ECMO

INTRODUCTION
Prolonged cardiopulmonary support is called
extracorporeal membrane oxygenation
(ECMO), extracorporeal life support, or
extracorporeal lung assist.
Two types of ECMO 1). Venoarterial (VA)
2). Venovenous (VV).
Both provide respiratory support, but only VA
ECMO provides hemodynamic support.

OUTCOMES
Survival — can be categorized according to
the indication for the ECMO:
Acute respiratory failure — survival rates
from 50 -71%

CESAR TRIAL
Conventional ventilatory support v/s ECMO for
Sev. Acute Resp. failure (CESAR; 2009) trial
Randomly assigned 180 pt`s with sev acute resp
failure to either ECMO or continued conventional
management.
ECMO group pt had significantly increased
survival without disability at six months
compared to conventional management (63 v/s
47%).

EOLIA TRIAL
 ECMO to rescue lung injury in severe ARDS (EOLIA;
2018) trial
 Randomly assigned 249 pts with severe ARDS to receive
early VV ECMO or conventional (low-TV, low-pressure)
ventilation.
 ECMO resulted in improved oxygenation, more days free of
renal failure (46 v/s 21%), and fewer pt`s with ischemic
stroke (0 vs 5%).
 Study was stopped early by the data safety and monitoring
board for interim results that were in favor of ECMO, after
the final analysis, the 11 % difference in actual 60-day
mortality, while also in favor of early ECMO, was not
significant (35 v/s 46%).

META-ANALYSES
One meta-analysis of two randomized trials
and three observational studies reported the
60-day mortality rate was lower in pt`s
receiving VV ECMO (34 v/s 47%; RR 0.73,
95% CI 0.58-0.92).

CARDIAC FAILURE
VA ECMO can provide acute support in card.
shock or cardiac arrest in adults.
Observational studies and case series have
reported survival rates of 20 – 50% among pt`s
who received ECMO for card. arrest, severe
card. shock, or failure to wean from CPB
following cardiac surgery.

ELSO registry: 9000 adults who underwent
ECMO, 41% survived to hospital discharge
with the lowest survival reported in those with
cong. heart disease (37 percent).
In a systematic review of adults with
refractory out of hospital cardiac arrest,
survival was 22% in the 833 pts who received
ECMO during resuscitation and half of these
had good neurological recovery.

PATIENT SELECTION
 INDICATIONS — acute sev. cardiac or pulm. failure that is
potentially reversible and unresponsive to conventional
management. Examples,
 Hypoxemic respiratory failure, PaO2/FiO2 <100 mmHg despite
optimization of the ventilator settings (TV, PEEP, and I:E ratio).
 The Berlin consensus document on ARDS, ECMO in (PaO2/FiO2 <70).
 Hypercapnic respiratory failure, pH <7.20.
 Ventilatory support as a bridge to lung transplantation.
 Cardiac/circulatory failure/Refractory cardiogenic shock.
 Massive pulmonary embolism.
 Cardiac arrest.
 Failure to wean from CPB after cardiac surgery.
 As a bridge to either cardiac or lung transplantation or placement
of VAD.

CONTRAINDICATIONS
The only absolute CI to ECMO is a pre-existing
condition that is incompatible with recovery (sev
neurologic injury, end stage malignancy).
Relative CI`s : uncontrollable bleeding and very
poor prognosis from the primary condition.
Results in resp. failure are better when ECMO is
instituted early (within seven days of intubation).

TECHNIQUE
ECMO should only be performed by clinicians
with training and experience in its initiation,
maintenance, and discontinuation.

ECMO can be venovenous (VV) or venoarterial (VA):
During VV ECMO, blood is extracted from the vena
cava or RA and returned to the RA.
VV ECMO provides resp. support, but the pt is
dependent upon his or her own hemodynamics.
During VA ECMO, blood is extracted from the RA and
returned to the arterial system, by passing the heart and
lungs.
VA ECMO provides both respiratory and hemodynamic
support.
The additional benefit of hemodynamic support comes
with additional risks.

