Oedema

Question 1

Loop diuretics

Common indications

Answer 1

1. Releif of breathlessness in acute pulmonary oedema in conjunction with O2 and nitrates
2. Symptomatic releif of fluid overload in chronic heart failure
3. Symptomatic releif of fluid overload in other oedema diseases e.g. Ascites, CKD

Question 2

Loop diuretics

MOA

Answer 2

• They work on the ascending loop of henle, where they inhibit the Na/K/2Cl co-transporter
• This protein is responsible for transporting Na, K and Cl ions from the tubular lumen into the epithelial cell. Water then follows by osmosis
• In addition to loop diuretics have a direct effect on the blood vessels causing dilation of the capacitance veins
• In acute heart failure, this reduces preload and improves contractile function of hte overstretched heart muscle
• Indeed, this is probably the main benefit of loop diuretics in HF

Question 3

Loop diuretics

Important adverse effects

Answer 3

• Water losses due to diuresis can led to dehydration and hypotension
• Inhibiting the Na/K/2Cl co-transporter increases urinary losses Na/K/Cl
• Indirectly, this increases excretion of Mg, Ca + H ions
• Associated with most low electrolyte state (including acidosis)
• A similar Na/K/2Cl co-transporter is responsible for regulating endolymph composition in the inner ear
• At high doses, loop diuretics can affect this too, leading to hearing loss and tinitus

Question 4

Loop diuretics

Warnings

Answer 4

• Contraindicated: Hypovolaemia, dehydration, AKI
• Caution; Hepatic encephalopathy (hypokalaemia can worsen/cause a coma), Hypokalaemia and/or hyponatraemia
• Loop diuretics inhibit uric acid excretion and this can worsen gout

Question 5

Loop diuretics

Interactions

Answer 5

• Loop diuretics have the potential to affect drugs that are excreted by the kidneys
• For example, Li levels are increased due to reduced excretion
• Digoxin toxicity may also be increased, due to the effect of diuretic-associated hypokalaemia
• Loop diuretics can increase the ototoxicity and nephrotoxicity of aminoglycosides

Question 6

Loop diuretics

Communication

Answer 6

• Explain that your patient that their body is overloaded with water
• You are therefore offering a treatment to increase urine flow, which will hopefully improve this
• The medicine will inevitably cause them to need to pass water more often
• Provided they do not take doses late in the day it should not affect them at night

Question 7

Loop diuretics

Monitoring

Answer 7

• Efficacy in the acute management of pulmonary oedema, evidence for good response will include improvements in the patients symptoms, tachycardia, hypertension and O2 requirements
• Increase UO typically occurs later and indicates onset of the diuretic effect
• In the longer-term therapy, you should monitor your patients symptoms and body weight (1kg/day)
• Safety: Periodic monitoring of serum Na, K and renal function is also advisable, particularly in the first few weeks of therapy