Following up from our article on the What-Why-When of Dialysis, presenting here a comprehensive insight on one of the commonest treatment modalities in kidney failure – Haemodialysis.

Haemodialysis or Hemodialysis www.allthingskidney.com

Find the table of contents below. Click on your topic of choice to get to your section-of-choice directly or scroll down to read the whole post (recommended!).


1. What is Haemodialysis?

2. Which medical conditions may be treated with Haemodialysis?

3. How does Haemodialysis help Kidney Patients?

4. Dissecting the haemodialysis machine

5. So what really goes on during the Haemodialysis procedure?

6. How long do Haemodialysis sessions last on an average?

7. Advantages of Haemodialysis 

8. Complications of Haemodialysis 

9. Is there a way to get Dialysis treatment without risk of complications?

10. Link to other Dialysis FAQs 👉 (Diet, Medicines, Work or travel with Dialysis, Expenses etc.)




What is Haemodialysis (HD)?

The word Haemodialysis comprises of two words:

Hemo = Blood ; Dialysis = Separating out excess wastes

Haemodialysis is an indispensable tool in clinical medicine that is used to treat patients who are sick because of an excess buildup of unwanted wastes or toxins in their bloodstream.

This can happen with any medical condition that affects the normal body waste-clearing mechanism in our body by Kidneys & Intestines either directly or indirectly & results in the levels of unwanted blood wastes to go haywire!

In Haemodialysis, the patient’s bloodstream is connected to a Dialysis machine with the help of some tubes & catheters. This allows the patient’s blood to be directly sent to the dialysis machine for “correction”



Which medical conditions may be treated with Haemodialysis?

If the patient presents with slow build-up of unwanted substances in blood over a few months to years, the medical team will try to treat this with medication first. These are usually a combination of meds taken by mouth, injections & infusions directly into the bloodstream. If patients do not respond to these medicines and continue to get more sick, patients are put on Dialysis as the last resort.

However, if there is a sudden, massive increase in harmful substances in blood over a very short frame of time such that the situation turns instantly life-threatening, haemodialysis may be one of the earlier aggressive treatment options.

Such medical conditions include but are not limited to:

1️⃣ Kidney failure following Chronic Kidney Disease (Stage 5 CKD or ESRD)

2️⃣ Acute Kidney Injury (AKI) complicated with high blood Urea, high blood Potassium, high blood acidity or fluid overload not responding to medication

3️⃣ Heart diseases that may cause:

– High blood potassium levels that do not respond to other medicines

– Excess fluid retention not responding to medication

– High blood acidity not responding to medicines

4️⃣ In some cases of Liver failure

5️⃣ In Stroke patients who are in Coma and are on strong doses of medicines that have harmful side-effects on kidney function.

6️⃣ Blood poisoning with kidney-harming drugs/chemicals (suicide attempts, some snake bites etc.)



How does Haemodialysis help in Kidney Failure due to Chronic Kidney Disease?

Both Dialysis & Kidney Transplant are considered what we technically term Renal Replacement Therapy (RRT). Simply put, these therapies “assist with or take over” the compromised function of unwell kidneys for an overall better blood-component balancing capacity.

When your kidneys fail, dialysis helps restore balance in your blood components by:

1️⃣ Removing metabolic wastes, excess salts and extra water to prevent them from building up in the body

2️⃣ Keeping a safe level of certain minerals / chemicals in your blood, such as potassium, sodium and bicarbonate.

3️⃣ Preventing your blood from turning too acidic or abnormally alkaline.

4️⃣ Helping to control your blood pressure


However, please understand, Dialysis only helps cover for a fraction of all functions normally performed by kidneys in good health.

Hence, talking in the strictest sense, Dialysis is more of an Assistive Therapy rather than a true Replacement Therapy. As of today, Kidney Transplants are the only viable Renal Replacement Therapy and hence, the best treatment for Kidney failure from CKD.  

Back to top


Dissecting Haemodialysis: What’s in the machine?

In haemodialysis, the dialyzer is used to remove waste and excess minerals and fluid from your blood.

