Dialysis

Experts in Pediatrics Overview

  • Event: 2025 Pediatric Virtual Symposium
  • Date: Live on October 10, 2025
  • Access: Sessions available through December 31, 2025
  • Speaker: Kaitlin Alexander, MSN, APRN, CPNP-AC/PC, Inpatient Pediatric Nephrology Nurse Practitioner, Children's Health/UT Southwestern Medical Center, Dallas
  • Disclosure: Nothing to disclose (Speaker Disclosure)

Objectives of the Session

  • Describe three different modalities of acute care dialysis.
  • Identify indications for acute dialysis.
  • Identify risks related to continuous renal replacement therapy (CRRT).

Indications for Dialysis

  • Mnemonic for Indications: A-E-I-O-U

    • A: Acidosis
    • E: Electrolyte derangements
    • I: Ingestions or intoxications
    • O: Oliguria/overload
    • U: Uremia
    • Other indications: Hyperammonemia and nutritional support.

  • Specific Ingestions Intoxications:

    • I: Isopropyl alcohol
    • S: Salicylates
    • T: Theophylline
    • U: Uremia
    • M: Methanol, Metformin
    • B: Barbiturates
    • L: Lithium
    • E: Ethanol, Ethylene glycol
    • D: Depakote

Dialysis Pearls

  • No absolute values for BUN/creatinine required to initiate treatment.
  • Early dialysis may improve clinical outcomes in various conditions.
  • Aggressive dialysis may be needed in hypercatabolic states.
  • Consider dialysis even with residual renal function under certain conditions:
    • Need to remove large fluid volumes.
    • Administering frequent or large volume blood products.
    • Optimizing nutritional support.

Access for Dialysis

  • Peritoneal Dialysis (PD): Requires a peritoneal catheter.
  • Hemodialysis (HD) and CRRT: Utilize hemodialysis catheters.
    • Catheter Placement:
    • Internal jugular, femoral (preferred), and less ideally subclavian vein.
    • Ideal to use the shortest and largest caliber catheter safely available.
  • Types: Temporary vs Tunneled Line.

Principles of Dialysis

  • Diffusion: Movement of solutes from an area of higher concentration to lower concentration until equilibrium is achieved.
  • Convection: Movement of molecules across a semipermeable membrane due to a pressure gradient; solvent drag plays a role as the water moves with the solutes.
  • Ultrafiltration: Water and fluid removal according to the pressure gradient across the membrane.

RRT Modalities

  • Types of Renal Replacement Therapy:
    • Hemodialysis (HD)
    • Peritoneal Dialysis (PD)
    • Continuous Renal Replacement Therapy (CRRT):
    • Includes devices like Prismax vs Prismaflex, Carpediem, and Aquadex.
    • Prolonged Intermittent Renal Replacement Therapy (PIRRT).

Acute Hemodialysis (HD)

  • Mechanisms:
    • Primarily diffusive clearance, but also includes convective clearance.
    • Highly effective for fluid and solute removal.
    • Maximum fluid removal rate: 13extmL/kg/hr13 ext{ mL/kg/hr}.
    • Can be utilized as both an acute and chronic modality.

Anticoagulation in HD

  • Typical Anticoagulant: Unfractionated Heparin.
    • Administered either as an initial bolus with a maintenance infusion or larger initial bolus with smaller boluses throughout the therapy.
  • Citrate: Not routinely used in HD, but not contraindicated.
  • If the patient can't tolerate anticoagulation, optimizing blood flow rate and intermittent pre-filter saline flushes are possible alternatives.

HD Advantages and Disadvantages

  • Advantages:

    • Reliable fluid removal if the patient is hemodynamically stable.
    • High efficiency in solute clearance.
    • Short treatment session duration.

  • Disadvantages:

    • Requires anticoagulation, which may pose risks.
    • Limited fluid removal in hemodynamically unstable patients.
    • Risk of access site or catheter infections.
    • Need for experienced HD staff.
    • Potential for intradialytic hypotension.

Acute Peritoneal Dialysis (PD)

  • Overview: Requires catheter access to the peritoneal cavity and adequate peritoneal perfusion. Can be performed continuously or intermittently.
  • Initiation: Often initiated acutely with rapid cycles (1-hour) and low fill volumes (10 mL/kg).

