Extracorporeal Membrane Oxygenation (ECMO)

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Extracorporeal Membrane Oxygenation (ECMO)

• Dr. Yan Wing Wa,
• MBBS, MSc, MRCP, FRCP(Lond, Edin), FHKCP,
  FHKAM(Medicine)
• Chairman, Specialty Board in Critical Care
  Medicine, Hong Kong College of Physicians
• President, Hong Kong Society of Critical Care
  Medicine
• ICU Director, Pamela Youde Nethersole Eastern
  Hospital, Hong Kong SAR
• 14 May 2010

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ECMO

• A form of extracorporeal life support where an
  external artificial circuit carries venous blood
  from the patient to a gas exchange device
  (oxygenator) where blood becomes enriched with
  oxygen and has carbon dioxide removed. This blood
  then re-enters the patient circulation.
• Flow 70ml/kg/min
• 3ml/kg/min in CRRT

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Evolution of ECMO

• Robert H Bartlett, MD
• Director of the Extracorporeal Life Support
  Program
• The University of Michigan Extracorporeal Life
  Support Team
• Largest ECMO experience in the world (gt1,000
  cases prior to 2000)
• 1985 Prospective Randomised Trial in
  Neonatal Respiratory Failure, Pediatrics
  1985,76(4)479-87
• 1 patient in conventional arm (died)
• 11 patients in the study arm (all survived)

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UK Neonatal Respiratory Failure ECMO Trial
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CESAR studyConventional ventilation or ECMO for
Severe Adult Respiratory failureLancet 2009,
3741351-63

• Survival without severe disability (confined to
  bed, or unable to dress/wash oneself) by 6 months
• ECMO 57 in 90 patients (63)
• Conventional ventilation 41 in 87 patients (47)
• Relative risk reduction in favour of ECMO
• 0.69 (0.050.97 P 0.03)
• NNT to prevent one death is 6

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ECMO circuit and oxygenator
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Veno-venous (VV) ECMO
R
L
L
R
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VV-ECMOAdvantages disadvantages

• Advantages
• Normal lung blood flow
• Oxygenated lung blood
• Pulsatile Blood Pressure
• Oxygenated blood delivered to root of aorta
• Must be used when native cardiac output is high
• Disadvantages
• No Cardiac support
• Local recirculation through oxygenator at high
  flows
• Reversed gas exchange in lung if FiO2 low
• Limited power to create high oxygen tensions in
  blood

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VV-ECMO

• Single drainage cannula
• Efficient CO2 removal
• Weak effect on Oxygenation
• Use for respiratory indications when severe
  hypoxia is not a problem

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VV-ECMO (Hi-flow)

• Two drainage cannulae
• Effectiveness of high flow limited by
  recirculation from return to drainage cannulae
• Oxygenation limited by effective flow
  (total-recirculated) (but not a problem for CO2)
• Used in lung conditions with severe hypoxia

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Veno-arterio (VA) ECMO
R
L
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VA-ECMO

• Central (ascending aorta)
• During sternotomy/ via subclavian artery
• VA-ECMO for CPR
• Simple and rapid to establish
• Temporary for retrieval
• Limb ischaemia
• Hi blood flow VA-ECMO
• Double drainage cannulae
• Distal limb perfusion

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VA-ECMO for CPR
Hi Blood flow VA-ECMO
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VA-ECMOAdvantages disadvantages

• Disadvantages NO
• Normal lung blood flow
• Oxygenated lung blood
• Pulsatile Blood Pressure
• Oxygenated blood delivered to root of aorta
  (except central)
• Advantages
• Cardiac support also
• No local recirculation through oxygenator at high
  flows
• No reversed gas exchange in lung
• Power to create high oxygen tensions in blood

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Quadrox PLS oxygenator

• Low pressure drop
• Efficient integrated heat exchanger
• CE certified continous use for 14 days
• Low priming volume 250ml
• Low membrane surface area 1.8m2
• Very high transfer rate of O2 and CO2

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Jostra Centrifugal Pump

• Jostra RotaFlow impeller pump
• 32ml priming volume
• The RotaFlow had no stagnant blood zones, no
  shaft and no seals

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Objectives

• H1N1 pandemic in 2009
• After a review of the published literatures
• CESAR study
• Australian New Zealand H1N1 ECMO study
• Introduce veno-venous extracorporeal membrane
  oxygenation (VV-ECMO) to the Intensive Care Unit
  (ICU) as a rescue therapy for potentially
  reversible refractory hypoxaemic patients.

