Effects of Lasix on Congestive Heart Failure

In congestive heart failure, a chronic condition which requires lifetime management, the blood vessels, lungs and other organs become overloaded with fluid 3. While a healthy heart pumps blood efficiently through vessels and organs, in CHF the heart’s pumping ability is weak. Because blood isn’t moving properly, the blood vessels and organs become congested with fluid.

Typically the lungs are the first organs affected as the blood vessels that empty from the lungs into the heart become overloaded. As CHF progresses, retained fluid causes swelling in the feet and legs. This swelling, called edema, may progress until all the organs are overloaded with fluid, resulting in fatigue and breathlessness. Lasix, one of the most commonly prescribed medications for heart failure, belongs to a class of medications known as loop diuretics 3. Often referred to as a “water pill,” Lasix triggers the kidneys to remove water from the body by increasing urination.

Reducing Fluid Overload

The primary effect of Lasix on CHF is reducing fluid congestion. By triggering the kidneys to make large amounts of urine, Lasix pulls excess volume out of the blood vessels and organs. Many people with CHF take small doses of Lasix daily--a 20 mg pill is typical--to maintain a normal fluid volume. When patients are admitted to the hospital with worsening CHF, doctors prescribe large doses of intravenous Lasix to get rid of excess fluid quickly.

Improved Breathing

Most people with with CHF have impaired breathing. Feeling shortness of breath that gets worse with exertion is typical, and many patients have an irritating, nonproductive cough that is worse when lying down. By pulling excess water out of the lungs, Lasix improves breathing, activity tolerance and sleep.

Reduced Swelling

Most people with CHF experience some degree of swelling in the feet and lower legs. In acute exacerbations of CHF, swelling can be extreme, involving the thighs, arms and lower trunk. Just as Lasix pulls water off the lungs to improve breathing, its diuretic effect pulls water out of body tissues. A daily dose of Lasix helps control chronic swelling. When swelling is severe, doctors may give a higher dose.

Side Effects

Lasix is a powerful aid in helping the body lose excess fluid, but it can go too far and cause dehydration. Dehydration, in turn, can cause low blood pressure. People taking Lasix need to be monitored for fluid balance to avoid these side effects. Lasix also causes potassium to be lost in the urine. Low potassium levels can be dangerous, especially for people with CHF. Low potassium can cause dangerous and even fatal heart arrhythmias. Also, many people with CHF take another drug called digoxin. Without a certain level of potassium in the body, a toxic overload of digoxin accumulates. Most people on Lasix replace potassium on a daily basis, either by eating potassium-rich foods or taking a potassium supplement.