PD Advantages and Disadvantages

  • Advantages:

    • Technically easier than other modalities.
    • Allows for gentle continuous fluid removal.
    • Less risk of hemodynamic instability.
    • Does not typically require anticoagulation.
    • Better preservation of residual renal function compared to HD.

  • Disadvantages:

    • Peritoneal filling may exacerbate respiratory distress.
    • Fluid removal can vary due to technical and hemodynamic factors.
    • Less efficient solute clearance than HD.
    • Risks include peritonitis, impaired drainage, and dialysate leaks.

Contraindications to PD

  • Absolute Contraindications:

    • Omphalocele
    • Gastroschisis
    • Diaphragmatic hernia
    • Severe adhesions
    • Peritoneal membrane failure

  • Relative Contraindications:

    • Planned or recent major abdominal surgery
    • Poor psychosocial conditions
    • Unhygienic home conditions
    • Single caregiver without support.

Complications of PD

  • Leakage: May require discontinuation of PD for 7-10 days or reduction of fill volume.
  • Peritonitis: Notable signs include acute clouding of dialysate, abdominal pain/distension, and vomiting. It necessitates an examination of PD cell count and culture, potential empiric antibiotics, and discussion with Nephrology.
  • Hernia Risk: Increased intraperitoneal pressure and weak spots in the abdominal wall can lead to hernias; the incidence inversely correlates with age, with the highest frequency in inguinal hernias among children younger than 1 year.

Acute PD Prescription Pearls

  • Initial Fill Volume: Start with 10 mL/kg, aiming for a goal of 40 mL/kg.
  • Fluid Removal Enhancement Strategies: Increase dextrose, fill volume, or number of exchanges per 24 hours.
  • Solute Clearance Adjustments: Change fill volume, adjust number of cycles, or consider changing modality based on the patient's needs.
  • Infants vs Adults: Infants possess a higher peritoneal surface area, which leads to more effective clearance of urea and creatinine and increased glucose absorption rates.

Continuous Renal Replacement Therapy (CRRT)

  • Overview: Utilized in patients requiring dialysis when traditional methods may pose a risk or be insufficient.
  • Indications: Same as previous
  • Vascular Access: Must be large and stiff enough for high blood flow rates; traditional central venous lines are generally inadequate.
    • Preferred Location: Right Internal Jugular (RIJ) vein, offering quick access and less vulnerability to future access complications compared to subclavian veins.

Albumin Dialysis: SPAD vs MARS

  • Indications: Primarily for clearing protein-bound solutes.
  • SPAD: Single Pass Albumin Dialysis.
  • MARS: Molecular Adsorbent Recirculating System.
    • Albumin is included in the dialysate to attract protein-bound solutes across membranes.

Continuous Renal Replacement Therapy (CRRT) Advantages & Disadvantages

  • Advantages:

    • Reliable fluid removal with less risk of hemodynamic instability.
    • Solute removal is slower but effectively managed.
    • Greater clearance of solutes and potentially enhanced cytokine/toxin removal.
    • Can be managed by ICU nurses and run concurrently with ECMO.

  • Disadvantages:

    • Requires anticoagulation.
    • Necessitates patient immobilization.
    • Drug dosing adjustments may vary with modality.
    • Nutritional needs are not clearly defined and often more costly than HD.

CARdiorenal PEDiatric EMergency Overview

  • Advantages:

    • Smaller extracorporeal blood volume, reducing exposure risk.
    • Lower blood flow rates to decrease shear stress and clotting risks.
    • Capability to use lower blood flow dialysate to enhance clearance.
    • Smaller catheter sizes for pediatric patients.

  • Disadvantages:

    • Less familiar in many institutions.
    • Circuit changes needed every 24 hours.
    • Absence of regional anticoagulation capabilities.
    • Not compatible with ECMO setups.

Aquadex (Aquapharesis)

  • Advantages:

    • Suitable for smaller pediatric patients due to smaller lines
    • Same machine can function for both intermittent and continuous uses.
    • Real-time monitoring of hematocrit for accurate fluid removal.
    • Reduced extracorporeal volume minimizes exposure risk.

