Dialysis Disequilibrium Syndrome Overview

Dialysis disequilibrium syndrome is a neurologic complication that occurs during or after dialysis treatment. As fluid and toxins are removed from the body with dialysis, physiological changes which can induce a number of neurological symptoms begin to occur. The symptoms can vary from mild ones like headache to the most severe forms where patients can develop coma, or even death. Here is a non-inclusive list of symptoms:

• Nausea
• Headache
• Disorientation
• Confusion
• Cramps
• Dizziness
• Seizures
• Coma, or death in severe cases

Causes

You would think that with dialysis being around for half a century, we would understand all its adverse effects by now. With dialysis disequilibrium though, that is not the case and the exact mechanism is still a matter of research. We do have some leads, though: 

1. One of the theories that has been proposed is something called reverse osmotic shift, or reverse urea effect. Essentially, dialysis removes urea from the bloodstream much more quickly than the urea inside the brain cells. In that interim, the urea concentration is higher in the brain cells, and water accordingly follows. This swelling of the brain cells via this mechanism has been thought of as one of the possible reasons for the usual neurological problems associated with dialysis disequilibrium syndrome.
2. Decreased pH of the brain cells. In layman terms, this would mean that the brain cells have a higher level of "acid". This has been proposed as another possible cause. 
3. Idiogenic osmoles produced in the brain (the details of numbers 2 and 3 are beyond the scope of this article).

Risk Factors

Fortunately, dialysis disequilibrium syndrome is a relatively rare entity and its incidence continues to drop. This has been thought to be due to the fact that patients are now initiated on dialysis at a much lower concentration of urea in the blood.

Here are some situations when a patient could be considered high risk for development of dialysis disequilibrium syndrome:

• Older patients and kids 
• New starts on dialysis
• Patients who already have a neurological disorder like seizures or a stroke
• Patients on hemodialysis (the syndrome is not seen in peritoneal dialysis patients)

Prevention

Since dialysis disequilibrium syndrome is thought to be related to rapid removal of toxins (urea) and fluid from the newly dialyzed patient, certain preventive measures might be helpful. Identifying the high-risk patient, as mentioned above, is the first step. Beyond that, there are certain strategies that might help:

• Slow initiation of dialysis, preferably limiting the first session to around 2 hours, with slow blood flow rates
• Repeating the session for first 3-4 days, daily, which not might be the typical frequency in the long run (hence more frequent, but "gentler" sessions)
• Infusion of something called mannitol 

Treatment

Treatment is mostly symptomatic. Nausea and vomiting can be treated medically using medications like ondansetron. If seizures ever happen, the typical recommendation is to stop dialysis and initiate antiseizure medications. The intensity and the aggressiveness of dialysis might need to be reduced for future treatments.