In this study, we reported the largest cohort of adults who received ECMO due to refractory hypotension or respiratory failure within 30 days after abdominal surgery. Overall, ECMO provided 5 patients with additional time to undergo salvage interventions. ECMO also successfully rescued 8 (50%) patients who were survived ECMO, including 5 (31.25%) patients who even lived to hospital discharge without significant sequelae. In the context of critical illness, both VV- and VA-ECMO provided surgeons with additional time for acute management of patients who would otherwise have died almost immediately due to a sudden deterioration. Salvage interventions may be able to rescue patients given a correct and timely diagnosis while the patient is receiving ECMO support, providing additional chances for patient survival as well as better communication between the family and physician .
The benefits of the use of ECMO in various critical contexts, including cardiogenic shock, refractory septic shock, in-hospital cardiac arrest, ARDS or transplantation, have been reported in other series . Among patients with cardiogenic shock or postcardiotomy syndrome who were receiving ECMO, the reported rate of survival to hospital discharge was between 24% and 45% [3, 12, 14]. A similar survival rate was reported when ECMO support was used as an acute resuscitation tool for in-hospital cardiac arrest [10, 11]. On the other hand, Lee et al.  reported that the survival rate of patients with refractory hypotension after liver transplantation who received ECMO was 25%. Enhanced survival after ECMO support was reported among patients who suffered from heart failure due to fulminant myocarditis and those who underwent VV-ECMO for H1N1-related ARDS. The reported rate of survival to hospital discharge in the former report was as high as 70%, while it was reported to be between 64 and 75% in the latter [15-17]. In our series, there was a compatible survival benefit identified in our cohort, indicating a need for extracorporeal life support as an important back-up system for patients who experience rapid deterioration after abdominal surgery, particularly in centres that perform large numbers and complicated types of surgical procedures.
In addition, an interesting finding in our study is that neither VV- nor VA-ECMO led to serious complications, such as surgical site bleeding or thromboembolic events, among patients who had undergone abdominal surgery. Although limb ischaemia occurred in 3 patients who underwent VA-ECMO implantation using the femoral cut-down technique, resolution was achieved after the placement of a distal reperfusion catheter. A previous study also suggested pressure criteria for pre-emptive placement of distal reperfusion catheters to prevent limb ischaemia . However, when ECMO was used for post-cardiotomy or cardiogenic shock, the rates of complications such as cerebrovascular events and major bleeding requiring rethoracotomy were reported to be as high as 17.4% and 58%, respectively, after a mean duration of ECMO support ranging from 47.9 to 132 hours . Similarly, when ECMO was used for heart failure due to fulminant myocarditis or bacterial sepsis, there were elevated rates and increased severity of complications, including 3 out of 14 patients (21%) who had limb ischaemia that required amputation and 14.3% of patients who required re-exploration for haemostasis after a median ECMO duration ranging from 72 to 139 hours, despite a better survival outcome [15, 16, 19-21]. In contrast, a low incidence of complications during ECMO use for refractory septic shock after liver transplantation was reported, with a median of 96 hours of ECMO support, echoing our finding in terms of the complications of ECMO use after abdominal surgery [8, 22]. This discrepancy indicates that the incidence of ECMO-related complications and patient clinical outcomes may vary widely, particularly between patients who underwent cardiothoracic surgery and abdominal surgery. ECMO should be considered relatively safe for use in patients who require extracorporeal life support after abdominal surgery.
Regarding potential prognostic factors, after comparing clinical and laboratory data before and after ECMO implantation, a significant reduction in the inotropic dose within 2 days after ECMO implantation was associated with a significantly higher likelihood of ECMO weaning and survival to hospital discharge. Although age may be one of the most powerful poor prognostic factors in clinical decision making, we did not find age to be a substantial risk factor for poor prognosis. Previous studies reported prognostic factors that were mostly associated with conditions that existed before the initiation of extracorporeal life support, including pre-existing diabetes, chronic kidney insufficiency, acute renal failure requiring renal replacement therapy, elevated lactate level, age more than 70 years, and logistic EuroSCORE greater than 20% [3, 12]. In contrast, our study identified factors that indicate early treatment response to ECMO and can be used to identify patients with a better prognosis at an early stage after ECMO implantation. This index may also be used to facilitate communication between surgeons and families and may potentially reduce futile use of extracorporeal life support.
In a further comparison of the outcomes of patients who required VV- and VA-ECMO, the average duration of VV-ECMO circulation was approximately 5 days, which mostly reflects the disease course of ARDS . Half of the patients in this cohort survived to be weaned off of ECMO, and 40% survived to hospital discharge without significant sequelae and continued to receive further treatment for their underlying diseases, such as malignancies, during follow-up. Thus, when ARDS developed during the early post-operative period after abdominal surgery, the timely utilization of VV-ECMO may avoid prolonged refractory hypoxia and may further reduce the risk of systemic hypotension and multi-organ dysfunction [23, 24]. While some clinicians may be concerned about ECMO-related complications in this context and thus hesitate to employ VV-ECMO in this population, especially those with a diagnosed malignancy, such concerns need to be revised on the basis of the data presented in this study. As a result of limited case availability, we did not demonstrate a survival difference between patients who required VV- and VA-ECMO (40% versus 16%, p = 0.3630). This study was also limited by its retrospective design and the fact that the decision to use extracorporeal life support was mainly based on clinical discretion. As this study demonstrated a clear survival benefit and a positive clinical safety profile in this selected patient population, future studies should include a larger cohort with a longer follow-up period to further elucidate the clinical benefits and safety of the use of extracorporeal life support in abdominal surgery patients who develop a critical illness in the postoperative period.