OVERVIEW

What is dialysis disequilibrium syndrome?

Dialysis disequilibrium syndrome (DDS) is a complication during hemodialysis treatment. Its exact mechanism remains unclear, but the prevailing theory suggests it results from a rapid decrease in plasma osmolality due to the swift reduction of uremic toxins during dialysis, causing water to shift into brain cells and lung tissues, leading to cerebral or pulmonary edema.

What are the types of dialysis disequilibrium syndrome?

Based on the affected organs, it is classified into two types: cerebral and pulmonary. Cerebral DDS is the classic form described in standard textbooks, while pulmonary DDS is a recently proposed concept in academic circles.

Is dialysis disequilibrium syndrome common?

Literature reports its incidence among patients undergoing blood purification therapy as 3.4%–20%. With advancements in blood purification technology, its occurrence has become increasingly rare in recent years.

Can dialysis disequilibrium syndrome occur in peritoneal dialysis patients?

There are currently no reported cases of dialysis disequilibrium syndrome in patients undergoing continuous peritoneal dialysis.

SYMPTOMS

What are the manifestations of dialysis disequilibrium syndrome?

Symptoms of this condition usually occur during or within hours after hemodialysis treatment.

• Cerebral DDS: Early symptoms include headache, nausea, disorientation, agitation, blurred vision, and asterixis, among others. Generally, the symptoms are self-limiting and often resolve within hours. However, a few patients may progress to confusion, seizures, coma, or even death. Many mild dialysis-related symptoms and signs that appear near the end of dialysis, such as muscle cramps, anorexia, and dizziness, are now also considered manifestations of DDS.

• Pulmonary DDS: Clinical manifestations include chest tightness, shortness of breath, dyspnea, and orthopnea (worsening of breathing difficulty when lying flat and relief when sitting upright). The main signs are extensive bilateral moist rales and abnormally rapid heart rate, resembling symptoms of pulmonary edema or right heart failure. In the past, these were often attributed to acute exacerbations of underlying cardiopulmonary diseases.

CAUSES

What Causes Dialysis Disequilibrium Syndrome?

The exact mechanism remains unclear, but the prevailing theory suggests it occurs due to a rapid decrease in plasma osmolality caused by the swift reduction of uremic toxins during dialysis. This leads to water shifting from the bloodstream into brain cells and lung tissue, resulting in cerebral or pulmonary edema.

Who Is More Likely to Develop Dialysis Disequilibrium Syndrome?

• First-time dialysis patients;

• Patients with significantly elevated pre-dialysis blood urea levels (>175 mg/dL or 60 mmol/L);

• Those with severe metabolic acidosis;

• Children and elderly individuals;

• Patients with pre-existing systemic conditions (e.g., head trauma, post-stroke, epilepsy);

• Patients with diseases characterized by cerebral edema (e.g., hyponatremia, hepatic encephalopathy, uncontrolled hypertension);

• Patients with conditions that increase cerebrovascular permeability (e.g., sepsis, vasculitis, encephalitis, meningitis);

• Patients with heart failure or cardiomyopathy;

• Chronic kidney disease patients are more susceptible than those with acute kidney injury;

• High-efficiency dialysis (e.g., high-flux dialysis, hemofiltration) carries a higher risk than low-efficiency therapies (e.g., CRRT, peritoneal dialysis).

DIAGNOSIS

How is dialysis disequilibrium syndrome diagnosed?

The occurrence of neurological or cardiopulmonary symptoms during dialysis should raise suspicion of DDS.

Currently, there are no diagnostic tests for DDS, and diagnosis relies on exclusion. Other conditions that must be ruled out include uremia itself, cerebral infarction, intracranial hemorrhage, meningitis, coronary heart disease, asthma, hyponatremia, hypoglycemia, and drug-induced encephalopathy (caused by accumulation of renally excreted medications in patients with renal failure).

For patients with altered mental status during dialysis, serum electrolytes, calcium, and blood glucose should be tested to exclude hypoglycemia and electrolyte imbalances. Imaging studies (CT, MRI) are usually required to rule out intracranial hemorrhage or cerebral infarction, while electrocardiography and echocardiography can exclude coronary heart disease. Chest X-rays, blood tests, and physical examinations help rule out infectious diseases.

TREATMENT

How to treat dialysis disequilibrium syndrome?

• For milder symptoms such as nausea, vomiting, restlessness, dizziness, or headache, reduce the dialysis blood flow rate. If symptoms persist or worsen, consider terminating the current dialysis session.

• If the patient experiences seizures, coma, or impaired consciousness, immediately stop dialysis and disconnect. Ensure airway and venous access patency while actively ruling out other conditions that may cause these symptoms beyond severe DSS.

• Most seizures resolve spontaneously within 5 minutes. However, if they persist beyond 5 minutes without improvement, intravenous antiepileptic drugs (preferably benzodiazepines) should be administered to stop the episode. Intravenous hypertonic saline or mannitol injections to increase blood osmotic pressure may help alleviate symptoms faster, though further clinical studies are needed for confirmation.

• For comatose patients due to DDS, supportive treatments such as maintaining airway patency, oxygen therapy, and fluid-electrolyte balance should be provided. Most patients show improvement within 24 hours.

• Patients with pulmonary-type DDS should receive aggressive oxygen therapy and albumin supplementation to correct pulmonary edema.

Can dialysis disequilibrium syndrome be fatal?

Most mild cases resolve within minutes to an hour after reducing blood flow, stopping dialysis, or receiving appropriate supportive treatment.

A small number of severe cases, such as those with prolonged seizures or right heart failure, may lead to death.

DIET & LIFESTYLE

None.

PREVENTION

How to Prevent Dialysis Disequilibrium Syndrome?

Preventive measures should be taken for first-time dialysis patients, those with high blood urea levels, and patients with underlying conditions such as epilepsy, stroke, chronic obstructive pulmonary disease, or cardiomyopathy. Specific measures include:

• Use a dialyzer with a small membrane area (0.9–1.2 m²), set a lower blood flow rate (150–250 mL/min), appropriately shorten dialysis duration (1–2 hours), and increase dialysis frequency (e.g., once daily for 3–4 consecutive days). The goal is to control the reduction in blood urea levels during each session, allowing a gradual decline over several days.

• For patients without DSS symptoms, gradually increase blood flow by 50 mL/min per session (up to a maximum of 400 mL/min) and extend treatment time by 30 min per session (up to 4 hours or longer as appropriate). The aim is to achieve optimal blood purification without triggering DSS.

• For patients with significant fluid overload, perform ultrafiltration first (which removes less urea per unit time and has minimal impact on plasma osmolality), followed by a short hemodialysis session.

• Patients with extremely high blood urea levels and current neurological symptoms should undergo blood purification therapy under close hospital monitoring.