Extracorporeal Membrane Oxygenation for COVID-19 Disease: The
Zürich Experience
At the time of the first confirmed COVID-19 case in Switzerland, our
department was equipped with 8 ECMO devices and 20 oxygenators. USZ put
together a task force to analyze the situation and take appropriate
precautions.The institutional decision was made to purchase 12 new ECMO
devices, in order to be prepared for an uncertain number of critically
ill patients. Two weeks later, our warehouse contained 23 ECMO devices,
150 oxygenators and more than 300 different cannulas. On March 28, 2020,
the first V-V ECMO for a COVID-19 patient with severe hypoxia,
refractory to invasive ventilation, was implanted by us. With reference
to the EuroELSO ECMO-COVID-19 Survey, 20 ECMOs have been implanted in
Switzerland (9 USZ Zürich, 6 CHUV Lausanne, 3 Inselspital Bern, 2 Basel)
during the COVID pandemic so far [22]. As the register is voluntary,
the numbers are likely to be slightly underestimated. Compared to other
European countries, the absolute number of ECMO cases in critical ill
COVID-19 patients is low in Switzerland. Possible explanations for this
can be the low overall population, the early lock down, which
successfully limited the spread of the virus but also a critical patient
selection.
During end of March and May 2020, ECMO was necessary in 9 critically ill
COVID-19 patients: 6 were supported with V-V ECMO and 3 with V-A ECMO
configurations. Three of these 9 ECMOs were implanted in an external
hospital. After successful implantation, the patients were transported
to our center in a helicopter on safe ECMO support during the flight.
All patients had severe, rapidly progressive acute respiratory distress
syndrome (ARDS). One patient suffered from pulmonary artery embolism,
which worsened the respiratory situation before ECMO implantation. In
the further course the patient was diagnosed with heparin induced
Thrombocytopenia (HIT) [23]. Three patients required V-A ECMO
support due to a septic condition with myocardial involvement. Seven
patients could be weaned successfully from ECMO support and survived the
disease. Two patients died due to intestinal ischemia with severe
sepsis. Median age at implant was 59 years (46-69). Patient
characteristics are listed in Table 1. All patients were healthy prior
to the COVID-19 infection, with only minor comorbidities. An association
with previously known diabetes, obesity or pre-existing respiratory
diseases (asthma) was found particularly often.
ECMO therapy is a well establish procedure in the USZ and numbers are
increasing. With around 150 ECMO implantations per year, our center runs
one of the leading national ECMO-programmes also focusing on
interhospital transport of patients on ECMO support over the past 10
years [15]. Within the last 6 years, we performed 165 ECMO
transports and covered a distance of 22,000 kilometers during these
missions.
High quality standards are guaranteed and checked by a regular training
and certification program. For this purpose, we developed a simulator on
which the operative/percutaneous vascular access and cannulation can be
replicated with the original material (Figure 1). The already
established infrastructure and team approach, including cardiac surgery,
cardiology, anesthesiology and intensive care medicine, perfusionists,
critical care and scrub nurses has created a solid foundation for the
successful implementation of an ECMO program in the critical field of
this global crisis. Previous studies during the Middle Eastern
respiratory syndrome (MERS) and H1N1 outbreak report lower mortality and
reduced organ failure when ECMO was offered to those, who failed optimal
ventilation strategies, compared to the non-ECMO group [24, 25]. The
WHO interim guidelines made general recommendations for treatment of
ARDS in COVID-19 patients, including referring patients with refractory
hypoxemia to expert centers capable of providing ECMO therapy. V-V ECMO
can provide respiratory support in critically ill patients and minimize
ventilator-induced lung injury, barotrauma and oxygen toxicity.
As patient selection is crucial, and key to success, we implemented an
ECMO Evaluation sheet, recording age, height and weight, comorbidities,
length of oro-tracheal intubation and actual ventilation parameters,
hemodynamics including catecholamine use and infection parameters, in
our daily routine. We used the PRESERVE-Score, Murray-Score and
Horowitz-Index to assess the indication and expected outcome. In-house
indications and contraindications for ECMO in COVID-19 patients, based
on the ELSO recommendations, were established and interdisciplinary
discussed before each implantation. The Cardiohelp System (Maquet,
Getinge AB, Rastatt, Germany) in combination with an HLS 7.0 oxygenator
was used routinely in all patients. For V-V ECMO support we used a
femoro-jugular approach (Figure 2). Cannulation was performed bedside in
the ICU, using ultrasound-guided femoral/jugular vein/artery puncture.
Cannula placement was guided using transesophageal echocardiography
(TEE) whenever possible. Avoidance of patient transports to the
operating room reduces the risk of COVID-19 transmission to other
patients and healthcare providers as well as environmental
contamination. For V-V ECMO implantation in COVID-19 patients, we do not
recommend the dual lumen cannula, as the implantation and positioning
may be challenging and time-consuming, furthermore assuring proper
cannula position while proning the patient is highly demanding. ECMO
patients should be anticoagulated using regular heparin. As we
experienced a prothrombotic state our COVID-19 patients, we kept target
activated clotting time (ACT) between 180-200 seconds. Heparin-induced
thrombocytopenia should be monitored and treated early. In addition to
the reckoned personnel and logistical effort, ECMO centers also face
additional challenges in terms of employee protection and safe patient
transportation during the COVID pandemic. The standard personal
protection equipment (PPE) guidance by Public Health England (PHE) for
healthcare workers involved in care of patients with COVID-19, include a
disposable apron, gloves, surgical mask and eye protection [26]
(Figure 3). During ECMO implantation and explantation in the ICU, the
whole team is working in a high-risk environment. Especially during TEE,
which is used for wire and cannula placement, there is an increased risk
of aerosol release. Therefore, it is recommended to wear a protective
respirator mask (N99 or FFP3 equivalent, which can be either valved or
unvalved) during these procedures. As the standard of PPE may vary
between different hospitals, we have put together a compact PPE kit for
the protection of our team, which is also used for external applications
(Figure 4).