Dialysis machines in a hospital appear as a “tall, boxy machine” with a monitor displaying some “numbers” and attached to numerous tubes. Some of these tubes “dock the patient” to the machine.

Haemodialysis or Hemodialysis machine www.allthingskidney.com
Haemodialysis Machine | Image sourced under license from CC 4.0


Let’s take you through “what’s inside the box” to help you appreciate how Dialysis works.

We start with a very brief insight on the various ways to connect you to that machine. In other words, let’s discuss your “Access” options. Here goes:


Before you can begin your Haemodialysis treatment, you need two access points to your bloodstream:

GreenTick Haemodialysis www.allthingskidney.com  One to draw waste loaded blood/fluid and send it to the dialyzer.

GreenTick Haemodialysis www.allthingskidney.com  The other, to return cleansed blood/fluid back from the Dialyzer

Haemodialysis or Hemodialysis ports of access
Ports of access for Haemodialysis


To insert these ports, the doctor needs to make an entrance into your blood vessels. Such an Access could be:

I. Surgically created access:

This is done by a minor surgery to join a suitable artery and a vein in your arm, wrist or leg.

If these blood vessels are joined directly to make a bigger, wider blood vessel, it is called a Fistula.

Haemodialysis Fistula
Illustration showing a Fistula created by joining blood vessels in the forearm by operation. It shows the vein (in blue) & the artery (in red) connected at two spots. Connecting these vessels creates a larger, bulged blood vessel space upon maturation over time. This makes it easier to insert needles of the port access before each Haemodialysis session without poking the patient’s skin unnecessarily.


Haemodialysis Fistula picture from real life dialysis clinic
Real life image of Haemodialysis Fistula (seen as two elongated bulges in the patient’s forearm)


Alternatively, if your blood vessels are not found suitable for Fistula creation, doctors can use a separate soft plastic tube to join the artery and the vein beneath your skin. This is called a Graft.

Haemodialysis Graft www.allthingskidney.com
Haemodialysis Graft | When a patient’s blood vessels are found unsuitable for direct connection via surgery to form a Fistula, a short plastic tube called a Graft can instead be used to “bridge” the artery with the vein.


Such a surgical access “designates” a spot for inserting the two ports for multiple dialysis sessions. It virtually eliminates the struggle to map-out and poke two separate needles each time you go for a session.


II. A Neckline / Central Line / Central Venous Catheter

Some patients may need Dialysis only for a short time before a planned kidney transplant. In such cases, instead of creating a Fistula or a Graft, your doctor can insert a narrow plastic tube or a Catheter directly into a large vein in your neck under local anaesthesia.

The technical name for such neck vein access is a Neckline or Central Line or a Central Venous Catheter.


Neckline Catheter for Dialysis
Illustration showing a Neckline Catheter for Dialysis inserted directly into a large vein in the patient’s neck

The components that are necessary for the Haemodialysis machine to work include:


Such a “tank” provides space for the patient’s waste loaded blood to collect outside the body for necessary correction.


The Dialysate is the chemical solution against which your blood sent to the Dialysis Machine “compares its waste load & mineral content”.

Your Dialysis nurse adjusts this Fresh Dialysate to contain minerals and blood proteins in quantities appropriate for restoring normal mineral, protein & fluid balance in the patient’s blood upon “contact”.

During the HD procedure, all excess waste & some fluid load from your blood “crosses over” to the Fresh Dialysate within the Dialysis Tank. At the same time levels of minerals like Sodium, Potassium, Chlorine, Magnesium, Bicarbonate also “balance out”. All of this takes place through a special filter membrane (as explained below). 


  • This membrane separates waste-loaded blood from the fresh dialysate and acts as the filter.
  • It allows for “controlled exchange” of minerals & plasma protein between the patient’s blood & the Dialysate until “desired correction”.

Think of this membrane as an Immigration Officer at Passport control, you get the idea.

  • Your Dialysis team can control this procedure by pre-setting the timer & expected blood correction to be achieved via Dialysis in the “monitor” on the machine.