INITIATION
Pt is anticoagulated (usually with IV heparin)
and then the cannulae are inserted.
ECMO support is initiated once the cannulae
are connected to the appropriate limbs of the
ECMO circuit.

CANNULATION
Cannulae are usually placed p/c by Seldinger
technique.
Largest cannulae that can be placed in the vessels
are used.
VV ECMO, venous cannulae are usually placed
in the right or left CFV (for drainage) and right
IJV (for infusion).
Tip of the femoral cannula should be maintained
near the jn of the IVC & RA, while the tip of the
internal jugular cannula should be maintained
near the jn of the SVC &RA.

VA ECMO, a venous cannula is placed in the
IVC or RA (for drainage) and an arterial
cannula is placed into Rt. FA (for infusion).
Femoral access is preferred for VA ECMO bcz
insertion is relatively easy.
Main drawback of femoral access is ischemia
of the I/L lower extremity.

TITRATION
Following cannulation, the pt is connected to
the ECMO circuit and the blood flow is
increased until resp and hemodynamic
parameters are satisfactory.
Reasonable targets include:
Arterial oxyhemoglobin saturation of >90% for VA
ECMO, or >75% for VV ECMO

MAINTENANCE
When the venous oxyhemoglobin saturation is
below target, interventions that may be helpful
include increasing one or more of the
following: blood flow, intravascular volume,
or hemoglobin concentration.
Decreasing the systemic oxygen uptake by
reducing the temp.
Unfractionated heparin or direct thrombin
inhibitor titrated to an ACT of 180 - 210 sec.

 Platelets are continuously consumed during ECMO bcz they
are activated by exposure to the foreign surface area.
 Platelet counts should be maintained greater than
50,000/microliter, which may require platelet transfusion.
 ECMO circuit is often the only source of oxygen in pts with
complete cardiac or pulmonary failure.
 Oxygen delivery depends on the amount of Hb and blood
flow.
 Risks of high blood flow outweigh the risk of transfusion,
so hemoglobin is maintained over 12 g/dL in ECMO pt`s.

Ventilator settings are reduced during ECMO
in order to avoid barotrauma, volutrauma (ie,
ventilator-induced lung injury), and oxygen
toxicity.
Plateau airway pressures should be maintained
<20 cm H2O and FiO2 <0.5.
Reduction of ventilator support is usually
accompanied by increased venous return,
which improves cardiac output.

SPECIAL CONSIDERATIONS
VV ECMO is typically used for resp. failure
VA ECMO is used for cardiac failure.
Unique considerations for each type of
ECMO, which influence management.
 Blood flow – Near-maximum flow rates are
usually desired during VV ECMO to optimize
oxygen delivery.

In contrast, the flow rate used during VA ECMO
must be high enough to provide adeq. perfusion
pressure and venous oxyhemoglobin saturation
but low enough to provide sufficient preload to
maintain LV output.
Diuresis – Since most pts are fluid overloaded
when ECMO is initiated, aggressive diuresis is
warranted once the pt is stable on ECMO.
Ultrafiltration can be easily added to the ECMO
circuit if pts are unable to produce sufficient urine
for diuresis.

 Left ventricular monitoring –LV output must be rigorously
monitored during VA ECMO because LV output may worsen.
 Cause is usually multifactorial, including the underlying LV
dysfunction and insufficient unloading of the distended LV due
to ongoing blood flow to the LV from the bronchial circulation
and RV.
 IABP to reduce afterload and facilitate LV output.
 LV decompression is essential to avoid pulmonary
haemorrhage if LV ejection cannot be maintained despite
IABP counter pulsation and inotropic agents.
 Methods of P/C LV decompression include transatrial balloon
septostomy or insertion of a LA or ventricular drainage
catheter.

Weaning from ECMO
For pt`s with respiratory failure-:
improvements in radiographic appearance,
pulmonary compliance, and arterial
oxyhemoglobin saturation indicate that the pt
may be ready to be liberated from ECMO.
For pt`s with cardiac failure- : enhanced aortic
pulsatility correlates with improved LV output
and indicates that the pt may be ready to be
liberated from ECMO.

