Transcript Divisional Update: Women Mar 2008

CRRT Prescription
Akash Deep
Director - PICU
King’s College Hospital
London
Chair
Renal/CRRT Section
European Society of Pediatric and
Neonatal Intensive Care (ESPNIC)
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Overview
Vascath – Size , location
Rates & Dose
Blood flow
Dialysis fluid
Suggested
Replacement fluid
Not necessarily a recipe
Ultrafiltration rate
Anticoagulation
Drug Dose
Is there a “typical” prescription?
• CRRT for AKI or Sepsis or Liver failure
– does the dose matter ?
• Modality : Do you do convective or diffusive or
both , does it matter?
• Blood Flow rate: based upon the size of the
child or what the vascular access can give you?
• Anticoagulation – Which, when, dose, mode of
delivery
• Drug dosing – a perennial debate!!!!
Essential steps in CRRT Prescription
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Decide the Indication to start CRRT
PRESCRIBE:
VASCULAR ACCESS – Size Location
Haemofilter and appropriate Sized Blood line set
Priming Solution
Blood Flow
Modality /Dose – Replacement Fluid/Dialysis Fluid
Prescribe Fluid loss rate
Prescription of electrolyte corrections
Anticoagulation – Dose,Modality, Monitoring
Drug Dosing
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
 Start lower and increase by about 10 minutes (?) – 50% of target
and then go up 10% every 10 minutes till desired flow reached
Blood flow rate
 No set “perfect rates”
 From 3 to ~10 ml/kg/min, depending on age though
we use minimum of 50 mls/min for newborns
 Examples:
0-10 kg:
25-50ml/min
11-20kg:
80-100ml/min
21-50kg:
100-150ml/min
>50kg:
150-180ml/min
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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:
- Patient hemodynamics – initial and subsequent
 which might change with CRRT
- Be aware of access and return pressure
- Visually inspect filter for clots
- Trans-membrane pressure – may need to increase blood flow
Treatment Dose
Dialysis and Replacement Fluid Rates:
Clearance & Dose
 Clearance mostly a function of:
 Dialysis fluid flow rate (Qd)
 Replacement fluid flow rate (Qr)
 Molecular weight and sieving coefficient
Qd + Qr (CVVHDF)
 Higher rates
= higher clearance for IEM, drug removal, severe high K
= more middle molecule clearance (CVVH/CVVHDF)
= more hypophosphatemia, kalaemia, magnesaemia
= more amino acid losses
= more drug clearance
= more work to change bags, give electrolyte infusions
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:
Urea clearance
Qd or Qr or Qd+Qr ~ 40-60 ml/kg/hour ~ 30-40 ml/min/1.73msq
OR 2 to 2.5 liters/hr/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
Prescribed and Delivered therapy dose
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Typically, therapy dose would be prescribed at 35 ml/kg/hr, in
practice the delivered therapy dose was on average 8ml/kg/hr less.
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Prescription should exceed that calculated to be adequate because
of the known gap.
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Why might we ‘lose’ significant amounts of therapy dose?
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Recirculation in vascular access
High filtration fractions
Filter clogging and clotting
Troubleshooting skills
Changing of circuits
Filter down time
Vesconi et al Delivered dose of renal replacement therapy and mortality in
critically ill patients with acute kidney injury Crit care 2009 13 (2);r57
CVVH
Qr = 300
ml/hour
CVVHDF
Qd = 150ml/hour
Qr = 150 ml/hour
CVVHD
Qd = 300 ml/hour
10 kg child: 30 ml/kg/hr “clearance”
OR ~ 0.26 msq: 2L/1.73msq/hour = 300
ml/hour
Dialysis Dose and Outcome
Ronco et al. Lancet 2000; 351: 26-30
425 patients
Endpoint = survival 15 days after D/C HF
146 UF rate 20ml/kg/hr
survival significantly lower
in this group compared
to the others
139 UF rate 35ml/kg/hr
p=0.0007
140 UF rate 45ml/kg/hr
p=0.0013
Conclusions:
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Minimum UF rates should be ~ 35 ml/kg/hr
Survivors had lower BUNs than non-survivors
prior to commencement of hemofiltration
ATN Study
Randomised Evaluation of Normal vs Augmented
Level Replacement (RENAL) Therapy )
1500 critically ill adults
CVVHDF
25 ml/kg/hour
40 ml/kg/hour
Mortality at 28 days was similar in the higherintensity and lower-intensity treatment groups
(38.5% and 36.9%, respectively), and mortality
at 90 days was the same (44.7%) in both
groups.
