his study found that the incidence of postoperative SSI in EAS patients was 7.5%, with Escherichia coli infection being the most common, which is comparable to that reported worldwide [9, 14, 15]. The occurrence of SSI significantly prolonged the hospital stay of patients and increased medical costs. The incidence of SSI can be reduced by laparoscopic surgery and shorter operation time, whereas high blood glucose levels, intestinal obstruction, and colorectal surgery increase the risk.
It has been shown that older people are more likely to develop SSI [16] ; in this study, age was not a predictor as observed using multivariate logistic regression analysis. Male patients had a significantly higher risk of SSI after EAS than females (OR 2.204, 95% CI 1.178 – 8.985, P = 0.010); while this is partly debated, multiple studies have found significantly higher rates of SSI in male patients than in females [17, 18]. This may be related to male bushy hair; shaving increases the risk of skin trauma. Guidelines for SSI prevention issued by the Surgical Infection Society strongly discourage the use of razors for hair removal and propose the use of clippers if necessary.
In our study, high blood glucose level ( > 124mg/dL ) was found to be a risk factor for SSI after EAS (OR 3.328, 95% CI 1.888 – 5.867, P < 0.001). Previous studies have shown that diabetes mellitus and preoperative hypergycemia are SSI risk factors [19]. Hyperglycemia can affect the function of white blood cells, which in turn reduces the body's defense. The EAS patients tend to be in an acute preoperative stress state, and the associated hyperglycemic levels can better predict SSI than diabetes. Decreased serum albumin is usually an indicator of malnutrition or combined chronic wasting disease. In the present study, low serum albumin levels did not significantly affect the occurrence of SSI after adjustment for other variables, which requires further investigation.
The incidence of postoperative SSI is generally higher in patients undergoing colorectal than other gastrointestinal surgeries [20]. Our data shows that patients undergoing emergency colorectal surgery are at 7.017 times (95% CI 3.577-13.805, P < 0.001) higher risk of SSI than patients undergoing other emergency gastrointestinal surgeries. There is a high colorectal bacterial load, including a variety of gram-negative and anaerobic bacteria. Necessary bowel preparation is difficult to achieve for emergency surgery and intestinal contents are easily spilled, contaminating the surgical area. This explains the high risk of SSI in emergency colorectal surgery patients.
Our study found that intestinal obstruction was a risk factor for SSI (OR 1.973, 95% CI 1.014 – 3.838, P = 0.045). The intestinal barrier function is impaired due to fasting and dilatation of the bowel lumen regardless of whether the bowel is removed, and bacteria are easily translocated outside the bowel lumen, increasing the risk of SSI. In our study, gastrointestinal perforation was not an independent risk factor for SSI. Gastrointestinal perforation usually occurs in the upper gastrointestinal tract, which has a relatively less bacterial load. At the same time, more attention is often paid to SSI prevention during the treatment of patients with gastrointestinal perforation, including adequate irrigation of the surgical site and post-surgical application of high-grade antibiotics. There is need to pay attention to the prevention of SSI in patients with intestinal obstruction regardless of whether bowel resection is performed or not.
Our study also evaluated the relationship of ASA score, NNIS risk index, and wound irrigation with SSI. None of these were independent risk factors for SSI in EAS patients after adjustment for logistic regression analysis. The NNIS risk index included ASA score, duration of surgery, and surgical wound grade. The majority of patients had an ASA score of 1 or 2, and surgical wounds were classified as clean-contaminated. The incidence of SSI was higher in patients whose incisions were irrigated with saline and povidone-iodine solution. This may be due to more contaminated incisions being irrigated than clean incisions during surgery, therefore spreading the infective microbes. The World Society for Emergency Surgery (WSES) states in the Intraoperative Surgical Site Infection Control and Prevention that there is insufficient data to support the role of irrigation of the incision with saline or polyvidone before closure in preventing SSI [21].
Previous studies have shown that laparoscopic surgery can significantly reduce the incidence of SSI compared to open surgery [20, 22]. This study supports this view. Laparoscopic surgery uses a small incision, greatly reducing the chances of exposure with little damage to the surrounding tissues, which reduces the risk of SSI. However, laparoscopic surgery has some limitations, especially for emergency cases. Laparoscopy requires certain equipment base, operating space, and experienced surgeons. In the 2016 WSES consensus on the management of intra-abdominal infections, laparoscopic surgery was determined to be safe and preferred for procedures such as appendectomy, repair of perforated peptic ulcer, and cholecystectomy when contraindications are excluded [23]. However, if peritonitis episodes were > 24 h, laparotomy was recommended.
The duration of surgery is a risk factor for SSI [24, 25]. This study found that EAS patients who had longer surgery were more likely to have an SSI. Longer surgery not only aggravates the destruction of the microenvironment in the surgical area, but also greatly increases the chances of bacterial colonization due to the increased exposure time of the surgical incision to the air. Precautions against SSI can be appropriately instituted for operation time greater than 122 min.
We also analyzed patients' perioperative antibiotic use. The Infectious Diseases Society of America recommended administering prophylactic antibiotics only when indicated [26]. However, EAS patients are mostly treated for the primary disease in the emergency department before surgery; in our study 707 (74.2%) patients had received different classes of antibiotics, preoperatively. This shows that there is lack of perioperative antibiotic standards for use in emergency surgery in China. Further randomized controlled trials are needed to determine the type and timing of antibiotic therapy. The WHO and the Infectious Diseases Society of America recommend that the administration of antibiotics should not be prolonged after surgery [1, 26]. Interestingly, we found that the high incidence of SSI was associated with prolonged antibiotic administration; EAS patients who were on prophylactic antibiotics, are usually continued on antibiotics post surgically. The study shows that prolonged prophylactic antibiotics use is not beneficial in reducing the incidence of SSI, but leads to intestinal flora disturbances, drug-resistant bacteria, and increased medical burden [27, 28].