PHYSIOLOGY ,CANNULATION AND

MONITORING OF VENO-ARTERIAL ECMO

Dr.Manoj.P. Lead Consultant Cardiovascular and Thoracic

Surgeon Aster Medcity

Extra corporeal Life Support is achieved by

- Draining venous blood

- Removing CO2

- Adding oxygen

- Returning to circulation

- Through either a vein or artery

Types of ECMO

ECMO can be categorised according to the circuit used

• Veno-arterial - VA ECMO provides both gas exchange and circulatory support (Heart & Lung failure)

• Veno-venous –VAECMO allows gas exchange only (Isolated Lung failure)

Modes of ECMO

Veno -arterial (VA)ECMO

•Provides both respiratory and cardiac support

•Blood is drained from venous system and given to arterial system.

Low flow veno-arterial ECMO is a transitory form of ECMO support in which small cannulae (quicker to insert) are inserted. It is an emergent resuscitative intervention, (Ecmo CPR)

VA ECMO – Technical Specifications

Peripheral-FA, pump outflow is retrograde, admixing at arch level.

If Respiratory failure co exists, heart pumps poorly oxygenated blood to coronaries and brain, while ECMO supports body distal to Aortic arch.

For this reason R Radial line is prudent

Mechanical ventilation continued to maintain Sao2 of blood ejected from LV at 90%

First successful ECMO patient, 1971

J Donald Hill MD and Maury Bramson BME, Santa Barbara, Ca, 1971. (Courtesy of Robert Bartlett, MD)

First Neonatal ECMO survivor..

Esperanza, Age 1 day 1975

Esperanza, age 21

FROM THIS

TO THIS

Advantages and Disadvantages

Advantages Disadvantages

Both cardiac and pulmonary support Cannulation of major artery and sacrifice of one carotid in newborn

More experience Poor coronary and pulmonary perfusion

Instant hemodynamic support Systemic thromboembolism

No recirculation Nonpulsatile flow

Right and left heart Myocardial stunning and LV distension

Increased incidence of neurological events

ECMO ??????

• Several considerations must be weighed

- Likelihood of organ recovery- Cardiac re-recovery- Disseminated malignancy- Advanced age- Graft vs . Host disease- Known severe brain injury- Unwitnessed cardiac arrest- Aortic dissection or aortic incompetence

• The physiologic goal is to improve tissue oxygen delivery , remove CO2 and allow normal aerobic metabolism whilst the lung rests

• ECMO circulation: - Dual circulation - Nonpulsatile flow

Dual circulation

• Native circulation + ECMO circulation

• Sometimes Results in North South syndrome if the return cannula is in femoral artery

• In most cases ECMO provides 60-80 % of CO resulting in a discernible pulse contour

• Reduces preload• Increases afterload Myocardial

stunning • Left sided decompression• Use of inodilators

In Veno Arterial ECMO

• Perfusate saturation is 100%• Without lung function LV saturation=RV saturation• ABG reflects Perfusate+RV saturation• If 50% blood flows through lungs,50% through

oxygenator –O2 saturation of arterial blood becomes 90%

Increase in Systemic PO2 may result from..

• Improved lung function at constant flow

• Increased ECC flow at constant CO

CO2 removal..

• Mainly depends on oxygenator surface area and sweep gas flow rate

• Independent of blood flow

• Moderately depends on inlet CO2

During Veno arterial ECMO..

• O2 consumption decreases ( catecholamines reduced,less metabolic stress)

• Arterial saturation >95 % and flow adjusted to maintain arterial/venous saturation

• Bleeding Decreased venous return Decrease in flow Transfusion

• Without lung function and ejection of heart arterial

saturation decreases

• Knowledge of the physiology of ECMO support the management of ECMO patient

• O2 content is of utmost importance in the physiologic management of critically ill patients

• DO2/VO2 ratio is reflected by mixed venous saturation - most important monitor in critically ill patients

CANNULATION

The establishment and maintenance of adequate vascular access is essential

for ECMO

CANNULATION

- Patient age and size- Underlying disease & condition- Cause of the cardiorespiratory compromise- Type of support:

• Veno-venous (VV) ECMO • Veno-arterial (VA) ECMO

- Time of the event in relation to the peri-operative period

- Location

CANNULATION

• For each modality, there are different kinds and sizes of cannulae that can be used

• Target ACTshould be accomplished before ECMO (heparin 100 units/kg)

3 minutes before cannulation.

