Dr Srinivas S

Extracorporeal membrane oxygenation (ECMO) is a modified adaptation of conventional cardiopulmonary bypass techniques for prolonged cardiopulmonary support using intrathoracic or extrathoracic cannulation.

Zwischenberger and Bartlett proposed the term “extracorporeal life support” (ECLS) to describe prolonged but temporary (1–30 days) support of heart or lung function using mechanical devices.

ACRONYM EXPANSION

ECMO Extra Corporeal Membrane Oxygenation

ECLS Extra Corporeal Life Support

ECCO2R Extra Corporeal CO2 Removal

PECCO2 Partial Extra Corporeal CO2 Removal

AVCOR Arterio Venous CO2 Removal

ECLA Extra Corporeal Lung Assist

IVOX Intravascular Oxygenator

ECMO was introduced for the treatment of severe acute respiratory distress syndrome (ARDS) in the 1970s.

Dr. Theodore Kolobow pioneered the perfection of flow patterns in the membrane lung, the method of layering silicone and the design of vascular access catheters.

Dr. Donald Hill in 1971 reported the survival of a 24-year-old polytrauma patient with ruptured aorta after a motorcycle accident.

Dr. Robert H. Bartlett in 1976 reported the first neonatal ECMO survivor, baby Esperanza

ECMO registry was established in 1980 at the University of Michigan

ECMO IN 1971

ECMO IN 2014

COMMON UNCOMMON

ARDS Air leak

Severe Pneumonia Smoke inhalation injury

Graft failure after lung transplant Status asthmaticus

Pulmonary contusion Airway obstruction

Reperfusion injury after pulmonary endarterectomy

Aspiration syndromes

Oxygenation Index (OI) > 40 or > 35 for 4 hoursOI = (MAP × FiO2 × 100) / PaO2

Ventilation Index (VI) > 90 for 4 hoursVI = RR × PIP – PEEP/1000

Alveolar–arterial oxygen difference [(A − a)DO2] >600 − 624 mmHg (at sea level) despite 4–12 hours of medical management(A − a)DO2 = [atmospheric pressure – 47] – (PaCO2 + PaO2)/FiO2 47 being vapor pressure at sea levelPaCO2 = carbon dioxide tension (partial pressure) of arterial blood

PaO2 < 50 mmHg for 2–12 hours (FiO2 of 100%)

Acute deterioration PaO2 < 30–40 mmHg (FiO2 of 100%)pH < 7.25 for 2 hours

Intractable hypotension

COMMON UNCOMMON

Graft failure post cardiac transplant Myocarditis

Post cardiotomy cardiac failure Chronic heart failure

Cardiogenic shock (cardiac rupture, papillary muscle ruture, VSD, refractory VT)

Pulmonary and cardiac vessel trauma

Septic Cadiomyopathy Anaphylaxis

Drug overdose with cardiac depression Pulmonary embolism

REGION 1

REGION 2

REGION 3

A negative pressure (20 to 100 mmHg), generated by the centrifugal pump, exists in the drainage limb (region 1).

A large positive pressure exists in the 2 limbs distal to the pump (regions 2 and 3).

Breaches in the circuit where the pressure is negative lead to air entrainment

Breaches in the circuit where the pressure is positive lead to blood loss.

A pressure drop of 30 to 150 mmHg normally occurs across the oxygenator (ie, between regions 2 and 3)

Three types of oxygenators have been used for ECMO:

silicone membrane,

microporous hollow fiber, and

PMP hollow-fiber membranes

PMP oxygenators are also highly efficient.

Hollow fibers are a true membrane - the blood and gas phases are separate, -less prone to plasma leak

PMP oxygenators last longer and have lower rates of thrombus formation and hemolysis.

Failure of a PMP oxygenator typically develops slowly over several days.

Failure of oxygenator causing increased resistance to blood flow and impaired gas diffusion

GAS

The FIO2 and flow rate of the sweep gas control the postoxygenator PO2 and PCO2, respectively.

