Post on 31-May-2020
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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
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
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
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).
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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