Abdominal aortic aneurysm rupture

　　1. Causes of Disease

　　Rupture of abdominal aortic aneurysm is an inevitable result of collagen failure due to the failure of elastic protein in the abdominal aortic wall, the transfer of pressure load to collagen, and the transformation of collagen into the main tensile component under the continuous action of various factors. In the evaluation of risk factors for abdominal aortic aneurysm rupture, the main factors are aneurysm diameter, expansion rate, diastolic pressure, and chronic obstructive pulmonary disease (COPD). Aneurysm diameter is considered to be a decisive factor; it is reported that the annual rupture rate of aneurysms with a diameter of 5-6 cm is 6.6%, and 19% when the diameter reaches 7 cm; some reports indicate that the 5-year rupture rate of abdominal aortic aneurysms with a maximum diameter of 4 cm is 10%-15%, approximately 20% when the diameter is 5 cm, approximately 33% when the diameter is 6 cm, and 75%-90% when the diameter is above 7 cm, indicating that the risk of rupture is very high when the diameter reaches 6 cm or more, and it is an absolute indication for surgery. The expansion rate of aneurysm diameter, according to CT and B-ultrasound tracking observations, suggests that the transverse diameter below 6 cm is 0.21-0.52 cm/year, and 0.69 cm/year when the diameter is 6-7 cm. If the diameter of the abdominal aortic aneurysm increases by 0.5 cm or more within 3 months, it is also prone to rupture, and early surgery is recommended. Increased diastolic pressure increases the pressure on the aneurysm wall. The presence of COPD increases the activity of collagenase and leukocyte proteinase, accelerating the destruction of the aneurysm wall and leading to rupture. In addition, it is found that aneurysms are usually elliptical, with faster lateral expansion, and it is also common in clinical practice to see lateral wall rupture of abdominal aortic aneurysms. Recent research by Inzoli et al. suggests that in addition to the aforementioned factors, thrombosis, atherosclerotic plaques, and pressure from the vertebral body also determine the pressure distribution on the aneurysm wall, and local pressure concentration is prone to cause rupture of abdominal aortic aneurysms. Thrombosis reduces the lumen of the abdominal aortic aneurysm and also reduces the maximum pressure on the aneurysm wall (Laplace's law), indicating that thrombosis has a certain protective significance. Surgical evidence shows that rupture of abdominal aortic aneurysm often occurs near the extraperitoneal spine, related to the lack of thrombosis and increased pressure from the vertebrae in the aneurysm wall at this location. In addition, the uneven stress on the aneurysm wall caused by atherosclerotic plaques is an indispensable factor that should not be ignored in the rupture of small abdominal aortic aneurysms.

　　Second, Pathogenesis

　　According to the bleeding site, extent of extension, general condition, and other factors, Szilagyi divides ruptured abdominal aortic aneurysms into three types:

　　1, Open type:An abdominal aortic aneurysm ruptures into the abdominal cavity, resulting in rapid onset of shock.

　　2, Restrictive type:An abdominal aortic aneurysm ruptures into the retroperitoneal cavity, forming a retroperitoneal hematoma, causing a temporary obstruction.

　　3, Sealed type:The rupture hole of an abdominal aortic aneurysm is small, and bleeding is confined and sealed by retroperitoneal tissue or the formed fibrous tissue capsule.

　　According to statistics, only about 20% of patients rupture into the abdominal cavity, resulting in massive bleeding and rapid death; about 80% of patients rupture into the retroperitoneal cavity and are more common on the left side. In addition, there are cases where an abdominal aortic aneurysm ruptures into adjacent veins or intestines to form a special manifestation of an aorto-caval fistula or an abdominal aortic enteric fistula, which are relatively rare.

　　The main complication of this disease is hemorrhagic shock, followed by insufficient blood supply to the entire body's tissues after bleeding, leading to metabolic acidosis due to oxygen deficiency in the body. At the same time, there is a decrease in blood pressure, and oxygen deficiency in brain cells can cause a decrease in the activity of the 'sodium-potassium pump' on the cell membrane, resulting in the inability of Na ions in the cell to be pumped out of the cell, leading to the occurrence of brain edema. This disease is a critical illness that requires immediate surgery; otherwise, it can directly threaten the patient's life.

