How to prepare hypotonic dialysate?

Preparation of Hypotonic Dialysate

Hypotonic dialysate should be prepared with a sodium concentration lower than 135 mEq/L, typically in the range of 30-100 mEq/L, with appropriate adjustments to other electrolytes to maintain safety and prevent complications. 1

Definition and Composition

Hypotonic dialysate is defined as having a sodium concentration lower than that of the aqueous phase of plasma (154 mEq/L) or standard isotonic dialysate (135-144 mEq/L). According to clinical guidelines:

• Sodium concentration: 30-100 mEq/L (significantly lower than isotonic solutions) 1
• Osmolarity: Lower than 273-279 mOsm/L (compared to isotonic solutions at 294-308 mOsm/L) 1

Indications for Hypotonic Dialysate

While isotonic dialysate is generally recommended for most patients, hypotonic dialysate may be indicated in specific clinical scenarios:

• Correction of hypernatremia 1
• Patients with significant renal concentrating defects (e.g., nephrogenic diabetes insipidus) 1
• Patients with voluminous diarrhea requiring free water replacement 1
• Patients with severe burns requiring specific fluid management 1

Preparation Protocol

1. Base solution preparation:

   • Start with purified water meeting dialysis standards
   • Add electrolytes in precise concentrations lower than standard dialysate

2. Sodium concentration adjustment:

   • Target sodium between 30-100 mEq/L depending on clinical need 1
   • For severely hyponatremic patients with ESRD, consider a dialysate sodium of 130 mEq/L 2

3. Other electrolyte adjustments:

   • Potassium: Add appropriate KCl based on patient's serum potassium 1
   • Calcium: Consider lower concentration (especially for cardiac-compromised patients) 3
   • Magnesium: Maintain standard concentrations unless specifically indicated

4. Buffer component:

   • Use bicarbonate as the primary buffer (avoid acetate) 1
   • Target bicarbonate concentration to achieve midweek pre-dialysis serum bicarbonate of 22 mmol/L 3

5. Dextrose addition:

   • Add dextrose (2.5%-5%) to maintain osmotic balance 1

Safety Considerations and Monitoring

Risks of Hypotonic Dialysate

• Increased risk of intradialytic hypotension and cramps 1
• Potential for disequilibrium syndrome
• Hemodynamic instability during treatment 4

Monitoring Requirements

• Frequent monitoring of serum sodium levels during dialysis 5
• For severely hyponatremic patients, limit sodium correction to 2 mEq/L/hour 2
• Monitor for symptoms of hyponatremic encephalopathy 6
• Regular assessment of volume status and blood pressure 1

Strategies to Minimize Complications

1. For hypotension management:

   • Slow ultrafiltration rate 1
   • Consider isolated ultrafiltration if needed 1
   • Reduce dialysate temperature 1

2. For sodium correction safety:

   • In severely hyponatremic patients, limit blood flow to 50 ml/minute 2
   • Avoid correction exceeding 10 mEq/L within 24 hours to prevent osmotic demyelination syndrome 6
   • Target correction rate of 4-6 mEq/L in first 1-2 hours for symptomatic patients 5

Special Considerations

• Individualization: While standard protocols provide a starting point, dialysate composition should be adjusted based on specific patient parameters 3
• Conductivity monitoring: Consider using conductivity kinetic models to optimize sodium balance 3
• Contraindications: Hypotonic dialysate is generally not recommended for routine use in most patients due to increased risk of complications 1
• Alternative approaches: For patients with recurrent hypotension, consider sodium profiling rather than consistently low sodium dialysate 1

Technical Implementation

1. Use modern dialysis machines with capability for precise electrolyte adjustment
2. Verify dialysate composition before each treatment
3. For severely hyponatremic patients requiring controlled correction:
   • Use dialysate sodium 130 mEq/L
   • Limit blood flow to 50 ml/minute
   • This approach can achieve controlled sodium correction of approximately 2 mEq/L/hour 2

By carefully preparing hypotonic dialysate according to these guidelines and closely monitoring patients during treatment, clinicians can safely manage specific conditions requiring lower sodium concentrations while minimizing associated risks.