The co-infection of severe pancreatitis is one of the most difficult problems in the treatment of severe pancreatitis, and it is also the main cause of prolonged course of severe pancreatitis, frequent complications and increased mortality. The main types of infections are abdominal infections, pulmonary infections, intravascular catheter infections, enterogenic infections and urinary tract infections. These infections can occur one after another in the course of severe pancreatitis, and can also occur in combination, often causing clinicians to lose sight of one another, resulting in treatment failure and a loss of success. Therefore, in the process of treating severe pancreatitis, according to the occurrence and development of such infections, timely measures should be taken and timely diagnosis and treatment.
1, the early systemic inflammatory response to severe pancreatitis and the differentiation of infection
The early onset of severe pancreatitis can be characterized by a non-infectious systemic inflammatory response syndrome (SIRS). The concept of SIRS is most meaningful in guiding the early treatment of severe pancreatitis. Patients present with fever, increased heart rate and respiratory rate and elevated white blood cells caused by chemical irritation of the peritoneum by the pancreas. This syndrome should not be treated as sepsis and antibiotics should be used playfully. In this case, the differential diagnosis can be made with repeated blood cultures. Never change antibiotics or increase antibiotic combinations without seeing blood culture results. In order to avoid possible dysbiosis in the later stages, the use of prophylactic anti-infective drugs should also be shortened as much as possible.
2.Pulmonary infection
Pulmonary infection is the most common infection in the intensive care unit, and patients with severe pancreatitis are no exception. Pulmonary infections mostly occur after tracheotomy and mechanical ventilation, namely ventilation-associated pneumonia (VAP), and also associated with prolonged bed-rest combined with pneumonic co-infection. Most of the pathogens are common hospital bacteria, such as Pseudomonas aeruginosa, Acinetobacter baumannii and Klebsiella pneumoniae, and most of them are multi-drug resistant or even pan-drug resistant bacteria. For pulmonary infections combined with severe pancreatitis, we must strengthen aspiration and other measures to improve pulmonary drainage, and regularly perform bacterial culture of sputum to guide antibiotic treatment. The patient should be taken off the machine at the right time and encouraged to sit up and move out of bed in time.
The pleural effusion combined with severe pancreatitis is mostly caused by intra-abdominal inflammation, early chemical peritonitis can stimulate pleural effusion, and late subdiaphragmatic infection can also cause. Therefore, after the discovery of pleural effusion, attention should be paid to check whether there is infection in the abdominal cavity. If the pleural effusion is so large that it affects breathing, the effusion can be removed at once (but not more than 800 ml). Repeated pleural effusions almost certainly indicate the presence of infection under the patient’s diaphragm. If there is an infectious effusion in the thoracic cavity, it also mostly develops from the retroperitoneum under the diaphragm, and the intra-abdominal and retroperitoneal infections should be actively sought and treated.
3, abdominal cavity infection
Ultrasound is of little value in the diagnosis of severe pancreatitis combined with abdominal infection. The accuracy of ultrasound is significantly affected by the pneumatization of the intestinal canal in the abdominal cavity, and the detection of abscesses by ultrasound is valuable, but the failure to detect a lesion by ultrasound does not mean that there is no abscess or other infectious foci. This view applies especially to abscesses that occur between intestinal collaterals and retroperitoneum.
For severe pancreatitis combined with abdominal abscess or infected effusion, the principle of minimally invasive treatment should be considered first. Ultrasound-guided aspiration of pus and drainage by indwelling catheter can be performed. CT-guided puncture and drainage of abscesses in the retroperitoneum or between intestinal collaterals is accurate and reliable. After drainage of abscesses, flushing should be performed two to three times daily to physically reduce bacteria, reduce pressure on antibiotic selection, and reduce the development of drug-resistant bacteria.
Colonic fistulas, including transverse colonic fistulas, colonic splenic flexure fistulas and descending colonic fistulas, are common types of intestinal fistulas in severe pancreatitis. The occurrence of colonic fistula is often combined with severe abdominal infection, and abdominal infection even becomes the main manifestation. Colonic fistula may manifest after the abdominal infection has been drained. Clinicians should consider the possibility of a combined colonic fistula when treating a prolonged abdominal infection. Most of these abdominal infections can be managed by damage control surgery. This means that the proximal intestinal tube of the fistula is dragged out of the stoma by performing another dissection. The distal intestinal tube with the fistula can be removed or left open depending on the local conditions of the operation. Because of the serious contamination of the abdominal cavity at this time, the patient has varying degrees of malnutrition and poor tissue healing ability, it is not advisable to force a one-stage anastomosis of the intestine to avoid the reoccurrence of colonic anastomotic fistula. As fecal contamination is the main cause of colonic fistula combined with abdominal infection, a single-lumen stoma should be performed for the proximal intestine, and the distal intestine can be closed with a suture. It is not advisable to perform a double-lumen stoma, otherwise it is difficult to achieve the purpose of fecal diversion. In patients with severe pancreatitis, the transverse colonic mesentery is often contracted due to inflammatory edema, so the hepatic flexure of the colon is often the best site for stoma, whether it is a transverse colonic fistula or a more distal fistula. Of course, in the case of occasional colonic fistulas, only the more proximal intestinal canal can be stomaed, but it should be a single-lumen stoma.
