Basic mechanism of dialysis

Before understating the dialysis disequilibrium syndrome, it is good to know the basics of dialysis and how it works on your body.

If your kidney get Acute Kidney Injury (AKI) or Chronic Kidney Disease (CKD), you may have to undergo a process called dialysis. What we do as dialysis is the providing of natural kidney functions by an artificial kidney attached to machine. The most important function of dialysis is the removal of waste products from the body like urea. In addition it help to maintain acid base balance and electrolyte balance of the body.

You can see more about dialysis here.

If you have understood this basic of dialysis, you might understand that urea is removed in each session of the dialysis.

Mechanism of dialysis disequilibrium syndrome (DDS)?

Osmotic pressure of our body is basically maintain by two particles. One is the Sodium (Na+). Other one is the Urea. Even though other electrolytes are affecting this process, only these two can give significant contribution to oncotic pressure.

As we mentioned we remove some amount of the urea with each dialysis. Therefore there is a reduction of osmotic pressure in the blood. When plasma osmotic pressure reduced, it can cause cells to take some fluid from plasma and keep the balance between them.

Same process occurs in the brain too. This will ultimately result in increased size (edema) in the brain cells. This cerebral edema can cause lot of neurological issues simply from headache to death at last. When the amount of removed urea is higher, the edema is higher and risk of dialysis disequilibrium syndrome is higher.

Who get the disequilibrium syndrome?

Dialysis induced disequilibrium syndrome (DDS) is commonly seen in patient who undergoes their 1st series of dialysis. However it can also be seen in other CKD patients too. Some studies show that it is common in patients who miss their dialysis sessions.In addition it can present in some patients who undergoes dialysis or CRRT following acute kidney injury.

Symptoms and signs of disequilibrium syndrome

1. Headache
2. Nausea
3. Dizziness
4. Confusion
5. Visual disturbance
6. Tremor
7. Seizures
8. Coma
   
   
   

How to prevent disequilibrium syndrome

Few decades ago, DDS is one of the common issues during dialysis. However with the development of the Nephrology and dialysis care, the disequilibrium syndrome has become a rare condition among the patients with Chronic Kidney Disease. Even though the dialysis disequilibrium syndrome is a rare complication, this should be considered as on of the serious complication of dialysis.

1. Initiate the dialysis with short cycles
   Usual hemodialysis session are continue upto 4 to 5 hours. However at the initiation of the dialysis, it is advice to limit the duration of dialysis for few hours. Usually 2.5hours – 3hours as maximum. As a result the risk of sudden reduction of urea is rare.
   
2. Use low blood flow rate
   When you dialysis, you can adjust the blood flow rate though the machine. Higher the rate of blood purification, higher the risk dialysis disequilibrium syndrome. Therefore you can try with a blood flow rate of 100 – 150 in initial dialysis sessions.
   
3. Monitor the Urea Reduction Ratio
   Usually you can monitor the urea reduction rate with pre and post dialysis blood urea samples. So if the URR is high, you can reduce the other parameters in future dialysis.
   
4. Initiate with low Ultrafiltrate (UF)
   In each dialysis session, we remove some amount of water from the body. When the volume of blood reduced, it cause sudden imbalance on osmolality. This also can lead to DDS. Therefore use low UF in early dialysis sessions.
   
   
   

Summery

As a summery dialysis disequilibrium syndrome (DDS) is not a common complication in novel Nephrology and dialysis care. However it was a common complication in history of hemodialysis. Why is this so important? Importance of dialysis disequilibrium syndrome is that its severe neurological complication. These can cause even sudden death. Therefore we have to take necessary precautions to prevent this condition during dialysis.

Reference articles

1. Zepeda-Orozco, D., & Quigley, R. (2012). Dialysis disequilibrium syndrome. Pediatric nephrology (Berlin, Germany), 27(12), 2205–2211.
   https://doi.org/10.1007/s00467-012-2199-4
   
2. S.M.Silver MD, R.H.Sterns MD, M.L.Halperin MD, Brain swelling after dialysis: Old urea or New Osmoles? American Journal of Kidney Diseases, Volume 28, Issue 1, July 1996, Pages 1-13
   https://doi.org/10.1016/S0272-6386(96)90124-9