PEDIATRIC CRRT
THE PRESCRIPTION:
RATES, DOSE, FLUIDS
Michael Zappitelli, MD, MSc
Montreal Children's Hospital
McGill University Health Centre
OVERVIEW
Rates & Dose
Blood flow
Dialysis fluid
Replacement fluid
Ultrafiltration rate
Fluids
Suggested
Not necessarily a recipe
BLOOD FLOW RATE
 Qb
 Age & weight – based
 Promote circuit lifespan + patient stability: clots vs alarms
 Highly access-dependent
 Aim return access pressures ~ < 200 mmHg, no alarms
 May be machine – dependent
 Prisma: 180 ml/min
 Prismaflex & Aquarius: 450 ml/min
 Start lower and increase by about 10 minutes (?)
BLOOD FLOW RATE
 No set “perfect rates”
 From 3 to ~10 ml/kg/min, depending on age:
 Examples:
0-10 kg:
25-50ml/min
11-20kg:
80-100ml/min
21-50kg:
100-150ml/min
>50kg:
150-180ml/min
Based on
previously most
commonly used
machine
 Neonates 8 to 12 ml/kg/min
 Children 4 to 8 ml/kg/min
 Older 2 to 4 ml/kg/min.
 Most not > 200 ml/min: not dangerous just not necessary
BLOOD FLOW RATE
 May need to modify:
 Be aware of access and return pressure
 Visually inspect filter for clots
 Transmembrane pressure – may need to increase blood flow
 Filtration fraction
SOLUTIONS
 Slow continuous ultrafiltration – none
 CCVHD – dialysis fluid for diffusive clearance
 CVVH – replacement fluid:
 replacing fluid you are removing to achieve solute
clearance by convection
 CVVHDF – both
Using these to correct metabolic abnormalities (remove) and
prevent treatment-related metabolic abnormalities (replace).
IDEAL SOLUTIONS
 Physiological/
compatible
Composition:






 Peritoneal dialysis fluid?
 Hyperglycemia, metab acidosis
Sodium: ~ 130 to 140
Soysal et al, Ped Neph, 2007
Reliable
Chloride: ~105 to 120 dependent on other anions (HCO3)
 Pre-made
IV solutions:
Potassium: MOST Zero – need
to add (some
have)
Inexpensive
Magnesium: 1 to 1.5 mEq/L  Saline, Lactated Ringers
Glucose/Dextrose: 0 to 110 mg/dL
Easy
to prepare
Multi-bag
systems:
why?
Lactate:
Most 0 to 3 mEq/L (35-40
mEq/L
if lactate
buffer)
 Custom-made solutions:
Simple to storeBicarbonate:
 Local pharmacy; outsource
Most 30-35 mEq/L
Quick to the bedside
Few ZERO  Commercially available solutions:
As low as 22 to 25
 mEq/L
Ready-bags (compartments)
Widely available
 Concentrate added to bag
Calcium:
0 to 3.5 mEq/L
CHOOSING SOLUTIONS
 Cost (Storing, frequency of use)
 Anticoagulation: +/- calcium with citrate anticoagulation
 There are citrate based solutions and data
 Patient safety – patient volume?
 Does everyone prescribing really understand?
 Regulatory issues (dialysis versus replacement fluid....)
Accusol
Prismasate
Some solutions
are more flexible than others
Normocarb
Duosol
Prismasol
Hemosol BO
...........
PHOSPHATE
 They WILL develop hypophosphatemia
 Can replace: IV boluses, TPN
 MANY add it to solutions – but no good data
 Worry about precipitation, calcium-magnesium binding
 How much too much? No good answer. Many 1.2-1.5 mmol/L
 Pharmacy versus nurse-based addition?
ADDING PHOSPHATE
Troyanov et al, Intens Care Med, 2004
Experiment
Added 1.2 mmol/L PO4to calciumet
– rich
Santiago
al, solutions
Therap Apher & Dialysis, 2010
5 hours: no effect on calcium,Consideration:
bicarb, pH, pCO2
No visual precipitation Experiment
Added
NaPO4
to dialysis/replacement fluid bags (12)
With and
without
filtering
Most
dialysis
or
replacement
fluid
containing calcium and magnesium
2 days: to precipitation
bags will not need to0.8
bemmol/L
hung for
mmol/L
Retrospective
clinical
Santiago more
et
al, KI,
2009
than
a1.5
day
2.5 mmol/L
14 adults CVVHDF
Experiment
KPO4
addedevaluation
when <1.5ofmmol/L
(protocolized)
Pre-post
adding
NaPO4
to
dial & replace
solution
No
change
inbicarb,
calcium,
magnesium,
sodium, gluc, pH
No negative
effects
caused
on
calcium,
pH
0.8 mmol/L, 47 children, solutions contained
Ca++
&
Mg++
2, 24 and 48 hours
No precipitation seen
Less IV PO4 needed
DIALYSIS FLUID? REPLACEMENT FLUID?