Back to top


So how does Haemodialysis “balance your blood”?

From the outside, Haemodialysis looks simple. You send your blood to the machine for “servicing” and get the finished product back.

But the procedure is far from lucid. Let’s unravel the details of the valiant journey that your blood undertakes from your body to the Dialyzer and back, to help you appreciate all that goes into assisting your unwell kidneys via Haemodialysis.

Schematic diagram of the Haemodialysis Machine
Schematic diagram of the Haemodialysis Machine

One port (needle accessing the bloodstream) sends the patient’s waste-loaded blood into the Dialyzer Tank. (blue tubing in diagram)

On the way to the tank, there is a thick syringe pumping a chemical called “Heparin” into the patient’s blood. This is a “blood thinner” that prevents the patient’s blood from clotting during the Dialysis procedure.


In addition, there are two pressure valves along the way to the Dialyzer Tank:

The First Pressure Valve helps control the rate at which blood flows out of the patient’s body.

It is crucial that the dialysis team adjusts this pressure to prevent sudden or too rapid outflow of the patient’s blood. Else, the patient stands a risk of losing consciousness & further damage to the kidneys, heart & brain.

The Second Pressure Valve is located after the “Blood Thinner” Syringe.

This valve helps to regulate the pressure at which the patient’s blood, now mixed with Heparin, enters the Dialyzer Tank.

Regulating the Pressure at this valve is essential to allow adequate correction of waste, mineral, protein & fluid levels within the patient’s blood.

Oh Yes, you read that right. Dialysis is all about “Pressure Tactics”!


The fresh dialysate is continuously pumped to the Dialyzer Tank (Yellow tubing in diagram towards tank):

  1. To “interact & correct” the mineral, fluid & plasma protein content.
  2. Rid the in the patient’s blood of accumulated metabolic wastes.

The special “bio-compatible porous membrane” within the tank allows for controlled crossing-over of “useful” components such as proteins in the patient’s blood in “adequate” quantities into the fresh dialysate area within the tank. In return, the waste-load, excess minerals & fluids “stay below”. This fluid now becomes the “Used Dialysate’


Once the “exchange” of the Fresh Dialysate helps restore the balance in the patient’s blood:

  • The used Dialysate returns to a separate collection area.
  • The “clean” blood is pumped back into the patient’s bloodstream.

1. The cleansed & balanced blood flows back to the body through another Pressure Monitor. This monitor checks the blood from gushing back to the patient’s bloodstream with unnecessary force which could otherwise potentially injure the vein and scar it.

2. In addition, an Air trap & bubble detector monitors the inflowing blood for large air bubbles. This is necessary to prevent large air bubbles from potentially blocking your natural blood flow within the body. Such bubbles could otherwise cause heart attacks, strokes or even sudden death.

Back to top


How long does Haemodialysis take?

The time needed for your haemodialysis session depends on:

1️⃣ How well your kidneys work

2️⃣ The fluid weight you gain between treatments

3️⃣ The waste content you have in your blood

4️⃣ Your body surface area (how big you are)

5️⃣ The type of dialyzer used


A typical hemodialysis treatment course requires three days of your week and 4 hours per session.

High flux dialysis is a type of hemodialysis that may take less time. You can speak to your doctor to see if this is an appropriate treatment for you.


Advantages of Haemodialysis (HD)

1️⃣ Kidney failure patients live longer with Dialysis than otherwise. If a matched & willing kidney donor is not available at the outset, patients must consider starting Dialysis to prevent their quality of life from declining rapidly, till a kidney donor is available.

2️⃣ Haemodialysis (HD) corrects blood component imbalances efficiently with less number of sessions per week.

3️⃣ HD is a good treatment choice for kidney failure patients who already have Congestive Heart Failure.

Such patients have poor heart pumping capacity. So, fluid overload due to kidney failure spells burdensome on their already weak heart. Haemodialysis is able to remove enough fluid from the body in each session to help patients with weak heart pumping cope with kidney failure better.