　　The clinical manifestations of abdominal aortic aneurysm rupture are serious and complex. For patients with obvious massive hemorrhage in the short term, there may be a 'triad', namely: severe abdominal pain or back pain, hypotension or shock, and pulsatile abdominal mass. About 80% to 90% of abdominal aortic aneurysm ruptures have sudden severe abdominal pain, which may be accompanied by back pain, and the pain often radiates to the lateral abdomen or inguinal region, mostly seen on the left side. Due to massive hemorrhage, the patient's circulatory status can deteriorate rapidly and present with shock, including dizziness, loss of consciousness, thirst, cold and moist extremities, decreased urine output, etc. There may be hypotension, tachycardia, pale conjunctiva, etc. If it ruptures into the retroperitoneal cavity, the blood clot can fill the cavity, and the blood pressure may recover after a decrease. Therefore, attention should be paid to the fact that a few patients may not show shock at the initial diagnosis.

　　Patients may have nausea, vomiting, abdominal distension, hematemesis, and hematochezia, which are manifestations of aortic enteric fistula formed when the abdominal aortic aneurysm ruptures into the digestive tract. Usually, there is a small amount of bleeding (also known as prodromal hemorrhage) followed by a large amount of hematemesis and (or) hematochezia, causing the patient to quickly enter a shock state and die. The First Affiliated Hospital of China Medical University has two cases of abdominal aortic aneurysm rupture into the duodenum, causing喷射性hematemesis. If there is a large amount of fresh blood in the stool, it should be considered that there is a possibility of rupture into the colon.

　　Rupture of abdominal aortic aneurysm into the inferior vena cava forms an aorto-caval fistula, causing high-output cardiac insufficiency, manifested as tachycardia, dyspnea, lower limb edema, venous congestion, varicose veins, etc.

　　In addition, when retroperitoneal hematoma involves the iliacolюмbar muscle, there may be sciatic nerve pain; closed rupture compressing extrahepatic bile ducts can cause obstructive jaundice; hematoma extending downward can form a mass at the inguinal region, which needs to be differentiated from painful inguinal hernia.

　　About 70% of patients with ruptured abdominal aortic aneurysms can feel a palpable pulsatile mass in the abdomen, mostly located on the left side, which may be tender but not severe. If the abdominal aortic aneurysm diameter is not large, or if the patient is obese or has significant abdominal distension, the pulsatile mass may not be palpable. Some people consider sudden severe abdominal pain and (or) back pain, hypotension or shock, and pulsatile abdominal mass as a triad of ruptured abdominal aortic aneurysm, but only about 50% appear simultaneously.

　　About 70% of patients may have abdominal tenderness, but the muscle tension is relatively mild. Patients may have abdominal distension and swelling, which is caused by secondary paralytic ileus due to intraperitoneal hemorrhage or retroperitoneal hematoma. If continuous vascular杂音 is heard in the abdomen, it should be considered that there is a possibility of rupture of the abdominal aortic aneurysm into the inferior vena cava, iliac vein, or left renal vein. If there are also manifestations of congestive heart failure, it is more helpful for diagnosis.

　　In addition, retroperitoneal blood渗漏 to the lateral abdomen and lumbar back can cause ecchymosis, similar to the Grey-Turney sign during acute pancreatitis.

　　We should first pay attention to and improve factors closely related to our lives, such as quitting smoking, reasonable diet, regular exercise, and weight reduction. Appropriate exercise can enhance physical fitness and improve the body's ability to resist diseases. Anyone who adheres to these simple and reasonable lifestyle common sense can reduce the chance of getting cancer. Pay attention to personal and environmental hygiene, avoid drug abuse, and take personal protection when working in harmful environments.

　　First, check the blood type, coagulation time, and blood cross test to detect the coagulation mechanism. Abnormalities should be corrected before surgery to avoid postoperative DIC.

