Correlation Between Acute Gastrointestinal Injury and Venous Return in Critical Ill Patients

Currently, altered intestinal blood flow in critically ill patients has been a hot research topic in recent years. In 2022, studies on acute mesenteric ischemia were published in top journals in critical care medicine \[Crit Care, 2022. 26(1): p.92. and Intensive Care Med, 2022. 26(2): p.92.\].

However, because the gastrointestinal tract is in the abdominal cavity and doctors lack methods to directly monitor the visceral perfusion. Therefore, there is little research on the relationship between gastrointestinal perfusion and acute gastrointestinal injury in critical ill patients. Currently, the diagnosis of acute gastrointestinal injury is mostly performed using subjective indicators and adverse outcomes that have already occurred, which results in the treatment of acute gastrointestinal injury often lagging behind.

The use of color Doppler ultrasonography to assess blood flow in intestinal vessels in healthy and outpatient patients has been in use since the 1980s. Our team showed that the resistance index of the superior mesenteric artery(SMA) in postoperative cardiac surgery patients correlated with lactate values and lactate clearance \[Front Med (Lausanne), 2021.8: p.762376.\], suggesting that gastrointestinal perfusion as reflected by SMA blood flow is important for systemic resuscitation, and that Doppler indices of SMA have the potential value of reflecting intestinal hypo-perfusion.

Intestinal venous blood enters the portal vein and then the liver before returning to the right heart via the inferior vena cava. Right ventricular dysfunction or abdominal hypertension could cause obstruction of portal venous return, which might lead to edema and dysfunction of the intestine.

Therefore, monitoring the venous return status is crucial for intestinal perfusion.

In 2012, the Venous Excess Ultrasound Score(VExUS) for evaluating venous return has been reported and it has been shown to correlate with acute kidney injury (AKI) \[Intensive Care Med, 2012. 38(3): p.384-94\]. However, there is currently no research on the correlation between acute gastrointestinal injury and venous return, and this study is innovative and exploratory.

Research Methods

1. The Venous Excess Ultrasound Score(VExUS):

   Blood flow parameters were measured by two ICU physicians and the mean values were recorded. Both ICU physicians had more than 4 years of experience in critical care ultrasound; they were certified by the Chinese Critical Care Ultrasound Study Group. Monitoring the status of venous return in the portal vein, hepatic vein, intra-renal vein.

   The status of venous returnwere evaluated in categorical variables as normal, mildly abnormal, or severely abnormal, as previously reported. Patients were then classified according to the assessment in Grades 0-3: Grade 0, no congestion; Grade 1, mild congestion; Grade 2, moderate congestion; and Grade 3, severe congestion.To minimize errors, it is important to take the average of three measurements in a magnified state.
2. Ultrasound score of transabdominal bowel function (AGUIS score) At the time of the ultrasound examination, the operator categorized the situation as "good quality", "poor quality" or "not assessable". The abdomen is then divided into four quadrants, each measuring one point, and the operator examines and scores the diameter of the bowel, changes in bowel folds (e.g., shortening, decreasing), thickness of the bowel wall, layering of the bowel wall, peristalsis, and movement of bowel contents. A total of four scores are obtained, and the average of the four measurements is the (AGIUS) score.
3. Gastrointestinal Dysfunction Score (GIDS): 0 score (No risk): No symptoms OR one of the following with oral intake: Absent bowel sounds; Vomiting; GRV \>200 mL; GI paralysis/dynamic ileus; Abdominal distension; Diarrhea (not severe); GI bleeding without transfusion; IAP \>20 mmHg. 1 score(Increased risk): Two of the following: No oral intake; Absent bowel sounds; Vomiting; GRV \>200 mL; GI paralysis/dynamic ileus; Abdominal distension; Diarrhea (not severe); GI bleeding without transfusion; IAP \>20 mmHg. 2 score(gastrointestinal dysfunction): Three or more symptoms of score 1 OR up to two of the following: Severe diarrhea; GI bleeding with transfusion; IAP \>20 mmHg. 3 score(gastrointestinal failure): Three or more of the following: Prokinetic use; GI paralysis/dynamic ileus; Abdominal distension; Severe diarrhea; GI bleeding with transfusion; IAP \>20 mmHg. 4 score(Life threatening): One of the following: GI bleeding leading to hemorrhagic shock; Mesenteric ischemia; Abdominal compartment syndrome
4. Serologic indices of intestinal mucosal epithelial injury Plasma citrulline, plasma intestinal fatty acid binding protein, and D-lactic acid were measured by ELISA. (R\&D Systems, Minneapolis, USA). Peripheral blood specimens were obtained and centrifuged, and the resulting plasma was frozen at -20°C and sent to the laboratory for analysis within 1 week.

Study Route:

On the day of enrollment, patients' hemodynamic parameters, measurement of VExUS, AGUIS score, GIDS score and serum specimen were recorded. Measurement of the above parameters was repeated at Day 1(ICU admission)，Day 2(between 24 and 48 h)，Day 3(between 48 and 72 h)，and Departure Day(ICU discharge).

Eligibility Criteria:
Inclusion Criteria:

1. Patients with sepsis with an expected ICU stay of more than 3 days.
2. ≥18 years of age and \<80 years of age.

Exclusion Criteria:

1. Severe mesenteric or abdominal artery stenosis;
2. Fixed body (such as recent spinal surgery or intracranial hypertension);
3. Patients with contraindications for IAP measurement (such as patients who have recently undergone bladder surgery, been injured, or become pregnant）
4. Having undergone abdominal surgery or chest lowering involving the intestines patients undergoing aortic surgery;
5. Poor quality of abdominal ultrasound images;
6. Hydrothorax or ascites.