4️⃣ Associated with better maintenance of blood (serum) Albumin protein levels as compared to Peritoneal Dialysis. This is also in part, because there is an active protocol in place to advise Protein supplements to HD patients.


Are there any complications?

Unfortunately, yes.

Despite being a life-saving intervention, we cannot deny the fact that Haemodialysis is ultimately an “external interference” in the usual work-flow of the human body. This is bound to invite some complications related to the procedure, especially in the long run.

We have listed below, the various complications reported with Haemodialysis worldwide over the years, for your reference.


It is not necessary that all complications would show up in one patient altogether or that every person on Haemodialysis would end up with these complications.


1. PORT ACCESS (Fistula/Graft/Neckline) COMPLICATIONS:

  • Infection of the fistula site with subsequent spread into the bloodstream
  • Clotting in and blockage of the operated blood vessels (fistula/graft site)
  • Easy bleeding from minor trauma
  • Aneurysm refers to excess bulging of fistula & weakening of vessel walls
  • Poor Skin integrity at the site over the bulged fistula

2. HAEMO-DYNAMIC PROBLEMS (related to disturbances in blood volume & flow)

  • Fluctuation in blood pressure

Sudden “correction” of fluid levels in the blood after a Haemodialysis session can frequently manifest as a sudden fall in Blood pressure & extreme tiredness.

  • Occasional Chest pain

This is likely due to abrupt changes in body water content during Dialysis that “burdens” the heart. It could also result from disease of blood vessels to the heart that is common in CKD.



  • Muscle cramps especially in the calves.

This is due to rapid changes in blood Sodium & Potassium levels during Dialysis cycles. This is avoidable by suitably adjusting the Fresh Dialysate within the Dialysis machine.

  • Poor control of raised blood phosphate levels from CKD.

This worsens Bone pain & increases chance of getting Kidney Stones.

  • Anaemia due to iron deficiency from loss of extra blood during each Haemodialysis session. This worsens the already anaemic state caused due to kidney failure.



  • Headache

Headaches are extremely common in all Haemodialysis patients due to abrupt & large changes in body fluid and mineral levels after every session.

  • Dialysis associated Dementia (forgetfulness)

This is attributed to abnormal buildup of a mineral called Aluminium in blood & low blood pressure in HD patients.

This is treatable by making adjustments to Aluminium levels in the Dialysate fluid and with medication to “bind to” & reduce blood Aluminium levels.

  • Wernicke’s Encephalopathy

This complication involves inflammation of brain tissue due to Vitamin B1 deficiency.

This condition manifests as difficulty in eye movements, imbalance in body movements & confusion. It is reversible by treating with Vitamin B1 injections/infusion.

  • Dialysis disequilibrium syndrome

Patients who are irregular with their Haemodialysis treatment sessions present with this rare complication.

It is a set of neurologic symptoms such as headache, nausea & blurred vision. It occurs due to excess fluid accumulation in the brain.

  • Stroke

Stroke or “brain attack” presents as paralysis due to sudden, poor blood supply to a part of the brain.

In hemodialysis patients, this could occur because of increased chances of abnormal blood clotting and poor heart pumping as side effects of the dialysis procedure over time.


Is there a way to get Dialysis treatment without the risk of all these complications?

Yes. There is another type of Dialysis called Peritoneal Dialysis:

1. It usually invites fewer complications and is milder on the heart as compared to Haemodialysis for the first few years.

2. Can be done at home by the patients themselves

3. Is a good choice for patients who handle employment or study commitments.

However, a subset of patients may not qualify for starting treatment with Peritoneal Dialysis.

Learn if it could suit your case & more about this modality here.


Other Dialysis FAQs

Apart from these core details about Haemodialysis, should you want to seek more clarity on issues like:

If you still need to take your kidney meds after starting Dialysis

– Your Renal Diet

– If you can Work while on Haemodialysis

– If you can travel while on Haemodialysis

– Dialysis expenses

and more,

Then click on the image link below 👇

Dialysis FAQs All Things Kidney Official

Back to top

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.