II. Indications
- Symptomatically reduce pulmonary and Peripheral Edema
- Congestive Heart Failure
- Nephrotic Syndrome
- Renal Insufficiency (GFR<30%)
- Other Diuretics (e.g. Thiazide Diuretics) are ineffective at low GFR
- Loop Diuretics (esp. Furosemide) may be used to prevent weight gain between Dialysis runs
- Emergency Management of Pulmonary Congestion (Lasix)
III. Contraindications
IV. Precautions
- All Loop Diuretics except Torsemide need to be dosed twice daily for effect
- Loop Diuretics are associated with significant Electrolyte abnormalities and volume depletion (FDA black box warning)
- Loop Diuretics have a threshold dose, below which they have no effect
- Loop Diuretics have a ceiling dose, above which increasing dose has little effect
- Better in these cases to increase frequency at the ceiling dose
V. Mechanism
- Loop Diuretics are the most potent of Diuretics
- Loop Diuretic potently inhibits reabsorption of Sodium and chloride
- Direct Venodilation in Pulmonary Edema
- Reduces venous return (Preload)
- Reduces Central Venous Pressure
- Synergistic effect with Morphine and Nitroglycerin
- Reduces Intravascular Volume
- Reduces Cardiac Output
- Beware Hypotension in Myocardial Infarction
VI. Medications: General
VII. Medications: Relative Potency (40 to 20 to 1)
- Furosemide (Lasix) 40 mg IV (equivalent to 80 mg oral, but variable Bioavailability)
- Torsemide (Demadex) 20 mg IV (equivalent to 20 mg oral)
- Bumetanide (Bumex) 1 mg IV (equivalent to 1 mg oral)
- References
VIII. Adverse Effects
- Risk of central volume depletion (Dehydration, Hypotension and contraction alkalosis)
- Renal dysfunction
- Minimize dosage when starting an ACE Inhibitor
- Avoid NSAIDs
-
Hypersensitivity (esp. Sulfonamide)
- Ethacrynic Acid is the only non-sulfonamide Loop Diuretic
-
Electrolyte abnormalities
- Hypokalemia
- Hypomagnesemia
- Metabolic Alkalosis
- Hyperosmolality
- Hyponatremia
- Hyponatremia is less common with Loop Diuretics than with Thiazide Diuretics
- Hypocalcemia
- Loop Diuretics increase Calcium excretion
- Contrast with Thiazide Diuretics which decrease Calcium excretion
- Ototoxocity
- Typically reversible (but permanent Deafness may occur)
- Risk Factors
- Higher Loop Diuretic serum concentrations (esp. high dose Furosemide)
- Renal dysfunction
- Concurrent Aminoglycoside use
- More common with Ethacrynic Acid
IX. Mechanism: Loop Diuretic Resistance
-
Renal Insufficiency
- Renal Toxin (e.g. NSAID) decreases GFR
- NSAIDs
- Decreased Diuretic oral absorption
- Structural changes in the Kidney
- Normal aging
- Distal tubular hypertrophy (long term use)
- Consider adding a Thiazide Diuretic
- Counters distal tubular reabsorption
- Significantly boosts Loop Diuretic effect
- Increased Dietary Sodium intake
- CHF patient is an avid Sodium retainer
- Sodium is common in most foods
- See Dietary Sodium