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Pathophysiology of dialysis disequilibrium syndrome

At a basic level this is a condition which results from the cerebral oedema that occurs when an ineffective osmole is enthusiastically extracted from the extracellular fluid by dialysis. In this, it resembles the cerebral oedema that can develop with the rapid overcorrection of glucose in a patient with a hyperosmolar hyperglycaemic state. Its one of those rare disease states that, when first recognised, was immediately and fully understood by the authors of the seminal article, with little else added in the subsequent years.

That seminal paper was Kennedy et al (1962), and is really just a letter to the editor of the Lancet.

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 Dialysis Disequilibrium Syndrome: A Neurological Manifestation of Haemodialysis

“The reverse urea effect”: Haemodialysis rapidly removes small solutes such as urea, particularly in patients who have marked uraemia. Urea is generally considered an “ineffective” osmole, because of its ability to permeate cell membranes. However, this ability to cross the cell membrane may take several hours to reach completion. This “lag period” may be particularly relevant in the brain where the blood-brain barrier may contribute to a plasma-brain urea concentration gradient. As a result, urea transiently acts as an effective osmole, promoting water movement into the brain. In addition, the reduction in BUN lowers the plasma osmolality, thereby creating a transient osmotic gradient that promotes water movement into the cells. In the brain, this water shift across the blood-brain-barrier produces cerebral oedema and a variable degree of acute neurological dysfunction

Articles of Interest

A vanishing complication of haemodialysis: Dialysis disequilibrium syndrome

DDS is rare, as measures have been initiated in dialysis centres to reduce its incidence; lower blood flow rates are used and smaller surface area dialysers. The pathogenesis of DDS is probably related to a rapid reduction in urea by HD. This lowers the plasma osmolality of the blood. Water therefore moves into cerebral cells, which results in cerebral oedema. DDS is a diagnosis of exclusion.

Dialysis disequilibrium syndrome

The dialysis disequilibrium syndrome is a rare but serious complication of hemodialysis. Despite the fact that maintenance hemodialysis has been a routine procedure for over 50 years, this syndrome remains poorly understood. The signs and symptoms vary widely from restlessness and headache to coma and death. While cerebral edema and increased intracranial pressure are the primary contributing factors to this syndrome and are the target of therapy, the precise mechanisms for their development remain elusive.

Dialysis Disequilibrium Syndrome: A Red Flag to Check Post Hemodialysis

DDS is a rare syndrome defined as a plethora of neurological symptoms seen during or following HD treatment. While it most commonly occurs after the first dialysis treatment in newly initiated patients, it can also occur in chronic dialysis patients, those who regularly miss dialysis treatments, or those with acute kidney injury on continuous renal replacement therapy. This rare syndrome has a low rate of incidence partly because the corresponding neurological symptoms are so nonspecific that they oftentimes go unnoticed...

Dialysis Disequilibrium Syndrome: A Swell Diagnosis?

The differing clinical presentations are the result of the varying severity of increased intracranial pressure. Preventative measures have made its occurrence much less frequent, but its diagnosis should be considered when neurological symptoms are temporally related to dialysis even when preventative measures have been implemented.

Dialysis Disequilibrium Syndrome: Causes, Signs and Treatment

Hemodialysis can result in a serious but rare complication known as dialysis disequilibrium syndrome (DDS). The majority of its symptoms are neurological. In most cases, the symptoms are brief, self-limiting, and rarely fatal. Patients with very high plasma urea concentrations, those with chronic kidney disease (CKD), and starting hemodialysis with aggressive urea removal are more likely to experience symptoms. Although the exact frequency of dialysis disequilibrium is unknown,

Dialysis Disequilibrium Syndrome: The Changes of Intracranial Pressure

Clinically, the diagnosis of DDS is one of exclusion and should be distinguished from the similar symptoms and signs of intracranial hypertension resulting from subdural hematoma, uremia, nonketotic hyperosmolar coma, acute stroke, dialysis dementia, hypoglycemia or hyponatremia.

Disequilibrium syndrome

DDS is thought to be caused by cerebral edema due to a lag in osmolar shifts between the blood and brain during dialysis, but changes in cerebral pH may also contribute.

The Return of Dialysis Disequilibrium Syndrome (DDS)

Severe DDS has become a rare “vanishing” entity owing to the improvements in modes of dialysis. In our index case, chronic consecutive missed dialysis with elevated urea, intracerebral acidosis followed by rapid urea removal resulting in transient cerebral edema which culminated into the severe presentation. The case describes an unusual presentation of severe DDS in a known HD patient that only missed 2 sessions.

Your Guide to DDS

The most important component of treating DDS is preventing it from occurring. The three key ways we do this is by slowing the dialysate blood flow (which decreases how quickly urea is removed from the bloodstream), shortening the duration of the hemodialysis session, and mitigating osmotic shifts through a process called sodium modeling.

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FlightBridgeED

During dialysis, acidosis is corrected, causing a reduction in the ventilatory rate and a subsequent rise in CO2 levels. The CO2 diffuses into the brain and CSF, increasing osmolality and causing cerebral edema. To review, patients with acidosis have a right shift on the oxyhemoglobin curve. During dialysis, alkalization causes a left shift, increasing hemoglobin affinity for oxygen. As a result, tissues experience less oxygen offloading, and cerebral hypoxia development can increase neurological symptoms.

StatPearls

Dialysis disequilibrium syndrome (DDS) refers to an array of neurological manifestations that are seen during or following dialysis. The symptoms can range from mild symptoms such as headache, nausea, or blurred vision, as well as other CNS symptoms such as restlessness and confusion, to severe manifestations with coma and seizures in rare cases.