　　Is only suitable for patients with completely stable general condition, and抢救 preparations should be made under strict surveillance. If the condition is unstable, surgery should not be delayed for the sake of diagnosis, and the patient should be immediately sent to the operating room for rescue.

　　1. Chest and abdominal X-ray film:Can determine whether there is a thoracic or abdominal aortic aneurysm or aneurysmal dissection of the aorta, and anteroposterior and lateral films can observe the presence of shell-like calcification. If the shadow of the psoas muscle disappears and the intestine is displaced forward in the lateral film, it should be considered that the rupture of the abdominal aortic aneurysm has caused a retroperitoneal hematoma.

　　2. Abdominal ultrasound:Can be performed at the bedside and is commonly used, as it can effectively understand the size, scope, and presence and degree of bleeding in the peritoneal cavity and retroperitoneal space, and can also be used for differential diagnosis.

　　3. CT examination:Can determine the presence of abdominal aortic aneurysm, defects in the aneurysm wall, and the formation of hematomas, and can be used to differentiate from inflammatory abdominal aortic aneurysms.

　　4. Other examinations:Electrocardiogram (including limb leads) can exclude myocardial infarction, pulmonary embolism, and other diseases, and angiography is generally not used.

　　1. Foods beneficial for abdominal aortic aneurysm rupture

　　Adopt a light diet, eat more vegetables and fruits, and rationally match the diet to ensure adequate nutrition.

　　2. Foods to avoid eating for abdominal aortic aneurysm rupture

　　Avoid smoking, drinking, spicy foods, greasy foods, and cold foods.

　　(The above information is for reference only, please consult a doctor for details.)

　　1. Treatment

　　For open and restrictive ruptured abdominal aortic aneurysms with obvious hemorrhage, it goes without saying that emergency surgery is the most effective diagnostic and therapeutic method. Given that the mortality rate of surgical treatment for ruptured abdominal aortic aneurysm is significantly higher than that for elective abdominal aortic aneurysm surgery, those highly suspected of this diagnosis should also undergo exploratory laparotomy as soon as possible. Darling reported that only 10% of abdominal aortic aneurysm patients with symptoms of ruptured abdominal aortic aneurysm can survive for 6 weeks, but no one has survived for more than 3 months. For restrictive ruptures, there is always a possibility of deterioration in condition, so emergency surgery should also be performed. Some suggest that if patients with such conditions have obvious cardiovascular, renal, and other diseases when they come for treatment, they can be given emergency surgery after improving their general condition under ICU surveillance. Once deterioration occurs, treatment should be performed immediately. Another study shows that the surgical efficacy of patients with pre-symptomatic symptoms of abdominal aortic aneurysm rupture is basically the same as that of elective abdominal aortic aneurysm surgery. Therefore, early surgical treatment should also be considered for such patients.

　　The treatment of ruptured abdominal aortic aneurysm lies in active and effective resuscitation, rapid control of bleeding, reasonable selection of surgery, and fine perioperative care.

　　1. Resuscitation and monitoring:At least two unobstructed venous infusion pathways should be established. For patients with collapsed peripheral veins, a cut should be made in the great saphenous vein. If possible, central venous catheterization should be performed, using a short and wide-bore Swan-Ganz catheter, which is not only beneficial for resuscitation and fluid administration but also can monitor hemodynamic changes during the operation. In recent years, some people have advocated the administration of colloidal solutions or hypertonic saline (3% or 7.5% sodium chloride) for hypovolemic shock, which can replenish blood volume in a short time through the administration of a small amount of fluid. The former can also reduce interstitial pulmonary edema, but there is still controversy about their combined use. The use of fluorocarbon solutions and hemoglobin-based oxygen carriers as blood substitutes is still limited to research. If there is a temporary lack of sufficient blood supply, 'O' type blood can be considered for transfusion. Vasoactive drugs should be used with caution to maintain systolic blood pressure at 10.7-13.3 kPa (80-100 mmHg) to prevent excessive blood pressure from aggravating bleeding. Endogenous morphine peptides and their receptors are associated with hypotension in hypovolemic shock. Clinical studies have confirmed that naloxone, a morphine antagonist, has good efficacy. The application of an anti-shock garment can be equivalent to autologous transfusion of 800-1000 ml of blood, thereby significantly improving cerebral and cardiac blood supply. Those who have worn it should be removed slowly after anesthesia and relative hemodynamic stability. Electric blankets, air conditioning, and other methods can be used to correct the patient's hypothermia, and the infused fluids should also be preheated to prevent hypothermia from causing cardiac dysfunction, abnormal coagulation mechanism, or even DIC. A urinary catheter should be placed routinely to monitor urine output. Timely blood gas analysis and blood biochemical tests should be performed to correct acid-base imbalance and electrolyte disorders. In addition, antibiotics should be used rationally during the perioperative period to prevent infection.

