The future of ECCO2Rmy guess

Antonio Pesenti

University of Milan

Ospedale Maggiore Policlinico

Milan Italy

antonio.pesenti@unimi.it

CCCF 2017

There are two kinds of forecasters:

those who don’t know, and those who don’t know they don’t know.

There are two kinds of forecasters:

those who don’t know, and those who

don’t know they don’t know.

John Kenneth Galbraith

Which Blood Flow?

• It depends: How much CO2 do we need to

remove? ( which patient?)

• Normally it is not advisable to remove all the CO2

content of blood ( pH problems)

• In any case we cannot remove more than the CO2

content of blood

PCO2 (mmHg)

0 10 20 30 40 50 60 70 80

pH

6.6

6.8

7.0

7.2

7.4

7.6

7.8

8.0

8.2

8.4

BE = 0

BE = -10

BE = 10

http://www.acba.it/

PCO2 (mmHg)

0 10 20 30 40 50 60 70 80

TC

O2

(m

l%)

0

20

40

60

80

100

BE = 0

BE = -10

BE = 10

http://www.acba.it/

PCO2 (mmHg)

0 10 20 30 40 50 60 70 80

TC

O2

(m

l%)

0

20

40

60

80

100

BE = 0

BE = -10

BE = 10

http://www.acba.it/

ARDS

PCO2 (mmHg)

0 10 20 30 40 50 60 70 80

TC

O2

(m

l%)

0

20

40

60

80

100

BE = 0

BE = -10

BE = 10

http://www.acba.it/

ARDS

COPD

Blood Co2 content

PCO2

mmHg

pH Tot Co2

mMol/l

Ml CO2

80 7.11 27.87 624

80 7.30 41.87 938

Why should we remove CO2?

• To minimize the risk of VILI ( supernova)

• To minimize Invasiveness ( COPD)

• To control the respiratory drive and allow spontaneous

breathing (ARDS, COPD)

ECCO2R

• CO2 can be removed by

– Hemodialysis

– Hemofiltration

– Membrane lung ( by far the most common)

• CO2 removal enhanced by:

– Acidification

– Carbonic anhydrase

– Special geometry

CO2 Scavenging Phase

• Gas or fluid?

• Dialyzers or artificial lungs?

• Hemofilters?

• Acidic gases?

Performance

Oxygenator

Input:

37°C

Bovine blood

PCO2 45 mmHg1.8 sq M

Intermittent vs Continuous

• CO2 stores ?

• How fast will CO2 go back to the original levels?

• How should we manage Acid Base balance?

JAP 7 (5) :472-484: 1955

Vd CO2 = 250 l

Second Time Constant

Ivanov SD Respir Physiol 1968 ,5,243

Wearable Lungs vs

Wearable kidneys

• Implantable lungs?

Wang D ASAIO J 2003

Implantable Bioartificial lung

Scaffold

Stem cells

Blood flow resistance

Air supply

The future of CO2 removal

• Maximize CO2 removal from a given ( low) blood flow

• Minimize invasiveness

• Regional anticoagulation or NO anticoagulation

BF 500-1000 vs BF 200-250 ml/min

Sistemicanticoagulation:major complicationsduring ECCO2R

Regionalanticoagulation:

Optimize Membranes

• Maximize gas permeability

• Catalytic ( Carbonic Anhydrase)

• Biocompatible ( avoid clotting?)

Increasing CO2 removal fom blood

Acidification ( organic, Sulfur Dioxide)

Immobilized Carbonic Anhydrase

Exp. N°4 >> ML on dialysate circuit

Blood Flow250 ml/min

Lactic Acid2.5 mEq/min

Gas flow 10 l/min100% O2

Evaluating efficacy and safety of enhanced extracoropreal CO2

removal through acidification and ventilation of dialysate

Zanella, J Heart Lung Transplant 2014

Am J Respir Crit Care Med 2015

Respiratory Electrodialysis

Anticoagulation

• Regional?

• Heparin or Citrate? What else?

• Surface Heparinization, does it work?

Citric Acid / Citrate anticoagulation

• At least 3 mM ( 9 mEq) /l blood flowEach liter/min blood

flow

• That means an increase of 170.2 liters per day CO2

production, i.e. 118 ml/min in excess to baseline per liter

blood flow.

• Each 100/ml min of anticoagulated blood flow CO2

production will increase between 11.8 ( best case, glucose

baseline burning) and 14 ml ( worst case, fat burning)

ml/min

• At 200 ml/min CO2 production will increase 12%

approximately.

Zanella et al SHOCK, 46, pp. 304, 2016

ECCO2R

• Lower blood flows: easier

• Anticoagulation: more difficult

• Vascular access: not so good at this time

• Maximize amount of CO2 removal from

given blood flows

• Regional Anticoagulation

– Prostigmine

– Citrate