 Personal suggestion: use the same solution
 If needed (e.g. alkalosis) can modify the replacement solution
 Regulatory issues may hinder:
 Replacement solution – saline, with additives
ALBUMIN DIALYSIS
 Removes protein bound small substances:
 e.g. copper/Wilson's, drugs, toxins of liver failure
 Albumin live a scavenger
Dialysis:
 albumin-containing solution across highly permeable membrane
 25% albumin “added” to dialysis fluid bag: 2-5% albumin solution
 it's “single pass” - bags are changed
 Shouldn't affect sodium – may affect (reduce) other electrolytes
 Theoretically may affect citrate anticoagg rates
 Allergic reaction
Collins et al, Pediatr Nephrol, 2008
Askenazi et al, Pediatrics, 2004
Ringe, Pediatr Crit Care Med, 2011
SOLUTIONS: WATCH FOR ERRORS!
Barletta et al, Pediatr Nephrol, 2006
Soysal et al, Pediatr Nephrol, 2007
Survey: ICU, Nephrology, CRRT
Country where resources dictate need to use PD solution for dialysis
16/31
programs
reported
solution compounding
errors
and NS
+ additives
for replacement
fluid
2 deaths
Many
electrolyte
1 non reported
lethal cardiac
arrest complications: glucose, sodium, acidosis
6 seizures (hypo/hypernatremia)
7 without complications
DIALYSIS AND REPLACEMENT FLUID
RATES: CLEARANCE & DOSE
 Clearance mostly a function of:
 Dialysis fluid flow rate (Qd)
 Replacement fluid flow rate (Qr)
Qd + Qr (CVVHDF)
 Higher rates
= higher clearance for IEM, drug removal, severe high K
= more middle molecule clearance (CVVH/CVVHDF)
= more hypophosphatemia, kalemia, magnesemia
= more amino acid losses
= more drug clearance
= more CITRATE clearance
= more work to change bags, give electrolyte infusions
 Lower rates simplify electrolyte balance and limit protein loss
DIALYSIS AND REPLACEMENT FLUID
RATES: CLEARANCE & DOSE
 No well-defined right “dose” of clearance .
 For CRRT:mostly expressed in terms of effluent (ml/kg) per hour
“Standard” suggestion:
Qd or Qr or Qd+Qr ~ 20-40 ml/kg/hour
OR 2 to 2.5 liters/hr/1.73msq.
Urea clearance
~ 30-40 ml/min/1.73msq
Some do much higher: some machines as high as 8L/hour
REALIZE:
What you prescribe is not necessarily what the patient gets !!
Time off circuit, microclots in filter over time, predilution
1 0 KG C H I L D : 3 0 M L / KG / H R “ C L E A R A N C E ”
OR ~ 0.26 MSQ: 2L/1.73MSQ/HOUR = 300 ML/HOUR
CVVH
Qr = 300
ml/hour
CVVHDF
Qd =
150ml/hour
Qr = 150
ml/hour
CVVHD
Qd = 300 ml/hour
ULTRAFILTRATION/FLUID REMOVAL RATES
 No Study has identified effective, safe UF rates in Children.
 General acceptance that 1-2ml/kg/hr is often safe (stable patient)
 Choose UF rate to:
 balance input (e.g. boluses, citrate, calcium, etc)
 remove excess fluid over time
 “make room” for IV fluids and nutrition
 Also provides solute clearance by convection
ULTRAFILTRATION/FLUID REMOVAL RATES
 Fluid removal should be safe AND effective – no need to
sacrifice one for other:
 Frequent communication
 Frequent reassessment (MD), Hourly reassessment (RN)
 Know what the “usual hourly input is”:
 IV fluids
 Citrate & calcium
 Nutrition (give!!)
 Meds/infusions
 Provide “rules” for removing “intermittent fluids”
Be aware of the “outs”
(tubes, urine, diarrhea) – account for
ULTRAFILTRATION/FLUID REMOVAL RATES
 Decide desired DAILY fluid removal, after understanding
TOTAL severity of Fluid Overload
 Assure safety of this desired daily fluid removal
 Decide desired hourly “negative balance”
 Even balance?: Simply remove hourly ins – significant outs
 Negative balance?: Same + remove desired negative balance
 Think about filtration fraction – make sure not too high
UFR/Plasma flow rate --- UFR/Qb
<20-25% CVVHD or post-filter CVVH
<30-35% pre-filter CVVH
SUMMARY
 Blood flow: balance access/circuit life with tolerability
 Solutions: Many choices
 Know their content, regional rules, CRRT type used
 Decide on desired flexibility
 Decide what's best for your institution (volume, expertise)
 Bicarbonate and calcium are most substantial differences
 Be aware of errors
 Dialysis/replacement fluid rates: ie clearance dose
 Balance desired clearance with undesired losses
 2-2.5 L/hour/1.73msq – suggested only
 Ultrafiltration rate:
 Frequent reassessment, team + targeted fluid removal decisions
 Safety AND efficacy are feasible