　　2. Rapid control of bleeding:Based on the hospital conditions, patient status, and the surgeon's experience, appropriate methods are chosen to control the proximal aorta of the tumor as soon as possible to stop bleeding.

　　(1) Occlusion of the descending aorta through left thoracotomy: When there is a suspicion of rupture of an abdominal aortic aneurysm into the abdominal cavity or a large retroperitoneal hematoma, a left anterolateral thoracotomy can be performed at the 6th or 7th intercostal space to expose the descending aorta. The descending aorta is occluded above the diaphragm by finger pressure or a non-invasive vascular clamp to control abdominal bleeding. This method can be completed in a short time, with less bleeding, avoiding blind clamping in a large amount of clotted blood, and allowing direct observation of the heart's beating. The disadvantage is that the ischemic time of the abdominal organs will be prolonged. If another surgical team quickly opens the abdomen, exposes, and occludes the proximal part of the abdominal aorta near the neck of the aneurysm, it can shorten the occlusion time above the diaphragm and reduce organ ischemia. The First Affiliated Hospital of China Medical University has applied this method to 2 of 8 patients with ruptured abdominal aortic aneurysms and achieved ideal results.

　　(2) Occlusion of the abdominal aorta below the diaphragm above the renal artery: First, make a median incision from the xiphoid process to the umbilicus, then the second assistant compresses the omentum and intestines that have extruded out of the incision to prevent rapid decompression of the abdominal cavity. The third assistant pulls the liver to the right, aspirates the blood under the liver, incises the lesser omentum, and separates the crus of the diaphragm to reach the abdominal aorta with the fingers. The index and middle fingers hold the aorta, and the right hand holds the aortic clamp to occlude the abdominal aorta above the celiac artery in the direction of the abdomen and back. Then, extend the upper abdominal incision to the superior part of the pubic bone and continue the operation.

　　(3) Balloon Catheter Method: Under local anesthesia, puncture and catheterize the brachial artery or femoral artery, place the balloon catheter in the proximal aorta of the abdominal aortic aneurysm, inflate the balloon with physiological saline to occlude the abdominal aorta for止血, and then perform a median abdominal incision from the xiphoid process to the pubic symphysis for abdominal operation. However, in patients with significantly reduced blood pressure or chest aorta and iliac artery tortuosity, the insertion of the balloon catheter may be very difficult.

　　(4) Finger Compression Method: Use the thumb or index finger to press the exposed proximal aorta towards the vertebral direction or use a compression device to compress. It is also possible to directly insert the thumb into the rupture hole and simultaneously insert a balloon catheter, which can both stop bleeding and serve as an indication for clamping.

　　3. Selection of Operation Method:基本上同非破裂性腹主动脉瘤一样，切除腹主动脉瘤，行人工血管移植术。有人主张在破裂性腹主动脉瘤重建血运时，应尽可能使用直管型人工血管以减少手术时间，即使存在轻度的髂总动脉瘤时亦可采用，且术后随访需再手术修补髂动脉瘤的病例也不多见。但对于髂动脉病变严重时，必须使用Y形人工血管，在人工血管的选择上以不需预凝的ePTFE为佳。术中应充分注意保护肾功能。

　　4. Preoperative Attention Points

　　(1) Rapid and accurate occlusion is the key to the success of rescue, so it is recommended to use the method that is convenient for occlusion and adhere to the principle of individualization.

