How is hemodialysis-associated hypotension managed?

Management of Hemodialysis-Associated Hypotension

Hemodialysis-associated hypotension should be managed through a systematic approach starting with ultrafiltration modifications and dialysate adjustments, with midodrine as a pharmacologic option for refractory cases, though recent observational data raises safety concerns about its long-term use. 1

Immediate Acute Management

When hypotension occurs during dialysis, implement these interventions sequentially:

• Reduce or temporarily stop ultrafiltration to prevent further blood pressure decline 2
• Administer intravenous normal saline bolus (typically 100-250 mL) 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 1, 2

Dialysate Modifications (First-Line Prevention)

These are simple, effective interventions that should be implemented before pharmacologic therapy:

Sodium Management

• Increase dialysate sodium concentration to 148 mEq/L, particularly early in the dialysis session 1, 2
• Implement sodium profiling (sodium ramping): start with higher sodium concentration and gradually decrease throughout treatment 1, 2
• Important caveat: This may cause increased thirst, interdialytic weight gain, and paradoxically worsen hypertension between sessions 1, 2

Dialysate Buffer

• Switch from acetate-containing to bicarbonate-containing dialysate 1
• Acetate inappropriately decreases total vascular resistance, increases venous pooling, and increases myocardial oxygen consumption 1, 3
• Bicarbonate dialysate also reduces headaches, nausea, and vomiting 1

Temperature Reduction

• Reduce dialysate temperature from 37°C to 34-35°C 1, 2
• This increases peripheral vasoconstriction and cardiac output through enhanced sympathetic tone 1, 3
• Reduces symptomatic hypotension from 44% to 34% of sessions 1
• Caveat: May cause uncomfortable or intolerable hypothermia in some patients 1, 2
• Greatest benefit in patients with frequent hypotensive episodes and those with baseline mild hypothermia (tympanic temperature <36°C) 1

Ultrafiltration Strategy Modifications

Rate and Volume Management

• Slow the ultrafiltration rate by extending treatment time when possible 1, 2
• Ultrafiltration rates as low as 6 mL/h/kg are associated with higher mortality risk 3
• Perform sequential ultrafiltration/clearance (isolated ultrafiltration followed by diffusive clearance) for severe cases 1
• Critical requirement: If using sequential ultrafiltration, extend total dialysis duration to compensate for time lost for diffusive clearance 1

Dry Weight Reassessment

• Reevaluate the estimated dry weight (EDW) if recurrent hypotension occurs 1, 2
• Clues that EDW may be set too low include: increasing dietary intake with biochemical signs of improving nutrition (rising serum albumin and/or creatinine, rising normalized protein catabolic rate) in the presence of hypotension 1
• Hypotension alone cannot be used to define intravascular volume status 1

Pharmacologic Management

Midodrine: Evidence and Controversy

The evidence for midodrine is conflicting, with short-term efficacy data but concerning long-term safety signals:

Supporting Evidence (Short-term studies):

• Administer midodrine within 30 minutes before dialysis initiation 1, 2
• Raises blood pressure by increasing peripheral vascular resistance (arteriolar vasoconstriction) and enhancing venous return (venular constriction) 1
• Meta-analysis showed nadir systolic blood pressure improved by average of 13 mm Hg (95% CI: 9-18 mm Hg, P < 0.0001) 1
• Multiple small RCTs (6-21 patients) demonstrated improved intradialytic blood pressure and reduced hypotensive symptoms 1, 4, 5, 6, 7
• Well tolerated with few side effects in short-term studies 1

Concerning Safety Data:

• Observational study found midodrine use associated with significantly higher risks of cardiovascular events, all-cause hospitalization, and mortality when matched users were compared to non-users (including matching by mean peridialytic blood pressure level) 1
• All supporting studies were of short duration with small sample sizes, and none examined clinical endpoints such as death or cardiovascular events 1
• Midodrine is removed by dialysis, requiring careful dosing 8
• Prolonged terminal half-life of active metabolite (desglymidodrine) in renal failure warrants careful administration 6

Clinical recommendation: Given the conflicting evidence, reserve midodrine for patients with refractory hypotension unresponsive to dialysate modifications and ultrafiltration strategies, and use the lowest effective dose with close monitoring for cardiovascular complications.

Anemia and Oxygen Management

• Raise hemoglobin to 11 g/dL per NKF-K/DOQI Anemia Guidelines 1, 2
• Administer supplemental inhaled oxygen during dialysis, especially for patients with cardiovascular or respiratory disease 1
• These interventions reduce intradialytic hypotension incidence by improving oxygen-carrying capacity and cardiovascular compensation 1, 3

Patient Behavior Optimization

Fluid and Dietary Management

• Limit fluid intake between dialysis sessions to reduce interdialytic weight gain 1, 2
• Avoid food intake immediately before or during hemodialysis 1, 2
• Food causes splanchnic vasodilation and decreased peripheral vascular resistance, redirecting blood flow away from peripheral circulation 1, 3

Medication Review

• Review and potentially adjust antihypertensive medications on an individual basis 1, 2
• The literature is contradictory: some studies show strong correlation between antihypertensive use and hypotension, while others do not 1
• Antihypertensives may prevent compensatory vasoconstriction and cardiac responses needed during ultrafiltration 3
• Consider holding or adjusting doses on dialysis days for problematic patients 1

Loop Diuretics

• Continue loop diuretics after hemodialysis initiation in patients with residual kidney function 1
• Observational data shows continuation associated with lower interdialytic weight gain, lower intradialytic hypotension rates, and lower hospitalization rates 1
• Helps preserve residual diuresis and limit fluid overload 1

Patient Education

• Engage patients actively in their hemodialysis care through comprehensive education about the value of complying with the hemodialysis regimen 1
• Failure to properly educate patients compromises the success of all aforementioned strategies 1

Clinical Pitfalls to Avoid

• Do not use hypotension alone to define volume status - it is an unreliable indicator of intravascular volume 1
• Do not ignore the possibility of secondary causes such as adrenal insufficiency in patients with refractory hypotension 9
• Avoid protracted hypotension as it may exaggerate urea rebound and compromise dialysis adequacy 1, 3
• Remember that recurrent intradialytic hypotension creates a cascade of end-organ ischemia affecting heart, brain, liver, gut, and kidneys, contributing to increased morbidity and mortality 3