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Scopes

• For ICU medical and nursing staff.
• Since ECMO service is still in its early stage of
  development in Hong Kong, changes will likely be
  made to this document with accumulation of
  experience in concordance with the Capability
  Maturity Model.

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Indications for VV-ECMO

• Potentially reversible and life-threatening
  respiratory failure unresponsive to optimum
  conventional ventilation and therapy.
• Severe respiratory failure was defined in the
  CESAR trial as
• Murray score 3 or
• Uncompensated hypercapnia with pH 7.20

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Murray score average score of all 4 parameters
Parameter / Score 0 1 2 3 4
PaO2/FiO2 (On 100 Oxygen) 300mmHg 40kPa 225-299 30-40 175-224 23-30 100-174 13-23 lt100 lt13
CXR normal 1 point per quadrant infiltrated 1 point per quadrant infiltrated 1 point per quadrant infiltrated 1 point per quadrant infiltrated
PEEP(cmH2O) 5 6-8 9-11 12-14 15
Compliance (ml/cmH2O) 80 60-79 40-59 20-39 19
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Absolute contraindications

• Advanced malignancy or any fatal diagnosis
• Unwitnessed cardiac arrest
• Progressive and non-recoverable respiratory
  disease
• Severe pulmonary hypertension and right
  ventricular failure (mean PAP approaching
  systemic pressure)
• Severe cardiac failure consideration should be
  given to veno-arterial (VA)-ECMO
• Immunosuppression
• Transplant recipients beyond 30 days
• Advanced HIV defined by secondary malignancy,
  prior hepatic or renal failure (cirrhosis or
  serum creatinine gt250µmol/L), or requiring
  salvage anti-retroviral treatment
• Recent diagnosis of haematological malignancy
• Bone marrow transplant recipients
• Body size lt20kg or gt120kg

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Relative contraindications

• Preexisting conditions which affect the quality
  of life
• Age gt70 year-old
• CPR duration gt60 minutes
• Multiple organ failure
• Central nervous system injury
• Contraindication to anticoagulation (no citrate)
• Patient who had been on high pressure (peak
  pressure gt30cmH20) or high FiO2 (gt0.8)
  ventilation for gt7days

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Equipments for cannulation
Consumable /Equipment Consumable /Equipment Qty Remarks
1. Maquet PLS set BE-PLS 2050 with Quadrox PLS Oxygenator Rotaflow RF 32 Centrifugal pump Tube connections with Bioline coating (heparin-albumin coating) 1 From vendor
2. NS (1L bag) 1 For priming of circuit
3. ECMO machine Clean tube clamps 14 Inform CCU
5. Venous cannula Percutaneous Insertion Kit 11 Confirm size with cannulating physician
6. Arterial cannula Percutaneous Insertion Kit 11 Confirm size with cannulating physician
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Prime the circuit

• Check for leakage of the heat exchanger by
  flushing it with water before priming the
  oxygenator.
• The circuit is primed with normal saline (1L bag)
  under sterile conditions.
• Make sure no bubbles in the circuit tubing,
  oxygenator and Rotaflow
• If concomitant CVVH is required, leave behind one
  of the 3-way stopcocks on the venous line for
  connection to the dialysis machine.
• The fluid in the circuit is warmed by the heat
  exchanger before it is attached to the patient
• For HSI patients, keep gt37oC

