MD Nexus

Venovenous Extracorporeal Membrane Oxygenation (VV-ECMO)

Types of Extracorporeal Life Support (ECLS)

Modalities

  • Cardiopulmonary Bypass (CPB) (see Cardiopulmonary Bypass)
  • Extracorporeal CO2 Removal (ECCO2R): originally developed by Gattinoni (JAMA, 1986) [MEDLINE]
  • Extracorporeal Membrane Oxygenation (ECMO)

Differences Between Cardiopulmonary Bypass and Extracorporeal Membrane Oxygenation (ECMO) (see Cardiopulmonary Bypass)

  • Cardiopulmonary Bypass is Equipped with Reservoir Into Which Blood from the Heart is Drained: allows a bloodless surgical field for valve and aortic operations
    • In Contrast, the ECMO Circuit Does Not Contain a Reservoir, So Blood Flow Needs to Be Continuous
  • Cardiopulmonary Bypass Can Be Utilized in Conjunction with Air Vent Tubing, Cardioplegia Line for Myocardial Preservation, or Cell Salvage Tubing
  • Requirement for Systemic Heparin Anticoagulation is Less Intense for ECMO Because Blood Flow is Continuous and There is No Blood-Air Interface in the Reservoir
    • Higher Flow Rates of >4 L/min are Used During ECMO (in Contrast to the Lower Flow Rates of 2 L/min Used During CPB)
    • However, Continuous Anticoagulation is Necessary to Prevent Thrombus Formation on the Synthetic Thrombogenic Surfaces of Both CPB and ECMO
  • ECMO Circuits are Designed for Longer-Term Use (May Be Used for Weeks, Depending on the Life of the Membrane Oxygenator), While CPB Use is Designed for Use for a Period of Hours

Indications

General Comments

  • Venovenous Extracorporeal Membrane Oxygenation (VV-ECMO) (Similar to Extracorporeal CO2 Removal, ECCO2R) Provides Only Respiratory Support: VV-ECMO is dependent on the patient’s intrinsic cardiac output

Acute Respiratory Distress Syndrome (ARDS) (see Acute Respiratory Distress Syndrome)

Clinical Efficacy

  • Early JAMA ECMO Trial (JAMA, 1979) [MEDLINE]
    • ECMO Had No Mortality Benefit
  • ECCO2R Trial (Am J Respir Crit Care Med, 1994) [MEDLINE]
    • ECCO2R Had No Mortality Benefit
  • ANZ ECMO Influenza Trial (JAMA, 2009) [MEDLINE]
    • ECMO Had No Mortality Benefit in Treatment of ARDS Associated with Influenza
  • CESAR Trial of ECMO in the UK (Lancet, 2009) [MEDLINE]
    • ECMO Decreased Mortality Rate/Severe Disability at 6 Months
    • However, the Study was Flawed by Not Defining the Usual Care Group and ECMO Patients Were Concentrated in One Center in the Trial
  • Systematic Review and Meta-Analysis of ECMO in Adult Patients with ARDS (J Crit Care, 2013) [MEDLINE]
    • ECMO Had an Unclear Hospital Mortality Benefit: further studies were recommended
  • Cochrane Review of VV-ECMO and VA-ECMO in Critically Ill Adults (Cochrane Database Syst Rev, 2015) [MEDLINE]
    • ECMO Had No 6-Month (or Prior to 6 Month) All-Cause Mortality Benefit: low-moderate quality of evidence from trials
  • Study of the Long-Term Survival and Quality of Life Following ECMO (Eur J Cardiothorac Surg, 2017) [MEDLINE]
    • Survival to Discharge was Higher in the Non-ECMO Group, as Compared to the ECMO Group: however, this difference was not statistically significant after propensity score matching
    • One Year Survival was 67% in the Non-ECMO Group vs 60% in the ECMO Group
    • Two Year Survival was 50% in the Non-ECMO Group vs 45% in the ECMO Group
  • Single-Center Swedish Retrospective Study of Outcomes After ECMO for ARDS Associated with Sepsis (Crit Care Med, 2017) [MEDLINE]
    • Approximately 64% of ECMO Patients Survived to Discharge
    • High Mortality Rate Within the First Few Months After Discharge
  • Systematic Review and Meta-Analysis of Mortality and Complications with the Use of Venovenous ECMO in ARDS (Ann Intensive Care, 2017) [MEDLINE]
    • Mortality Rate at Hospital Discharge was 37.7%
    • Factors Associated with Increased Hospital Mortality
      • Age
      • Year of Study
      • Mechanical Ventilation and Prone Positioning Days Prior to ECMO
  • Systematic Review of Venovenous ECMO for ARDS (J Crit Care, 2017) [MEDLINE]: n = 27 studies
    • Mortality Benefit of ECMO is Unclear
  • French EOLIA Trial of VV-ECMO in Severe ARDS (NEJM, 2018) [MEDLINE]
    • Clinical Triggers for Randomization
      • pO2/FiO2 Ratio <50 mm Hg for >3 hrs
      • pO2/FiO2 Ratio <80 mm Hg for >6 hrs
      • Arterial Blood pH <7.25 with pCO2 ≥60 mm Hg for >6 hrs
    • VV-ECMO Did Not Improve the 60-Day Mortality in Severe ARDS, as Compared to Conventional Ventilator Management (with VV-ECMO as Rescue Therapy) (Relative Risk 0.76; 95% Confidence Interval 0.55 to 1.04; P = 0.09)
    • Crossover to ECMO Occurred a Mean (± SD) of 6.5 ± 9.7 Days After Randomization in 28% of Patients in the Control Group, with 57% of These Patients Dying
    • VV-ECMO Group Had Higher Rate Bleeding Events and Severe Thrombocytopenia, But Lower Rate of Ischemic Cerebrovascular Accidents

