The Daily Dose • Monday, May 20, 2024

Reviving CPR: Innovations for Enhanced Cardiac Arrest Survival

Christian S. Guay, MD

Cardiac arrest presents a critical medical emergency where swift and effective interventions can mean the difference between life and death. Recent advancements in cardiopulmonary resuscitation (CPR) techniques offer promising avenues to optimize patient outcomes in these emergencies. The session, “Hot Topics in Cardio‐Cerebral Resuscitation ‐ From Adjunct Tools to eCPR,” cosponsored by SOCCA, examined these new strategies on Sunday, May 19 at the 2024 Annual Meeting, presented by IARS and SOCCA.

Matthias Riess, MD, PhD, FASA, a physician-scientist and professor in the department of anesthesiology and pharmacology at Vanderbilt University Medical Center, moderated this thought-provoking discussion.

Matthew Barajas, MD, assistant professor, department of anesthesiology at Vanderbilt University Medical Center, started by reviewing the fundamental physiology of CPR. He emphasized the crucial role of both compression and decompression phases of CPR. During compression, intrathoracic pressure increases and blood is pumped out of the left heart, enabling vital perfusion of coronary and carotid arteries. During decompression, intrathoracic pressure declines and blood returns to the heart. In addition to modulating intrathoracic pressure, the compression and decompression phases of CPR also increase and decrease intracranial pressure, respectively. Traditional manual CPR often fails to achieve complete decompression and adequate chest wall recoil, leading to inadequate preload, rising intracranial pressure, and reduced cerebral blood flow. To address these limitations, mechanical CPR systems like the LUCAS (Lund University Cardiopulmonary Assist System) have emerged as highly effective alternatives to manual CPR. The latest iteration, LUCAS 3, integrates a suction cup for active decompression, in addition to optimizing compression depth and recoil rates. Suction devices are also available to assist manual CPR. Complementary to active decompression, impedance threshold devices (ITDs) offer real-time feedback on decompression quality via intrathoracic pressure estimation. Combining decompression suction devices with ITDs in CPR has shown promising results in improving one-year survival rates after cardiac arrest, as demonstrated in the RESQ trial.

Building upon Dr. Barajas’ presentation, Johanna Moore, MD, MSc, an emergency physician at Hennepin County Medical Center, and associate professor of emergency medicine at the University of Minnesota, introduced “head-up CPR,” which integrates one additional innovation to the active decompression and ITD bundle. In head-up CPR, the patient’s head and chest are elevated at an angle to reduce intracranial pressure, leading to increased cerebral perfusion and blood flow during compression phases. It has shown promising outcomes in enhancing survival rates, particularly in out-of-hospital cardiac arrest (OHCA). Of all patients who suffered OHCA in 2023, only 27% achieved return of spontaneous circulation (ROSC), 10% survived to hospital discharge and 8% survived with good or moderate cerebral performance. Clearly, there is room for improvement. In preclinical studies, pigs who underwent 10 minutes of ventricular fibrillation followed by 19 minutes of CPR had improved neurological function at 24 hours if they received head-up CPR instead of traditional CPR. Human studies using propensity score matching have recapitulated this finding, demonstrating improved rates of survival with good neurological outcomes in patients who received head-up CPR compared to those who received traditional CPR.

Jason Bartos, MD, PhD, associate professor in the cardiac division, critical care physician and interventional cardiologist at University of Minnesota, concluded the session with a discussion of the most extreme example of mechanically assisted CPR: extracorporeal CPR (ECPR). He emphasized from the start that the ECPR program at the University of Minnesota isn’t simply venoarterial extracorporeal membrane oxygenation (VA ECMO), but rather a comprehensive system of care designed to shepherd patients across integrated phases of care starting the moment they have suffered a cardiac arrest. It begins with out-of-hospital care and high-quality CPR. A central dispatcher then activates mobile ECMO or expedites transfer to the closest ECMO initiation hospital. ECMO cannulation then proceeds with ultrasound and fluoroscopically guided femoral arterial (15-17 French) and venous cannulas (25 French) on the same side, along with a distal perfusion cannula in all patients. The goal needle-to-ECMO time is 4-5 minutes. Patients are then brought to the catheterization (cath) lab to identify and intervene on any culprit coronary pathology, followed by transfer to the ECMO ICU.

An active survivorship clinic is also established to follow up after discharge. The success of ECPR hinges on various factors, including patient selection criteria, cannulation techniques, and most importantly, timely intervention. At the University of Minnesota, inclusion criteria for consideration of ECPR include age younger than 75, an initial rhythm of ventricular tachycardiac or fibrillation, ongoing CPR with LUCAS, end-tidal CO2 > 10 mmHg, PaO2 > 50 mmHg, SpO2 > 85%, and lactate < 18 mmol/L. They also prefer patients to be located within a 30-minute drive time of the nearest cannulation site. Swift cannulation within the first 30 minutes of cardiac arrest has resulted in remarkable neurologically intact survival rates. With the advent of a mobile ECMO vehicle, which Dr. Bartos described as a “cath lab on wheels,” they can now reach more patients within this time window. Despite challenges such as neurologic injury and multisystem organ failure, ECPR offers a beacon of hope for patients facing cardiac arrest. Recovery should be viewed as a marathon, and Dr. Bartos’ team does not pursue neuroprognostication until one week after ECMO initiation. He noted that some patients have taken up to a month to recover behavioral responsiveness, which is difficult to predict.

These groundbreaking advancements in CPR techniques underscore the transformative potential of innovative approaches in improving cardiac arrest survival rates. By optimizing compression and decompression dynamics, embracing ITDs and head-up CPR techniques, and leveraging extracorporeal mechanical support, clinicians can usher in a new era of resuscitative care.