Blood Pressure Trends Variable with Hemodialysis: Definition and Clinical Significance
Blood pressure (BP) trends variable with hemodialysis (HD) refers to the fluctuations in blood pressure that occur during and between dialysis sessions, which are associated with increased cardiovascular morbidity and mortality in dialysis patients. 1
Types of BP Variability in Hemodialysis
Intradialytic BP Changes
Intradialytic hypotension: A decrease in BP during dialysis, defined as any symptomatic decrease in BP or a nadir systolic BP (SBP) <90 mmHg during treatment 1
Intradialytic hypertension: An increase in BP during or immediately after dialysis 1
Interdialytic BP Patterns
- Progressive rise in BP during the interdialytic period (between dialysis sessions) 2
- Loss of normal nocturnal BP decline (non-dipping pattern) as interdialytic period progresses 2
- High prevalence of non-dippers among HD patients (77-83%) 2
BP Variability Timeframes
Blood pressure in HD patients varies across multiple timeframes 1:
- Very short-term (beat-by-beat)
- Short-term (within 24 hours)
- Mid-term (day-by-day)
- Long-term (visit-to-visit)
All these patterns of variability are associated with target-organ damage, cardiovascular events, and mortality in HD patients 1.
Clinical Significance
- BP variability in HD patients is linked to increased morbidity and mortality 1, 3
- Intradialytic BP increases >10 mmHg are associated with 6% increased hazard of death per 10 mmHg rise 3
- The relationship between BP changes and outcomes depends on baseline BP - patients with predialysis SBP <120 mmHg who experience BP increases during HD are at highest risk 3
- Time of HD affects risk of BP variations - later dialysis sessions have lower risk of intradialytic hypotension but higher risk of intradialytic hypertension 4
Pathophysiological Mechanisms
- Volume shifts during ultrafiltration 1
- Arterial stiffness 1
- Activation of sympathetic nervous and renin-angiotensin systems 1
- Endothelial dysfunction 1
- Volume overload (major factor in hypertension in dialysis patients) 1
- Effects of erythropoietin therapy 1
Management Implications
Any symptomatic decrease in BP or SBP <90 mmHg should prompt reassessment of BP management 1
SBP increase >10 mmHg from pre- to post-dialysis in ≥4 of 6 consecutive treatments warrants evaluation of volume management 1
Management considerations include 1:
- Ultrafiltration rate
- Dialysis treatment time
- Interdialytic weight gain
- Dry-weight estimation
- Antihypertensive medication timing and selection
Volume control should be the first approach before medication adjustments 1
Antihypertensive medications may need adjustment around dialysis sessions to prevent complications 1
Certain medications may pose risks during dialysis - ACE inhibitors can cause anaphylactoid reactions during dialysis with high-flux membranes 5
Monitoring Recommendations
- Regular assessment of pre- and post-dialysis BP 1
- Consider ambulatory BP monitoring or home BP measurements for better assessment of interdialytic BP load 1
- Evaluate BP patterns over time rather than isolated readings 1
- Monitor for both hypotensive and hypertensive episodes during and after dialysis 1
Pitfalls and Caveats
- Neither pre- nor post-dialysis BP readings alone are good predictors of interdialytic BP 1
- Avoiding intradialytic hypotension should not compromise achieving euvolemia or adequate dialysis time 1
- BP variability may be a marker of underlying pathology rather than a modifiable risk factor itself 1
- There are no studies of interventions specifically targeting BP variability in HD patients 1
- Indirect BP measurements may be inaccurate in patients with severe vascular calcifications 1