The process of ECMO retrieval is illustrated in Fig. 1. Predominantly, we offer primary transports for adults, which means that the mobile team performs ECMO cannulation at the referring institution and then accompanies the patient to our center. When needed, we also conduct secondary and tertiary transport for adults as defined by ELSO [16].

Fig. 1

ECMO retrieval decision tree

Request and evaluation

Referring institutions may be ICUs, emergency departments and intermediate care units; however, emergency transport companies may also request evaluation for ECMO retrieval. Contact details as well as basic information about the program are published online (https://www.muv.ac.at/13i2). Requests are usually received by telephone. Each case is discussed individually in a conversation between the attending senior physician at ICU 13i2 and the treating physician at the referring institution. We regard the use of our adapted patient checklist based on our own evaluation sheet [17] as mandatory (see Fig. 2a, b) to meet our demands for both evaluation and documentation standards.

Fig. 2

a Patient checklist page 1. b Patient checklist page 2

DOB date of birth, ICU intensive care unit, FiO2 fraction of inspired oxygen, Pplat/insp Plateau/inspiratory pressure, PEEP positive end-exspiratory pressure, VT tidal volume, AF respiratory rate, NMBA neuromuscular blocking agents, PaO2 arterial oxygen partial pressure, PaCO2 arterial carbondioxide partial pressure, SaO2 arterial oxygen saturation, NO nitric oxide, PLT platelets, aPTT activated partial thromboplastin time, PTZ prothrombin time, FBG fibrinogen, Hb hemoglobin, LVF left ventricular function, RVF right ventricular function, AR aortic regurgitation, incl. including, vasc. vascular, CVC central venous catheter, CXR chest X-ray, CT computed tomography, yrs years, w/o without, alloPBSCT allogeneic peripheral blood stem cell transplantation, yr year, NYHA New York Heart Association, COPD chronic obstructive pulmonary disease, CPR cardiopulmonary resuscitation, ECMO extracorporeal membrane oxygenation, Y yes, N no, V version.

Candidacy for ECMO treatment and ECMO retrieval are assessed separately.

Indications for ECMO

We primarily consider patients for respiratory ECMO including the subcategory of extracorporeal CO2 removal. The evaluation of respiratory ECMO indication itself adheres to our standard in-house principles complying with the ELSO Patient Care Practice Guidelines [18,19,20] and the European Society of Intensive Care Medicine (ESICM) guidelines [21] summarily shown in Table 1. We also assess patients for cardiac ECMO following the respective VA ECMO guidelines [4, 18, 19, 22]; however, except for unforeseen emergency situations, retrieval options for VA ECMO patients remain a focus for future development. For the final rule-in we always take definite decisions on an individual patient-centered basis. When the ECMO indication is borderline, the attending senior physician involves peer experts to discuss the case. In patients eligible for bridging strategies such as to organ transplantation, we involve the cardiac or thoracic surgeon on call into the decision-making process.

Table 1 Indications for VV ECMO in adult patients according to ELSO guidelines [20] and ESICM guidelines [21]. Both presume potential reversibility of respiratory failure and optimal conservative managementIndications for ECMO retrieval

The paramount goal remains to assess the patient as early as possible and, if feasible, to offer a safe center admission without antecedent intervention by a mobile ECMO team. The ECMO retrieval is generally considered when the risk of a conventional transport is deemed unacceptable. The candidacy for retrieval is impacted by clinical factors, transport-related circumstances and the critical appraisal of all clinicians involved. We regard states of circulatory and/or respiratory instability, no transport option without ECMO, and rapid deterioration as rule-in criteria. Among others, this may be the case in severe gas exchange disorders, such as a Horovitz index of < 50 mm Hg despite optimal conservative management, pre-cardiac arrest situations or antecedent cardiopulmonary resuscitation (CPR) due to the underlying condition, need to reposition the patient from prone to supine position for transport although thereby provoking imminent instability, transport denial by an emergency medical physician, high vasopressor doses or hyperlactatemia. Also, we reflect the degree of pretransport hypoxemia, hypoperfusion, and acidosis on the expected duration of transport to anticipate the risk of further deterioration arising from the transport duration itself; however, the consensus of the entire teams at the referring institution, the mobile ECMO team and the ICU team remaining in-house are a sine qua non for the conduction of an ECMO retrieval.

