problem shooting in venovenous ecmo - critical care€¦ · problem shooting in venovenous ecmo ......

Problem shooting in

Veno Venous ECMO

Norbert WelkovicsSurgeon & Intensivist

Private Practice and Division of Critical Care, University of Pretoria

Disclosure

• TAU Medical sponsored attendance to ELSO ECLS course

• Performing EMCO in private practice

• Busy setting up ELSO accredited ECMO centre at Unitas Hospital

• Not remunerated for this talk

Introduction

• Increasing interest and usage in adult population• CESAR trail (2009)

• Severe ADRS patients EMCO vs conventional ventilation

• Improved survival

• H1N1 influenza pandemic (2009 / 2010)• Increased numbers of previously healthy patients

• Reported survival 68 – 77%

• Improved equipment• Second generation centrifugal and levitating pumps

• Polymethylpentene (PM)P membrane oxygenators

• ECMO specific catheters

ExtraCorporeal Live Support (ECLS)

AVCO2RECCO2RPECO2R

VV ECMO

CPB/MCSVA ECMO

VVA ECMOECPR

CO2

RemovalRespiratory

SupportCirculatory

Support+ +

Introduction

• Increasing interest and usage in adult population

• VV ECMO most common modality• Cardiac dysfunction due to ventilation settings

• Rest settings improve cardiac performance markedly

• Avoids problems associated with VA ECMO• Arterial cannulation

• Upper body hypoxemia and position of mixing cloud

• LV strain due to increase in afterload

• Air and micro embolism systemic

• Maintains pulsatile flow

ECMO setup Double lumen Bi-Caval Catheter

Intra-hepatic

IVC

SVC

Open

Centrifugal

Pump

4.5 l/min5600 rpm

Pump

Head


Drainage limb• Negative pressure (-20 to -100mmHg)

dependant on • Size of drainage catheter

• Position of catheter

• Kinking in tubing

• Pump speed

• Sweet spot

4.5 l/min5600 rpm


Oxygenator

O2

Sweep

gas flow


flow directed

over

Tricuspid Valve


P1P2P3

P1= Drainage pressure (limiting factor)(not more negative -100)

∆ P2 / P1 = Trans-pump shearing force∆ P2 / P3 = Transmembrane pressure

(around 50 – 80 mmHg)Membrane flow resistancePump speed dependant


P1 SvO2 = Mixed venous saturation∆ P3 PaO2 / P2 PaO2 = Membrane efficiency

3 – 5 * FiO2

De-airing port

T1T2

Heater


Exhalation port

• 29F female, 31F for males

• Advantage• Better patient mobilization

• Less risk for recirculation

• Disadvantage• RIJV only registered access

• Needs screening (AOT) therefore transport

• More drainage dependent due to size

• Less flow

• More negative P1 pressures


• Femoral drainage (22F – 28F)

• Jugular return (17 - 21F)

• Can be placed at bedside with TEE confirmation

• Advantage• More suitable for unstable patients (no

need for screening)

• Can manage higher flows

• Disadvantage• Impedes mobilization

• Higher risk for recirculation

ECMO setup Double Catheter

Mechanics• Catheter setup

• Centrifugal pump (vs Roller in CPB)• Coupled

• Pump and pump head separate

• Increased fiction at interface

• Potential problems with pump overheating

• Able to hand crank – no need for second pump



• Levitating • Pump and pump head single unit

• Decreased friction at interface

• Less risk for overheating

• More expensive

• Not able to hand crank

• Need for separate backup pump



• Levitating

• Open centred• Non occlusive when stops

• Reverse flow however possible even at low speed

• With stopping flow always clamp the return limb

• Potential for air embolism (decreased importance in VV ECMO)

Mechanics • Catheter setup


• Levitating

• Open centred

• Preload sensitive (P1), afterload dependent (BP)• Changes in pre or afterload will effect flow

• Pump flow ≠ pump speed

• Need for flow meter

• Less risk for over-pressurization

Pump Speed(rpm)

Flo

w (

l/m

in)

Minimum pump speed to start flow

Increasing afterload



• Levitating

• Open centred

• Preload sensitive(P1), afterload dependent(BP)

