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Ambulatory Extracorporeal Membrane Oxygenation

      Introduction

      The rationale for ambulatory extracorporeal membrane oxygenation (ECMO) is simple:
      • (1)
        Upright patients who are ambulatory and socially interactive provide the most effective vehicle for clinical recovery or subsequent bridge to transplant.
      • (2)
        No lung disease or pulmonary injury benefits from paralysis, sedation, and intubation with nonphysiological positive pressure ventilation.
      The objective data for these simple observations are well established and include the traditional morbidities of ventilator-associated pneumonias, barotrauma as a consequence of positive pressure ventilation, the requirements of sedation and paralytics to facilitate permissive hypercapnea as a strategy to limit barotrauma, and the profound deconditioning of both respiratory and skeletal muscle because of “ventilated, bed-bound” care.
      Although the use of ambulatory ECMO is an extension of traditional extracorporeal technologies, it is more “goal directed” and dynamic. The multiple cannulation strategies common to ambulatory ECMO are designed to facilitate an extubated and ambulatory patient. It is neither new nor novel and is analogous to the ventricular assist technologies common to patients with acute cardiogenic shock and congestive heart failure. Early deployment of technology to resuscitate the sick patient rather than reanimate the moribund is always the goal of extracorporeal support technologies. Nonetheless, the “peripheral” hybrid technologies of venovenoarterial ECMO and the application of “central” cannulation with “oxyRVADs” (right ventricular assist device with an in-line oxygenator) can salvage the sickest patients with medically refractory end-stage lung disease to ambulatory status.
      The following description of cannulation strategies is “goal directed” and “case specific.” Each is designed to support ambulatory patients with distinct clinical needs. Hypercapnea, hypoxia, or cardiopulmonary collapse as a consequence of cor pulmonale require different strategies of initial ECMO deployment. The described techniques are not exhaustive. Any cannulation strategy that delivers an adequate cardiac output with adequate gas exchange in an ambulatory patient is effective. Clinical need determines cannulation strategy. “Thought algorithms” regarding the application of ECMO—why are you doing this and what do you hope to accomplish—and the deployment of ECMO—how do we do it and when do we try—are useful in establishing conceptual ground rules for device deployment.

