Recent improvements in extracorporeal life support (ECLS) technology have expanded its use in adults.1 Patients with acute cardiac failure can be stabilized with venoarterial extracorporeal membrane oxygenation (VA ECMO) and transported on ECMO to a tertiary referral center for implantation of a ventricular assist device in preparation for heart transplant or as a bridge to recovery. Similarly, patients with respiratory failure refractory to mechanical ventilatory support can be bridged to recovery with ECMO if they can be transported to a center with expertise in managing such patients.2 Without mechanical support, these patients would be too unstable to transport.
Although in select situations ECMO can be life saving, it requires expertise and resources that are limited to highly specialized centers. The possibility of transporting patients on ECMO, however, allows the resources and expertise at a tertiary referral center to be made available to patients in surrounding hospital systems and consolidates the management of these challenging patients.
Mechanical device assistance in the pediatric population is well established, and transportation of pediatric patients on ECMO has been shown to be safe.3,4 However, few centers in the world have significant experience with transporting adult ECMO patients.2,5 One of the largest studies in the United States reported 68 adult patients transported on ECMO over 10 years, ending in 1999. Foley et al.6 showed a 60% adult survival rate to discharge and an overall 17% complication rate. Since its publication, significant advances have been made in ECLS technology—new centrifugal pumps, oxygenators, and cannulae that may decrease the number of adverse events during transport. As ECMO systems continue to improve, it will be easier to cannulate patients at remote sites and transport them on ECMO to regional centers.
Our institution has experienced an increased number of ECMO consultations from neighboring hospitals. This may be attributable to the increasing awareness of ECMO's efficacy in the treatment of select patients with acute respiratory distress syndrome (ARDS) and ECMO's ability to act as a bridge to decision in patients with cardiogenic shock. We report our experience of transporting critically ill patients on ECMO using the newest available technology including a streamlined circuit.
This study, which was approved by the Columbia University Medical Center Institutional Review Board, is a retrospective review of a single institution's experience with transporting adult patients on ECMO from outside hospitals to our intensive care units (ICUs). Over a 2.5-year period ending in December 2010, 17 patients were placed on ECMO at an outside hospital and then transported back to our institution.
Physicians from various institutions directly consult our ECMO team, which consists of cardiothoracic surgeons and intensivists. Patients were considered if they had potentially reversible hypoxemic or hypercapnic respiratory failure or respiratory failure that could be bridged to lung transplantation assuming they were already listed for transplantation at our center.7 Specific inclusion and exclusion criteria were considered for patients with respiratory failure (Table 1). Patients in cardiogenic shock refractory to maximal medical therapy and/or intraaortic balloon pump were also considered for transport on VA ECMO.
Once the decision to accept the patient was made, the ECMO transport team (surgeon, perfusionist, and critical care paramedics) was mobilized. All referring hospitals were within 1.5 hours driving range, so the mode of transport was exclusively by ambulance.
All patients were expected to have an arterial line and central venous catheter. These were inserted by the ECMO team, if not available. Sedation was standardized to narcotics and benzodiazepines, and a single dose of paralytics was administered for the transport.
Typically, the right internal jugular vein was accessed using a Seldinger technique, and the cannula was advanced under image guidance. Our preferred cannula was the Avalon Elite Bicaval Dual Lumen catheter (Avalon Laboratories, LLC, Rancho Domingez, CA), which afforded the benefit of single-site cannulation. Dual lumen catheter placement was confirmed by fluoroscopy or transesophageal echocardiogram.8
If single-site venovenous (VV) ECMO was not available or technically prohibited, then a conventional dual-site VV ECMO technique was used. In this case, the internal jugular was cannulated with an EOPA cannula (Medtronic, Brooklyn Park, MN), and the femoral vein was cannulated with a Biomedicus cannula (Medtronic). For primary cardiogenic failure, patients were placed on VA ECMO from the outset along with an antegrade perfusion catheter in the distal superficial femoral artery (Figure 1).