Criteria to Start Venovenous Extracorporeal Membrane Oxygenation (VV-ECMO)

  • French REVA (Reseau Europeen De Recherche En Ventilation Artificielle) Criteria (2009)
    • pO2/FiO2 Ratio <50 Despite High PEEP (10-20 cm H2O) and High FiO2 (>80%)
    • Plateau Pressure At Least 35 cm H2O Despite Decrease in Tidal Volume to 4 mL/kg
  • NEJM, 2011 Review of ECMO in ARDS Criteria [MEDLINE]
    • Severe Hypoxemia: pO2/FiO2 Ratio <80 Despite High PEEP (15–20 cm of H2O) for at Least 6 hrs in Patient with Potentially Reversible Respiratory Failure
    • Uncompensated Hypercapnia with Acidemia (pH <7.15) Despite the Optimized Ventilator Management
    • Excessively High Plateau Pressure (>35–45 cm of H2O, According to the Patient’s Body Size) Despite Optimized Ventilator Management
  • Extracorporeal Life Support Organization (ELSO) Criteria (Extracorporeal Life Support Organization (ELSO) Guidelines for Adult Respiratory Failure v1.3, 2013) [LINK]
    • pO2/FiO2 Ratio <150: ECMO should be considered
    • pO2/FiO2 Ratio <80: ECMO should be utilized
    • pCO2 >80 m Hg or Plateau Pressure >30 cm H2O: ECMO should be utilized

Contraindications

Absolute

  • Contraindication to Anticoagulation: although in patients with severe bleeding, anticoagulation can be held for limited periods of time

Relative (NEJM, 2011) [MEDLINE]

  • Any Condition or Organ Dysfunction that Would Limit the Likelihood of Overall Benefit from ECMO, Such as Severe, Irreversible Brain Injury or Untreatable Metastatic Cancer
  • High FiO2 Requirement >80% for >7 Days
  • High-Pressure Ventilation (Plateau Pressure >30 cm of H2O) for >7 Days
  • Limited Vascular Access

Physiology

Blood Flow Rate During VV-ECMO

  • Determinants of VV-ECMO Blood Flow Rate
    • Resistance to Flow in the Drainage Cannula
      • Maximal Flow for Commonly Used Venous Cannulas (at 100 cm H2O Suction): approximately 4-5 L/min
    • Suction Produced by the Pump or Siphon
    • Geometry of the Cannulated Vessel (Usually the Inferior Vena Cava or Right Atrium)