It is usual to have the FIO2 of the sweep gas at 1.0 and to titrate the gas flow to the patient’s pH, targeting a value of 7.3 to 7.4.

marked respiratory alkalosis, which may adversely affect the cerebral blood flow.

A sweep gas flow 1 to 2 times the circuit blood flow usually is required to achieve a normal PaCO2. With an FIO2 of 1.0, the postoxygenatorPO2 should be 40 to 80 kPa (300-600 mmHg).

SaO2 85-95%

PaO2 45-55 mm Hg

Hematocrit > 5% of baseline

Carotid cannulation and ligation

Thromboembolism to systemic artery

Neurological injury

Ischemic lung injury

Normal pulsatile physiology

Increasing ECMO flow

Decreasing % of recirculated flow

Increased Hb

Increased SVO2

Increased cardiac output

Centrifugal pumps contain a magnetically driven impella inside a spiral housing.

The impella spins rapidly, up to 5,000 rpm (rpm), creating a negative upstream pressure and positive downstream pressure, forcing blood through the pump.

Centrifugal pumps are small, very easy to prime, and have a very low volume (32 mL in the case of the Rotaflow, MAQUET)

Centrifugal pumps are both pre- and afterload dependent.

Hypovolemia (low preload) or circuit obstruction (high afterload/ low preload) reduces blood flow

There is no fixed relationship between pump speed and blood flow.

When a centrifugal pump is turned off, there is the potential for reverse flow to occur in the circuit. This is a very real concern with VA ECMO

The circuit always should be clamped before turning off the pump

The pump, connector tubing, oxygenator, and cannulae are coated with heparin .

ECMO cannulae are constructed from wire-reinforced polyurethane and are inserted by seldinger , semiseldinger and surgical methods

The goal of any cannula configuration for VV ECMO is to maximize flow and minimize recirculation

Circuit flow 50 -80 ml/kg/min

Sweep gas flow 50 -80 ml/kg/min

FiO2 1.0

PCO2 35 -45 mm Hg

pH 7.35 -7.45

Hct 30 -40%

Clotting parameters

Platelets > 100 K

“A simple technique for use in a complex environment.”

Adjusting Gas Flow will affect the PaCO2.

Adjusting Blood Flow will affect the PaO2.

Adjusting Temperature will affect the SvO2.

Gas Flow Blood Flow

Temperature (VO2)

High-frequency oscillatory ventilation has been identified as an alternative method of applying low tidal volume, controlled pressure ventilation in the setting of ARDS.

Its use in adults is based on the hope that it will improve oxygenation without further injuring the lung.

High frequency oscillatory ventilation attempts to deal with potential risks of mechanical ventilation, barotrauma, volutrauma, atelectrauma, and oxygen toxicity and can be considered when conventional ventilation fails to safely and adequately provide respiratory support.

High frequency ventilation is generally considered beneficial for patients with severe pulmonary failure because

(a) it uses much smaller tidal volumes than conventional ventilation,

(b) it maintains the lungs/alveoli open on the deflation limb of the pressure-volume curve at a relatively constant airway pressure and thus may prevent atelectrauma and barotrauma and

(c) it improves ventilation/perfusion (V/Q) matching by ensuring uniform aeration of the lung.

The variables that are controlled directly are respiratory frequency, amplitudeof ventilation (also called the power or P), mean airway pressure (Paw), bias gas flow rate, percentage of inspiratory time, and FiO2.

Ph < 7.1 4 HZ

PH 7.10 -7.19 5 HZ

PH 7.2 -7.35 6 HZ

PH > 7.35 7 HZ

AMPLITUDE 70-90 cm H20

Paw 5 cm H2O > plateau pressure onCV to max of 35 cm H2O

Bias Flow 40l/min

Inspiratory Time 33%

FiO2 100%

Unconventional machinery

Under and overdistension of chest

Pneumothorax

Hemodynamic compromise

MDIs ineffective

Tube block

Two major RCTs have failed to show benefit….one showed possible harm!

ECMO is increasingly being used across the world

Can support respiratory and /or cardiac function

High cost intervention

High risk of fatal complications

Thrives on team work …..reflects critical care

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