  • Disadvantages:

    • Ineffective for solute clearance.
    • Limited familiarity in newer institutions.
    • Potential for hypothermia, necessitating a separate warmer.
    • No regional anticoagulation abilities.

Dialysis Techniques Overview

  • SCUF (Slow Continuous Ultrafiltration): Focuses on fluid removal.
  • CVVH (Continuous Veno-Venous Hemofiltration): Utilizes convective clearance.
  • CVVHD (Continuous Veno-Venous Hemodialysis): Involves diffusive clearance.
  • CVVHDF (Continuous Veno-Venous Hemodiafiltration): Employs both convective and diffusive clearance.

Anticoagulation Protocols for CRRT

  • Systemic Anticoagulation:

    • Unfractionated Heparin: Commonly infused pre-filter with monitoring guidelines based on institutional protocols. Heparin is not typically removed by CRRT.
    • Low Molecular Weight Heparin: More expensive than UFH; however, studies do not show it extends the lifespan of hemofilters significantly.

  • Regional Citrate Anticoagulation:

    • Works by chelating ionized calcium, creating calcium+citrate complexes that prevent clotting.
    • Requires careful titration of calcium levels in both patient and circuit to avoid hypocalcemia.
    • Monitoring for instances of citrate toxicity or complex imbalances is essential, especially in patients with liver or skeletal muscle dysfunction.

Components of CRRT Prescription

  • Components:
    • Prime Solution: Normal saline or 5% albumin and blood.
    • Blood Flow Rate: Varied by age group:
    • Neonates: 8−12extmL/kg/min8-12 ext{ mL/kg/min}
    • Children: 4−8extmL/kg/min4-8 ext{ mL/kg/min}
    • >50 kg: 2−4extmL/kg/min2-4 ext{ mL/kg/min}
    • Fluid Removal Rate Target: Aim for net hourly deficit of 0.5−2extmL/kg/h0.5-2 ext{ mL/kg/h} depending on patient’s fluid removal goals.

Complications Associated with CRRT

  • Possible complications include:
    • Bleeding.
    • Infection.
    • Hypotension.
    • Electrolyte imbalances.
    • Hypothermia.
    • Loss of nutrients.
    • Membrane reactions (especially with certain filters).
    • Metabolic alkalosis and citrate toxicity or lock.
    • Clotting in the circuit requires vigilance.

Nutrition Considerations in CRRT

  • Carbohydrate Management: Important for metabolism, but excess can lead to lipogenesis; citrate as an active carbohydrate may impact insulin metabolism.
  • Fat Management: Less affected due to molecular weight; important to monitor for mitochondrial dysregulation.
  • Protein and Amino Acid Needs:
    • Vital to prevent malnutrition, muscle atrophy, and support healing; Meets ASPEN guidelines.
    • Specific Guidelines:
    • Ages 0-2 years: 3−3.5extg/kg/day3-3.5 ext{ g/kg/day}
    • Ages 2-13 years: 2−2.5extg/kg/day2-2.5 ext{ g/kg/day}
    • Ages 13-18 years: 2−2.5extg/kg/day2-2.5 ext{ g/kg/day} (documentation suggests higher doses).
  • Vitamin and Trace Element Management:
    • Trend levels for water-soluble vitamins and supplement as needed, mindful of thiamine depletion.
    • Fat-soluble vitamins generally retained.
    • Monitor trace elements, especially selenium.

Prolonged Intermittent Renal Replacement Therapy (PIRRT)

  • Purpose: CRRT combined with scheduled breaks to accommodate other therapies.

  • Typical Treatment Timing: 6-12 hours, governed by nursing availability, with less than 12-hour sessions allowing sufficient staffing.

  • Benefits of PIRRT:

    • Allows for planned downtime for other procedures and therapies.
    • Acts as an intermediary to intermittent HD for hemodynamically stable patients.
    • Reduces anticoagulation needs.

  • Challenges:

    • Requires careful considerations regarding clearance and prescription adjustments.
    • Medication clearance needs to be addressed comprehensively.