Is hypotension expected in dialysis patients?

Hypotension During Hemodialysis: Prevalence, Causes, and Management

Yes, hypotension is a common and expected complication during hemodialysis, occurring in approximately 15-50% of dialysis sessions depending on the definition used. 1 This condition represents a significant clinical challenge that impacts patient morbidity, mortality, and quality of life.

Prevalence and Definition

Intradialytic hypotension is typically defined as:

• A decrease in systolic blood pressure by ≥20 mmHg or
• A decrease in mean arterial pressure by 10 mmHg
• Associated with symptoms such as abdominal discomfort, yawning, nausea, vomiting, muscle cramps, dizziness, and anxiety 2

The KDIGO guidelines specifically note that any symptomatic decrease in BP or a nadir intradialytic systolic BP of <90 mmHg should prompt reassessment of blood pressure management 1.

Pathophysiology of Dialysis Hypotension

Several mechanisms contribute to hypotension during dialysis:

1. Volume-related factors:

   • Rapid ultrafiltration exceeding plasma refilling rate
   • Excessive interdialytic fluid accumulation requiring aggressive ultrafiltration
   • Inadequate assessment of dry weight 1

2. Cardiovascular factors:

   • Autonomic dysfunction (especially common in diabetic patients)
   • Impaired vascular tone response
   • Diastolic dysfunction limiting cardiac filling 3
   • Reduced vascular tone occurring early in dialysis (within 20 minutes), even before significant volume reduction 4

3. Neurohormonal factors:

   • Paradoxical reduction in sympathetic tone
   • Adenosine release due to tissue ischemia
   • Activation of the Bezold-Jarisch reflex 3

Management Strategies

1. Ultrafiltration Modifications

• Avoid excessive ultrafiltration by:

  • Educating patients on fluid and sodium restriction (2-3g/day sodium intake) 1
  • Extending dialysis time when large fluid removal is needed 1
  • Using ultrafiltration profiling (varying rates during treatment) 1

• Consider isolated ultrafiltration separate from diffusive clearance for patients with severe fluid overload 1

2. Dialysate Modifications

• Reduce dialysate temperature to 34-35°C (increases peripheral vasoconstriction) 1
• Increase dialysate sodium concentration (148 mEq/L), especially early in treatment with gradual reduction ("sodium ramping") 1
• Use bicarbonate-buffered dialysate instead of acetate-containing dialysate 1

3. Pharmacological Interventions

• Midodrine administration before dialysis:
  • Selective alpha-1 adrenergic pressor agent
  • Typical dose: 5-10 mg given 30 minutes before dialysis
  • Significantly increases minimum systolic BP during dialysis (from ~93 to ~107 mmHg) 5, 6
  • Improves post-dialysis blood pressure 6
  • FDA-approved for orthostatic hypotension; studies show efficacy for dialysis hypotension 7

4. Other Interventions

• Correction of anemia to recommended targets 1
• Supplemental oxygen during dialysis 1
• Critical reassessment of dry weight - particularly important in patients with intradialytic hypertension 1

Special Considerations

1. Diabetic patients and those with cardiovascular compromise are at higher risk for intradialytic hypotension 2

2. Paradoxical hypertension: Some patients experience increased blood pressure during dialysis, which may require different management approaches 1

3. Timing of antihypertensive medications: For hypertensive dialysis patients, antihypertensive drugs should preferentially be given at night to reduce nocturnal blood pressure surge and minimize intradialytic hypotension 1

4. Balancing priorities: While preventing hypotension is important, it should not come at the expense of maintaining euvolemia or ensuring adequate dialysis time 1

Monitoring and Follow-up

When hypotension occurs during dialysis, a systematic approach should include:

• Reassessment of ultrafiltration rate
• Evaluation of dialysis treatment time
• Review of interdialytic weight gain
• Re-evaluation of dry weight estimation
• Assessment of antihypertensive medication use and timing 1

Simple changes to the dialysis prescription can result in significant reduction in the incidence of intradialytic hypotension, improving patient outcomes and quality of life 2.