Motivation: In the past few days, I realized that doing CPR is exhausting and doing quality CPR is even more tiring. But, even with our Herculean efforts, critical organs like brain and kidney teeter at the edge of survival. Today, as we were drilling through CPR, I wondered wouldn't it be great if we could hook up the circulation to a machine and focus on restarting the heart? Such a machine, of course, already exists and is used in children - the ECMO or extracorporeal membrane oxygenation. ECMO assisted CPR for adults is currently in the experimental stages. Given the dire nature of CPR, no randomized trials have been conducted, but a group in South Korea recently implemented an ECMO assisted CPR protocol and reported retrospective results.
Paper: Extracorporeal cardiopulmonary resuscitation in patients with inhospital cardiac arrest: A comparison with conventional cardiopulmonary resuscitation. Shin, TG et. al., Crit. Care Med. (2011) 39: 1-7.
Methods: The study considered patients between ages 18-80, who had witnessed in-hospital cardiac arrests. Patients were considered for ECMO only if regular CPR was conducted for greater than 10 minutes without return of spontaneous circulation (ROSC). Contraindications for ECMO assisted CPR (E-CPR) included previous neurologic damage, other terminal disease, or arrest of septic origin. During chart review, the authors also excluded patients who had cardiac arrest from known trauma, hemorrhage, asphyxia, or non-cardiac cause. Importantly, during the study, the decision to invoke ECMO was left to the physician (in other words, there were no standardized criteria).
Results:
Study Population: In the six year period reviewed, 406 patients met the inclusion criteria. Of these, 321 patients received conventional CPR (C-CPR) while 85 patients received ECMO assisted CPR (E-CPR). Of the 85 patients on E-CPR, successful cannulation was performed in 81 patients. At baseline, patients receiving E-CPR were more likely to have primary cardiac disease (74.1% vs 56.7%, p = 0.004) and located in the ICU/OR/cath lab (63.5 vs 31.8%, p < 0.001). Other baseline values such as age, gender, other cardiovascular risk factors, and initial rhythm at arrest were equivalent.
Outcome: Without adjusting for baseline differences, ROSC was achieved more frequently in E-CPR (75.3 vs. 52.05, p < 0.001). Intact neurologic survival at discharge was also higher in E-CPR (28.2 vs 7.8%, p < 0.001). Importantly, at six months post-arrest, intact neurologic status was higher in patients receiving E-CPR versus C-CPR (28.2 vs 7.5%, p < 0.001).
Adjusted Data: Since the E-CPR and C-CPR groups were not randomized and had baseline differences, the authors matched the two groups to be equivalent in age, gender, comorbidites, cause of arrest, rime of arrest, initial rhythm, and other baseline parameters. Even after adjusting, E-CPR group had better intact neurological survival at discharge (23.3 vs 5.0%, p = 0.013) as well as six month overall survival (26.7 vs 8.3%, p = 0.019).
Discussion: Although the study has many weaknesses, I was very impressed by the promise of E-CPR. With ECMO, an astonishing 28% of patients suffering from cardiac arrest had minimal neurologic damage. Also, at baseline, the patients getting ECMO tended to be sicker since they were more likely to be in the ICU (though this difference was adjusted for). Also, ECMO was used as a last resort by physicians in prolonged arrest situations, and the effects of ECMO may be even better if it is applied as soon as possible. One of the promises for ECMO is that if survival in arrest situations can be prolonged, then more definitive interventions like PCI or thrombolytics can be administered to save patients after cardiac arrest.
While promising, the paper has many weaknesses. The primary weakness in the design is that there were no standardized criteria when E-CPR should be applied. This introduces a whole host of possible selection bias that may not have been adjusted for. Also, the authors considered a very select group of patients - in-hospital witnessed cardiac arrest of presumed cardiac etiology. The applicability of this result to the broader population of patients (such as a septic patient suffering from PEA arrest) is unclear. However, given the promising results, the next step is likely a prospective study. In ten-fifteen years from now, we may all be practicing ECMO-CPR and give up on lengthy, tiresome chest compressions!
Paper: Extracorporeal cardiopulmonary resuscitation in patients with inhospital cardiac arrest: A comparison with conventional cardiopulmonary resuscitation. Shin, TG et. al., Crit. Care Med. (2011) 39: 1-7.
Methods: The study considered patients between ages 18-80, who had witnessed in-hospital cardiac arrests. Patients were considered for ECMO only if regular CPR was conducted for greater than 10 minutes without return of spontaneous circulation (ROSC). Contraindications for ECMO assisted CPR (E-CPR) included previous neurologic damage, other terminal disease, or arrest of septic origin. During chart review, the authors also excluded patients who had cardiac arrest from known trauma, hemorrhage, asphyxia, or non-cardiac cause. Importantly, during the study, the decision to invoke ECMO was left to the physician (in other words, there were no standardized criteria).
Results:
Study Population: In the six year period reviewed, 406 patients met the inclusion criteria. Of these, 321 patients received conventional CPR (C-CPR) while 85 patients received ECMO assisted CPR (E-CPR). Of the 85 patients on E-CPR, successful cannulation was performed in 81 patients. At baseline, patients receiving E-CPR were more likely to have primary cardiac disease (74.1% vs 56.7%, p = 0.004) and located in the ICU/OR/cath lab (63.5 vs 31.8%, p < 0.001). Other baseline values such as age, gender, other cardiovascular risk factors, and initial rhythm at arrest were equivalent.
Outcome: Without adjusting for baseline differences, ROSC was achieved more frequently in E-CPR (75.3 vs. 52.05, p < 0.001). Intact neurologic survival at discharge was also higher in E-CPR (28.2 vs 7.8%, p < 0.001). Importantly, at six months post-arrest, intact neurologic status was higher in patients receiving E-CPR versus C-CPR (28.2 vs 7.5%, p < 0.001).
Adjusted Data: Since the E-CPR and C-CPR groups were not randomized and had baseline differences, the authors matched the two groups to be equivalent in age, gender, comorbidites, cause of arrest, rime of arrest, initial rhythm, and other baseline parameters. Even after adjusting, E-CPR group had better intact neurological survival at discharge (23.3 vs 5.0%, p = 0.013) as well as six month overall survival (26.7 vs 8.3%, p = 0.019).
Discussion: Although the study has many weaknesses, I was very impressed by the promise of E-CPR. With ECMO, an astonishing 28% of patients suffering from cardiac arrest had minimal neurologic damage. Also, at baseline, the patients getting ECMO tended to be sicker since they were more likely to be in the ICU (though this difference was adjusted for). Also, ECMO was used as a last resort by physicians in prolonged arrest situations, and the effects of ECMO may be even better if it is applied as soon as possible. One of the promises for ECMO is that if survival in arrest situations can be prolonged, then more definitive interventions like PCI or thrombolytics can be administered to save patients after cardiac arrest.
While promising, the paper has many weaknesses. The primary weakness in the design is that there were no standardized criteria when E-CPR should be applied. This introduces a whole host of possible selection bias that may not have been adjusted for. Also, the authors considered a very select group of patients - in-hospital witnessed cardiac arrest of presumed cardiac etiology. The applicability of this result to the broader population of patients (such as a septic patient suffering from PEA arrest) is unclear. However, given the promising results, the next step is likely a prospective study. In ten-fifteen years from now, we may all be practicing ECMO-CPR and give up on lengthy, tiresome chest compressions!
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