Oxygenation During VV-ECMO

  • Determinants of Oxygen Supply from the VV-ECMO Membrane
    • VV-ECMO Blood Flow Rate
    • Hemoglobin
    • Difference Between the Outlet Minus Inlet Oxygen Content
      • Because the Outlet Blood is Typically 100% Saturated and PO2 is >500 mm Hg, the Dissolved Oxygen Can Be as Much as 10% of the Oxygen Content
  • Major Determinants of Oxygenation During VV-ECMO
    • VV-ECMO Blood Flow Rate
      • Small Study of the Determinants of Oxygenation and CO2 Removal During VV-ECMO (Int Care Med, 2013) [MEDLINE]
        • Arterial Oxygenation was Determined by VV-ECMO Blood Flow Rate and ECMO FIO2
        • ECMO Blood Flow was the Main Determinant of Arterial Oxygenation
        • CO2 Elimination Depended on the Sweep Gas Flow Rate Through the Oxygenator
        • ECMO Blood Flow/Cardiac Output Ratio >60% was Associated with Adequate Blood Oxygenation
        • Packed Red Blood Cell Transfusion Increased O2 Delivery, Allowing Lower ECMO Flows to Reach an Adequate SaO2
    • VV-ECMO FIO2
      • Small Study of the Determinants of Oxygenation and CO2 Removal During VV-ECMO (Int Care Med, 2013) [MEDLINE]
        • Arterial Oxygenation was Determined by VV-ECMO Blood Flow Rate and ECMO FIO2
        • ECMO Blood Flow was the Main Determinant of Arterial Oxygenation
        • CO2 Elimination Depended on the Sweep Gas Flow Rate Through the Oxygenator
        • ECMO Blood Flow/Cardiac Output Ratio >60% was Associated with Adequate Blood Oxygenation
        • Packed Red Blood Cell Transfusion Increased O2 Delivery, Allowing Lower ECMO Flows to Reach an Adequate SaO2

Mixture Between Venovenous Extracorporeal Membrane Oxygenation (VV-ECMO) Oxygenated Blood Flow and the Patient’s Native Venous Blood Flow

  • Background
    • In Severe ARDS with VV-ECMO, the Lungs Contribute Little or Nothing to Gas Exchange and the Oxygen Saturation and Carbon Dioxide Levels of the Blood in the Right Ventricle is the Summation of Mixing of Oxygenated ECMO Blood with Deoxygenated Native Venous Blood
      • Due to the Lack of Meaningful Lung Function, The Blood in the Right Ventricle Will Have the Same Oxygen Saturation and Carbon Dioxide Levels of the Blood on the Arterial Side of the Circulation
    • Mixing Point
      • Single (Avalon Catheter, Crescent Catheter) Catheter Setup (Inserted Via the Right Internal Jugular Vein): mixing point occurs in the right atrium
      • Double Catheter Setup

