1. 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

2. 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

3. 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 (>1,000 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)

4. UK Neonatal Respiratory Failure ECMO Trial

5. CESAR study Conventional ventilation or ECMO for Severe Adult Respiratory failure Lancet 2009, 374:
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 (0.05–0.97; P = 0.03)
NNT to prevent one death is 6
BMC Health Services Research Dec 23;6:163
Preliminary results : announced at 37th Society of Critical Care Medicine Congress in Honolulu in February 2008 5

6. ECMO circuit and oxygenator

7. Veno-venous (VV) ECMO R L R L

8. VV-ECMO Advantages & disadvantages
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

9. VV-ECMO Single drainage cannula Efficient CO2 removal
Weak effect on Oxygenation
Use for respiratory indications when severe hypoxia is not a problem

10. 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

11. Veno-arterio (VA) ECMOL

12. VA-ECMO Central (ascending aorta) VA-ECMO for CPR
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

13. VA-ECMO for CPR
Hi Blood flow VA-ECMO

15. VA-ECMO Advantages & 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

17. 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

18. Jostra Centrifugal Pump
Jostra RotaFlow impeller pump
32ml priming volume
The RotaFlow had no stagnant blood zones, no shaft and no seals

22. 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.

23. 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.

24. 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

25. Murray score = average score of all 4 parameters
Parameter / Score 1 2 3 4
PaO2/FiO2
(On 100% Oxygen)
≥300mmHg
≥40kPa
30-40
23-30
13-23
<100
<13
CXR
normal
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

26. 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 >250μmol/L), or requiring salvage anti-retroviral treatment
Recent diagnosis of haematological malignancy
Bone marrow transplant recipients
Body size <20kg or >120kg

27. Relative contraindications
Preexisting conditions which affect the quality of life
Age >70 year-old
CPR duration >60 minutes
Multiple organ failure
Central nervous system injury
Contraindication to anticoagulation (no citrate)
Patient who had been on high pressure (peak pressure >30cmH20) or high FiO2 (>0.8) ventilation for >7days

28. Equipments for cannulation
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)
For priming of circuit 3.
ECMO machine + Clean tube clamps
1+4
Inform CCU 5.
Venous cannula +
Percutaneous Insertion Kit
1+1
Confirm size with cannulating physician 6.
Arterial cannula +

29. 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 >37oC

30. 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)
Arterial cannula
(15cm in length)
(23cm in length)
Venous cannula
(55cm in length)
Cannula caliber (Fr) 19
4.0
3.5
--- 21
5.0
4.5
4.3 23
6.0
5.5 25

31. 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.

34. The cannulation sites are dressed and covered with Tegaderm
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

35. For internal jugular vein insertion, the cannula and tubing are bound to the head with elastic bandages

36. 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.

37. 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 1:1
? 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

38. Anticoagulation
Bolus heparin 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

39. Ventilator management
While on VV-ECMO, the ventilator should be adjusted to a low setting to allow for lung rest:
Low FiO2 (<40%)
Low tidal volume (<6ml/kg ideal body weight) and peak airway pressure (<35cmH2O) to avoid volutrauma
A higher PEEP (10-20cmH2O) to keep alveloli open and prevent atelectotrauma.

41. 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

42. 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

43. Haemoglobinuria

44. 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.

45. 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

47. 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

49. 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

50. 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

51. Hong Kong’s Experience on the Use of Extracorporeal Membrane Oxygenation for the Treatment of Influenza A (H1N1) 2009
Kenny K C Chan 陳勁松 FHKCA, FHKAM(Anaesthesiology)
K L Lee 李家龍 FHKCP, FHKAM(Medicine)
Philip K N Lam 林冠毅 FJFICM, FHKAM(Medicine)
K I Law 羅建業 FHKCP, FHKAM(Medicine)
Gavin M Joynt 喬伊諾 FJFICM, FHKAM(Anaesthesiology)
W W Yan 殷榮華 FRCP, FHKCP
* Submitted and under review, some slides omitted

52. Epidemic Curve

53. Day 0 at A&ED

54. Day 1

55. Day 7

56. Outcome of VV-ECMO, PYNEH

57. Mortality for Controls
Sample size required for showing difference in mortality --- a case control study
Mortality for Controls
# Control
Controlled with sex, age, comorbidities, Murray’s 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

58. Thank you for your attention.