Acute Type A Aortic Dissection (ATAAD) is a serious medical condition that requires immediate surgical intervention. The repair of Acute Type A Aortic Dissection (ATAAD) combines different surgical procedures, including the use of Cardiopulmonary Bypass (CPB). This study focuses on the gastrointestinal (GI) system and the complications arising in the gastrointestinal (GI) system as a result of this procedure. Retrograde Inferior Vena Cava Perfusion (RIVP) is a technique used during Cardiopulmonary Bypass (CPB) that could show potential in mitigating latent gastrointestinal (GI) complications. The study aims to evaluate the effectiveness of Retrograde Inferior Vena Cava Perfusion (RIVP) in patients receiving Acute Type A Aortic Dissection (ATAAD) repair with Cardiopulmonary Bypass (CPB) in reducing Ischemic Reperfusion (IR) injury and inflammatory responses that affect gastrointestinal (GI) integrity. It intends to compare the postoperative gastrointestinal (GI) complications and long-term gastrointestinal (GI) function between patients treated with Antegrade Cerebral Perfusion (ACP) and Retrograde Inferior Vena Cava Perfusion (RIVP), and those treated with Antegrade Cerebral Perfusion (ACP) alone. The patients will be placed in their respective groups as per the decision of the surgeons, perfusionists, and the condition of the patient. Data collection will be facilitated by a comprehensive Case Report Form (CRF). This pilot study, guided by established methodologies, places the study's sample size at 30 to ensure statistical reliability and prevent resource wastage. Through this approach of sample collection, baseline data collection, peri-operative data recording, and follow-up assessments, the study aims to shed light on the impact of Retrograde Inferior Vena Cava Perfusion (RIVP) during Acute Type A Aortic Dissection (ATAAD) repair on gastrointestinal (GI) complications and systemic/intestinal inflammation. The integration of specialized Case Report Forms (CRFs) and structured questionnaires ensures standardized data collection and management, while prioritizing patient confidentiality. The study's data analysis, powered by R software, will provide valuable insights into the efficacy of Retrograde Inferior Vena Cava Perfusion (RIVP) in enhancing clinical outcomes and improving patient's prognosis in the surgical treatment of Acute Type A Aortic Dissection (ATAAD).

Retrograde Inferior Vena Cava Perfusion ( RIVP) is a adjunct technique used in surgery during the repair of Acute Type A Aortic Dissection (ATAAD). This procedure generally involves perfusing oxygenated blood into the inferior vena cava, directing it toward the visceral organs and lower extremities. This technique plays an important role in reducing the risk of ischemic injury to these vital regions during deep hypothermic circulatory arrest (DHCA) when combined with Antegrade Cerebral Perfusion (ACP).

Recent study showed that the use of Retrograde Inferior Vena Cava Perfusion (RIVP), in conjunction with Antegrade Cerebral Perfusion (ACP), may lead to lower rates of organ dysfunction in the lower body, reduced mortality and shorter Cardiopulmonary Bypass (CPB) duration. It has also been associated with maintaining higher higher body temperature during circulatory arrest which may be beneficial for the overall patient well-being.

However, despite these promising results , there is a need for further research to explore the scientific impact of Retrograde Inferior Vena Cava Perfusion (RIVP) on gastrointestinal function during and after Acute Type A Aortic Dissection (ATAAD) repair. Gastrointestinal complications are a crucial aspect of a patients outcomes, and more often neglected. Understanding the relationship between Retrograde Inferior Vena Cava Perfusion (RIVP) and these complications may be essential and have the potential to lead better prognosis among patients, resulting in improved outcomes.

In summary, Retrograde Inferior Vena Cava Perfusion (RIVP) is a valuable technique that helps protect abdominal organs and lower extremities during Acute Type A Aortic Dissection (ATAAD) surgery. While it shows promise in improving patient outcomes, ongoing research is necessary to comprehensively assess its effect on gastrointestinal function, thus optimizing its use in the surgical management of Acute Type A Aortic Dissection (ATAAD).

