Improved Survival With Extracorporeal Cardiopulmonary Resuscitation Despite Progressive Metabolic Derangement Associated With Prolonged Resuscitation

Abstract

Background: The likelihood of neurologically favorable survival declines with prolonged resuscitation. However, the ability of extracorporeal cardiopulmonary resuscitation (ECPR) to modulate this decline is unknown. Our aim was to examine the effects of resuscitation duration on survival and metabolic profile in patients who undergo ECPR for refractory ventricular fibrillation/ventricular tachycardia out-of-hospital cardiac arrest.

Methods: We retrospectively evaluated survival in 160 consecutive adults with refractory ventricular fibrillation/ventricular tachycardia out-of-hospital cardiac arrest treated with the University of Minnesota (UMN) ECPR protocol (transport with ongoing cardiopulmonary resuscitation [CPR] to the cardiac catheterization laboratory for ECPR) compared with 654 adults who had received standard CPR in the amiodarone arm of the ALPS trial (Amiodarone, Lidocaine, or Placebo Study). We evaluated the metabolic changes and rate of survival in relation to duration of CPR in UMN-ECPR patients.

Results: Neurologically favorable survival was significantly higher in UMN-ECPR patients versus ALPS patients (33% versus 23%; P=0.01) overall. The mean duration of CPR was also significantly longer for UMN-ECPR patients versus ALPS patients (60 minutes versus 35 minutes; P<0.001). Analysis of the effect of CPR duration on neurologically favorable survival demonstrated significantly higher neurologically favorable survival for UMN-ECPR patients compared with ALPS patients at each CPR duration interval <60 minutes; however, longer CPR duration was associated with a progressive decline in neurologically favorable survival in both groups. All UMN-ECPR patients with 20 to 29 minutes of CPR (8 of 8) survived with neurologically favorable status compared with 24% (24 of 102) of ALPS patients with the same duration of CPR. There were no neurologically favorable survivors in the ALPS cohort with CPR ≥40 minutes, whereas neurologically favorable survival was 25% (9 of 36) for UMN-ECPR patients with 50 to 59 minutes of CPR and 19% with ≥60 minutes of CPR. Relative risk of mortality or poor neurological function was significantly reduced in UMN-ECPR patients with CPR duration ≥60 minutes. Significant metabolic changes included decline in pH, increased lactic acid and arterial partial pressure of carbon dioxide, and thickened left ventricular wall with prolonged professional CPR.

Conclusions: ECPR was associated with improved neurologically favorable survival at all CPR durations <60 minutes despite severe progressive metabolic derangement. However, CPR duration remains a critical determinate of survival.

Keywords: cardiopulmonary resuscitation; death, sudden, cardiac; extracorporeal membrane oxygenation; heart arrest; ventricular fibrillation.

Figure 1.

Patient flow diagrams for the University of Minnesota Extracorporeal Cardiopulmonary Resuscitation (UMN-ECPR) and ALPS (Amiodarone, Lidocaine, or Placebo Study) cohorts. A, Patients transported for the UMN-ECPR protocol. B, Patient selection for the ALPS cohort. ABG indicates arterial blood gas; CCL, cardiac catheterization laboratory; CICU, cardiac intensive care unit; CPC, Cerebral Performance Category; CPR, cardiopulmonary resuscitation; EMS, emergency medical services; mRS, modified Rankin Scale; and Pao₂, arterial partial pressure of oxygen.

Figure 2.

Neurologically favorable survival and cause of death related to duration of professional cardiopulmonary resuscitation (CPR). A, Neurologically favorable survival related to duration of professional CPR in the University of Minnesota Extracorporeal Cardiopulmonary Resuscitation (UMN-ECPR) and ALPS (Amiodarone, Lidocaine, or Placebo Study) cohorts. The Patients at Risk table shows the number of patients receiving CPR of each duration. B, Cause of death in the UMN-ECPR cohort related to duration of CPR. Data are shown as percent of the overall patient cohort. CCL indicates cardiac catheterization laboratory; and CPC, Cerebral Performance Category.

Figure 3.

Metabolic effects of prolonged professional cardiopulmonary resuscitation (CPR). Arterial blood gas and arterial lactic acid levels in the University of Minnesota Extracorporeal Cardiopulmonary Resuscitation cohort before extracorporeal membrane oxygenation (n=160). A, pH, (B) arterial lactic acid, (C) arterial partial pressure of carbon dioxide (Paco₂), and (D) arterial partial pressure of oxygen (Pao₂) are shown. Results are mean±SEM.

Figure 4.

Association of left ventricular lateral wall thickness with professional cardiopulmonary resuscitation (CPR) duration and patient outcome. Patients were assessed by transthoracic echocardiography within 24 hours of admission to the cardiac intensive care unit (n=121). A, Duration of professional CPR in relation to thickness of the left ventricular (LV) lateral wall. B, LV lateral wall thickness in neurologically intact survivors vs patients who died or survived with Cerebral Performance Category (CPC) score of 3 to 4. Results are mean±SEM. *P<0.05.