A streamlined “mini” configuration was used for the transport of ECMO circuit (Figure 2). This included a Jostra Quadrox D oxygenator (Maquet Inc., Rastatt, Germany) and a centrifugal pump. The pump was either a Jostra Rotaflow (Maquet Inc.) or a Levitronix Centrimag (Levitronix, GmbH, Zurich, Switzerland).
Before departing to the outside hospital and boarding the ambulance, a report was provided to the receiving ICU staff. All lines and medications were rechecked before departure. Upon arrival at our institution, patients were taken to our ICU. They were transitioned to a conventional ECMO circuit, and the heat exchanger was connected. The patients were managed by the ECMO team according to lung protective ventilation strategies or “rest” settings (tidal volume 3 ± 0.5 ml/kg; respiratory rate 6 ± 2 breaths/min; and fraction of inspired oxygen 0.4 ± 0.1).9 A low-dose heparin regimen was used for anticoagulation. This regimen consisted of a 3,000-unit bolus at the time of cannulation followed by a heparin drip titrated to an activated partial thromboplastin time of 40–70 seconds. With the goal of minimizing the number of transfusions and their numerous associated risks including further lung injury, a conservative transfusion protocol was also in place.10,11 Patients were only transfused for a hemoglobin count less than 7 g/dl unless they had refractory hypoxemia in which case the transfusion threshold was increased to 10 g/dl. These established protocols for ventilator management, anticoagulation, and transfusion are used in all ECMO patients in our institution.12
Before decannulation, the blood in the device was auto-transfused back into the patient with a normal saline flush. Decannulation was done at the bedside. Manual pressure was held for 30 minutes after decannulating 23 or 27 French catheters. For the 31 French catheter, a deep suture was placed to reinforce the subcutaneous tissue and pressure was held for 30 minutes.8 Decisions regarding decannulation were made by the surgeon and the intensivist.
Survival was defined as time from initiation of ECMO to death or last follow-up through March 2011. Survival estimates and statistical comparisons were calculated using Stata/IC 11.0 (Stata Corporation, College Station, TX).
All 17 patients (mean age 38.4 ± 15 years) were successfully placed on ECMO and safely transported to our institution. There were 15 patients with respiratory failure refractory to mechanical ventilation (Table 2). The etiology for the respiratory failure did not influence selection. There were two instances of diffuse alveolar hemorrhage (DAH) requiring ECMO. One patient with underlying pulmonary arterial hypertension had an acute vasculitis flare and developed DAH in the setting of a high international normalized ratio (INR) (5.90). She required VA ECMO for combined cardiopulmonary failure. The other patient had multiple cosmetic procedures involving subcutaneous silicone injections that were complicated by silicone embolism syndrome, which progressed to DAH. This patient was supported on VV ECMO. The median PaO2:FiO2 ratio for the 15 patients with hypoxemic respiratory failure was 0.54 (interquartile range 0.51–0.61).
Two patients had isolated cardiogenic shock requiring VA ECMO (Table 2). One day after arrival to our institution, both patients maintained a clear chest x-ray and demonstrated good lung compliance. They were both transitioned to biventricular assist devices (BiVADs), each using two Levitronix Centrimag pumps as a right and left ventricular assist device combination. One of these two patients expired with the BiVAD in place, whereas the other had a long-term left ventricular assist device inserted. This patient survived and was discharged to a rehabilitation facility.
Twelve of the 14 VV ECMO patients were cannulated via a single-site VV ECMO technique using a bicaval dual-lumen catheter in the right internal jugular vein. The remaining two patients required a conventional dual-site VV ECMO approach as described earlier. Three patients in total required VA ECMO via a femoral cannulation along with a distal superficial femoral artery perfusion catheter.