Cannula Consideration

• Venous cannula should be with the largest lumen and shortest length possible.

• Venous cannula should have side holes.• M-number• Resist kinking• Smallest double lumen cannula is size 12 Fr ( for V V ecmo in neonate)

Veno-Arterial (VA) ECMO

Provides cardiac as well as respiratory support and is

mainly used for post op cardiac case

Cannulation can either be..

• Through neck vessels(RCC artery and RIJV and or an additional vein)

• Central cannulation

or

• Cannulation of groin vessels

Access and return cannula sites

Access Return

RA Aorta

Femoral Vein Femoral Artery

Subclavian Vein Axillary artery

Internal Jugular Vein Carotid artery

CANNULATION TECHNIQUE

• Open• Semi-open • Percutaneous

CANNULATION

• In central cannulation Aorta and RA are cannulated

• LV decompression is important :Can be done either by creating an

atrial communication or by a Left atrial vent

CANNULATION

Right atrium and

Ascending aorta

CANNULATION

A Left atrial vent line can be utilized to monitor the LA

pressure

CANNULATION

Internal jugular vein and the common

carotid artery

Veno arterial access via the neck vessels

CANNULATION

Femoral vein and

Femoral artery

Venoarterial access via the femoral vessels

Peripheral Femoral Cannulation – VA ECMO

Femoral artery cannulation:

• Chances of distal limb ischemia• Distal perfusion catheter is commonly

used

Distal Leg Perfusion 7/9 Fr Cannula

CANNULATION

-In situations where ECMO support is anticipated

-Chest will be left open and covered by a Silastic patch

-Purse-string sutures will be left snared in place

CANNULATION PROBLEMS

• Threading the venous catheter• Vein division• Proximal vein lost in

mediastinum• Lack of venous return• Intrathoracic vein perforation

Complications

• Vascular injury( tear, intimal dissection, perforation).

• Obstruction (kinking, positional).

• Misplacement( AI, afterload LV failure).

• Bleeding.

Monitoring

• Success lies with vigilant monitoring which helps in early

recognition and diagnosis of problems and timely and

accurate action

• Monitoring includes: -Clinical parameters-Biochemical and

Laboratory parameters-Radiologic monitoring-Circuit monitoring

Clinical parameters

• Vital parameters(ECG rhythm,Pulse rate,Blood Pressure ,Temperature , and respiratory rate)

• Arterial and venous saturation(MAP and mixed venous saturation)

• Daily Echocardiography• Right hand saturation gives hints regarding

coronary perfusion

• Hematological parameters(CBC,HCT 35-40%,Plasma Free Hemoglobin <0.1g/dl)

• If possible cerebral oxygenation with NIRS• EtCO2• RBS : 80-140 mg/dl• ABG and RBS to be done every 4-6 hours• Vascular and neurological status• Urine output and urine colour

Coagulation Monitoring

•Pre ECMO ACT 300 seconds•On ECMO –Check ACT 2 hourly till

ACT drops to 200 seconds•Maintenance with ACT 160-200 seconds•ACT to be repeated every 6-8 hours•aPTT : 60-70 seconds

Circuit monitoring..

• Circuit blood flow• Circuit gas flow• Circuit pressure• Circuit integrity

These variables should be monitored continuosly

Factors affecting Circuit Blood flow

Increased Blood flow Decreased Blood flow

Increased RPM Decreased RPM

Decreased Resistance :Vasodilation :Improved arterial cannula position

Increased Resistance :vasoconstriction :Kinking of tubing :Improper cannula position

Increased preload :Increased filling :Improved venous cannula position

Decreased preload :Hypovolemia :Improper cannula position :Kinking of tubing

Circuit Pressure

• Pre pump pressure: too much negative pressure results in Hemolysis, cavitation, endothelial damage of Right atrium and vena cava

• Reasons : Hypovolemia, Improper catheter placement,

Inadequate cannula size.

•Pre membrane pressure•Post membrane pressure•Transmembrane pressure

Circuit integrity

• Check for : Clot : Air : Leak

• Pump is checked for abnormal noise or crack

Clot in the oxygenator

Other things to be checked regularly.

• Insertion site/dressing security

• Functioning of heat exchanger

• Access line for kinking/movement

Thank You