating dehydration) 7
• Watch for signs of dehydration: decreased skin turgor, sunken fontanelle, lethargy
• Report decreased urine output, as this may indicate inadequate dosing or worsening renal function 2

Digoxin Education

• Administer at same time daily for consistent levels 6
• Never double dose if one is missed 6
• Watch for signs of toxicity: poor feeding, vomiting, extreme lethargy, irregular heartbeat 6
• Report heart rate <90-100 bpm in infants before giving dose 6

General CHF Management

• Feeding difficulties are expected; may require 20+ minutes per bottle 1, 7
• Small, frequent feedings may be better tolerated 7
• Elevate head during and after feeds 7
• Monitor for increased work of breathing, increased diaphoresis, or poor weight gain 1, 7

Critical Pitfalls to Avoid

Furosemide Pitfalls

• Do NOT administer in hypovolemic states; ensure adequate intravascular volume first 2
• Avoid rapid IV push; always give over 5-30 minutes 2
• Do NOT use high doses (>6 mg/kg/day) for >1 week due to permanent hearing loss risk 2
• Monitor for hypokalemia when using with digoxin, as this increases digoxin toxicity risk 1, 6

Digoxin Pitfalls

• Do NOT use loading doses in chronic heart failure 6
• Serial digoxin levels are unnecessary unless toxicity suspected 6
• Be cautious with concomitant medications that increase digoxin levels (quinidine, verapamil, spironolactone, amiodarone) 6
• Hypokalemia from furosemide significantly increases digoxin toxicity risk 6

Oxygen Therapy Consideration

• Oxygen should generally be withheld until anatomic diagnosis confirmed, as it can cause pulmonary vasodilation and systemic vasoconstriction 1, 7
• However, post-cardiac catheterization with confirmed VSD, oxygen may be used judiciously if needed 1

Combination Therapy Considerations

• If furosemide alone is inadequate at 2 mg/kg/day, add spironolactone rather than increasing furosemide dose 1
• Spironolactone decreases potassium excretion and may obviate need for potassium supplementation 1
• Monitor for hyperkalemia when using spironolactone, especially with potassium supplementation 1
• The combination of chlorothiazide and spironolactone is an alternative to furosemide 1