Calculation of the Oxygen Delivery/Oxygen Consumption Ratio

  • General Comments
    • Calculation of the Oxygen Delivery/Oxygen Consumption Ratio is a Standard Means to Determine if Oxygen Delivery is Adequate in Patient on VV-ECMO
      • This Calculation is Critical Since the Arterial pO2 May Be Significantly Lower than the pO2 of a Patient in ARDS Who is Not on VV-ECMO
      • These Low pO2 Values May Alarm Staff Who are Used to Meeting Specific pO2 Goals in Patients in ARDS
      • In a Patient on VV-ECMO, the Oxygen Delivery/Oxygen Consumption Ratio Goal is More Clinically Relevant (than the Arterial pO2) in Maintaining Tissue Oxygenation
  • Step 1: Calculation of Oxygen Content of Arterial Blood, Pre-Oxygenator (Venous) Blood, and Post-Oxygenator Blood
    • Arterial Oxygen Content = 13.4 x Hemoglobin x Arterial SaO2 + (Arterial pO2 x 0.031)
    • Pre-Oxygenator Oxygen Content = 13.4 x Hemoglobin x Pre-Oxygenator SaO2 + (Pre-Oxygenator pO2 x 0.031)
    • Post-Oxygenator Oxygen Content = 13.4 x Hemoglobin x Post-Oxygenator SaO2 + (Post-Oxygenator pO2 x 0.031)
    • Terms
      • Constant 13.4 mL O2/g Hb: accounts for the fact that 1.34 ml of O2 is carried per g of Hb (13.4 is used in the equation to correct the units from dL to L)
        • The Normal Oxygen Carrying Capacity is 1.39 ml O2 per g of Hb
        • However, Due to the Presence of Abnormal Hemoglobins (Such as Carboxyhemoglobin and Methemoglobin), this Value is Decreased to 1.34 ml O2 per g of Hb
      • Hemoglobin: in g/dL
      • SaO2: as decimal
      • pO2: in mm Hg
      • Constant 0.0031 mL O2/L/mm Hg: solubility coefficient of oxygen at body temperature
  • Step 2: Calculation of Flows
    • General Comments
      • When Two Blood Flows Containing Different Oxygen Contents Mix, the Resultant Oxygen Content is the Average of the Amount of Oxygen Content in Each of the Two Flows (Not the Average of the Partial Pressures of Oxygen, i.e. the pO2’s) (Extracorporeal Life Support: The ELSO Red Book (5th Edition, 2017) [LINK]
    • Total Oxygen Content = [(Post-Oxygenator Oxygen Content x VV-ECMO Flow)/Total Flow] + [(Pre-Oxygenator Oxygen Content x Native Venous Flow)/Total Flow]
      • Assumes No Native Lung Function
    • Solving for Total Flow (i.e. Total Cardiac Output)
      • Total Flow = VV-ECMO Flow [(Post-Oxygenator Oxygen Content – Pre-Oxygenator Oxygen Content)/(Arterial Blood Oxygen Content – Pre-Oxygenator Oxygen Content)]
    • Solving for Native Venous Flow
      • Native Venous Flow = Total Flow = VV-ECMO Flow
  • Step 3: Calculation of Oxygen Delivery (DO2)/Oxygen Consumption (VO2) Ratio (see Hypoxemia)
    • Oxygen Delivery = [Arterial Oxygen Content] x CO = [Hb x 13.4 x SaO2 + (pO2 x 0.0031)] x CO
      • Hemoglobin (Hb): in g/dL
      • Constant 13.4: accounts for the fact that 1.34 ml of O2 is carried per g of Hb (13.4 is used in the equation to correct the units from dL to L)
      • Arterial Oxygen Saturation (SaO2): as a decimal
      • Thermodilution-Measured Cardiac Output (CO) (from Swan-Ganz Catheter, etc) or Flow: in L/min
      • Normal Arterial Oxygen Content: approximately 200 mL O2/L (or 20 mL O2/dL)
        • Note: the Equation Used Here Yields the Arterial Oxygen Content in mL O2/L, Which Allows the Arterial Oxygen Content Value to Be Plugged into the Oxygen Delivery Equation without Unit Conversion
      • Normal Oxygen Delivery (Using Cardiac Output = CO): approximately 1000 mL O2/min
    • Calculation of Approximate Oxygen Consumption
      • Oxygen Consumption = Weight (in kg) x 3 mL O2/kg/min
    • Calculation of the Oxygen Delivery (DO2)/Oxygen Consumption (VO2) Ratio
  • Recommendations (Extracorporeal Life Support: The ELSO Red Book (5th Edition, 2017) [LINK]
    • Maintain Oxygen Delivery/Oxygen Consumption Ratio >3
      • In Sepsis Where Cardiac Output is Typically Elevated, This 3:1 Ratio Can Only Be Maintained if Flow is Augmented

Factors Contributing to Hypoxemia During VV-ECMO (Excluding Equipment Failure)

  • Mixture Between ECMO Oxygenated Blood Flow and Patient’s Native Venous Blood Flow: as described above
  • Recirculation
    • Recirculation is Defined as the Fraction of Oxygenated Blood Which is Infused into the Right Atrium and Subsequently Aspirated Back into the Venous Limb of the ECMO Circuit
      • Factors Contributing to Recirculation
        • Cannula Type/Size
        • Cannula Position: catheter position can be most problematic with the use of a single (Avalon) catheter, where the inflow and outflow ports are in closer proximity than they are with a double catheter setup
        • Pump Speed
        • Blood Flow Rate
        • Direction of Extracorporeal Blood Flow
        • Intrathoracic/Intracardiac/Intra-Abdominal Pressures
  • Intrapulmonary Shunt
    • This is the Main Mechanism of Hypoxemia in ARDS (Occurs Due to Alveolar Filling with Protein-Rich Fluid/Red Blood Cell/Neutrophils and Interstitial Changes)
      • Degree of Intrapulmonary Shunt is Related to Vascular Pressures, Vasoactive Medications/Substances, and Degree of Lung Inflation
      • Cardiac Output is Positively Correlated with the Degree of Intrapulmonary Shunt
  • Flow Exceeding Oxygenator Performance
    • Rarely Occurs with the Current Generation of Technology

