What are the effects of excessive fluid removal during dialysis in patients with end-stage renal disease (ESRD)?

Effects of Excessive Fluid Removal During Dialysis

Removing more fluid than necessary during dialysis causes intradialytic hypotension, end-organ ischemia, and increased mortality risk, requiring immediate dry weight target increase of 0.3-0.5 kg when hypotension occurs. 1

Immediate Hemodynamic Consequences

Acute hypotension develops when ultrafiltration depletes intravascular volume faster than plasma refilling from interstitial spaces can compensate, signaling the patient has reached or gone below their actual dry weight. 1 This manifests as:

• Symptomatic blood pressure drops (≥20 mmHg systolic or ≥10 mmHg mean arterial pressure) accompanied by dizziness, fainting, nausea, muscle cramps, and restlessness 2
• Hypovolemia that precipitates when attempting to accelerate ultrafiltration beyond physiologic tolerance 3
• Cardiovascular collapse requiring normal saline administration and ultrafiltration cessation, which paradoxically expands extracellular volume further and prevents achievement of volume removal goals 3, 1

End-Organ Ischemic Injury

Excessive ultrafiltration causes multiorgan damage through systemic circulatory stress and inadequate tissue perfusion:

• Cardiac complications including myocardial stunning, cardiac arrhythmias, and left ventricular hypertrophy with associated increased morbidity and mortality 2, 4, 5
• Cerebral ischemia from inadequate cerebral perfusion during hypotensive episodes 2, 4
• Mesenteric ischemia potentially leading to bowel infarction 2
• Vascular access thrombosis from reduced blood flow during hypotensive states 2
• Accelerated loss of residual kidney function from recurrent ischemic insults 3

The biological plausibility data demonstrate that higher ultrafiltration rates (even as low as 6 ml/h/kg) associate with end-organ ischemia affecting heart, brain, liver, gut, and kidneys. 3

Mortality Risk

Observational data consistently show higher ultrafiltration rates correlate with increased mortality risk, even at rates as low as 6 ml/h/kg. 3 While no randomized controlled trials have definitively proven that lowering ultrafiltration rates improves outcomes, the biological plausibility evidence strongly supports this relationship. 3

Long-Term Sequelae

Recurrent hypotensive episodes from excessive ultrafiltration create a cascade of complications:

• Development of left ventricular hypertrophy through repeated ischemic stress 2
• Paradoxical interdialytic hypertension as a compensatory response to recurrent volume depletion 2
• Inadequate dialysis dose due to premature session termination when hypotension forces treatment cessation 2
• Seizures when rapid dry weight reduction occurs too aggressively 1

High-Risk Patient Populations

Certain patients tolerate excessive ultrafiltration particularly poorly and require even more cautious fluid removal:

• Patients ≥65 years old have increased intradialytic hypotension risk 2
• Diabetic patients with autonomic neuropathy lack compensatory cardiovascular responses and require slower dry weight reduction over 6-12 months 1, 2
• Patients with cardiomyopathy or cardiovascular disease cannot adequately augment cardiac output during volume depletion 1, 2
• Patients with pre-dialysis systolic blood pressure <100 mmHg have insufficient hemodynamic reserve 2
• Malnourished patients with hypoalbuminemia have impaired plasma refilling capacity 2

Clinical Management Algorithm

When hypotension occurs during dialysis, immediately:

1. Increase the dry weight target by 0.3-0.5 kg for subsequent sessions 1
2. Reduce ultrafiltration rate for the remainder of the current session to allow plasma refilling to catch up 1
3. Reassess volume status between sessions looking for edema, hypertension, elevated jugular venous pressure, and interdialytic weight gains >4.8% body weight 1

For patients requiring dry weight reduction:

• Reduce dry weight by only 0.1 kg per 10 kg body weight per dialysis session 1
• Accomplish true dry weight reduction gradually over 4-12 weeks (or 6-12 months in high-risk patients), never in a single session 1
• Patients with diabetes or cardiomyopathy require even slower reduction due to impaired compensatory mechanisms 1

Critical Distinction: Rate vs. Total Volume

The ultrafiltration rate matters as much as total volume removed. 3 If a patient has clear volume overload (hypertension, edema, weight gains >4.8% body weight) but develops hypotension during dialysis, the problem is ultrafiltration rate intolerance, not the total volume goal. 1 In this scenario:

• Lengthen dialysis sessions or add additional treatments to lower ultrafiltration rates below 10 ml/h/kg while achieving the same total volume removal 3, 1
• Implement strict dietary sodium restriction to <2 g/day to reduce interdialytic weight gains 1
• Consider that conventional dialysis time may be too short for patients with large interdialytic weight gains to achieve adequate ultrafiltration safely 3, 1

Common Pitfall

Attempting to remove excess fluid too rapidly leads to a counterproductive cycle: hypotension develops, normal saline is administered, ultrafiltration is discontinued, and the patient ends the session with more volume than targeted, worsening their overall volume status. 3, 1 The solution is slower ultrafiltration over longer treatment times, not abandoning volume removal goals. 3, 1