Veno-venous extracorporeal membrane oxygenation (VV ECMO) is a life-saving therapy for severe respiratory failure. It involves using an external circuit to oxygenate and remove carbon dioxide from the blood, providing temporary support to the lungs. This allows the patient's lungs to rest and recover while maintaining oxygen delivery to the body. VV ECMO can be a bridge to recovery or lung transplantation for patients with acute respiratory distress syndrome (ARDS), pneumonia, or other conditions causing respiratory failure. It requires specialized equipment and expertise for cannulation, management, and monitoring.
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2. TABLE OF CONTENT
➢ Introduction of VV-ECMO
➢ How does VV-ECMO works
➢ Compounds of VV-ECMO
➢ Cannulation sites and sizes of ECMO
➢ Xray of VV-ECMO patient
➢ Indications of VV-ECMO
➢ Patients management of VV-ECMO
➢ Outcomes of VV-ECMO
➢ weaning protocol of VV-ECMO
3. INTRODUCTION OF VV-ECMO
DEFINITION
VV ECMO stands for Veno-Venous Extracorporeal Membrane
Oxygenation. It is a medical technique used to provide life support for
patients with severe respiratory failure. VV ECMO involves temporarily
diverting a patient's blood from a large vein, passing it through an external
artificial lung (oxygenator) to remove carbon dioxide and add oxygen, and
then returning the oxygenated blood back into the patient's body. This
process allows the patient's lungs to rest and heal while maintaining
adequate oxygenation and carbon dioxide removal.
9. INDICATIONS OF VV-ECMO
➔ VV ECMO is used for respiratory support in those who do not respond to
mechanical ventilation or any acute potentially reversible respiratory failure.
➔ Acute respiratory distress syndrome secondary to either severe bacterial or
viral pneumonia, including COVID-19 or aspiration pneumonitis. ECMO
bypasses the compromised activity of the lungs and maintains oxygenation
and ventilation with the removal of CO2.
➔ Covid-19 Severe Respiratory Failure: ARDS due to SARS-CoV-2 infection
when prolonged mechanical ventilatory support fails. In some cases, when
ventilation fails, ECMO support (venovenous ECMO) has been initiated.
➔ Extracorporeal assistance to support lung in cases of airway obstruction,
pulmonary contusion (barotrauma), smoke inhalation, drowning, air leak
syndrome, hypercapnia, or hypoxic respiratory failure
10. CONT….
➔ Status asthmaticus
➔ Massive hemoptysis or pulmonary hemorrhage
➔ Bridge to lung transplant
➔ Support for lung resections in unstable patients.
11. PATIENTS MANAGEMENT IN VV-ECMO
1. Patient selection
2. pre-ECMO assessment
3. Cannulation
4. Monitoring
5. Initiation of ecmo
6. Anticoagulation management
7. Ventilator management
8. Nutritional support
9. Complication management
10.Weaning and decannulation
11.Post-ecmo care
12.rehabilitation
12. OUTCOMES OF VV-ECMO
1. Survival
2. Lung recovery
3. Bridge to recovery or transplant
4. Improved quality of life
13. WEANING PROTOCOL OF VV-ECMO
➔ When weaning from VV ECMO as described above with VA ECMO,
all respiratory function should be recovered.
➔ Before weaning from ECMO support, the patient’s respiratory function
should be thoroughly inspected. The patient's native lung should be
able to support 50 to 80% of the total gas exchange within the native
lung. The majority of severe lung disease patients can begin weaning
when their native lungs have gained 80% of their oxygen delivery
function. The patient's respiratory mechanics must demonstrate
significant improvement. The gas exchange when considering a
weaning trial on moderate ventilator settings should have a PF ratio
>100. The FiO2 should be less than 50% with reasonable PEEP
levels < 10.
14. CONT….
➔ As the native lung function improves, the ECMO support can be
decreased. The extracorporeal blood flow can be slightly
decreased, but with VV ECMO, the sweep gas flow controls the
oxygenation to the native lungs through the ECMO circuit.
➔ The majority of patients on VV ECMO have a sweep gas at 100%.
As their lung's oxygenation and ventilation improved, we
recommend decreasing the ventilator FiO2 before decreasing the
sweep gas oxygen concentration. This will help avoid any major
oxygen toxicity to the healing lungs. Some centers do recommend
weaning VV ECMO sweep gas prior to weaning FiO2 on the
ventilator.
15. CONT….
➔ When weaning, there are no particular ventilator settings that are
recommended for better outcomes. Some centers use controlled
mechanical ventilation when on support, then transition to assist
control with pressure support when weaning off. The vent settings
should be changed to values that are acceptable to non-ECMO
patients. Sedation will also have to be managed accordingly.
➔ As the sweep gas and FiO2 are decreased, an hourly arterial
blood gas should be performed within 30 minutes of the
adjustment to check for oxygenation and ventilation.
16. CONT….
➔ If the patient tolerates the wean with tolerable arterial blood gas levels
and vent settings, the sweep gas can continue to be titrated. Some
ECMO programs report that decreasing flow rates less than 2.5 L/min
puts the patient at a higher risk for blood clot formation in the circuit or
cannulas. Some physicians wean the flow rate to 2.5L/min, then
decrease the sweep gas down while monitoring the patient, while other
physicians will lower the flow rate to 1-1.5 L/min while weaning the circuit
once the sweep gas has been titrated to off. As mentioned above, the
flow rate does not matter nearly as much during VV ECMO. The sweep
gas is the major determinant of oxygenation and ventilation of the patient.
Therefore higher or lower flow rates are per physician preference
regarding clot formation
17. CONT….
➔ Around 20 minutes after the sweep gas has been turned off, the
patient’s O2 saturation and arterial blood gas will confirm if the
patient can support oxygenation and ventilation while being off VV
ECMO. The ECMO flow rate can be continued with no adjustment
in the heparin dose.
➔ If the patient shows signs of distress or hemodynamic instability at
any point, the weaning trial should be aborted, and the patient
should be put back on full ECMO support. Weaning failure is
indicated by an SPO2 level of less than 88% or an increase in the
patient's respiratory rate greater than 30 to 35 breaths per minute.
18. CONT….
➔ Some centers recommend a trial of 1 hour or up to 6 hours to prove that
the patient has passed weaning from VV ECMO. During this time, the
patient must be monitored closely for any signs of hemodynamic
instability, arterial blood gas analysis to confirm the adequacy of
oxygenation and ventilation, and the patient’s ventilator settings and
respiratory mechanics must be carefully assessed as well. If the patient
remains hemodynamically stable with normal lab values during this time,
the ECMO support can be discontinued, and the patient can undergo
decannulation.
19. CONT….
➔ Regarding VV ECMO decannulation, the circuit can be disconnected
once the patient is weaned, and the cannulas can be left in place for up
to 48 hours in case the patient needs to be restarted on ECMO. If the
cannulas are to be left in place, they require periodic flushing with
heparin to avoid thrombosis up the cannula with the continuation of the
patient anticoagulation. Once the cannulas are removed, pressure can be
held over the site for around 30 to 45 minutes. Some centers then
perform venous Doppler ultrasound of the cannulated vessels' limbs to
ensure there is no thrombosis present.
