Fluid Overload (Hypervolemia)

What fluid overload is

The body keeps its fluid volume in a narrow range by balancing what you drink and eat with what the kidneys excrete. Salt (sodium) is the key: where sodium goes, water follows. Fluid overload happens when the body retains sodium and water faster than the kidneys remove them, or when more fluid is given (usually through a drip) than the body can clear.

The extra fluid first expands the blood volume. Pressure inside the blood vessels rises and fluid seeps out into the tissues (edema), into the lungs (pulmonary edema) and into the belly (ascites). Doctors use "fluid overload", "volume overload" and "hypervolemia" interchangeably.

Fluid overload is different from simple local swelling such as a sprained ankle, and from fluid retention before a period, which is mild and temporary.

Fluid overload signs and symptoms

Symptoms build as fluid accumulates:

Early signs

• Rapid weight gain: 1 liter of retained fluid weighs about 1 kg (2.2 lb). Weight usually rises before swelling is visible.
• Swelling of the feet, ankles and legs (peripheral edema) or, in people lying in bed, over the lower back
• Tight rings, puffy hands and puffy eyes
• High blood pressure
• Reduced exercise tolerance and tiredness

As it worsens

• Shortness of breath on exertion, then at rest
• Breathlessness lying flat (orthopnea), needing several pillows
• Waking at night gasping (paroxysmal nocturnal dyspnea)
• A dry cough or wheeze, especially at night
• Swollen belly, early fullness and nausea from fluid in the abdomen or a congested liver and gut
• Swollen, bulging neck veins

Severe fluid overload

• Fluid in the lungs (acute pulmonary edema): severe breathlessness, crackling breath sounds, frothy pink sputum
• Low blood oxygen, with blue lips and confusion
• Confusion or seizures if the extra water dilutes the blood sodium (hyponatremia)

Fluid overload does not usually cause pain directly, but tense, swollen legs ache, a congested liver causes discomfort under the right ribs, and fluid in the belly causes pressure and bloating.

What causes fluid overload

Heart failure and chronic kidney disease are the two most common causes. In people on dialysis, fluid overload often follows drinking more than the daily allowance or missing a session.

Risk factors

• age over 65
• heart failure, kidney disease or liver disease
• being in the hospital on IV fluids, especially in intensive care or after major surgery
• a high-salt diet
• not taking diuretics as prescribed

How fluid overload is diagnosed

Diagnosis combines symptoms, examination and simple tests:

• Weight trend: comparing today's weight with your usual "dry weight"
• Examination: pitting edema, raised neck vein pressure, crackles in the lungs, an enlarged liver and fluid in the belly
• Blood pressure and oxygen level
• Blood tests: sodium, potassium, kidney function, albumin and BNP or NT-proBNP (raised in heart strain)
• Urine tests: protein and sodium levels
• Chest X-ray: fluid in the lungs, enlarged heart, fluid around the lungs (pleural effusion)
• Echocardiogram: heart pumping and valve function
• Ultrasound of the lungs, belly and the large vein entering the heart (inferior vena cava) to estimate fluid status

Treatment

The aim is to remove extra fluid safely and fix the cause.

Diuretics

Loop diuretics such as furosemide make the kidneys pass more salt and water. They are given by mouth for mild cases and by IV in the hospital. Other diuretics are added when one is not enough. During treatment, doctors check weight, urine output, kidney function and potassium closely, because diuretics can cause dehydration, low potassium and kidney strain.

Salt and fluid restriction

• Limit sodium, often to about 2,000 mg a day, depending on the cause. Most sodium comes from processed and restaurant food rather than the salt shaker.
• Your care team may set a fluid limit, often around 1.5 to 2 liters a day for heart failure or a lower amount for dialysis patients.

Treating the cause

• Heart failure medicines that improve pumping and reduce salt retention
• Stopping medicines that cause retention
• Treating nephrotic syndrome or liver disease
• Slowing or stopping IV fluids in the hospital

Removing fluid directly

• Dialysis or ultrafiltration when the kidneys cannot respond
• Paracentesis (draining fluid from the belly) for large ascites
• Oxygen and breathing support in acute pulmonary edema

Complications

• acute pulmonary edema and respiratory failure
• worsening heart failure from extra strain
• low blood sodium
• poor wound healing, skin breakdown and infections in swollen legs
• in hospital patients, longer stays and higher risk of death, which is why fluid balance is tracked closely

Living with a risk of fluid overload

If you have heart or kidney disease:

• Weigh yourself every morning, after passing urine and before eating, in similar clothes. Write it down.
• Call your care team if your weight rises by the amount they set, typically 1 kg (2 to 3 lb) overnight or 2 kg (4 to 5 lb) in a week.
• Read food labels for sodium and avoid canned soups, processed meats, salty snacks and fast food.
• Count all fluids, including soups, ice and gelatin desserts, if you have a fluid limit.
• Take your diuretic at the time advised and do not skip doses without talking to your team.

Frequently asked questions

What are the first signs of fluid overload?

The earliest sign is usually weight gain over a day or two, followed by ankle or leg swelling, tight shoes or rings and puffy eyes. Breathlessness when walking or lying flat, and needing extra pillows at night, show that fluid is reaching the lungs.

What are the signs and symptoms of fluid volume overload?

Signs a doctor finds include pitting edema, high blood pressure, swollen neck veins, crackles in the lungs and rapid weight gain. Symptoms you notice include swelling, breathlessness, a cough at night, a bloated belly and tiredness. Severe cases cause gasping and frothy sputum.

Can fluid overload cause pain?

Fluid overload itself is not usually painful, but its effects can be. Tight, swollen legs ache, a congested liver causes discomfort under the right ribs, fluid in the belly causes pressure, and breathlessness can feel like chest tightness. New chest pain always needs urgent assessment.

How long does it take to get rid of fluid overload?

Mild overload often improves within a few days of diuretics and salt restriction. Hospital patients with severe overload commonly lose 0.5 to 1 kg (1 to 2 lb) a day with IV diuretics, so recovery can take one to two weeks. Dialysis removes fluid within hours.

Is fluid overload the same as edema?

Not quite. Edema is visible swelling from fluid in the tissues and can be local, like a swollen sprained ankle. Fluid overload means the whole body has too much fluid, which usually shows as edema plus weight gain, breathlessness and high blood pressure.

Can drinking too much water cause fluid overload?

In healthy people, the kidneys excrete large amounts of water, so overload is rare. It can happen with extreme intake, as in psychogenic polydipsia or endurance events, usually causing dangerously low sodium. People with heart, kidney or liver disease become overloaded much more easily.