In recent years, ECMO technology is increasingly used in the treatment of refractory circulatory failure and cardiac arrest[6–8]. Kim SJ, et al conducted a meta-analysis ravealing that ECPR showed improved survivor comparing to CCPR. American Heart Association Guidelines also recommend ECPR for cardiac arrest. In a study involving 156 patients, ECPR can effectively improve the prognosis of the nervous system, of course, it needs to be verified by larger sample of studies. Therefore, we believe that ECMO should be more widely used in emergency department, where is the first window for most of patients with cardiac arrest, especially for patients with out-of-hospital cardiac arrest(OHCA). At present, there is a lack of international evaluation system for predicting the prognosis of patients with ECPR.
We conducted a retrospective study of 74 adult patients treated with ECPR, and a total of 31 patients survived. The survival rate(41.9%) was slightly higher than the data of international studies[5, 11]. At the same time, we found that both APACHE II and SAVE score could predict the prognosis of patients. ROC curve analysis showed that the area under the curve of the two scoring systems was similar, and the specificity of SAVE score was slightly higher while the combined multivariate ROC analysis of both two parameters showed an AUC of 0.90 (95%CI: 0.83–0.97), showing an excellent predictive value. The coincidence rate of the two scoring systems in predicting the mortality of patients with ECPR reached 91.9% (68/74).
APACHE II score has been widely used to evaluate and predict the prognosis of various types of critically ill patients[12–15] since it was proposed. There was a study revealing low evaluation value of APACHE II score in critically ill patients after cardiac surgery, and they attributed this to the lack of specificity of the APACHE II score in patients with heart disease . For the reason that the subjects of our study were patients with respiratory and cardiac arrest treated with ECPR, all patients obtained a lower Glasgow score, which further reduced the differentiation of APACHE II scores. However, in our study, APACHE II score is quite accurate in predicting the prognosis of ECPR patients. As shown in the figure, there was a remarkable increase in probability of 28-day mortality if APACHE II score was more than 32.
ELSO recommended SAVE (Survival After Veno-arterial ECMO) score to evaluating the severity of patients with VA-ECMO. As compared to APACHE II score, SAVE score is more specific in the evaluation of cardiovascular disease, but there is still a lack of large sample data to prove the value of SAVE in predicting the prognosis of adult patients with ECPR. In our cohort, SAVE score also showed considerable predictive accuracy. When the SAVE score is less than − 9, the mortality rate can be as high as 80%. Compared with the vital signs and internal environment contained in the APACHE II score, the SAVE score emphasizes more the importance of the primary disease, the functional status and support of organs, which is consistent with our clinical experience. Besides, studies[18, 19] have shown that ECMO patients with acute kidney injury or acute liver failure tend to have a poorer prognosis.
According to our study, we recommend that the combination of APACHE II and SAVE scores could be used to predict prognosis in adult patients with ECPR considering the different emphases of the two scoring systems. Given the high cost, the frequent and fatal complications of ECMO and the uncertainty of outcome, it is of great necessity for us to conduct a detailed evaluation of patients to maximize the benefits of ECMO. If patients achieve both high APACHE II score and low SAVE score, the necessity of ECMO treatment should be reconsidered.
Our ECMO center is located in the emergency department, which is the primary area of care for cardiac arrest, especially OHCA patients. When a cardiac arrest patient enters the emergency channel, the ECMO team can be mobilized as soon as possible to assess the patient's condition and initiate ECMO, which can greatly reduce the time it takes for personnel to arrive and transfer equipment and this may be one of the reasons why the survivor rate of ECPR in our center is slightly higher than the international data. As the last line of defense for critically ill patients, ECMO should be vigorously promoted, besides, we believe that it is particularly important to carry out ECMO treatment in the emergency departments.
This paper still has some limitations, as a retrospective single-center study, the sample size collected of our study is small, so we still need larger sample size and multicenter data support. In addition, APACHE II and SAVE scores are cumbersome, which may be difficult in clinical frontline application.