COMPLICATIONS
• The major complications are bleeding and
thromboembolism.
Bleeding — 30 - 50 % of pt`s who receive
ECMO and can be life-threatening .
It is due to both the continuous anticoagulation
and platelet dysfunction.
Intervention is necessary when major bleeding
occurs.
Bleeding from surgical wounds often requires
prompt exploration with liberal use of
electrocautery.

 Plasminogen inhibitors (eg, aminocaproic acid) can be
infused or heparin can be discontinued for several hours-
but may increase the risk of circuit thrombosis.
 Infusion of activated factor VII has been reported with
mixed results and should only be considered for life-
threatening hemorrhage after all other options have failed.
 Target ACT is usually reduced once bleeding occurs and
infusions of anticoagulant are reduced or held.
 With modern devices the anticoagulation can be stopped
altogether for days if bleeding is a problem.
 Recombinant factor VIIa has been administered to some
cases of refractory bleeding.
 Eur J Cardiothorac Surg. 2016 Jan;49(1):78-84. Epub 2015 Apr 23

THROMBOEMBOLISM
Systemic thromboembolism due to thrombus
formation within the ECMO circuit
Pulmonary embolism as high as 16%.
A CT Scan Study. Crit Care Med 2020; 48:192.
DVT may be higher (up to 70%) and may be
associated with cannulation, especially femoro
femoral cannulae. Its impact is greater with (VA)
ECMO than (VV) ECMO bcz infusion is into the
systemic circulation.
Anticoagulation - target ACT, vigilant observation
of the circuit for signs of clot formation.

 NEUROLOGICAL —Incidence of neurologic injury ELSO
registry is 10% (adult resp pt).
 In those with card. failure and those in whom ECMO is
administered during CPR = 50%
 Arch Neurol 2011; 68:1543.
 CANNULATION-RELATED — Vessel perforation with
hemorrhage, arterial dissection, distal ischemia, and incorrect
location (eg, venous cannula within the artery). These complications
are rare (<5%).
 HEPARIN-INDUCED THROMBOCYTOPENIA —HIT can
occur in pt`s receiving ECMO. When HIT is proven, the heparin
infusion should be replaced by a non-heparin anticoagulant.
e.g argatroban bcz its half-life is short and a similar ACT target
range is effective.

VA ECMO-specific complications
PULMONARY HEMORRHAGE – Pulm. edema
and h`ge can occur in pt`s who have no LV
emptying during VA ECMO.
Edema occurs when LA pr. >25 mmHg. It is
treated by venting the LA or LV.
CARDIAC THROMBOSIS – There is retrograde
blood flow in the asc.aorta whenever the femoral
artery and vein are used for VA ECMO.
Stasis of the blood can occur if LV output is not
maintained, which may result in thrombosis.

NEUROLOGICAL INJURY – approx. 50 %.
neurological injury - coma of uncertain cause,
encephalopathy, anoxic brain injury, stroke, brain
death and myoclonus.
These findings may be a consequence of the
condition that prompted ECMO, rather than a
complication of the ECMO process.
Low levels of hemolysis that can occur during
VA-ECMO may predispose to nonhemorrhagic
stroke.

CORONARY OR CEREBRAL
HYPOXIA
 During VA ECMO, fully saturated blood infused into the FA from the
ECMO circuit will preferentially perfuse the lower extremities and the
abdominal viscera.
 Blood ejected from the heart will selectively perfuse the heart, brain, and
upper extremities.
 As a result, the oxyhemoglobin saturation of the blood perfusing the lower
extremities and abdominal viscera may be substantially higher than that
perfusing the heart, brain, and upper extremities.
 Cardiac and cerebral hypoxia could exist and be unrecognized if
oxygenation is monitored using only blood from the lower extremity.
 To avoid this complication, arterial oxyhemoglobin saturation should be
monitored in the right upper extremity.
 Poor arterial oxyhemoglobin saturation measured from the upper extremity
is corrected by infusing some oxygenated blood into the right atrium
(called VA-V access).

ECMO

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