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Vascular access in VV-ECMO

• Select appropriately sized cannulae to provide
  the desired extracorporeal blood flow
• The flow through a single Maquet HLS cannula at
  pressure drop of 60mmHg is as follows

Flow (l/min) Flow (l/min) Flow (l/min)
Arterial cannula (15cm in length) Arterial cannula (23cm in length) Venous cannula (55cm in length)
Cannula caliber (Fr) 19 4.0 3.5 ---
Cannula caliber (Fr) 21 5.0 4.5 4.3
Cannula caliber (Fr) 23 6.0 5.5 5.0
Cannula caliber (Fr) 25 --- --- 6.0
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Vascular access in VV-ECMO (2)

• If the desired blood flow cannot be achieved with
  a single access cannula, insert a second access
  cannula.
• Decide on 2 cannulation sites for blood drainage
  and return.
• Jugular vein cannulation is contraindicated in
  unilateral internal jugular vein thrombosis.
• Cannulation into the subclavian vein for ECMO is
  not preformed.
• Xray, fluro or echocardiogram can be used to
  guide cannula positioning.
• The access and return cannulae should be placed
  at some distance apart to minimize access
  recirculation.

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The cannulation sites are dressed and covered
with Tegaderm. The cannula and tubing are firmly
secured to the skin with non-circumferential
Elastoplast or Mefix
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For internal jugular vein insertion, the cannula
and tubing are bound to the head with elastic
bandages
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Oxygenation

• Begin extracorporeal blood flow at 70ml/kg/min
  for adults.
• Titrate blood flow to maintain systemic arterial
  oxygen saturation while on low ventilator
  settings.
• A systemic arterial saturation around 80 will be
  adequate for systemic oxygen delivery if the
  haematocrit is over 40 and cardiac function is
  good.
• The absence of persistent metabolic acidosis is
  indicative of an adequate systemic oxygen
  delivery.
• In-line venous saturation monitor may not reflect
  the true venous saturation in the presence of
  circuit recirculation.
• If oxygenation cannot be maintained with
  persistent metabolic acidosis, the followings can
  be considered
• Increase extracorporeal blood flow
• In access insufficiency, increase intravascular
  volume, or insert a second access cannula.
• Blood transfusion to maintain a haematocrit level
  between 40-45
• Increase ventilator FiO2 and ventilatory support
• In cardiac failure, increase cardiac output using
  volume, inotropes, or conversion to VA-ECMO for
  cardiac support.

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CO2 removal

• Use 100 oxygen as sweep gas.
• Begin with a sweep gas flow rate of 6L/min. After
  the extracorporeal blood flow has been adjusted,
  set the sweep gas to extracorporeal blood flow
  ratio to 11
• ? A higher PaCO2 is beneficial to subsequent
  weaning
• Titrate sweep gas flow rate according to carbon
  dioxide partial pressure Increase sweep gas flow
  rate to increase carbon dioxide clearance

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Anticoagulation

• Bolus heparin 50-100 units/kg after successful
  cannulation followed by continuous infusion.
• Continuous heparin infusion at 10-15units/kg/hour.
  
• Titrate dose to maintain APTT of 50-60s.
• A higher APTT level should be targeted for
  extracorporeal blood flow in the range of 0.5 to
  2.5L/min.
• Monitor APTT every 6 hours.

Some centres may choose to monitor ACT instead of
APTT
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Ventilator management

• While on VV-ECMO, the ventilator should be
  adjusted to a low setting to allow for lung rest
  
• Low FiO2 (lt40)
• Low tidal volume (lt6ml/kg ideal body weight) and
  peak airway pressure (lt35cmH2O) to avoid
  volutrauma
• A higher PEEP (10-20cmH2O) to keep alveloli open
  and prevent atelectotrauma.

