Loop diuretics Flashcards
What are examples of loop diuretics?
- Furosemide
- Bumetanide
What are indications for loop diuretics?
- Relief of breathlessness in acute pulmonary oedema
- Treatment of fluid overload in chronic heart failure
- Fluid overload in renal failure
- Fluid overload in liver failure
How do loop diuretics work?
Act principally on the ascending limb of the loop of Henle, where they inhibit the Na+/K+/2Cl−co-transporter. This causes potent diuresis. In addition, loop diuretics have a direct effect on blood vessels, causing dilatation of capacitance veins.
How do diuretics work in acute heart failure?
Diuretics reduce preload and improve contractile function of the ‘overstretched’ heart muscle. This is probably the main benefit of loop diuretics in acute heart failure, as the clinical response is usually evident before a diuresis is established
What are important adverse reactions associated with loop diuretics?
- Dehydration
- Hypotension
- Hypomagnasaemia
- Hypocalcaemia
- Hypokalaemia
- Hyponatraemia
- Metabolic alkalosis
- Hearing loss/Tinnitus
Why can loop diuretics cause hearing loss and tinnitus?
Na+/K+/2Cl− co-transporter is responsible for regulating endolymph composition in the inner ear
What are contraindications to loop diuretics?
- Hypovolaemia
- Dehydration
When do you have to be careful when using loop diuretics?
- Hepatic encephalopathy
- Hypokalaemia
- Hyponatraemia
- Gout
What are important interactions to consider when using loop diuretics?
- Lithium
- Digoxin
- Aminoglycosides
How are loop diuretics administered?
- Oral
- IV
What dose of furosemide would you start someone on to treat oedema?
Initially 40 mg in the morning (twice daily if nocturnal dyspnoea), then maintenance of 20-40mg daily, or 40 mg alternate days
What is the maximum rate of IV furosemide infusion that you can give?
4mg/minute
How would you initially administer a loop diuretic in acute pulmonary oedema?
IV bolus in the once only section. Then depending on response - more boluses, or oral maintenance or IV infusion
Why should oral loop diuretics be given in the morning?
To avoid nocturia
How would you monitor effectiveness of loop diuretics in acute pulmonary oedema?
Improvements in the patient’s symptoms, tachycardia, hypertension and oxygen requirement. Increased urine output typically occurs later and indicates onset of the diuretic effect