When potentially reversible pathologies such as untreated pneumothorax are contributing to the patient’s condition, the retrieval is delayed, and the candidacy is re-evaluated after the cause has been addressed.

Currently, we do not routinely launch to patients in cardiac arrest to perform eCPR; however, when time from conventional CPR start to the expected time of our team’s arrival is below 30 min, and eCPR criteria are met, we continue our retrieval process with the aim of emergency VA cannulation. This may particularly be the case in patients already accepted for retrieval, who develop cardiac arrest during our approach. In these cases, we adhere to our in-house emergency department’s recommendations [22].

Principally, we also extend our portfolio to scenarios which may necessitate the change of an already running ECMO circuit or a modification in cannula configuration prior to the transport.

Resource management

Upon acceptance for ECMO retrieval and reassurance of the available target bed, we assess our own unit’s staff resources for ECMO retrieval which includes considerations for both the outreach team and the ICU team remaining in-house. The latter must be able to meet the clinical demands even when unexpected events occur during the absence of the retrieval team. To provide retrieval availability even during peak times or personnel shortages, we expanded our capabilities for ECMO retrievals with a pool of ICU nursing staff. This initiative allows us to mostly guarantee the participation of at least one nurse capable of managing both intensive care nursing and ECMO management.

When ECMO retrieval cannot be offered due to any reason, the hazards of a primary transport to our center without antecedent ECMO implementation will be taken after careful consideration.

Preparation

After a positive decision to retrieve the patient, the preparation phase ensures that 1) the mobile ECMO team is assembled and informed, 2) equipment is packed and checked, 3) transport for both team approach and ICU transfer is organized and 4) the referring institution is briefed.

Team assembly

The assembly of the retrieval team is done by the ECMO team leader in collaboration with either the 13i2 head of nursing, if present, or with the most experienced ECMO nurse in charge.

The team composition is flexible depending on personnel resources and transport factors. It allows four different versions when a ground-based approach is conducted (see Fig. 3). For an air-bound transport, team compilation is adapted to the air ambulance operator’s individual specifications. The option with one physician only necessitates the availability of medical capacities at the referring institution (at least one physician or nurse for sterile guided assistance during cannulation), which is ascertained during the telephone conversation. The same requirement applies when no ECMO nurse is available for transport.

Fig. 3

Mobile ECMO team versions dependent on staffing. Asterisk Can be the cannulation provider

Self-protection by means of personal protective equipment according to our institution’s hygiene standards and reflective vests for the interhospital period is provided.

Packing procedure

Our transport equipment is mainly prepacked and located in the ICU. The remaining items are individually added. The ECMO-specific sterile goods are enclosed in duplicate. We include a versatile handheld ultrasound device as a back-up. For retrieval purposes, Cardiohelp® (Maquet, Getinge Group, Rastatt, Germany) consoles are used comprising sensors for real-time pressure and blood measurements. Alternatively, we use Xenios (Xenios AG, Heilbronn, Germany) devices. We prefer the transport of ready primed ECMO circuits to the patient to keep preparation time at the referring institution as short as possible. Depending on the travelling distance, patient-related factors and weather conditions, an ECMO heat exchange device is added.

Transport

When a ground-based approach is performed, equipment and ECMO team are transported to the referring hospital by a designated emergency team transport vehicle of the Johanniter. It is exclusively available for medical and equipment transfers on a 24/7 basis. Each vehicle provides seats for five team members plus driver and a 220 V power supply. The Johanniter emergency coordination center uses a specified transport code for ECMO retrieval purposes ensuring correct dispatch of one of the dedicated vehicles regardless of the person answering the request. The air-bound approach is individually organized to meet all aeronautical and medical demands.

Before the mobile ECMO team launches, intensive care transport availability for the subsequent patient transfer is checked. For this purpose, we use a prioritized list including 10 organizations offering intensive care transfer capabilities (6 of which are land-based and 4 are air-bound). This list also includes the respective information about individual response time, place of departure, oxygen and air supply, 220 V power supply, solution for ECMO fixation and other specifics, such as seats available in the case of full attendance. Before the mobile team launches, the selected organization is prealerted and confirmation of transfer capacity is obtained. Ultimate alerting is done by the referring hospital subsequently to ECMO implantation.

