ECMO

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ECMO
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Introduction

• ECMO is frequently instituted using cervical
  cannulation, which can be performed under local
  anesthesia.
• ECMO is used for longer-term support ranging from
  3-10 days.
• The purpose of ECMO is to allow time for
  intrinsic recovery of the lungs and heart

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Equipment

• Blood pump with raceway tubing, a venous
  reservoir, a membrane oxygenator, and a
  countercurrent heat exchanger
• The blood pump is either a simple roller pump or
  a constrained vortex centrifugal pump. The roller
  pump causes less hemolysis and is used for
  neonatal ECMO. The oxygenator is responsible for
  exchanging both oxygen and carbon dioxide and is
  central to the successful performance of
  prolonged ECMO.

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Neonatal extracorporeal membrane oxygenation

• Patients with the following 2 major neonatal
  diagnoses require the use of extracorporeal
  membrane oxygenation (ECMO)
• Primary diagnoses associated with primary
  pulmonary hypertension of the newborn (PPHN),
  including idiopathic PPHN, meconium aspiration
  syndrome, respiratory distress syndrome, group B
  streptococcal sepsis, and asphyxia
• Congenital diaphragmatic hernia (CDH)

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Selection criteria for neonates

• Gestational age of 34 weeks or more
• Birth weight of 2000 g or higher
• No significant coagulopathy or uncontrolled
  bleeding
• No major intracranial hemorrhage (grade 1
  intracranial hemorrhage)
• Mechanical ventilation for 10-14 days or less
• Reversible lung injury
• No lethal malformations
• No major untreatable cardiac malformation
• Failure of maximal medical therapy
• Failure to meet these criteria is a relative
  contraindication for ECMO

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Qualifying patient criteria for ECMO

• Qualifying criteria are applied only when the
  infant has reached maximal ventilatory support of
  100 oxygen with peak inspiratory pressures (PIP)
  often as high as 35 cm H2 O.
• Alveolar-arterial (A-a) gradient of 600-624 mm Hg
  for 4-12 hours at sea level, which may be
  computed as follows (where 47partial pressure of
  water vapor)
• (A-a)(Diffusing capacity D of O2 equals
  atmospheric pressure - 47 - (PaCO2 PaO2)/FiO2

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Qualifying patient criteria for ECMO

• Oxygenation index (OI) greater than 40 in 3 of 5
  postductal gas determinations obtained 30-60
  minutes apart, which may be computed as follows
  (where MAP is mean airway pressure)
• OI (MAP x FiO2 x 100)/ PaO2
• PaO2 35-50 mm Hg for 2-12 hours
• Acute deterioration 
• PaO2 less than or equal to 30-40 mm Hg for 2
  hours
• pH less than or equal to 7.25 for 2 hours
• Intractable hypotension

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Pediatric ECMO

• Low cardiac output resulting from right, left,
  and biventricular failure following repair of
  congenital heart defect
• Pulmonary vasoreactive crisis following repair of
  congenital heart defect leading to severe
  hypoxemia, low cardiac output, or both
• Rarely, as a bridge to cardiac surgery in
  patients with serious end-organ damage resulting
  from profound low cardiac output related to
  congenital heart disease

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Types of ECMO

• Venoarterial bypass. a cannula is placed through
  the right jugular vein into the right atrium.
  Blood is drained to a venous reservoir located
  3-4 feet below heart level. The blood is actively
  pumped by a roller pump through the oxygenator,
  where gas exchange occurs via countercurrent flow
  of blood and gas. Next, the blood is warmed to
  body temperature by the heat exchanger before
  returning to the patient through a cannula placed
  through the right carotid artery into the aortic
  arch. Systemic anticoagulation therapy with
  heparin is administered throughout the bypass
  circuit, with frequent monitoring of activated
  clotting time (ACT), which should be maintained
  at 180-240 seconds.

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Types of ECMO

• venovenous bypass, a double-lumen cannula is
  placed through the right jugular vein into the
  right atrium. Desaturated blood is withdrawn from
  the right atrium through the outer fenestrated
  venous catheter wall, and oxygenated blood is
  returned through the inner lumen of the catheter
  and is angled to direct blood across the
  tricuspid valve.