Strategies to Improve Systemic Oxygenation During VV-ECMO

  • Increase Blood Oxygen Content
    • Increase ECMO Blood Flow Rate
      • In Some Cases, Increasing the Blood Flow Rate Will Not Improve Oxygenation, Due to Increased Recirculation
      • Higher Flow Rates Increase the Risk of Hemolysis (see Hemolytic Anemia): may occur when using high RPM with venous occlusion in the catheter (due to coughing, hypovolemia, catheter kinking, etc), resulting in a vacuum created in the pump head
    • Increase Hematocrit (Oxygen-Carrying Capacity)
      • The ECMO Oxygenator Functions Optimally at a Normal Hematocrit
      • ECMO Utilization is Blood Resource Intensive: due to the need for frequent PRBC transfusion related to both hemolysis/bleeding issues and the need to maintain a high hematocrit to increase oxygen delivery
      • Extracorporeal Life Support Organization (ELSO) Guidelines Recommend Maintaining a Hemoglobin of 12-14 g/dL with a Normal Hematocrit (v1.3 (2013) [LINK]: due to the fact that oxygen delivery is determined by blood flow through the artificial lung, and if anemia is present, a higher blood flow will be necessary to obtain the same level of oxygen delivery
      • While There are No Trials Examining Restrictive Transfusion Protocols in VV-ECMO, Data Suggest that Red Blood Transfusion is a Clinical Predictor of Mortality (Crit Care Med, 2005) [MEDLINE] and (Chest, 2007) [MEDLINE]
  • Decrease ECMO Recirculation
    • Maximize the Distance Between the Two Cannulas
  • Decrease Oxygen Consumption
  • Manipulation of Cardiac Output and Intrapulmonary Shunt
    • Beta Blockers (see β-Adrenergic Receptor Antagonists)
      • Esmolol Has Been Used to Decrease the Cardiac Output (in Patients with Cardiac Output >7 L/min), Improving the Ratio Between the Cardiac Output and the ECMO Blood Flow (Preventing the Need for Increases in the ECMO Blood Flow Rate): this treatment did not decrease the oxygen delivery (DO2)
        • Decreasing CO Also Decreases Intrapulmonary Shunt
    • Proning: while trials of combined proning and VV-ECMO have been performed, the efficacy of this strategy is unclear
  • Switch to Venoarterial ECMO (VA-ECMO) or Hybrid Configuration
    • Utilization of VA-ECMO Allows Complete Bypass of the Native Lung: allowing a strategy to manage refractory hypoxemia occurring during VV-ECMO
      • Arterial Catheterization Needs to Be as Close to the Heart as Possible to Avoid the “Harlequin Syndrome” (Blue Head and Red Legs): this occurs due to competition between the anterograde blood flow related to native cardiac output and ECMO flow delivered via a femoral cannula, resulting in compromised perfusion of the upper body

Technique

Equipment

  • Maquet Cardiohelp
    • Centrifugal Pump (Constrained Vortex Pump)
      • Centrifugal Pump Moves Blood by Creating a Pressure Differential Across the Pump Head Which Contains a Magnetically Driven Impeller Spinning at Approximately 3000 RPM
      • Centrifugal Pumps Require Lower Levels of Anticoagulation than Roller Pumps
      • Centrifugal Pumps Result in Lesser Degree of Hemolysis than Roller Pumps
      • Centrifugal Pumps Exhibit an Increased Risk of Non-Surgical (Gastrointestinal, Pulmonary, and Neurological) Bleeding, as Compared to Roller Pumps, Despite Lower Levels of Heparin Anticoagulation (ASAIO J, 2015) [MEDLINE]
    • Duration of Use: Maquet Cardiohelp may be used for up to 30 days (per manufacturer recommendation)

