PCRRT on ECMO

Norma J MaxvoldPediatric Critical Care

PCRRT on ECMO

• What is the incidence of PCRRT in ECMO?

• How does it differ to standard PCRRT• Where do you put the filter?• What are the risks?• What factors effect solute clearance?• Weaning ECMO in an anuric child• What outcome data is available?

PCRRT on ECMO

• Incidence (ELSO registry 1997) Neonatal ECMO = 14% require

PCRRT Pediatric ECMO = 31% require

PCRRT

PCRRT HF/ECMO

Access Acute ECMO Access

Anticoagulation PCRRTprotocols

ECMOanticoagulation

UltrafiltrationControl

PCRRTmachinecontrolled

IV pump controlled

PCRRT on ECMO vs Standard PCRRT

PCRRT HF/ECMO

BFR ~ 5 ml/kg/minmax 180

ECMO BFRdependent (100-280 mls/kg/min)

DxFR/ReplFR

2000mls/hr/1.73m2

2000mls/hr/1.73m2

SAM 0.3-0.6 m2 0.3-0.6 m2

PCRRT on ECMO vs Standard PCRRT

Hemofiltration on ECMO

Risks of PCRRT on ECMO

• Excessive ultrafiltration (VA ECMO will support hemodynamics independent of volume status)– due to ultrafiltration controller error– due to higher then greater blood flow

rate

RESULTS(Smoyer et al, CRRT 1997)

0 100 200 300 400 500 600 700 800 900 1000-4

-3

-2

-1

0

1

2

3

4

0 100 200 300 400 500 600 700 800 900 1000

Dialysate

Ultrafiltrate

IV Pump Flow Rate (ml/hr)

% E

rror

Trilogy Pump: Accuracy over Range of Flow Rates

Clinical Scenario

• 3 kg infant on VA ECMO• SCUF for 4 days at 250 cc/day net

– K 4.5 mEq/L, Phos 5.7 mg/dl– Albumin 3.8 gm/dl– Na prior to SCUF 139

• IVF were TPN, antibiotics

Clinical ScenarioLab data-4 days later

• Euvolemic, Anuric• Na 118 mEq/L, Cl 74 mEq/L

Clinical Scenario

• 3 kg child with intravascular blood volume of 240 ccs

• Net Na loss was based upon Na content of ultrafiltrate/day ~120 mEq or 40 mEq/kg

• Without adequate replacement fluid or counter current dialysis excessive solute loss occurs

What determines Solute Clearance?

• Blood Flow Rate (BFR)• Dialysate Flow Rate (DxFR) in

CVVHD or Replacement Flow Rate (ReplFR) in CVVH

• Surface Area of membrane/porosity of the membrane

Comparison of Urea Clearance: CVVH vs

CVVHD(Maxvold et al, Crit Care Med April 2000)

0

5

10

15

20

25

30

CVVH CVVHD

U

rea

Cle

aran

ce(m

ls/m

in/1

.73

m2)

BFR = 4 mls/kg/minFRF/Dx FR = 2 l/1.73 m2/hrSAM = 0.3 m2

p = NS

Impact of Surface Area of hemofilter-1(Maxvold et al, ELSO 1994)

• 70 kg child on VA ECMO and anuric

– PCRRT BFR 200 mls/min– ccDx @ 2000 mls/hr– HF with 0.24 m2

Impact of Surface Area of hemofilter-2(Maxvold et al, ELSO 1994)

• Over 24 hours of hemofiltration the following metabolic changes occurred

– Bun dropped from 180-174 mg/dl– Potassium increased from 6.5-7.2 meq/l– HCO2 dropped from 19-22 meq/l

• (we be in trouble!!)

Impact of Surface Area of hemofilter-3

• The hemofilter was changed from the 0.24 m2 to a 1.7 m2 HD membrane and over the next 24 hours– Bun dropped 174-84 mg/dl (to rapid of a

shift)– K 7.2-3 meq/l– HCO2 22-> 40 meq/l– pH increase from 7.15 to 7.75

Metabolic consequences when weaning ECMO

• Mixed metabolic and respiratory acidosis

• hypotension• need for blood transfusions with

secondary hypocalcemia and hyperkalemia

Anticipate Metabolic Consequences

• plan to decrease the serum potassium

• plan to make alkalotic• THESE ARE MOST IMPORTANT IN A

PATIENT WHO IS ANURIC/OLIGURIC

• COMMUNICATION PRIOR TO DECISION

Post ECMO Renal Effect(Meyers et al, Peds Crit Care Coll, Portland, OR

1999)

• 35 children requiring HF on ECMO/8 yrs• 20 died (withdrawn) on ECMO and CRRT

due to lack of recovery of underlying cause

• 15 survived ECMO requiring ongoing PCRRT

• 14/15 had recovery of renal function within 7-10 days post discontinuation of ECMO

PCRRT and ECMO• Especially in the smaller children and

infants solute clearance on ECMO is greater then standard PCRRT due to the relatively high blood flow rates

• Ultrafiltration error may not be easily recognized due to the maintenance of hemodynamic stability that ECMO gives

PCRRT and ECMO• These are the sickest of the sick• ECMO is not a substitution for

dialysis• Recovery of renal function will

occur in majority of patients within days in those who had normal renal function prior to need for ECMO