Given the patient population selected for transport, there is a high risk for complications and clinical decompensation. While ECMO provides a safety net for transport of selected critically ill patients, the same complications that are prevalent in the hospital environment must be considered for transport, in addition to the inherent risks of the transport itself [19, 20].

When planning for an ECMO transport to include considerations of the potential complications, the mission is divided into four phases of transport: (1) patient selection, (2) pre-transport, (3) patient packaging, and (4) transport. Each phase of the mission carries unique challenges. Successful transport requires planning, anticipation, and risk mitigation.

During the patient selection phase, it is paramount to clearly establish patient history, disease transmission risk, clinical course, and active medical conditions. Pertinent medical history is crucial to mitigate transport risk, which include current medications, time of administration, need for vasopressors, hemodynamic stability, bleeding complications, and history of pneumothorax. As transport times may vary from hours to days, it is paramount that plans ensure no transport-related delays in care. Routine (yet critical) treatments, such as antibiotic administration, must be continued uninterrupted to prevent worsening of underlying clinical conditions during transport and avoid any unexpected delays. The BAMC referral flyer and referring hospital guidance is included as Fig. 3 and the intake form is included as Fig. 4.

ECMO referral and guidance

ECMO transport intake form

Transport teams typically carry standard critical care medications, to include vasopressors, but the transport stock supply is usually relatively limited. During the planning phase, knowing whether the patient requires vasoactive medications may help determine the appropriate mode of transport, the appropriate ECMO modality (veno-venous vs veno-arterial), and help with medication planning. When the medications are known ahead of time (especially vasopressors, sedation, and antibiotics), it should be requested that the sending facility provide all the anticipated medications to ensure timely administration and that there is an adequate supply for the entirety of the mission. Estimated medication needs based on mission duration follow the principles of the USAF Critical Care Air Transport team practices of ensuring 24–72 h of medications depending on the estimated flight time.

During the patient selection phase, it is critical to understand the patient’s risk of common transport-related complications. Bleeding is the most common complication encountered with ECMO cannulation, so awareness of the patient’s hemoglobin, platelets, coagulation profile, and anticoagulation status will help guide decisions to mitigate bleeding risk [19]. As there is no monitoring or testing of coagulopathy in the en route environment, it is critical for the team to assess and treat as necessary prior to transport and prioritize repeat testing upon arrival at destination facility. Per our institutional policy for ECMO transports, regardless of the patient’s condition, we request that all referring facilities prepare (on standby) four units of packet red blood cells for cannulation; if unused, the transport team brings them with the patient. If a concern for major bleeding exists, additional blood products may also be requested. Lastly, it is important to always review chest imaging prior to transport for endotracheal tube position and presence of a pneumothorax. Asymptomatic, small, undrained pneumothoraces may rapidly become significant during transport, particularly with air transport due to the partial pressure changes. In general, regardless of perceived resolution of pneumothorax, established chest tubes should remain in place during transport, and chest tubes are usually placed when an undrained pneumothorax is identified.

Prior to transport, several factors must be considered including local vs destination weather, crew rest status, availability of aircraft or mode of transportation, and equipment status. Weather conditions can have a major impact on transport mode and timing. There should be no delay in ECMO support once the team has arrived to the patient. Cannulation should be performed and ECMO support started as soon as possible. The team must have a formulated plan to support direct care of the ECMO patient for 24–48 h in place if return transport is delayed. Using a shift rotation of those qualified to manage an ECMO patient is crucial. This allows for constant supervision while allowing the team adequate rest periods.

To ensure that the appropriate equipment is available and functioning prior to travel, pre-transport checklists are used to lessen the cognitive burden. Checklists are necessary, especially during times of high operational tempo, to ensure functioning IV pumps, available backup ECMO circuits, and adequate cannulation supplies. Additionally, personnel rosters may ensure adequate crew rest and prevent ill-prepared teams [21]. The equipment and supplies are inventoried and replaced and/or replenished immediately after each transport. A second set of equipment and supplies is always available in case of concurrent or immediately consecutive transports. The assigned ECMO nurse specialists and transport coordinator are responsible for performing these inventories utilizing the checklist.

BAMC provides military-related support for worldwide ECMO evacuation, including austere settings; therefore, it becomes critically important to understand the patient’s local environment to help the team anticipate space and resource limitations. The majority of the ECMO cannulations from our institution occur in hospitals within the USA, where resources are typically plentiful; during the COVID-19 surge, however, even US hospitals faced space, medication, and blood product limitations that impacted ECMO retrieval activities. In our experience, several cannulations were performed in makeshift hospital rooms that were previously dialysis units, human resource offices, or converted PACUs. Atypical cannulation settings pose risks for patient monitoring and infection control, and may limit team activities due to space constraints. Understanding the treatment area prior to arrival allowed teams to bring additional supplies and request changes to patients’ location to ensure safe cannulation and packaging.