• Haemolysis dependent on• Shearing (∆ P1/P2)

• Pump residence time

• Cavitation at very low P1 (-500mmHg to -600mmHg) – Roller pumps • Bubble formation with shock waves


• Centrifugal pump

• Membrane gas exchange “Oxygenator”• PMP Oxygenators

• Rated for prolonged use (up to 4 weeks)

• More efficient with lower priming volumes

• Decreased plasma leaks

• Decreased thrombus formation

• Decreased risk for haemolysis

• Failure tends to develop slowly



• Membrane gas exchange “Oxygenator”• CO2 elimination

• Independent of blood flow

• Dependant on sweep gas flow rate (O2 l/min) and membrane surface

• Sweep gas flow = VE and usually 2* set CO

• Guard against correcting PaCO2 to fast • Risk of cerebral oedema

• Maintain pH at > 7.30



• Membrane gas exchange “Oxygenator”• CO2 elimination

• O2 loading• Blood flow dependent

• Rated to a maximum flow due to increase in resistance

• Where flow of 60% native CO cannot be achieved second oxygenator advised

Mechanics • Catheter setup


• Oxygenator

• Returning blood to the venous circulation• No change in pre or afterload (closed circuit)

• Oxygenated blood to lungs admixed with native circulation• Circuit flow >60% of Native CO

• SpO2 target at > 70% only

• Micro emboli/Air filtered in Lungs

• Normal pulsatile LV native circulation

Mechanics• Drainage of venous blood


• Oxygenator

• Returning blood to the venous circulation

• No bypass and organs• Exit and entry sites in similar

anatomical location

• Oxygenator in series with native lungs

• No DIRECT influence on CO, only respiratory support • PvO2 mediated pulm vasodilatation

• Decreased ITP

• Guard against “under support”

COMMON Problems• Low SpO2 (< 70 %)

• Resist inclination to restart ventilation

• Circuit check• Drainage and return limbs both dark

• Is O2 connected to Oxygenator

• Thrombosis in Oxygenator

• Change in ∆ P3 /P2 without change in rpm/flow

• P3 PaO2 less than 100 mmHg

• Consider circuit change or “coughing” the oxygenator

• Water vapour build up

• 60s sweep gas flow at 15 l/min




• Drainage and return limbs same colour • Consider recirculation

• Confirm catheter positions esp in double catheter setup

• Confirm with high P1 SvO2




• Drainage and return limbs same colour

• Drainage and return limbs “normal colour difference”• Is there a change in native CO (60% support)

• Increase ECMO flow (P1)

• Consider cooling if pyrexial (coagulopathy)

• Placement of second drainage catheter (femoral with jugular bi-caval)

• Check that flow rating on oxygenator is not exceeded

• Changing to oxygenator with higher flow rating

• Consider second oxygenator in parallel

• Check Hct and consider PRC transfusion esp if < 30% (35)


• More negative P1• Circuit check

• Patient position and neck rotation

• Catheter position (esp with bi-caval catheter)

• Any kinking of lines pre pump

• Change in set flow/rpm

• Decreased in native venous return• Blood and or fluid loss

• Confirm with ABG (BE/lactate and Hct)


• More negative P1

• Increased ∆ P2 / P3• Circuit check

• Clots forming in oxygenator

• Kinking in return limb

• Change in set flow/rpm



• Increased ∆ P2 / P3

• Pump chattering• Circuit check

• Pump head seating in pump

• Increase in P1 with low flow• ICV collapse due to positioning and or changes in native pre-load

• Turn flow off and re-introduce slowly



• Increased ∆ P2 / P3

• Pump chattering

• Decrease in ECMO CO• Circuit check for obstruction

Re-Education• SpO2 > 90%

• Transfusion trigger Hb > 8g/dl

• CXR white out can only recover with recruitment

• Steroids only work in late ADRS

• Sedation and paralysis

• SpO2 > 70%

• Transfusion trigger Hb 10 – 12

• Vent rest settings with additional measures

• Early steroids if infection free

• Awake, animated and interactive patient

problem shooting in venovenous ecmo - critical care€¦ · problem shooting in venovenous ecmo ......

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