X. ECMO Supportfor COVID-19 Patients
COVID-19 is a novel, highly infectious disease primarily targeting pulmonary alveoli, which
damages primarily the lungs of critically ill patients and leads to severe respiratory failure.
For the application of extracorporeal membrane oxygenation (ECMO) in COVID-19 treatment,
medical professionals need to pay close attention to the following: the time and means of
intervention, anticoagulant and bleeding, coordination with mechanical ventilation, awake
ECMO and the early rehabilitation training, strategy of handling for complications.
ECMO Intervention Timing
1.1 Salvage ECMO
In the state of mechanical ventilation support, measures such as lung protective
ventilation strategy and prone position ventilation have been taken for 72 h. With the
onset of one of the following conditions, salvage ECMO intervention needs to be
considered.
(1) Pa02/Fi02 < 80 mm Hg (regardless of what the PEEP level is);
(2) Pplat s 30 mm Hg, Pa CO2> 55 mm Hg;
(3) The onset of pneumothorax, air leakage> l /3 tidal volume, duration> 48 h;
(4) Circulation deterioration, the dosage of norepinephrine > 1 µg/(kgxmin);
(5) Cardio-pulmonary resuscitation in vitro life support ECPR.
1.2 Replacement ECMO
When the patient is not suitable for long-term mechanical ventilation support, i.e., the
patient is not able to obtain the expected results, ECMO replacement needs to be
adopted immediately. With the onset of one of the following conditions, ECMO
replacement needs to be considered.
(1) Decreased lung compliance. After the pulmonary recruitment maneuver, the
compliance of the respiratory system< 10 mL/cmH,O;
(2) Persistent exacerbation of pneumomediastinum or subcutaneous emphysema. And
the parameters of mechanical ventilation support cannot be reduced within 48 h,
according to the estimation;
(3) Pa02/Fi02 < 100 mmHg. And it cannot be improved by routine methods in 72 h.
1.3 Early Awake ECMO
Early awake ECMO can be applied to patients who have been supported by mechanical
ventilation with the expected high parameters for more than 7 days and who meet the
necessary conditions of awake ECMO. They might benefit from it. All the following
conditions must be met:
(1) The patient is in a clear state of consciousness and is fully compliant. He or she
understands how ECMO works and its maintenance requirements;
(2) The patient is not complicated with neuromuscular diseases;
(3) Pulmonary damage score Murry> 2.5;
(4) Few pulmonary secretions. The time interval between the two airway suction
procedures> 4 h;
(5) Stable hemodynamics. Vasoactive agents are not required for assistance.
f)
Cathetering Methods
Because the ECMO supporting time for most COVID-19 patients is greater than 7 days,
the seldinger method should be used as much as possible for the ultrasound guided
peripheral catheter insertion, which reduces the bleeding damages and infection risks
brought about by intravascular cathterization by venous angiotomy, especially for the
early awake ECMO patients. lntravascular catheterization by venous angiotomy may be
considered only for the patients with bad blood vessel conditions, or the patients
whose catheterization cannot be identified and selected by ultrasound, or the patients
whose seldinger technique failed.
C,
Mode Selection
(1) The first choice for the patients of respiratory impairment is the V-V mode. The V-A
mode should not be the first option just because of the possible circulation problems.
(2) For the respiratory failure patients complicated with cardiac impairment, PaO2/FiO2
< 100 mm Hg, the V-A-V mode ought to be selected with the total flux> 6 Umin and V/A
= 0.5/0.5 is maintained by current limiting.
(3) For the COVID-19 patients without severe respiratory failure but complicated with
serious cardiovascular outcomes leading to cardiogenic shock, the V-A assisted by
ECMO mode ought to be selected. But IPPV support is still needed and the awake ECMO
should be avoided.the awake ECMO should be avoided.
0
Flux Set-value and Target Oxygen Supply
(1) The initial flux> 80% cardiac output (CO) with a self-cycling ratio< 30%.
(2) SPO2 > 90% is to be maintained. FiO2 < 0.5 is supported by mechanical ventilation or
the other oxygen therapy.
(3) To ensure the target flux, 22 Fr (24 Fr} vein access canula is the first choice for the
patient with a body weight below (above) BO kg.
0
Ventilation Setting
Normal ventilation maintenance by adjusting the sweep gas level:
(1) The initial air flow is set to be Flow: sweep gas= 1 :1. The basic target is to maintain
Pa CO2< 45mmHg. For the patients complicated with COPD, Pa CO2< 80% basal level.
(2) The patient's spontaneous respiratory strength and respiratory rate (RR} should be
maintained, with 10 <RR< 20 and without chief complaint of breathing difficulty from
the patient.
(3) The sweep gas setup of the V-A mode needs to ensure the 7.35-7.45 PH value of the
bloodstream out of the oxygenator membrane.
0
Anti-Coagulation and Bleeding Prevention
(1) For the patients without active bleeding, without visceral bleeding, and with platelet
count> 50xl09/L, the recommended initial heparin dosage is 50 U/kg.
(2) For the patients complicated with bleeding or with platelet count < 50xl 09/L, the
recommended initial heparin dosage is 25 U/kg.
(3) The activated partial thromboplastin time (aPPT} being 40-60 sec is proposed to be
the target of anticoagulation maintenance dosage. The trend of D-dimer change
should be considered at the same time.
(4) Heparin-free operation may be performed in the following circumstances: the ECMO
support must continue but there is fatal bleeding or active bleeding that has to be
controlled; whole heparin coated loop and catheterization with blood flow> 3 L/min.
The recommend operation time< 24 hour. Replacement devices and consumables need
to be prepared.
(5) Heparin resistance. Under some conditions of heparin usage, a PTT is not able to
reach the standard and blood coagulation happens. In this case, the activity of plasma
antithrombin Ill (ATIII) needs to be monitored. If the activity reduces, fresh frozen
plasma needs to be supplemented to restore heparin sensitivity.
(6) Heparin induced thrombopenia (HIT). When HIT happens, we recommend to perform
plasma exchange therapy, or to replace heparin with argatroban.
f) Weaning from ECMO and Mechanical Ventilation
(1) If a patient treated by v-v ECMO combined with mechanical ventilation satisfies the
awake ECMO condition, we suggest to first try to remove the artificial airway, unless the
patient has ECMO related complications, or the expected time of removal of all the
assisting machines is less than 48 h.
(2) For a patient who has too much airway secretions that frequent artificial suction
clearance is needed, who is expected to have a long-term mechanical ventilation
support, who satisfies the conditions PaO,/FiO, > 150 mm Hg and time> 48 h, whose lung
image changes for the better, and whose damages related to mechanical ventilation
pressure have been controlled, the ECMO assistance may be removed. It is not
recommended to keep ECMO intubation.
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