Does the dose of solution exposure
per unit of time matter
• These adult studies have failed to note a dose
response curve of survival
• These studies are flawed for IHD vs CRRT was
compared and CRRT was both convective and
diffusive
So
• If you start with a standard prescription
• Eg
– BFR 5-10 mls/kg/min (access dependent)
– Membrane surface area proportional to patient
body surface area
– Decision of convective or diffusive at approx
2000-3000/mls/hr/1.73m2
and
• If the marker of your clearance is not achieved
– E.g.
• inadequate clearance of Urea, Ammonia,
intoxicant, lactate
• Then increase your solution exposure per unit of time
• Maximize convective clearance before adding
diffusive clearance
• Consider increasing the BFR and increasing surface
area of the membrane
• Filter downtimes to be minimised
Solutions
CVVHD – dialysis fluid for diffusive clearance
CVVH – replacement fluid:
replacing fluid you are removing to achieve solute
clearance by convection
CVVHDF – both
Priming solutions – Saline /blood prime
Anticoagulant solutions
Using these to correct metabolic abnormalities (remove) and
prevent treatment-related metabolic abnormalities (replace).
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
Solutions: watch for errors!
Barletta et al, Pediatr Nephrol, 2006
Survey: ICU, Nephrology, CRRT
 16/31 programs reported solution compounding errors with
manually dispensed solutions
 2 deaths
 1 non lethal cardiac arrest
 6 seizures (hypo/hypernatremia)
 7 without complications
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)
Decide desired DAILY fluid removal based on:
 Haemodynamics
 TOTAL severity of Fluid Overload
SINGLE PASS Albumin dialysis -SPAD
 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
 20% albumin NOT “added” to dialysis fluid bag- it sinks however
it is mixed with normal dialysate via 3 way tap -it's “single pass”
- bags are changed
 Shouldn't affect sodium – may affect (reduce) other electrolytes
Collins et al, Pediatr Nephrol, 2008
Askenazi et al, Pediatrics, 2004
Ringe, Pediatr Crit Care Med, 2011
ANTICOAGULATION
ANTICOAGULATION-Points to consider
• Choice of anticoagulant
• Dose
• Route of delivery – systemic, into the circuit
Anticoagulation
• Heparin
• Citrate
• Prostacyclin
Dosing and Route
• Heparin – 10-20 U/kg/hour
• Prostacyclin – 2-8 ng/kg/min
• Citrate – separate protocol
• All anticoagulants to be used pre-filter with post
filter monitoring ( ACT in heparin, ionised Ca in
citrate)
Drug Dose Alteration
• Drug dosing- important ( antibiotics,
anticonvulsants, sedation, inotropes)
• Hepatic failure + CRRT – Bigger issues
• Based on:
– Protein Binding Information
– Volume of Distribution
– Molecular Weight
Drug Prescribing in Renal Failure
edited by George Aronoff et al
• Commonly carried text by
pharmacists
• http://www.kdpbaptist.louisville.edu/renalbo
ok/
• New edition to come out
soon
• Recommendations for new
drugs
• IHD and CRRT
recommendations
• Pediatric recommendations
(T bunchman)
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 – can be life threatening
 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
Acknowledgements
• T Bunchman
• pCRRT Foundation
• CRRT team at King’s