Can dialysis cause hypotension (low blood pressure)?

Dialysis-Induced Hypotension: Mechanisms and Management

Yes, dialysis can cause low blood pressure (hypotension), affecting approximately 25% of all hemodialysis sessions. 1 This condition, known as intradialytic hypotension (IDH), is defined as a decrease in systolic blood pressure by ≥20 mmHg or a decrease in mean arterial pressure by 10 mmHg, accompanied by symptoms such as abdominal discomfort, nausea, dizziness, and anxiety. 1

Mechanisms of Dialysis-Induced Hypotension

• Ultrafiltration and plasma refilling: Rapid removal of fluid during dialysis can exceed the rate at which fluid refills from tissue spaces into the vascular compartment, leading to reduced blood volume and hypotension. 1

• Autonomic dysfunction: Many dialysis patients, particularly those with diabetes, have impaired autonomic nervous system function, resulting in inadequate vasoconstriction in response to volume removal. 1

• Reduced vascular responsiveness: Dialysis patients have defective reactivity of resistance and capacitance vessels during hemodialysis sessions. 1

• Cardiac factors: Pre-existing cardiac conditions like left ventricular hypertrophy, diastolic dysfunction, or systolic dysfunction can contribute to hypotension during dialysis. 1

Risk Factors for Intradialytic Hypotension

• Diabetic kidney disease 1
• Cardiovascular disease (especially LVH and heart failure) 1
• Poor nutritional status and hypoalbuminemia 1
• Uremic neuropathy or autonomic dysfunction 1
• Severe anemia 1
• High ultrafiltration requirements 1
• Predialysis systolic BP ≤100 mmHg 1
• Age ≥65 years 1
• Female sex 1
• Use of nitrates before dialysis 1

Management of Intradialytic Hypotension

Acute Interventions

• Reduce or temporarily stop ultrafiltration to prevent further blood pressure drop 2
• Administer intravenous normal saline bolus to rapidly expand plasma volume 2
• Place patient in Trendelenburg position (head down, legs elevated) to improve venous return 2
• Provide supplemental oxygen to improve tissue oxygenation and reduce symptoms 2

Preventive Strategies

Dialysis Prescription Modifications

• Slower ultrafiltration rate by extending treatment time when possible 2
• Cool dialysate (34-35°C instead of 37°C) to increase peripheral vasoconstriction and cardiac output 2
• Sodium profiling (starting with higher sodium concentration and gradually decreasing it) to maintain vascular stability 2
• Use bicarbonate-containing dialysate instead of acetate-containing dialysate to prevent inappropriate decreases in vascular resistance 2

Pharmacological Approaches

• Midodrine: Administer 30 minutes before dialysis to prevent hypotension (mean effective dose 5.5-8 mg) 3, 4
  • Acts as a selective alpha-1 adrenergic agonist that increases peripheral vascular resistance 5
  • Significantly increases minimum systolic pressure during dialysis (from ~93 mmHg to ~107 mmHg) 3
  • Improves post-dialysis blood pressure and reduces symptoms like cramps, fatigue, and dizziness 4

Patient Education and Lifestyle Modifications

• Limit fluid intake between dialysis sessions to reduce interdialytic weight gain 2
• Avoid food intake immediately before or during hemodialysis to prevent decreased peripheral vascular resistance 2
• Optimize hemoglobin levels to improve oxygen-carrying capacity 2

Long-Term Considerations

• Dry weight assessment: Regularly reevaluate the patient's estimated dry weight, as hypotension may indicate it is set too low 2

• Medication review: Evaluate and potentially adjust antihypertensive medications that may contribute to hypotension 2

• Blood pressure paradox: Some dialysis patients exhibit a "U-shaped" relationship between blood pressure and mortality, with excess mortality risk in patients with both the lowest and highest blood pressure levels 1

• Lag phenomenon: In 90% of patients, extracellular fluid volume normalizes within a few weeks of achieving dry weight, but elevated blood pressure may continue to decrease for another 8 months or longer 1

Special Considerations

• Chronic hypotension (defined as systolic BP <100 mmHg in the interdialytic period) affects 5-10% of hemodialysis patients and is more prevalent among patients on long-term hemodialysis 6

• Patients with severe sustained hypotension may experience significant improvement after successful kidney transplantation 7

• Attempting to achieve NKF/KDOQI blood pressure targets may lead to more frequent episodes of intradialytic hypotension in some patients 1

• For patients approaching dry weight, the ultrafiltration rate should be reduced toward the end of dialysis to accommodate the reduced vascular refilling rate 1