Related Subjects: Chronic Heart Failure
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Heart Failure and Pulmonary Oedema
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Loop Diuretics
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Entresto Sacubitril with Valsartan
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Ivabradine
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Furosemide
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Angiotensin Converting Enzyme Inhibitors
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Cardiac Resynchronisation Therapy (CRT) Pacemaker
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💊 About
- Always check the BNF or equivalent (e.g., local formulary) for prescribing advice.
- Potent diuretics that promote rapid excretion of sodium, chloride, and water.
- Frequently used in acute left ventricular failure (LVF) and conditions with marked fluid overload.
⚙️ Mode of Action
- Inhibit reabsorption of sodium and chloride in the thick ascending loop of Henle, and to some extent in proximal/distal tubules.
- Highly protein bound (albumin), secreted into renal tubule via active transport.
- Diuretic efficacy depends on renal function → reduced effect in advanced CKD or elderly patients with low clearance.
📌 Indications
- Acute LVF / Pulmonary oedema (first-line IV therapy).
- Chronic heart failure with fluid overload.
- Fluid retention in liver failure (ascites) and nephrotic syndrome.
- Adjunct in resistant hypertension (not recommended as monotherapy).
- Electrolyte disorders:
- Hypercalcaemia (↑ calcium excretion).
- Hyperkalaemia (promotes kaliuresis, used with fluids/insulin in emergencies).
🚫 Contraindications / Cautions
- Avoid combination with other ototoxic drugs (e.g., aminoglycosides).
- Monitor renal function and electrolytes closely.
- Hypokalaemia → increases digoxin toxicity risk.
💉 Dose
- Furosemide (oral): 20–80 mg once daily initially; may titrate higher.
- Bumetanide (oral): 1–2 mg once daily initially.
- Acute LVF (IV): Furosemide 40–80 mg IV as a single bolus (may repeat/titrate).
⚠️ Side Effects
- Volume depletion, dehydration, orthostatic hypotension → risk of falls in elderly.
- Electrolyte disturbances:
- Hypokalaemia, metabolic alkalosis.
- Hypomagnesaemia, hypocalcaemia, hypercalciuria.
- Hyperuricaemia (can precipitate gout).
- Ototoxicity (tinnitus, hearing loss) - especially with rapid IV administration or aminoglycosides.
- Hyperglycaemia, worsening diabetes control.
🔄 Interactions
- Digoxin: Risk of toxicity ↑ with hypokalaemia.
- Lithium: Clearance reduced → lithium toxicity risk.
- Other antihypertensives → additive hypotension.
💡 Pearls for practice:
- In acute pulmonary oedema: give furosemide IV with oxygen, nitrates, and morphine as per local protocol.
- Always monitor U&E, creatinine, and volume status.
- Loop diuretics increase calcium excretion (contrast with thiazides which retain calcium).
