Extracorporeal Membrane Oxygenation (ECMO) for Refractory Cardiac Arrest.

AUDIENCE

Our target audience includes emergency medicine residents/physicians.

INTRODUCTION

Treating cardiac arrest is a common theme during simulated emergency medicine training; however, less time is focused on treating cases of cardiac arrest. There are varying definitions of refractory cardiac arrest, but it is most commonly defined as the inability to obtain return of spontaneous circulation (ROSC) after 10-30 minutes of appropriate cardiopulmonary resuscitation (CPR).1,2 More specifically, refractory ventricular fibrillation (VF) is defined as VF persisting despite 3 shocks, or the combination of 3 unsuccessful shocks plus amiodarone.1,3 Extracorporeal Membrane Oxygenation (ECMO) is becoming an increasingly utilized tool in the emergency department for severe cases of both pulmonary and cardiovascular pathology, and has been shown to be successful in cases of refractory cardiac arrest. Using ECMO in this scenario is known as Extracorporeal Cardiopulmonary Resuscitation (ECPR), referring to the emergent implementation of veno-arterial (VA) ECMO, and data have shown significantly improved neurologically-intact survival compared to routine CPR.3-7.

EDUCATIONAL OBJECTIVES

Our objectives go beyond the basics of advanced cardiac life support (ACLS), forcing the learner to think about alternative treatments for refractory cardiac arrest. By the end of this session, the learner should be able to:Recognize refractory cardiac arrest and realize when advanced management is required beyond the basics of ACLSRecite the indications/contraindications to ECMODifferentiate the physiology and clinical requirements between using venous-venous (VV) ECMO for respiratory failure, and using VA ECMO for cardiovascular failureIdentify the anatomical cannulation sites for VV vs VA ECMOPerform the procedural skills to cannulate for both VV and VA ECMO.

EDUCATIONAL METHODS

This simulation is flexible. We used a high-fidelity mannequin with the "Endo-Circuit" to practice cannulating for ECMO, but the learning objectives can still be achieved with a lower-fidelity mannequin and cannulation device. The "Endo-Circuit" is a novel, low-cost vascular model developed by Dr Tomoyuki Endo from Sendai, Japan to practice ECMO cannulation.8,9 Endo-Circuit: Author's own imageAlternatively, a lower-fidelity model can be utilized if the Endo-Circuit is not available. We recommend using clear silicone tubing, which can be found at your local hardware store. This tubing should be at least 12mm in internal-diameter to accommodate the large ECMO catheters. We cut the tubing into 6-inch pieces so they could easily be swapped out for multiple participants to practice cannulating, all in a cost-effective manner. Red and blue tape was applied to differentiate the artery from the vein. Low-fidelity tubing: Author's own imageWe split our educational session into different stages. The first stage included the high-fidelity mannequin without the Endo-Circuit because we did not want to reveal our ultimate goal of starting the patient on ECMO by having the tubing overlying the mannequin. Neither standard ACLS methods nor advanced medications for refractory cardiac arrest lead to achieving ROSC in this scenario. Stage 1 ends when the learners suggest starting the patient on ECMO and call the appropriate consultants. After a short debrief on stage 1, we then transition to a 2 mannequin that we had in the back of the room. This mannequin had the Endo-Circuit overlying, and everything was covered with a sheet, again so as not to reveal the goal of the simulation from the beginning. On this 2 mannequin, we practiced cannulating for VA ECMO in the setting of cardiac arrest. Below are photos of the ECMO cannulation kit, the cannulated Endo-Circuit, as well as the cannulated lower-fidelity silicone tubing. ECMO Cannulation Kit: Author's own image Cannulated Endo-Circuit: Author's own image Cannulated low-fidelity silicone tubing: Author's own image.

RESEARCH METHODS

The learners filled out a post-simulation survey, which included questions specifically focused on the educational objectives (as mentioned above). We used a 1-5 Likert scale ranging from strongly disagree (1) to strongly agree (5) to quantify how the residents' understanding of the learning objectives improved after the simulation. This survey also included questions taken directly from the Debriefing Assessment for Simulation in Healthcare (DASH), which is a validated evaluation tool developed by the Center for Medical Simulation (CMS) for evaluating the efficacy of the educational content.10 The DASH scoring system involves a 7-point scale ranging from extremely ineffective/detrimental (1) to extremely effective/outstanding (7).

RESULTS

Thirty-one resident-learners participated in the simulation, and we received 22 survey responses. All of the learning objectives obtained a mean score >4 out of 5, with the exception of improving the learners' differential diagnosis for refractory cardiac arrest, which received a mean score of 3.86. The most successful of the learning objectives was improving the learners' procedural skills for ECMO cannulation, which received a mean score of 4.68. The DASH questions also reflected the success of the simulation, with 3 of the 6 questions receiving a mean score >6 out of 7, and the other 3 questions receiving a score >5.

DISCUSSION

According to this data, the learners found the simulation to be effective in expanding their knowledge base and improving procedural skills for starting critically-ill patients in refractory cardiac arrest on ECMO. Practicing the cannulation procedure on the Endo-Circuit was shown to be the most useful aspect of this simulation. The DASH survey questions further demonstrate that our methods created an engaging, structured environment to identify knowledge gaps and simultaneously fill them using hands-on, active learning.

TOPICS

Extracorporeal membrane oxygenation, ECMO, cardiac arrest, refractory cardiac arrest, V fib, ventricular fibrillation, CPR, cardiopulmonary resuscitation, ECPR, extracorporeal cardiopulmonary resuscitation, ACLS, advanced cardiac life support, HOCM, hypertrophic obstructive cardiomyopathy, critical care, emergency medicine.