What are the recommended dialysis procedures for a patient with hypotension (low blood pressure) undergoing dialysis due to impaired renal function?

Management of Hypotension in Dialysis Patients

For patients experiencing hypotension during dialysis, immediately reduce or stop ultrafiltration, place the patient in Trendelenburg position, and administer supplemental oxygen while reassessing the dialysis prescription to target ultrafiltration rates below 6 mL/h/kg through extended treatment time or increased frequency. 1, 2

Immediate Acute Interventions

When hypotension occurs during dialysis treatment, a systematic approach is essential:

• Stop or reduce ultrafiltration immediately to prevent further blood pressure decline and end-organ ischemia 2, 3
• Place the patient in Trendelenburg position (head down, legs elevated) to improve venous return and increase blood pressure 2, 3
• Administer supplemental oxygen to improve tissue oxygenation and reduce symptoms 2, 3
• Consider intravenous normal saline bolus only if the patient is truly volume depleted, but avoid routine saline administration as this perpetuates volume overload 2, 3

Critical Dialysis Prescription Modifications

The ultrafiltration rate is the single most important modifiable factor, as rates exceeding 6 mL/h/kg are associated with higher mortality risk and increased hypotension 1, 2:

• Extend treatment time to minimum 4 hours per session to slow ultrafiltration rate below the critical 6 mL/h/kg threshold 2, 3
• Increase dialysis frequency from twice to three times weekly to reduce the ultrafiltration burden per session and prevent recurrent hypotension 2, 4
• Target ultrafiltration rate <13 mL/kg/hour when possible to minimize cardiovascular stress 4

The evidence strongly supports that higher ultrafiltration rates cause end-organ ischemia affecting the heart, brain, liver, gut, and kidneys, even though no randomized controlled trials have definitively proven that lowering rates improves outcomes 1.

Dialysate Modifications to Prevent Hypotension

Several dialysate adjustments can improve hemodynamic stability:

• Reduce dialysate temperature from 37°C to 34-35°C to increase peripheral vasoconstriction and cardiac output 3, 4
• Increase dialysate sodium concentration to 148 mEq/L to prevent hypotension, especially early in the dialysis session 3
• Switch from acetate-containing to bicarbonate-containing dialysate to minimize inappropriate decreases in total vascular resistance 3

However, be aware that increased dialysate sodium may lead to increased thirst, interdialytic weight gain, and hypertension between treatments 3. Reduced dialysate temperature may cause uncomfortable hypothermia in some patients 3.

Dry Weight Reassessment

Hypotension often indicates the target dry weight is set too low 1, 3:

• Gradually probe the dry weight upward over 4-12 weeks (potentially 6-12 months in patients with diabetes or cardiomyopathy) without inducing hypotension 1
• Reduce ultrafiltration rate toward the end of dialysis when approaching dry weight, as the vascular refilling rate from tissue spaces decreases 1
• Recognize that patients can have fluid excess without gross clinical evidence of volume expansion (termed "silent overhydration") 1

The "lag phenomenon" is important to understand: in 90% of patients, extracellular fluid volume normalizes within weeks, but elevated blood pressure continues to decrease for another 8 months or longer 1.

Pharmacological Management

Midodrine for Prevention

• Administer midodrine 2.5-25 mg orally within 30 minutes before dialysis initiation to prevent hypotension through selective α1-adrenergic agonist activity 3, 5
• Midodrine significantly increases minimal systolic pressure by approximately 14 mmHg and diastolic pressure by approximately 6 mmHg during hemodialysis 5

Antihypertensive Medication Adjustment

• Review and reduce all antihypertensive medications, particularly those that are dialyzable like metoprolol 4, 6
• Consider holding or reducing beta-blocker doses if heart rate is <60 bpm with concurrent hypotension, as these medications blunt compensatory tachycardia and cardiac output increases needed during volume removal 1, 4
• Administer antihypertensive medications preferentially at night rather than before dialysis to minimize intradialytic hypotension, though evidence supporting routine withholding is limited 4, 6

The K/DOQI guidelines recommend ACE inhibitors or ARBs as first-line therapy for hypertension in dialysis patients, as these reduce left ventricular hypertrophy and are associated with decreased mortality 1.

Long-Term Prevention Strategies

Volume Management

• Limit sodium intake to <5.8 g/day (ideally 2-3 g/day) to reduce thirst and interdialytic weight gain 2, 4
• Restrict interdialytic weight gain to <3% of body weight between sessions to prevent excessive ultrafiltration requirements 2, 4
• Avoid food intake immediately before or during hemodialysis to prevent decreased peripheral vascular resistance 3

Anemia Correction

• Maintain hemoglobin at 11 g/dL to improve oxygen-carrying capacity and cardiovascular compensation during ultrafiltration 2, 4

Special Considerations for Chronically Hypotensive Patients

Patients with chronic hypotension are particularly challenging 1:

• Increase dialysis time as the primary strategy for these individuals 1
• Consider transition to peritoneal dialysis, as these patients may tolerate PD better than hemodialysis, though further study is needed to confirm superior outcomes 1
• For PD patients with hypotension, reduce ultrafiltration volume by adjusting solutions (using less hypertonic glucose solutions) 1

Critical Pitfalls to Avoid

• Never continue twice-weekly dialysis in hypotensive patients, as this forces dangerously high ultrafiltration rates and inadequate solute clearance 2
• Do not routinely administer saline for every hypotensive episode, as this perpetuates volume overload 2, 4
• Do not use hypotension alone to define volume status, as patients may be hypotensive yet volume overloaded 4
• Do not compromise dialysis adequacy in attempts to manage hypotension 4
• Do not administer multiple antihypertensive medications before dialysis, as this significantly increases hypotension risk 4

Blood Pressure Targets

While managing hypotension, maintain awareness of appropriate blood pressure goals 1:

• Target predialysis blood pressure of 140/90 mmHg (measured sitting), provided there is no substantial orthostatic hypotension and these levels are not associated with substantial symptomatic intradialytic hypotension 1
• This target minimizes occurrence of left ventricular hypertrophy and death in the dialysis population 1