What is the meaning of fluid overload (hypervolaemia)?

Fluid overload, also known as hypervolaemia, is a medical condition characterised by an excessive accumulation of fluid in the body. Treatment aims to the amount of fluid in your body.

Pulmonary oedema on CXR, with pleural effusion arrowed.

Here are 10 key facts about fluid overload.

1. Causes

Fluid overload is not a diagnosis on its own. It is a syndrome with many causes, including:

Acute and chronic heart failure (CHF; commonest) – and its causes
Acute kidney injury (AKI)/chronic kidney disease (CKD) – and its causes
Nephrotic syndrome – and its causes. This includes pre-eclampsia and eclampsia in pregnancy
Acute and chronic liver disease – and its causes
Malnutrition/malabsorption – and its causes
Excessive intravenous fluid administration
Fluid shift into the intravascular space – e.g. fluid remobilisation after burns treatment; administration of hypertonic fluids, e.g. mannitol or hypertonic saline solution; administration of plasma proteins, such as albumin.

Note. How to describe a patient with fluid overload. For example, the way to describe the diagnosis in a patient could be “fluid overload due to acute cardiac failure due to a STEMI or AF” .. then .. “the patient also has CKD3B (presumed secondary to renovascular disease) that may be a factor in their condition”.

2. Symptoms

Symptoms include:

Swelling (oedema) – particularly in the legs, ankles, and feet. It can also occur around the eyes (peri-orbital oedema) and around the genitals

Peri-orbital oedema

Shortness of breath – due to pulmonary oedema (or pleural effusion), where fluid accumulates in or around the lungs – and can be fatal
Coughing – and frothy sputum +/- haemoptysis in severe cases
Paroxysmal nocturnal dyspnea (PND) – fluid can also collect in the lungs when lying down at night, causing shortness of breath at night
Weight gain
High blood pressure. Though FO can occur with low blood pressure (hypotension). This is called cardiogenic shock and is a poor prognosis sign.

Pitting leg oedema

Note. Dependent oedema – which is common in less mobile older frailer people – is not a FO state and will not respond to diuretics. In fact, the non-response to diuretics, is often the clue to the diagnosis.

3. Signs on examination

Of left heart failure

Tachycardia – very typical of acute fluid overload, unless on beta-blockers
Bibasal crackles
Triple or gallop rhythms
Cardiac murmurs – either associated with cause (valvular heart disease, or infective endocarditis); or effect (e.g. functional MR or TR).

Of right heart failure

Raised JVP
Leg and other areas of oedema – and if in arms/hands, there may be tightness of jewellery, clothing or accessories
Ascites
Hepatomegaly.

Of underlying cause

Rash – in renal vasculitis
Finger, palm and nail signs – of infective endocarditis.

4. Diagnosis (and investigations)

Diagnosis often involves history and examination, and investigations including:

Blood tests – electrolytes, kidney function, liver enzymes; tests for anaemia and cholesterol
B-type natriuretic peptide (BNP) blood test. BNP is a hormone your heart releases. High BNP blood levels can indicate heart failure
Urinary dipstick/uACR
Urinary sodium – may help differentiate acute kidney injury (AKI) from other (nonrenal) acute causes of fluid overload. In renal failure, the urinary sodium is > 20 mmol/L, as compared to < 10 mmol/L in heart failure, cirrhosis, and nephrotic syndrome.
Chest x-ray
ECG
Echocardiogram – to assess heart function. This is sometimes better done when the oedema has been treated with diuretics.

5. Electrolyte imbalance

Fluid overload is associated with various electrolyte imbalances, e.g.

AKI/CKD – if that is the cause
Abnormal liver enzymes – as cause, or effect (right heart failure)
Hyponatraemia (‘hypervolaemic hyponatraemia’; low sodium level)
Hypokalaemia (high potassium level; may be secondary to loop or thiazide diuretics) or hyperkalaemia (low potassium level; potassium-sparing diuretics or AKI/ACD).

Note. U&E may be normal, e.g. in cardiac failure.

6. Treatment

Treatment includes:

Treat the underlying cause – e.g. immunosuppression for AKI/CKD caused by an acute glomerulonephritis; or antibiotics for acute heart failure due to infective endocarditis
Diuretics – e.g. loop diuretics like Furosemide and Bumetanide, to remove excess fluid
Fluid (1.5L a day commonly) and salt restriction
Of arrhythmias – tachy- or bradycardia
Later (especially in chronic disease) – add ACE/ARB, beta-blocker, SGLT2i; and spironolactone or eplerenone (MRAs), isosorbide mononitrate, or hydralazine in some patients
ESRF. Patients on long-term dialysis, many need more dialysis; or if they have a kidney transplant (especially if it’s failing), may need to start/or receive more diuretics, or to start dialysis
Liver disease/ascites – may need paracentesis.

Acute fluid overload

This may need additional treatment, e.g.

High dose oxygen
Intravenous vasodilator – e.g. GTN
Dialysis – severe AKI/CKD
Ventilation.

7. Surgical treatments (for heart failure)

Coronary bypass surgery – to route blood around a blocked artery
Heart valve repair or replacement – to fix or repair a damaged valve in your heart
Implantable cardioverter defibrillator – to put your heart back into a normal rhythm, if it goes out of rhythm
Cardiac resynchronisation therapy – also called a biventricular pacemaker, to help your two lower heart chambers pump blood at the same time
Ventricular assist device – to pump in place of your heart until you can have surgery to fix the problem
A heart transplant – is an option for people with very severe heart failure who haven’t improved with surgery or medicine. The surgeon replaces your damaged heart with a healthy heart from a donor.

8. Complications

If left untreated, fluid overload can lead to severe complications especially:

Pulmonary oedema
Pleural effusion(s)
Pericarditis
Ascites
Leg oedema – with impaired wound healing/increased risk of infection.

9. Monitoring and follow-up

Careful monitoring and follow-up are crucial for patients with fluid overload. It is important to have regular check-ups by a GP and/or hospital specialist (e.g. cardiologist or nephrologist; or their specialist nurses), weight monitoring, and adhere to treatment plans.

10. Cardio-renal syndrome

Some patients have fluid overload due to a combination of CHF (due to IHD) and CKD (due to renovascular disease, RVD) – i.e. atheroma causes both. This can be called cardio-renal syndrome.

Other names for fluid overload

Oedema, œdema, biventricular failure, fluid retention, water retention, dropsy, hydropsy.

Summary

We have described what is the meaning of fluid overload (hypervolaemia). We hope it has been helpful.

Last Reviewed on 11 July 2024