Although there is often a rush to rapidly place the patient on ECMO soon after team arrival, once support is established the priority should be ensuring safe patient packaging for transport. There is a standard load plan for transport by aircraft, which includes patient headfirst in the aft right of the aircraft. Knowing this configuration determines the positioning of the monitors, IV pumps, ECMO pump, and other equipment for easy accessibility from the patient’s left side. Conveniently, this positioning works for the ambulances too, as patient’s on ground transports are loaded headfirst with the personnel bench to the patient’s left side.

During the patient packaging phase, teams must pay close attention to patient position, patient restraint, sedation, and securing all tubes and lines. Prior to movement the patient must generally be deeply sedated and/or paralyzed to minimize the risk of pain and movement during transport, which could result in inadvertent tube and line dislodgement. All ventilator tubing connections should be reinforced to prevent inadvertent disconnection. Adequate venous access, including central venous access, should be obtained prior to movement. Central venous lines and arterial lines should be secured with sutures, and IV tubing should be organized to prevent snagging during transport. Chest drains, if present, must be assessed for drainage volume and the presence of an air leak; chest drain collection devices should be replaced prior to departure if full or nearly full. Naso- and/or oro-gastric tubes and Foley catheters must also be secured appropriately. Lastly, monitors and IV access sites must be functioning and easily accessible at all times to allow continuous assessment and rapid treatment as necessary [21].

Our team has found that a percutaneous access with 2 single-lumen cannulas in the femoral-femoral configuration for either VV- or VA-ECMO is the safest transport cannula configuration for a variety of reasons: (a) ease of securement, (b) positioning of the ECMO pump between the patient’s legs, and (c) lower risk of cannula movement/dislodgement compared to a configuration that involves the internal jugular (IJ) vein. Bilateral femoral cannulas create an area on the thighs where sutures and additional securement devices and be placed and accessed easily. Having the drainage and return tubing close to the pump (as the pump is usually placed between the patient legs for transport) reduces the possibility of tubes pulling or snagging while in transport. It is more difficult to secure an IJ return cannula when the tubing is over the patients head. The risk of dislodgement may be increased. Although rarely used, the ECMO team is equipped with dual-lumen cannulas should patient circumstances require a dual-lumen cannulation strategy.

The transport phase is the most dangerous period of time, but appropriate planning reduces the risk of complications and poor outcomes. Several important transport-specific considerations include ensuring adequate oxygen supply for all phases of transport, and preparing for the various unique environmental stresses of movement and flight. When transporting a patient, oxygen supplies must be adequate to cover movement to the ambulance or ground transport time to the aircraft. These oxygen requirements should be calculated based on the patient’s oxygen requirement, oxygen supply canister/machine/source, and the duration of time that oxygen is needed during transport. Additional oxygen beyond calculated requirement should be determined by each team on a case-by-case basis based on patient and transport characteristics. In contrast to standard critical care transports with a ventilated patient, an additional oxygen tank is required to for ECMO transports for the ECMO blender. Ensuring a full and back-up oxygen supply that accounts for transport time will avoid a potentially catastrophic situation. If fixed wing transport is required, knowing the type of aircraft ahead of time is critical as certain military airframes like the C-130 do not have an integrated oxygen supply whereas C-17 s include this capability. Depending on the mode of transport, power sources should be established to ensure adequate voltage, current, and wattage for connections to all electrical equipment for the duration of the transport.

Other environmental factors must be accounted for during the transport phase. Vibration from ground and/or air travel may worsen patient pain and discomfort. To mitigate these factors, additional care must be taken to ensure that the patient is appropriately padded, secured, and provided with adequate levels of analgesia and sedation. Patients must also be protected from the extreme temperature changes. Patients will be exposed to ambient air when moving to and from the hospital to the transport vehicle; furthermore, temperature control may not be possible during flight. Invasive temperature monitoring is mandatory as is ensuring the patient is adequately covered with blankets when appropriate. Additionally, during flight patients must be provided appropriate hearing protection. Lastly, the standard cabin altitude for a fixed wing aircraft is around 8000 feet; at this cabin altitude gas expands nearly 35% when compared to sea level, so trapped air (i.e., pneumothoraces, pneumomediastium, and gastrointestinal tract gas) may rapidly become clinically significant [19]. This reinforces the fact that in all phases of care the transport team must ensure appropriately functioning chest tubes (if present), drains, and gastric decompression. It is also standard protocol to assess the endotracheal tube cuff pressure prior to departure, at altitude, and after landing with a specific pressure goal of 20–30 mmHg per cuff manometer.

The most common complications during ECMO transports include bleeding, hypotension, tube/line dislodgement, and equipment failure [19,20,21]. Ensuring adequate blood and resuscitation product availability during transport is paramount. Also, coagulation studies generally cannot be monitored on long fixed wing transports so decisions to not titrate, to decrease, or even to stop full-dose anticoagulation must be considered. Appropriate planning, comprehensive knowledge of the individual patient’s medical condition, ensuring adequate supply of medications and blood, functioning equipment, and anticipating the environmental stresses of transport will reduce the risk of complications associated with ECMO transport.