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Sedation

• should be thoroughly sedated at the time of
  cannulation and for the first 12 to 24 hours
• facilitate successful cannulation
• avoid air embolism in the presence of spontaneous
  breathing
• minimize metabolic rate
• enhance comfort.
• Once the patient is stable on VV-ECMO, sedation
  should be minimized

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Possible complications

• Haemolysis
• Intravascular haemolysis can result from Access
  insufficiency
• Insufficient venous return
• Obstructed access cannula
• Access cannula too small
• Clots within the circuit
• Inappropriate pump speed
• Bleeding
• Apply direct pressure to accessible sites.
• In case of bleeding at the cannulation site, rule
  out decannulation.
• Circuit rupture
• Cleaning circuit (polycarbonate components) with
  alcohol predisposes to fracture and should be
  avoided

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Haemoglobinuria
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Possible complications (2)

• Pump failure
• Causes
• Pump head disengagement from accidental contact
  or incorrect placement
• Motor failure
• Battery failure in the absence of AC power
• Air in circuit
• To prevent air embolism, it is necessary to
  maintain the pressure at the blood side higher
  than that at the gas side
• Keep the oxygenator below the level of the
  patient.
• Clotting in circuit
• Clots larger than 5mm or enlarging clots on the
  return side of the circuit should be removed.
• Decannulation
• Accidental removal of either or both cannulae.

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Connections for continuous renal replacement
therapy (CRRT)

• For CRRT circuit, the blood drainage side is
  conventionally labeled as arterial, and the blood
  return side as venous. This is in opposite to
  that of the ECMO circuit.
• The return line of the CRRT circuit is connected
  to the luer lock connector on the arterial
  cannula or a distal connector placed between the
  oxygenator and return cannula on the ECMO circuit
  via a 3-way tap

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Connections for continuous renal replacement
therapy (2)

• If a Prismaflex dialysis machine with adjustable
  access pressure alarm or its equivalent is used,
  the access line of the CRRT circuit is connected
  to a proximal connector between the oxygenator
  and return cannula on the ECMO circuit via a
  3-way tap.
• If a dialysis machine with no adjustable access
  pressure alarm is used, the access line of the
  CRRT circuit is connected to a connector placed
  before the pump on the ECMO circuit via a 3-way
  tap

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Weaning off VV-ECMO

• Increase ventilator support to a setting
  acceptable off VV-ECMO.
• Turn off the sweep gas but continue pump rate to
  maintain extracorporeal blood flow.
• Monitor systemic arterial oxygen saturation and
  pCO2. If parameters remain adequate after one
  hour of ventilation at an acceptable setting with
  the sweep gas turned off, the patient is ready to
  come off VV-ECMO.
• Stop heparin infusion once the decision has been
  made to come off VV-ECMO. The circuit can be
  removed after 4 hours

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Decannulation

• Involved staff should put on PPE for standard
  precaution.
• Turn off pump and clamp lines on both the access
  and return sides.
• Remove the cannulae. Apply direct pressure
  manually or with a C-clamp

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Hong Kongs Experience on theUse of
ExtracorporealMembrane Oxygenationfor the
Treatment ofInfluenza A (H1N1) 2009

• Kenny K C Chan ??? FHKCA, FHKAM(Anaesthesiology)
• K L Lee ??? FHKCP, FHKAM(Medicine)
• Philip K N Lam ??? FJFICM, FHKAM(Medicine)
• K I Law ??? FHKCP, FHKAM(Medicine)
• Gavin M Joynt ??? FJFICM, FHKAM(Anaesthesiology)
• W W Yan ??? FRCP, FHKCP

Submitted and under review, some slides omitted
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Epidemic Curve
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Day 0 at AED
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Day 1
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Day 7
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Outcome of VV-ECMO, PYNEH
P0.03
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Sample size required for showing difference in
mortality --- a case control study
Mortality for Controls Control Controlled with sex, age, comorbidities, Murrays score, immune therapy.
50 200
55 39
60 20
65 12
70 8
80 5

• Mortality for Cases
• 1/10 (10)
• Alpha 0.05
• Power 0.8

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• Thank you for your attention.