      Conclusions

      Although ECMO deployment is not technically difficult, many patients require multiple revisions of cannulation strategy to transition from mechanical ventilation to ambulation. A patient management algorithm is outlined here.
      • Hoopes C.
      • Gurley J.C.
      • Zwischenberger J.B.
      • et al.
      Mechanical support for pulmonary veno-occlusive disease: Combined atrial septostomy and venovenous extracorporeal membrane oxygenation.
      In brief, appropriate patients are stabilized on femoral venoarterial ECMO (25 Fr venous and 17 Fr aortic). All patients undergo open tracheostomy at the time of ECMO deployment. All sedation and vasopressor support is weaned and patients with significant neurologic deficits are removed from ECMO support. The “awake” patient without echocardiography (ECHO) criteria for compromised ventricular function undergoes “PECLA triage” (pumpless extracorporeal lung assist) with removal of the centrifugal pump and antegrade flow from the femoral arterial cannula to the right atrium via a long venous cannula using native cardiac output. Patients with stable hemodynamics are switched to double-lumen venovenous ECMO (Fig. 1) for ambulation. Patients with any hemodynamic concerns are deployed on hybrid venovenoarterial ECMO using the axillary approach (Fig. 2). Patients with moderate to severe pulmonary hypertension have double-lumen venovenous ECMO deployed with an associated atrial septostomy to preload the underfilled left ventricle with membrane oxygenated blood ( Figs. 3 and 4). Patients with RV failure due to end-stage lung disease undergo central cannulation w ith an “oxyRVAD” configuration as an ambulatory bridge to transplant (Figure 5, Figure 6). Patients with mixed end-stage heart and lun g disease are placed on “walking bypass” (Fig. 7).
      Figure thumbnail gr1
      Figure 1Percutaneous dual-lumen cannulation (DLC) for venovenous (VV) ECMO. The Avalon Elite Bi-Caval Dual Lumen Catheter (Maquet) is positional and requires interventional deployment with transesophageal echocardiography or fluoroscopy or both. Distinct venous inflow from both IVC and SVC and directional outflow across the tricuspid valve limit mixing of preoxygenator and postoxygenator blood and improve efficacy to facilitate ambulation. The cannula can be deployed via internal jugular or left subclavian veins. In patients with suprasystemic pulmonary artery pressures, combined DLC VV ECMO and atrial septostomy can provide hemodynamic support of the ambulatory patient without central cannulation.
      • Hoopes C.
      • Kukreja J.
      • Golden J.
      • et al.
      ECMO bridge to pulmonary transplant.
      We routinely use the 27-Fr dual-lumen venovenous cannula (adult cannula are 31 cm in length and vary in diameter from 20-31 Fr). Pediatric cannula (13-19 Fr) can provide effective extracorporeal carbon dioxide removal as an integrated tool with mechanical ventilation. IVC = inferior vena cava, SVC = superior vena cava.
      Figure thumbnail gr2
      Figure 2(A) “Hybrid” DLC VV ECMO with right axillary arterial return (venovenoarterial, VVA ECMO). The right axillary artery is exposed through a transverse incision. (B) An 8-mm Hemashield vascular graft (MAQUET Cardiovascular LLC, NJ) is sewn end to side to the axillary artery with a taper so as to orient the blood path retrograde into the innominate artery. No surgical bleeding is tolerated. The graft is tunneled subcutaneously to the skin. A 24 Fr RMI Edwards (Edwards Lifesciences LLC, CA) or Sarns Softflow 7-mm cannula (Terumo Cardiovascular Systems Corporation, MI) is placed within the Dacron graft and the tip of the inflow cannula is secured with ligatures 2 cm proximal to the axillary anastomosis . The skin is closed to prevent infection and an upper extremity sling can prevent bleeding complications associated with increased patient mobility. DLC = dual-lumen cannulation; VV = venovenous.
      Figure thumbnail gr3
      Figure 3“Partial bypass” walking ECMO. Venous drainage from percutaneous right IJ access via a 20 Fr EOPA CAP arterial cannula (Medtronic). Postoxygenator arterial inflow is via the right axillary approach as described in . Venous drainage limits full hemodynamic support but patients with mixed cardiopulmonary disease can effectively ambulate with 3-4 L/min of flow.
      Figure thumbnail gr4
      Figure 4“Pulmonary bypass.” A 10-mm Dacron outflow graft (Abiomed AB5000 cannula) is sewn to the main pulmonary artery distal to the pulmonary valve. An angled 28 Fr metal-tip cannula is placed within the left atrial appendage. The surgical approach is determined by clinical intent: median sternotomy for subsequent combined heart and lung transplant or “clamshell” anterior thoracotomies for subsequent bilateral lung transplant. Patients with acute cor pulmonale are initially stabilized with femoral VA ECMO and transitioned to VVA hybrid ECMO or VV ECMO with atrial septostomy. Central cannulation is reserved for patients inadequately supported by the percutaneous approach and actively listed for solid organ transplant. VA = venoarterial; VVA = venovenoarterial; VV = venovenous.
      In patients with suprasystemic pulmonary artery pressures and preserved RV function native right-sided cardiac output can deliver up to 3 L/min of flow across a Quadrox oxygenator in the absence of a centrifugal pump (pumpless extracorporeal lung assist; PECLA). This is our preferred approach in patients with cor pulmonale being bridged to transplant. If flows are insufficient, a centrifugal pump can be spliced into the circuit to provide adequate LV preload. RV = right ventricle; LV = left ventricle.
      Figure thumbnail gr5
      Figure 5The “oxyRVAD.” In patients with compromised RV function due to end-stage pulmonary disease, the “oxyRVAD” configuration provides full hemodynamic support with gas exchange to a “normal” left ventricle. A 28 Fr angled metal-tip catheter within the right atrium provides venous drainage, a 10-mm Dacron outflow graft (Abiomed AB5000 cannula) sewn with 4.0 prolene to the main pulmonary artery can deliver up to 5 L/min of right-sided cardiac output. RV = right ventricle.
      Figure thumbnail gr6
      Figure 6“Walking CPB.” In patients awaiting combined heart-lung transplant “walking cardiopulmonary bypass” can provide adequate hemodynamic support for ambulation. A 31-Fr catheter in the right atrium is required for venous drainage, a 15-mm Dacron outflow graft (Thoratec PVAD cannula) is sewn to the ascending aorta (4.0 prolene) for postoxygenator blood return. CPB, cardiopulmonary bypass.
      Figure thumbnail gr7
      Figure 7.Management algorithm for ambulatory ECMO.
      Ambulatory ECMO is labor intensive, and program development requires both a significant change in critical care culture and a significant investment in institutional resources. Institutional culture is the most significant predictor of effective ambulatory ECMO utilization and program sustainability.

      References

        • Hoopes C.
        • Gurley J.C.
        • Zwischenberger J.B.
        • et al.
        Mechanical support for pulmonary veno-occlusive disease: Combined atrial septostomy and venovenous extracorporeal membrane oxygenation.
        Semin Thorac Cardiovasc Surg. 2012; 24: 232-234
        • Hoopes C.
        • Kukreja J.
        • Golden J.
        • et al.
        ECMO bridge to pulmonary transplant.
        J Thorac Cardiovasc Surg. 2013; 145: 862-867