Multiple organ dysfunction syndrome (MODS) after surgical repaire for acute type A aortic dissection(ATAAD) is a life-threatening condition. In this study, patients who undergoing surgical repaire of ATAAD immdediately or presenting sever MODS after surgical repaire of acute type A aortic dissection will be treated with umbilical cord-derived mesenchymal stem cell.

Multiple organ dysfunction syndrome(MODS) are common debilitating complications after surgical repaire for ATAAD. MODS is one of the chief causes of post-operative death for acute type A aortic dissection(ATAAD) patients, and it was reported that MODS accounted for more than half of the death after surgery for ATAAD. Despite recent advance in surgical technique, mortality rate remains high in such critical care conditions.

In animal models, studies have demonstrated the beneficial effects of MSCs with respect to ischemia-reperfusion injury of heart, lungs, kidney, brains and livers. Several pilot studies have provided evidence that MSC may be effective in treating critically ill patients with traumatic brain injury, acute renal failure, or acute respiratory distress syndrome. Therefore, in the present pilot study, the investigators hypothesized that timely initiation of mesenchymal stem cells(MSC) will positively influence survival and biochemical indexesof patients with MODS after ascending aortic replacement combined with open placement of triple-branched stent graft for ATAAD. The trial contain two parts:

Part one(prenvention scheme): to explore the safety and efficacy of umbilical cord-derived MSC, we will recruit patients who are diagnosed with ATAAD, and 8 patients will be administrated intervenously with MSC immediately after ascending aortic replacement combined with open placement of triple-branched stent graft while other 8 not. Then we will monitor their MODS related biochemical indexes, sequential organ failure assessment(SOFA) scores, comparing to those don't be treated with MSC.

Phase two(treatment scheme): for patients presenting severe MODS(SOFA score≥10) after ascending aortic replacement combined with open placement of triple-branched stent graft, we will randomly use MSC to 8 of patients while other 8 not. Then we will monitor their MODS related biochemical indexes, SOFA scores, comparing to those don't be treated with MSC.

The dosage of the MSC was determined on the basis of the previous clinical studies, which is 1000000 cells per kilogram of body weight and administrated intervenously .

Inclusion Criteria:

Part 1:

• Patients who are diagnosed with ATAAD and received emergency surgery with ascending aortic replacement combined with open placement of triple-branched stent graft
• elder than 60 years old
• Preoperative PaO2/FiO2 > 400mmHg, platelets ≥ 150*109/L, bilirubin < 20μmol/L, no hypotension (without vasoactive drugs), Glasgow Coma Score Scale = 15, creatine <110μmol/L

Part 2:

• Patients who are diagnosed with ATAAD and received emergency surgery with ascending aortic replacement combined with open placement of triple-branched stent graft
• Patients who have failure of at least 2 organs
• Patients who meet the criteria as below:

sequential organ failure assessment score (SOFA) ≥ 10

Exclusion Criteria:

• uncontrollable underlying disease life expectancy of less than 4 days history of long-term corticosteroid use during the past 6 months.
• The pre-operative computer tomography angiography(CTA) demonstrate the visceral arteries are involved
• pre-existing severe disease of any major organs