Briefing of the referral institution

During the telephone conversation with the referring institution, information about the upcoming ECMO retrieval is provided. Subsequently, a 1-page preparation sheet is sent to the institution (Fig. 4). It serves as an information source containing key points about the upcoming retrieval and including specific preparation recommendations, such as ordering packed red blood cells at call or preparation of the ultrasound machine.

Fig. 4

Preparation sheet for the referral hospital

Conduction of the ECMO retrieval

After completion of the preparation process delineated above, a final team and equipment check is done together using the “Let’s-go” checklist shown in Table 2. Then, the mobile ECMO team launches.

Table 2 “Let’s-go” checklistApproach

As soon as the emergency team transport vehicle is heading for the referring hospital, information about the expected time of arrival is provided to the referring institution by telephone. This conversation is also used to exchange updates about the patient’s condition. All members of the mobile ECMO team are updated about the current situation and the patient’s condition including the most probable strategies for ECMO configuration, cannula implantation and alternative solutions for an unexpected deterioration as well as potential back-up capacities (e.g., local cardiac catheterization laboratory for additional guidewires).

Arrival

Upon arrival and introduction, the team splits: the ECMO team leader reviews the diagnostic findings together with the attending doctor of the referring institution to confirm the ECMO indications. Simultaneously, the ECMO assistant physician performs a preliminary echocardiography assessment to estimate cardiac function, volume status and valve function. This protocol also includes exploratory sonography of both pleural spaces and abdomen. Then, bilateral vascular sonography is performed of both groin and neck veins and arteries including diameter measurements. Also, simultaneously the ECMO circuit as well as the console are checked by the ECMO nurse and preparation of the cannulation is started. When the indications for ECMO and ECMO retrieval remain unchanged, all parties involved are informed and briefed. These steps may be shortened or partly omitted when the patient’s condition does not allow any time delay.

Cannulation

According to our idea of an optimal retrieval, the procedure for ECMO implantation itself should deviate as little as possible from the familiar protocols followed in-house; however, when placing ECMO in an unfamiliar environment with possible back-up limitations for complications, we aim for a maximum margin of safety (also see “Risk mitigation” section).

Once arrangements are completed, role allocation and chronological order of the steps are fixed and communicated. Cannulation is done using Seldinger’s technique under real-time sterile ultrasound guidance. We do not routinely provide surgical techniques such as cut down for cannulation under vision. Typically, we serially place the guidewires after ultrasound-guided puncture, followed by sonographic reassurance of the correct wire position. When the patient’s coagulation is within normal limits, heparin is given as a bolus of 50 IU/kg bodyweight at the earliest when both cannulas are in place. Further reassurance of the correct cannula positions may be obtained by means of blood gas analysis at any time point or after circuit connection by opening all clamps prior to blood flow application to detect unexpected backflow due to cannula displacement; however, as mentioned previously, the detailed methods of operation are subject to the personal experience of the cannulation providers and should follow their habitual style as close as possible.

We routinely start ECMO with an initial blood flow of 1 lpm and a sweep gas flow of 1 Lpm for the first minute, unless the patient’s condition requires an instant increase of blood flow. We determine optimal settings primarily using monitoring of the vital parameters, arterial and venous blood gas analysis (BGA), end-tidal CO2 (etCO2), echocardiography as well as clinical judgement.

The preparation for departure begins with ECMO start. The first section of the “back-to-base” checklist ensures that all necessary actions are taken immediately after ECMO start (Table 3).

Table 3 “Back-to-base” checklistDeparture and interhospital transfer

The interhospital transfer vehicle is alerted according to the previously arranged workflow.

During another telephone call with the destination ICU, the expected time of arrival is announced and both the necessity and possibility of a diagnostic stopover such as for a contrast-enhanced computed tomography (CT) are discussed and arranged when appropriate.

Once the patient is on the stretcher and prepared for departure, the second section of our “back-to-base” checklist (Table 3) ensures that our transport prerequisites are met. Usually, the ECMO team leader and the ECMO nurse accompany the patient inside the interhospital transfer vehicle together with at least one paramedic. The emergency team transport vehicle transports the remaining team members and the equipment not in use. It follows in convoy or travels individually when air-bound transfer is conducted.

Completion

After arrival and handover procedure, the retrieval is finalized with the completion of the documentation and a team debriefing. Equipment is restocked and prepared for the next transport. Short-term and long-term feedback possibilities are offered for all parties involved.