What are the goals and recommendations for hemodialysis (HD) in pregnant women, including target Blood Urea Nitrogen (BUN) levels and dialysis frequency?

Hemodialysis Management in Pregnancy

For pregnant women with end-stage kidney disease, intensive hemodialysis should be provided with a target of 36+ hours per week (at least 6 sessions weekly) and maintaining predialysis BUN levels below 35 mg/dL to optimize maternal and fetal outcomes. 1, 2, 3

Dialysis Prescription for Pregnant Women

Frequency and Duration

• Provide intensive hemodialysis with at least 6 sessions per week, totaling 36-48 hours weekly 1
• A dose-response relationship exists between dialysis intensity and pregnancy outcomes, with live birth rates of:
  • 48% with ≤20 hours/week
  • 75% with 30 hours/week
  • 85% with >36 hours/week 1

Target BUN Levels

• Maintain predialysis BUN <35 mg/dL (this is the optimal cutoff associated with better fetal outcomes) 2, 3
• Lower BUN levels correlate significantly with:
  • Higher birth weight
  • Longer gestational age
  • Reduced risk of perinatal death or extreme prematurity 2, 3

Dialysis Adequacy Measures

• For pregnant women, standard adequacy targets (spKt/V 1.4 per session) are insufficient 1
• Aim for higher clearance with a standard Kt/V of at least 2.3 volumes per week 1
• Monitor residual kidney function regularly, as it contributes to overall clearance 1

Technical Considerations

Dialysis Parameters

• Use biocompatible dialysis membranes 1
• Limit ultrafiltration to avoid hemodynamic instability that could compromise placental perfusion 4
• Consider microdose heparin to minimize bleeding risk while preventing clotting 4

Monitoring During Dialysis

• Closely monitor vital signs, particularly blood pressure, to avoid hypotension 1
• Regular assessment of fluid status is essential to prevent both dehydration and fluid overload 5, 6
• Proper BUN sampling techniques are crucial for accurate monitoring:
  • Draw predialysis samples before starting dialysis
  • Avoid dilution with saline or heparin
  • Use arterial needle for sampling 1, 5

Expected Outcomes

• With intensive hemodialysis (>36 hours/week) and BUN <35 mg/dL:
  • Live birth rates can reach 85-89% 1, 2
  • Mean gestational age of 36 weeks (vs. 27 weeks with conventional dialysis) 1
  • Higher mean birth weight (>2000g vs. <1800g with conventional dialysis) 1

Common Pitfalls and Considerations

• Inadequate dialysis intensity is a major pitfall - conventional thrice-weekly dialysis is insufficient for pregnant women 1
• Failure to monitor and maintain BUN <35 mg/dL correlates with poorer outcomes 2, 3
• Medication adjustments are necessary during pregnancy:
  • Antihypertensives may need modification
  • Anemia management requires close attention
  • Mineral-bone disease medications often need adjustment 7
• Risk factors for adverse fetal outcomes include:
  • Preeclampsia
  • Lupus
  • Primigravida status
  • Higher average midweek BUN levels 2

Nutritional Considerations

• Higher protein intake (>1.5 g/kg/day) is recommended to support fetal growth and compensate for dialysis-related losses 8
• Monitor and supplement other nutrients as needed, particularly iron and folate 7