Cardiac Drugs 4 of 5 Loop Diuretics

Cardiac Drugs 4- loop diuretics

This is the 4th drug in my popular cardiac drug series.

Not strictly cardiac drugs, classes of diuretics have been used first and second line in cardiac patients since before the 80s.   This edition looks at the loop diuretics and specifically the drug Frusemide (Furosemide) marketed as Lasix for decades. Quite simply tradenamed because it lasts six hours.

This drug causes a reduction of sodium reabsorption in the ascending limb of the loop of Henle in the nephrons of the kidney.
If sodium is reabsorbed from the nephron, so to is water as it is osmotically attracted to salt.  Lasix inhibits this process causing the patients kidneys to lose or excrete sodium and consequently, water as urine. The process is called a diuresis.

Now let's explore why you would want to remove water from someone...

1.  Too much pressure in the veins causing overfilling and inefficiency in the patients heart. By removing water, we remove blood pressure making the heart work using less energy and oxygen. Doing this can improve the efficiency of a heart in a patient with congestive heart failure.

2.  After administering a unit of packed cells (RBCs) the osmotic pressure in the vascular space increases.  This drags water via osmosis into the blood stream.  Fluid overload here can make hard work for the heart, so Lasix pulls off this excess vascular water, and promotes its excretion via the kidneys.

3. Acute blood pressure control.
Less circulating blood volume means less pressure in the closed vascular system.    In patients with high blood pressure, the removal of a modest volume of water can reduce blood pressure.  Blood pressure that the heart has to pump against... For this reason is assists to
Reduce afterload, an inhibitor of the cardiac output.

4.  Pulmonary oedema and ankle swelling. As vascular volume is depleted, the interstitial fluid shifts into the vascular space to balance it.  So in a patient with oedema, Lasix can help strip the swelling excess fluid making breathing more comfortable, improving gas exchange, and survivability from an oedematous event often caused by heart failure.

Adverse effects:
Ototocicity or deafness caused by neural damage in the ears has been linked to high rapid doses of Lasix.

Hypotension.  It's effects can be dramatic on blood pressure.  Especially when first started on this drug, and when standing up, they can get a case of the dizzies.

Potassium depletion. In allowing excretion of sodium, occasionally potassium can be depleted too. For this reason, often they need a supplement of potassium.

Frequency.  Naturally these class of drugs makes someone want to pee more often. The patient needs to be told to expect this.

There you have it, a short yadda yadda on the loop diuretic Frusemide.

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