Haemodialysis – Blood Purification for Kidney Failure

What is Haemodialysis?

Haemodialysis is a life-sustaining medical procedure used to replace the filtering function of the kidneys when they can no longer perform adequately. Healthy kidneys continuously filter blood to remove waste products, excess fluids, and toxins. When kidney function falls below a critical level – due to chronic kidney disease or acute kidney failure – haemodialysis takes over these vital functions using an artificial kidney called a dialyser.

Millions of people worldwide depend on regular dialysis treatments to survive. Haemodialysis is the most widely used form of renal replacement therapy globally.

How Does Haemodialysis Work?

During haemodialysis, the blood is pumped out of the body and passed through a dialyser, which contains thousands of tiny hollow-fibre membranes. These semi-permeable membranes allow waste products such as urea, creatinine, and excess electrolytes to pass from the blood into a special cleansing solution called dialysate, while retaining essential blood components.

The process relies on two key physical principles:

• Diffusion: Dissolved substances move across the membrane from an area of higher concentration (blood) to lower concentration (dialysate).
• Ultrafiltration: A controlled pressure gradient draws excess fluid out of the blood.

When is Haemodialysis Indicated?

Haemodialysis is indicated when kidney function is severely impaired. Key indications include:

• End-stage renal disease (Stage 5 CKD): Kidney function has dropped to less than 15% of normal capacity.
• Acute kidney injury: A sudden, severe loss of kidney function due to poisoning, severe infection, or haemodynamic shock.
• Fluid overload: Life-threatening accumulation of fluid that cannot be managed by other means.
• Severe electrolyte imbalances: Such as dangerously elevated potassium levels (hyperkalaemia).
• Uraemia: A toxic build-up of nitrogenous waste products in the blood causing systemic symptoms.

Procedure and Treatment Schedule

Haemodialysis requires a reliable vascular access point. The most common form is the arteriovenous (AV) fistula, a surgically created connection between an artery and a vein that provides high blood flow rates. Alternatives include an AV graft (synthetic tube) or a temporary dialysis catheter for urgent cases.

A standard haemodialysis session lasts between 3 and 5 hours and is typically performed three times per week, either at a dialysis centre or at home (home haemodialysis). Throughout the session, blood is continuously circulated through the dialysis machine, cleaned, and returned to the body.

Possible Side Effects and Complications

While haemodialysis is an effective and well-established treatment, it can be associated with various side effects and complications:

• Low blood pressure (hypotension): The most common complication, often caused by rapid fluid removal.
• Muscle cramps: Frequently related to rapid fluid shifts or electrolyte changes during treatment.
• Nausea and vomiting: May occur during or after the session.
• Infections: Particularly at the vascular access site; bloodstream infections pose a serious risk.
• Anaemia: Common in kidney disease due to reduced erythropoietin production.
• Bone and mineral disorders: Resulting from impaired regulation of phosphate and calcium.
• Fatigue and exhaustion: Many patients experience persistent tiredness and reduced quality of life.

Haemodialysis vs. Other Renal Replacement Therapies

In addition to haemodialysis, other renal replacement options are available:

• Peritoneal dialysis: Uses the body's own peritoneal membrane as a natural filter. Dialysate is instilled into the abdominal cavity and drained after several hours. This method can often be performed at home.
• Kidney transplantation: The preferred long-term option for suitable patients. A successful transplant allows most patients to live a near-normal life without ongoing dialysis.

The most appropriate treatment depends on the underlying condition, overall health, lifestyle, and the preferences of the individual patient.

Living with Haemodialysis

Regular haemodialysis places significant demands on daily life. Patients must carefully manage their diet and fluid intake. General recommendations include:

• Restricting daily fluid intake
• Limiting dietary potassium, phosphate, and sodium
• Adjusting protein intake in line with medical guidance
• Regular medications such as phosphate binders, erythropoiesis-stimulating agents, and antihypertensives

With appropriate medical care, dietary adaptation, and psychosocial support, many patients on haemodialysis are able to lead active and fulfilling lives.

References

1. Kidney Disease: Improving Global Outcomes (KDIGO) – Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease. KDIGO 2024.
2. Kasper DL et al. – Harrison's Principles of Internal Medicine, 21st Edition. McGraw-Hill Education, 2022.
3. National Kidney Foundation (NKF) – KDOQI Clinical Practice Guidelines for Haemodialysis Adequacy. Available at: www.kidney.org