The majority of the patients in this study quickly developed respiratory failure that progressed to ARDS. The median days of ventilator support before initiation of ECMO were 2 days (interquartile range 1–5 days). The median duration of ECMO support was 8 days (interquartile range 4–11 days). Thirteen patients (76%) were successfully decannulated. Two-sided Fisher's exact testing revealed a significant association between decannulation rates and a duration of mechanical ventilatory support before ECMO of 1 week or less (p = 0.03). Subsequently, 10 of the 13 patients (77%) who were decannulated were also weaned from mechanical ventilation. The overall extubation rate was 59% (n = 10). The overall survival and discharge rates were 53% (n = 9) (Table 3). The survival rate among patients who had prolonged intubation (greater than 7 days before initiation of ECMO) was 25%. This compares to 62% survival rate for patients with less than 7 days of ventilator support before ECMO. Among patients with multiple pre-ECMO comorbidities (n = 7), the survival rate was 28%.
When only the subgroup of VV ECMO patients (n = 14) were included in the survival analysis, the results changed slightly. The median duration of ECMO support was 10 days (interquartile range 7–12 days). Ten patients (71%) were successfully decannulated. Eight patients (57%) were extubated and survived to discharge. The causes of death for the patients on VV ECMO included multisystem organ failure (n = 4), sepsis (n = 1), and acute cardiac arrest (n = 1). With the exception of two patients, all the other patients in this subgroup expired while on the ECMO circuit. One patient died from sepsis after decannulation. The other patient was unsuccessfully bridged to lung transplant and died from multisystem organ failure after being weaned from ECMO.
When the three VA patients were evaluated separately, the duration of VA ECMO was 2.3 days, with a 67% (n = 2) extubation rate and a 33% (n = 1) survival and discharge rate. The causes of death were multisystem organ failure (n = 1) after decannulation and extubation, and acute cardiac arrest (n = 1) after decannulation from ECMO.
The median ICU to ICU transport time was 60 minutes (interquartile range 50–92 minutes), and the median distance traveled was 23 miles (interquartile range 17–55 miles). There were no complications directly related to cannulation or the transfer process. Specifically, there were no instances of power failure or ECMO-circuit failure including malfunction of specific components such as the centrifugal pump, circuit tubing, cannula, or oxygenator. The simplified circuit facilitated transport (Figure 2). Both the Rotaflow and CentriMag centrifugal pumps seemed to be equally effective.
The adult ECMO program at Columbia University Medical Center has developed a regional transport ECMO network with referring hospitals. The purpose of this study was to review a model for a regional ECMO center and establish reproducible safety standards for successfully placing a patient on ECMO at one institution, and transporting the patients on ECLS to a referral center. Compared with previous reports on transporting adult patients on ECMO, we achieved similar survival rates, but the advances in technology allowed for a decrease in transportation- and circuit-related complications.6
On the basis of our experience, we believe that regional ECMO centers can be an asset to neighboring community hospitals by consolidating expertise and providing complex support systems. Critically ill patients with severe refractory ARDS or cardiogenic shock can be safely transported on ECMO to specialized referral centers. ECMO offers a bridge to recovery, a bridge to transplant, or a bridge to decision regarding alternative mechanical circulatory support systems, such as ventricular assist devices.
Prompt evaluation through early consultation will lead to the earlier initiation of ECMO for ARDS-related transports and will likely improve outcomes. Our data are consistent with prior studies that suggest there is a benefit to early decision making regarding the use of ECLS.13,14 Patients with acute, reversible processes are those best served by mechanical circulatory support. On the basis of our experience, patients with ARDS and multiple comorbidities (>3) including chronic renal failure and cardiac disease may not benefit from transport ECMO.
Despite a relatively high number of patients transported on ECMO over a 2.5-year period, the small sample size was a clear limitation and impeded statistical analysis. Although this study was insufficiently powered for statistical significance, the trends were suggestive.
Further development of regional ECMO centers with associated networks of ICUs at neighboring hospitals will facilitate the early identification of patients who can benefit from transport ECMO. Standardized protocols will improve outcomes and ensure optimal utilization of resources.
Transport ECMO is a resource-intensive process. Optimizing results by establishing well-designed protocols including careful patient selection criteria and developing specialized ECMO teams will ensure appropriate access to and utilization of a potentially life-saving resource. This approach provides a safe and effective method of using current technology to transport patients on ECMO.
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