Vascular Access

  • Requirement for Technical Support
    • Requires Continuous Monitoring by Technical Support Personnel (i.e. Perfusionist)

Avalon Catheter Placement into the Right Internal Jugular (IJ) Vein (Avalon Laboratory, Los Angeles, CA, USA)

  • Required Supplies
    • Arrow Dilator Kit
    • Avalon Catheter
  • Insertion and Set-Up
    • Procure Right Internal Jugular (IJ) Access
    • Insert Long Stiff Wire
    • Serial Grey Dilators
    • Insert Black Wire Sheath Over Wire
    • Serial Dilation of Tract with Blue Dilators Over Wire/Sheath (Both Remain in Place During Dilation)
    • Insert Avalon Catheter Over Wire: orient arterial port toward patient chin (this angles the arterial port toward the tricuspid valve)
    • Remove White Stylet from Avalon Catheter
    • Use Trans-Esophageal Echocardiogram (TEE) to Assure that Arterial Port is Angled Toward the Tricuspid Valve
    • After Avalon Catheter Placement, Immediately Give Heparin 10,000 units IV: to prevent Avalon catheter from clotting
    • Fill Avalon Catheter Lines with Saline: squirt into ends of catheter just to fill
    • Connect Straight Venous Port (Green Arrow in Photograph) to ECMO Machine: unoxygenated blood should be seen in this line
    • Connect the Angled Arterial Port (Red Arrow in Photograph) to ECMO Machine: oxygenated blood should be seen in this line

Anticoagulation

  • Heparin Drip (see Heparin)
    • Titrate to Achieve ACT 220-260 sec
    • However, Anticoagulation May Be Held for Short Periods During EMCO (Using Heparin-Bonded Circuits)

Extracorporeal Life Support Organization (ELSO) Guidelines for Adult Respiratory Failure v1.3 (2013) [LINK]

  • Titrate Heparin Drip to Maintain ACT 180-200

Management (Extracorporeal Life Support Organization (ELSO) Guidelines for Adult Respiratory Failure v1.3, 2013) [LINK]

Adjustments To Increase the Arterial pO2

  • Increase ECMO Circuit Blood Flow Rate (Green Arrow in First Panel Photograph)
    • This Represent the Blood Flow Rate through the Exchanger
    • Start with 50-80 ml/Dry Weight/min (Approximately 3.5-5.6 L/min for a 70 kg Patient): this will achieve a DO2 of approximately 3 mL/kg/min (assuming a cardiac output of 5 L/min and hemoglobin concentration of 15 g/dL)
      • Start with the Maximum End of This Range Initially, Then Decrease to Lowest Blood Flow Rate to Maintain SaO2 >80-85% (at Resting Vent Settings)
        • Arterial pO2 Will Be 45-55 mm Hg in this Scenario: the lower limit of pO2 below which brain injury may occur during VV-ECMO is unknown (ASAIO J, 2015) [MEDLINE]
        • Note that the Compensatory Increase in Cardiac Output Which Occurs and Transfusion to Achieve a Hematocrit >40% Will Ensure Adequate Oxygen Delivery (DO2)
      • Goal DO2:VO2 Ratio >3 (Corresponds to an SvO2 Which is 25-30% Less than the SaO2)
        • Total DO2 = Patient Lung DO2 + Circuit DO2
        • Circuit DO2 = Flow x Outlet-Inlet O2 Content
        • VO2 = 3 ml/kg/min
      • The Ability to Achieve a Specific Blood Flow Rate Will Depend on the Vascular Access Characteristics, Drainage Tubing Resistance, and Pump Properties
        • Typical Pven (Venous Limb Pressure, Yellow Airway in Photograph) is Approximately -70 mm Hg (Example: -140 mm Hg Indicates an Excessively High Negative Pressure in Venous Limb of the Avalon Catheter, Which Might Prevent an Increase in the Blood Flow)
  • Increase Sweep Gas FIO2 (Red Arrow in Second Panel Photograph)