This study is designed as a single centered, prospective, cohort study with an exploratory framework. The study will be conducted at the Second Affiliated Hospital of Nanjing Medical University Cardiovascular Center. This study will focus on patients undergoing Acute Type A Aortic Dissection (ATAAD) repair with or without Retrograde Inferior Vena Cava Perfusion (RIVP). Patients will be assigned to these groups based on surgical and patient specific criteria in the ratio 1:1 and will follow patients in the Cardiovascular Critical Care Unit ( CCU) pre-operatively. Group A will receive selective ACP+RIVP, while group B will receive ACP alone under mild to moderate hypothermia. As per the general rule of thumb, the study anticipates to recruit up to 30 patients for the pilot study in total. 15 in each group.

Patients will undergo diagnostic assessments to confirm diagnosis of Acute Type A Aortic Dissection (ATAAD) and depending on urgency they will proceed either to surgery or Cardiovascular Critical Care Unit (CCU). Informed consent will be obtained, but this will in no way delay the treatment protocol for the patients. In case of urgent surgery, a surgical fellow will obtain the consent. Patients can withdraw without repercussions and no replacements will be sought.

All data will be collected and recorded systematically in a well drafted case report form. A protocol has been written to conduct this study and we have followed the SPIRITS guidelines. Any changes in the protocol will be timely reported and adjusted.

We will collect blood samples at specific time intervals, pre operatively (PO1), post operatively day 1 (PO2), day 3 (PO3), day 7 (PO4). The study will include biomarker evaluation: CRP, intestinal barrier indicators ( D-amine oxidase(DAO), Fatty Acid Binding Protein 2 (FABP2), D-Lactate, Endotoxins) and 12 cytokine panel.

All baseline data ranging from clinical parameters, anthropometric data, baseline gastrointestinal (GI) assessment and clinical data will be obtained before surgery and recorded in the case report form.

Peri operative data, duration of Cardiopulmonary Bypass (CPB), duration of deep hypothermic circulatory arrest (DHCA), cross clamp time, surgery time, number of units of whole blood, fresh frozen plasma, pooled platelets and cryoprecipitate administered will be collected within the surgical room by the perfusionist and the anesthesiologist.

A prospective longitudinal study will assess long term gastrointestinal (GI) dysfunction post surgery through follow up methods such as outpatient, Wechat application, in hospital or telephone based follow up evaluation at specified intervals (1,3,6,12 months) post hospital discharge. A meticulously drafted questionnaire will be used as a tool for assessment.

To establish presence of gut barrier dysfunction, the investigators will look at the specific patterns or deviation in values of the biomarkers from the normal or baseline levels. An increase in pro-inflammatory cytokines may suggest an inflammatory response associated with gut barrier dysfunction. Elevated levels of D- Lactate, Fatty Acid Binding Protein 2 (FABP2) and endotoxins and decreased activity levels of D-amine oxidase (DAO) could suggest gut barrier dysfunction.

The investigators will perform comprehensive statistical analysis to evaluate continuous variables, like inflammatory markers. This includes calculating the mean, standard deviation and interquartile range for values related to C- reactive protein (CRP), cytokines and intestinal barrier markers. The investigators will use the t-test to analyze differences in these variables. For ordinal data from the Case Report Form (CRF) and follow up questionnaire, wilcoxon rank sun test for hypothesis testing will be used. Categorical data will be presented as percentages , and the differences in these categories will be assessed using the chi-squared test. To handle data at multiple time points, ANOVA will be used to assess variance. When dealing with multiple dependant variables like various cytokine levels simultaneously , the investigators will employ a multivariate analysis of variance. We will consider results statistically significant if the p value is <0.05, in lone with established research and data analysis practices.

Inclusion Criteria:

1. Patients undergoing ATAAD repair under CPB.
2. Age: 18-70 years
3. Give consent

Exclusion Criteria:

1. Variables that can influence gut microbiome like antibiotics or probiotics 2 weeks prior to surgery
2. On chemotherapy
3. Evidence of pre-operative malperfusion of the GI system
4. Presence of GI any pathology (IBD,GERD,PU)
5. Continuous enteral feeding prior to surgery
6. Refuse to participate in the study

The study groups with be patients undergoing ATAAD repair under CPB with and without RIVP. This is a cohort study and the patients will not be assigned any specific group randomly or by a computer. The patients will be placed in their respective groups as per the decision of the surgeons, perfusionist and the condition of the patient. Patients admitted through the emergency department will be initially enrolled into the cardiovascular department and subsequently invited to participate in this study.