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Venoarterial ECMO Venovenous ECMO
Higher PaO2 is achieved. Lower PaO2 is achieved.
Lower perfusion rates are needed. Higher perfusion rates are needed.
Bypasses pulmonary circulation Maintains pulmonary blood flow
Decreases pulmonary artery pressures Elevates mixed venous PO2
Provides cardiac support to assist systemic circulation Does not provide cardiac support to assist systemic circulation
Requires arterial cannulation Requires only venous cannulation
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Clinical Management-Pulmonary

• ECMO is used temporarily while awaiting pulmonary
  recovery.
• The typical ventilator settings are FiO2 of
  21-30, PIP of 15-25 cm H2 O, a positive
  end-expiratory pressure (PEEP) of 3-5 cm H2 O,
  and intermittent mechanical ventilation (IMV) of
  10-20 breaths per minute. In some centers, a high
  PEEP of 12-14 cm H2 0 has been used to avoid
  atelectasis this has been found to shorten the
  bypass time in infants. Pulmonary hygiene is
  strict and requires frequent positional changes,
  endotracheal suctioning every 4 hours depending
  on secretions, and a daily chest radiograph.

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Clinical Management-Cardiovascular

• Systemic perfusion and intravascular volume
  should be maintained. Volume status can be
  assessed clinically by urine output and physical
  signs of perfusion and by measuring the central
  venous pressure and the mean arterial blood
  pressure. Native cardiac output can be enhanced
  with inotropic agents. Echocardiography should be
  performed to exclude any major congenital heart
  anomaly that may require immediate intervention
  other than ECMO

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Clinical Management-CNS

• CNS complications are the most serious and are
  primarily related to the degree of hypoxia and
  acidosis. Avoiding paralytic agents and
  performing regular neurologic examinations are
  recommended. If feasible, head ultrasonography
  should be performed before beginning ECMO in a
  neonate. Reevaluation with serial head
  ultrasonography may be needed on a daily basis,
  especially after any major event. In patients
  with seizures or suspected seizures, aggressive
  treatment is recommended (eg, phenobarbital)

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Clinical Management-Renal

• During the first 24-48 hours on ECMO, oliguria
  and acute tubular necrosis associated with
  capillary leak and intravascular volume depletion
  are common because ECMO triggers an acute
  inflammatory like reaction. The diuretic phase,
  which usually begins within 48 hours, is often
  one of the earliest signs of recovery. If
  oliguria persists for 48-72 hours, diuretics are
  often required to reduce edema. When renal
  failure does not improve, hemofiltration or
  hemodialysis filters may be added to the circuit.

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Clinical Management-Hemalogic

• To optimize oxygen delivery, the patient's
  hemoglobin should be maintained at 12-15 g/dL
  using packed RBCs (pRBCs). As a result of
  platelet consumption during ECMO, platelet
  transfusions are required to maintain platelet
  counts above 100,000/mcL. Activated clotting time
  (ACT) should be maintained at 180-240 seconds to
  avoid bleeding complications.

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Clinical Management- Infection

• Strict aseptic precautions are required. The
  presence of infection is monitored by obtaining
  cultures from the circuit at least once a week.
  Based on institutional experience, the protocol
  frequency may vary. Other appropriate cultures
  (eg, fungal and viral) should be obtained as
  needed.

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Clinical Management-Fluids

• Patients on ECMO require close monitoring of
  fluids and electrolytes. The high-energy
  requirements should be met using
  hyperalimentation techniques. The patient's
  weight increases in the first 1-3 days on ECMO
  because of fluid retention.

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Hazards

• As the blood travels around the circuit, there is
  a risk of clots forming as the blood is outside
  the body and in contact with the plastic of the
  circuit.
• There is a risk of infection with any invasive
  procedure
• When the blood in the body is thinned, bleeding
  into the head may occur.

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ECMO Lecture

• http//www.youtube.com/watch?vrmGM984aVKU
• http//www.youtube.com/watch?vISHOFf5QMyc