How to manage hyponatremia (low sodium levels) in a patient with impaired renal function, secondary to hemodialysis intolerance?

Managing Hyponatremia in Hemodialysis-Intolerant Patients

For patients with impaired renal function who cannot tolerate hemodialysis and have hyponatremia, transition to peritoneal dialysis (PD) with careful attention to dialysate sodium concentration and dwell time management, while simultaneously addressing volume status and avoiding overly rapid sodium correction.

Initial Assessment and Modality Selection

Consider transitioning from hemodialysis to peritoneal dialysis, as chronically hypotensive patients often tolerate PD better than HD 1. This is particularly relevant when hemodialysis intolerance manifests as recurrent intradialytic hypotension that prevents adequate volume and solute management 1.

Key Diagnostic Steps

• Determine the patient's volume status (hypovolemic, euvolemic, or hypervolemic hyponatremia), as this fundamentally guides treatment approach 2, 3
• Measure urine osmolality and urine sodium to differentiate the underlying cause of hyponatremia 2, 3
• Assess whether the patient is below their true dry weight, as this is the most common cause of persistent hypotension in dialysis patients 4
• Check for signs that dry weight is set too low: persistent hypotension despite adequate nutrition, increasing serum albumin and creatinine levels, improved appetite, and recurrent symptomatic hypotension 4

Peritoneal Dialysis Prescription for Hyponatremia Management

Dialysate Sodium Concentration Strategy

Use lower dialysate sodium concentrations (132-135 mmol/L) to promote negative sodium balance during each dialysis treatment 1, 5. This approach helps manage both volume overload and hyponatremia simultaneously, though it requires careful monitoring for hypotension 1.

• The sodium balance should be negative during each dialysis treatment to balance vascular stability during individual treatments with lower interdialytic weight gain 1, 5
• Lower dialysate sodium is associated with lower interdialytic weight gain and blood pressure, though it increases risk of intradialytic hypotension and cramps 1

Dwell Time Management

Implement shorter, more frequent exchanges (4-5 per day) using CAPD rather than APD to prevent sodium and water reabsorption 5. This is critical because:

• Shorter dwell times (avoiding dwells longer than 4-6 hours with glucose-based solutions) minimize sodium sieving and optimize fluid removal 5
• The sodium gradient reverses over time, leading to net sodium and water reabsorption back into the patient, particularly after 4-6 hours with glucose-based solutions 5
• CAPD naturally provides optimal dwell times (4-6 hours per exchange) that prevent significant fluid reabsorption while maximizing sodium removal 5

Icodextrin for Long Dwells

Use icodextrin exclusively for any long dwell (day or night), as it maintains ultrafiltration throughout extended dwell times without the reabsorption seen with glucose 5. Randomized controlled trials demonstrate icodextrin increases peritoneal ultrafiltration and decreases extracellular fluid volume in volume-overloaded patients 5.

Managing Hypotension During PD

Volume and Prescription Adjustments

• Reduce ultrafiltration volume by adjusting solutions (e.g., using less hypertonic glucose solutions or changing icodextrin to conventional 1.5% glucose solution) 1
• Omit day dwell (in automated PD) or night dwell (in continuous ambulatory PD) in those with significant residual kidney function without compromising clearance 1
• Consider increasing the target dry weight by 0.5-1.0 kg if the patient cannot tolerate current ultrafiltration goals 4

Medication and Dietary Modifications

• Withhold antihypertensive medications, particularly those taken in the morning before dialysis 1, 4
• Liberalize salt intake to prevent excessive hypotension, balancing this against volume management goals 1
• Avoid overly stringent salt restriction, which can worsen hypotension 1

Sodium Correction Rate Guidelines

When correcting hyponatremia in dialysis patients, limit the correction rate to a maximum of 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome 6, 2. For patients with impaired renal function, a more cautious correction rate of 4-6 mmol/L per day should be considered 6.

Monitoring Requirements

• Monitor serum sodium levels every 4-6 hours initially to ensure appropriate correction rate 6
• Calculate net ultrafiltration (drain volume minus instilled volume) for each dwell period separately 5
• Assess blood pressure and volume status through clinical examination monthly, with particular attention to extracellular fluid volume 5

Critical Pitfalls to Avoid

• Never continue aggressive ultrafiltration in a hypotensive patient, as this can cause end-organ ischemia and increase mortality risk 4
• Avoid standard APD with long day dwells in volume-overloaded patients, as ultrafiltration should never be negative for any exchange 5
• Do not assume all hypotension requires more aggressive ultrafiltration, as excessive ultrafiltration may be causing the hypotension 4
• Avoid eating during or immediately before dialysis, as this can worsen hypotension by causing splanchnic vasodilation 4

Alternative Considerations

If peritoneal dialysis is not feasible and hemodialysis must be continued despite intolerance:

• Increase dialysis time to >4 hours to allow slower ultrafiltration rates and better hemodynamic stability 1, 4
• Limit ultrafiltration rate to <6 mL/h/kg to reduce mortality risk and prevent end-organ ischemia 4
• Lower dialysate temperature to 35-36°C (instead of 37°C) to increase peripheral vasoconstriction and reduce hypotensive episodes 4
• Use a low dialysate sodium concentration (130 mEq/L) with limited blood flow (50 mL/minute) to control the rate of sodium correction during hemodialysis 7