4. Intravascular catheter-related infections
Catheter-related infections are almost inevitable in patients with severe pancreatitis because they receive parenteral nutrition support, hemodialysis or filtration. In particular, hemofiltration catheters have up to four connections, and catheter-related infections can occur after a short period of placement. The connectors of various micropumps and infusion catheters are the most vulnerable to contamination and are one of the causes of intravascular catheter-associated infections. In patients with severe pancreatitis with intravascular catheters, especially in the early and middle stages of the disease when symptoms of infection appear, the first thing that needs to be differentially diagnosed and managed is catheter-associated infection. The specific management can be referred to the recent guidelines.
It is important to note that attention should be paid not only to catheter infections in large vessels, but also to catheter-related infections caused by long-term placement of cannula needles in peripheral veins. Catheter-associated infections should be prevented by intensive dressing changes at the skin entry point and junction of the catheter. Once catheter-associated infection is suspected, the intravascular catheter should be removed without hesitation. Clinical practice has shown that catheter-associated infections cannot be eliminated by relying exclusively on antibiotics without catheter removal. If catheter-associated infection is diagnosed, the catheter should be reintubated after the bacteraemia is eliminated.
5.Intestinal-derived infection
Intestinal-derived infection is the main form of infection in the late stage of severe pancreatitis, although there is no accurate clinical means to confirm the diagnosis of intestinal-derived infection. However, the measures taken for it can be effective. The barrier of intestinal mucosa and immune barrier caused by the long-term lack of intracavitary nutrition, the dysbiosis of intestinal flora caused by the long-term application of various antibiotics, the use of antacids and the alkalinization of gastric juice are the basis of intestinal-derived infection. Therefore, in patients with severe pancreatitis, enteral nutritional support and appropriate amounts of tissue-specific nutritional factors such as glutamine and dietary fiber should be provided to strengthen various intestinal barrier functions in order to prevent intestinal-derived infections. If the source of infection cannot be determined after excluding other infections, the possibility of enterogenic infection should be considered, and selective intestinal decontamination (SDD) should be taken to stop various measures that lead to enterogenic infection, and enteral nutrition should be relied on to eliminate enterogenic infection eventually.
6.Urinary tract infection
Urinary tract infection can also be one of the causes of infection in patients with severe pancreatitis due to long-term indwelling catheter, long-term bed rest and the use of broad-spectrum antibiotics. Patients should be encouraged to defecate on their own, and if necessary, it is best to perform suprapubic cystocentesis with an indwelling catheter instead of a transurethral catheter. Once the urinary tract infection is clearly identified, bladder irrigation is also feasible along with antibiotics.
7. Other types of infections
Severe pancreatitis has a long course, and various infections may occur. These infections may be common infections caused by pressure sores or surgical incisions; they may also cause purulent parotitis due to blockage of the parotid ducts caused by a long-term lack of transoral diet. Prolonged fasting, total parenteral nutrition support and prolonged use of growth inhibitors can also cause biliary stasis and eventually biliary cholecystitis. Clinicians should be familiar with these surgical infections in order to accurately locate and eliminate them.
8. Conclusion
It is almost impossible to expect prolonged use of anti-infective drugs to eliminate the infection. In patients with severe pancreatitis, once fever appears, especially in the late stage of the disease, blood tests should be performed promptly to determine whether the fever is caused by infection. At the same time, the corresponding blood, sputum and urine cultures should be performed, and stool routine should be checked. According to the patient’s symptoms, arrange for appropriate imaging examinations, such as chest X-ray and CT scan of the whole abdomen. Never use the excuse that the patient’s condition is heavy and it is not easy to move, and just wait passively. If the infection is not clear at the time, we should take measures according to the ease of treatment, such as removing intravascular catheter, changing catheter to bladder puncture tube, thoracentesis and drainage, or even re-operation by caesarean section to eliminate all visible lesions, together with timely restoration of enteral nutrition and reasonable anti-infective drugs, the infection problem can be solved.