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Pediatric CRRT: The Prescription
Stuart L. Goldstein, MD
Professor of Pediatrics
Baylor College of Medicine
What’s in a CRRT Prescription? Indication (Why? Who? When?) Technical Aspects (What?)
Nutrition (Maxvold)Anticoagulation (Brophy)Access (Bunchman)
CRRT Delivery (How?)Blood pump flow ratesModalityPrimingDose
Why CRRT in AKI?
Critically ill patient Advantages
Slower blood flows Slower UF rates UF rates can be prescriptive (versus PD) Adjust UF rates with hourly patient intake Increased cytokine (bad humors) removal?
Disadvantages Increased cytokine (good humors) removal? Non-dialysis personnel with many other bedside
responsibilities required to monitor circuit
When Should CRRT Be Started?
Standard AKI criteria not responsive to medical therapy OR only preventable with limiting adequate nutritionUremiaHyperkalemiaAcidosisFluid Overload
Prevention of worsening fluid overload?
Timing of Pediatric RRT
No adequate definition for “timing of initiation” Absence of a generally accepted, validated and
applied AKI definition has impeded the adequate investigation of this question
The decision to initiate RRT affected by Strongly held physician beliefs Patient characteristics Organizational characteristics
Retrospective evaluation of 226 children who received RRT for AKI from 1992-1998
Pressor use surrogate marker for patient severity of illness
Survival defined at PICU discharge
Percent Fluid Overload Calculation
% FO at CVVH initiation =[ Fluid In - Fluid OutICU Admit Weight ] * 100%
Fluid In = Total Input from ICU admit to CRRT initiationFluid Out = Total Output from ICU admit to CRRT initiation
Lesser % FO at CVVH (D) initiation was associated with improved outcome (p=0.03)
Lesser % FO at CVVH (D) initiation was also associated with improved outcome when sample was adjusted for severity of illness (p=0.03; multiple regression analysis)
Mean+SEMean-SE
Mean
OUTCOME
%F
O a
t CV
VH
Initi
atio
n
0
5
10
15
20
25
30
35
40
45
Death Survival
p = 0.03
Fluid Overload Thresholds at CRRT Initiation and Mortality
Author FO Threshold Outcome
Goldstein Fluid thresholds not assessed
Gillespie 10% OR death 3.02 > 10% FO
Foland 10% increment1.78 OR death for
each 10% FO increase
Goldstein (ppCRRT)
20%<20% FO: 58% survival
>20% FO: 40% survival
Hayes 20% OR death 6.1 > 20% FO
Prospective Pediatric CRRT (ppCRRT ) Registry: Phase 1 Design
Collect prospective data from 10 pediatric centers treating 15 to 20 patients annually (376 patients over 5 years)
Each center follows own institutional practice Patient selection Initiation and termination Anti-coagulation protocols Convection versus diffusion versus
hemodiafiltration Fluid composition
Pediatric CRRT Circuit Priming
Heparinized (5000 units/L) for most patients
Smaller patients require blood priming to prevent hypotension/hemodilutionCircuit volume > 10-15% patient blood volumePacked RBCs
Citrated – low ionized calcium Acid load Potassium load
Bradykinin Release Syndrome
Mucosal congestion, bronchospasm, hypotension at start of CRRT
Resolves with discontinuation of CRRT Thought to be related to bradykinin release
when patient’s blood contacts hemofilterMost common with AN-69 membranes
Exquisitely pH sensitive
Technique Modifications to Prevent Bradykinin Release Syndrome
Buffered systemTHAM, CaCl, NaBicarb to PRBCs
Bypass systemprime circuit with saline, run PRBCs into
patient on venous return line Recirculation system
recirculate blood prime against dialysate
Does Modality Make A Difference?
Equal clearance of smaller molecules Middle and large molecule clearance
enhanced by convection
Creatinine 113 DCreatinine 113 D
Urea 60 DUrea 60 D
Glucose 180 DGlucose 180 DVit. BVit. B1212
1,355 D1,355 D
2-M2-M11,800 D11,800 D
AlbuminAlbumin66,000 D66,000 D
IgG 150,000 DIgG 150,000 D
Membrane Selectivity
Courtesy of J. Symons
Solute Molecular Weight and Clearance
Solute (MW) Sieving Coefficient Diffusion Coefficient
Urea (60) 1.01 ± 0.05 1.01 ± 0.07
Creatinine (113) 1.00 ± 0.09 1.01 ± 0.06
Uric Acid (168) 1.01 ± 0.04 0.97 ± 0.04*
Vancomycin (1448) 0.84 ± 0.10 0.74 ± 0.04**
*P<0.05 vs sieving coefficient**P<0.01 vs sieving coefficient
ppCRRT Pediatric Sepsis Outcome Data
57/102 (56%) pts survived. Ventilated pts had similar survival rate as non-
ventilated pts (53% vs. 68%, p=0.1). There was no significant difference in the
survival rate among CRRT modalities. Tendency toward better survival with
convective therapies
Flores FX et al: CRRT 2006 abstract
Survival Based on CRRT Modality?
Confounded Center Timing of initiation Sepsis definition not
standardized
Suggestive If all else equal, why
not convect?
67%64%
47%
0%
10%
20%
30%
40%
50%
60%
70%
p=0.19
CVVH
CVVHDF
CVVHD
Flores FX et al: CRRT 2006 abstract
Dialysate/ Ultrafiltration Rates
The UF rate/plasma flow rate [=BFRx(1-HCT)] ratio should < 0.35-0.4 in order to avoid filter clotting (Golper AJKD 6: 373-386,1985)
Dialysate or effluent flow rates ranging from 20-30 ml/min/m2 (~2000ml/1.72m2/hr) are usually adequate (experiential but consistent with adult data)