Adjustments To Change the Arterial pCO2

  • Maintain Arterial pCO2 at 40 mm Hg by Altering the Sweep Gas Flow Rate (Green Arrow in Second Panel Photograph): oxygen flow rate through exchanger (range: 1-10 L/min)
    • Increase in Sweep Gas Flow Rate Will Decrease the Arterial pCO2: functions similarly to the minute ventilation (VE) on the ventilator
    • Decrease in Sweep Gas Flow Rate Will Increase the Arterial pCO2: functions similarly to the minute ventilation (VE) on the ventilator
    • Sweep Gas Flow Rate is Usually 1:1 with the ECMO Blood Flow Rate
      • However, Sweep Gas Flow Rate Can Be Decreased to as Low as 1 L/min to Increase the Arterial pCO2
      • However, Sweep Gas Flow Rate Can Be Increased to as High as 10-15 L/min to Decrease the Arterial pCO2

Maintenance of a Near-Normal Hematocrit

  • Maintain Hemoglobin 12-14 g/dL (with a Normal Hematocrit)
    • Extracorporeal Life Support Organization (ELSO) Guidelines Recommend Maintaining a Hemoglobin of 12-14 g/dL with a Normal Hematocrit (v1.3 (2013) [LINK]
      • Due to the Fact that Oxygen Delivery (DO2) is Determined by Blood Flow Through the Artificial Lung, and if Anemia is Present, a Higher Blood Flow Rate Will Be Necessary to Obtain the Same Level of Oxygen Delivery (DO2)

Ventilator Management During Venovenous Extracorporeal Membrane Oxygenation (VV-ECMO)

  • Optimal Ventilator Management During ECMO is Unknown
    • Rationale is to Use Adequate Tidal Volume to Prevent Lung Atelectasis and Use Low Respiratory Rate to Prevent Ventilator-Induced Lung Injury
  • Suggested Settings (Same as Used in the CESAR Trial)
    • Turn Down Ventilator Settings Gradually, While Monitoring Serial Arterial Blood Gases (ABG’s)
    • Pressure Control Ventilation (PCV) with RR 10, PIP 20-25 cm H2O (with Tidal Volume <4 mL/kg PBW), PEEP +10-15, and FiO2 30%

Addition of Prone Positioning to Venovenous Extracorporeal Membrane Oxygenation (VV-ECMO) Therapy

  • Clinical Efficacy
    • Systematic Review of Prone Positioning as Add-On Therapy to VV-ECMO (Respir Care. 2016) [MEDLINE]
      • Addition of Prone Positioning to VV-ECMO Had Unclear Benefit
      • Risk of Hemodynamic Instability and Catheter Dislodgment Were Low

Use of Combination Continuous Venovenous Hemodialysis (CVVHD) with Venovenous Extracorporeal Membrane Oxygenation (VV-ECMO)

  • Clinical Efficacy
    • The Pulmonary and Renal Support in Acute Respiratory Distress Syndrome Study (Crit Care Med. 2015) [MEDLINE]
      • Combination CVVHD and ECMO is Safe and Effective
      • Oxygenator Blood Flow Rate was 410 +/= 30 mL/min (Around 10% of Cardiac Output): at these low flow rates, oxygenation would be expected to be minimal (due to the low blood flow rate) and CO2 removal would be around 20-30% of total CO2 production (since sweep gas flow rate could remain at an adequate level)

Monitoring of Arterial Oxygen Saturation and pO2 During Venovenous Extracorporeal Membrane Oxygenation (VV-ECMO)

  • During VV-EMCO, the Arterial Oxygen Saturation Typically Ranges from 60-90%, Depending on the Relative Amount of ECMO Blood Flow, Native Venous Blood Flow, Lung Function, and Cardiac Output
    • This Desaturated Arterial Blood Results in Normal Systemic Levels of Oxygen Delivery as Long as the Cardiac Output and Hemoglobin Concentration (i.e. Arterial Oxygen Content) are Adequate
      • This Observation May Be Confusing to ICU Staff, Since the Usual Goal of Management is to Keep the Arterial Oxygen Saturation >90%

Adverse Effects/Complications (NEJM, 2011) [MEDLINE]

Prognosis

References

General

Indications

Prognosis