　　(2) Heparin should be used with caution during the operation because shock, hypothermia, massive blood transfusion, and artificial vascular replacement can cause abnormal coagulation mechanism. Improper use can exacerbate bleeding, and it can be locally applied before vascular occlusion and anastomosis.

　　(3) It is recommended to use the autologous blood recovery device (CellSaver), which is simple to operate, can return the required blood in time, reduce transfusion reactions, and has little impact on blood cells and platelets, especially suitable for patients with severe bleeding.

　　(4) Pay attention to maintaining body temperature during the operation. All infused fluids and blood should be warmed to prevent hypothermia from affecting cardiac function and coagulation mechanism.

　　(5) Pay attention to avoid secondary injury. Retroperitoneal hematoma can cause displacement of the inferior vena cava, left renal vein, and duodenum, so it should be avoided during the operation to prevent exacerbation of bleeding.

　　(6) Antibiotics should be used during the operation to ensure a high blood drug concentration and prevent infection.

　　5. Postoperative Complications and Management

　　(1) Myocardial Infarction: Patients often have concurrent arteriosclerotic diseases, and hemorrhagic shock can induce myocardial infarction. Wakefield et al. reported that the incidence of myocardial infarction after the operation for ruptured abdominal aortic aneurysm was 16%, and Lawrie et al. reported that about 67% of patients with ruptured abdominal aortic aneurysm who developed myocardial infarction after the operation died. Therefore, prevention and treatment of myocardial infarction is very important.

　　(2) ARDS: Factors such as hemorrhagic shock, surgical invasion, and massive blood transfusion often lead to ARDS, which requires artificial respiration assistance after surgery, and blood gas monitoring should be performed to prevent pulmonary infection and prevent the occurrence of ARDS.

　　(3) Acute renal failure: It is caused by prolonged ischemia of the kidneys due to shock and the occlusion of the abdominal aorta during surgery, manifested as oliguria or anuria. In addition to the use of diuretics, timely dialysis treatment should be carried out.

　　(4) Colon ischemia: It occurs due to factors such as shock, intestinal mesenteric injury during surgery, and vascular embolism, which reduce the blood supply of the inferior mesenteric artery. If there are symptoms such as hematochezia or peritoneal irritation, chronic intestinal obstruction, etc., a timely fiberoptic colonoscopy should be performed. Once necrosis of the colon is found, the necrotic intestinal tract should be resected, and an artificial anus stoma on the abdominal wall should be created.

　　(5) Gastrointestinal bleeding: Stress ulcer can occur after the operation of a ruptured abdominal aortic aneurysm, resulting in upper gastrointestinal bleeding. Conservative therapy is often effective. In recent years, the First Affiliated Hospital of China Medical University has successfully treated 8 cases of ruptured abdominal aortic aneurysm after the operation, all of which had stress ulcer and were cured by conservative therapy.

　　II. Prognosis

　　The surgical mortality rate of ruptured abdominal aortic aneurysm is 31% to 70%, and the factors affecting the postoperative mortality rate include: ①Elderly (over 80 years old); ②History of congestive heart failure or myocardial infarction; ③Preoperative shock, blood pressure below 10.6 kPa (80 mmHg) at the time of visit; ④Disability; ⑤Hematocrit below 30%; ⑥Ruptured abdominal aortic aneurysm into the peritoneal cavity; ⑦Hematoma extending above the renal artery; ⑧Abdominal aortic aneurysm diameter above 6 cm; ⑨Blood transfusion above 10000 ml during surgery; ⑩Elevated blood BUN and Cr values; oliguria below 100 ml during surgery, etc., all of which significantly increase the postoperative mortality rate. In addition, complications such as venous injury, bleeding during surgery, and poor anastomosis also affect the surgical mortality rate. The main cause of postoperative death is: ARDS, renal failure, myocardial infarction, gastrointestinal bleeding, etc. Slaney et al. reported that the 5-year survival rate of patients with successfully treated ruptured abdominal aortic aneurysm is 64.8%, similar to elective surgery, indicating that a good prognosis may be possible if the rescue is successful.