序

The traditional wound infection classification system was developed in the wake of the ultraviolet light study of 1964.[9] This classification system was primarily designed to provide a clinical estimate of the inoculum of bacteria likely to be encountered during the procedure and does not address the other determinants of infection defined above. Four separate classes of procedures were identified, each with a unique infection rate.

傷口分類

傷口本身污染的程度與手術後是否發生感染有很大的關係，一種廣為接受的傷口分類方法如下：

1. 清潔傷口﹝Clean-Wounds﹞
   • 無發炎現象。
   • 未進入消化道、生殖道、泌尿道。
   • 完全縫合的傷口；若有引流，則採密閉引流者。
   • 非穿刺性的傷口。
   
   Clean Wounds:The wound is judged to be clean when the operative procedure does not enter into a normally colonized viscus or lumen of the body. Elective inguinal hernia repair is an example of a clean operative procedure. SSI risk is minimal and originates from contaminants of the OR environment or from the surgical team, or most commonly from skin colonists. The most common pathogen is Staphylococcus aureus. SSI rates in this class of procedures should be 2% or less, depending upon other clinical variables.
2. 清潔污染傷口﹝Clean-Contaminated Wounds﹞
   • 進入呼吸道、消化道、生殖道、泌尿道等管道，而無特殊污染的手術傷口。
   • 無感染性的膽道、闌尾、陰道、口咽的手術傷口。
   • 手術過程中沒有明顯的污染。
   
   Clean-Contaminated Wounds:A clean-contaminated surgical site is seen when the operative procedure enters into a colonized viscus or cavity of the body, but under elective and controlled circumstances. The most common contaminants are endogenous bacteria from within the patient. For example, sigmoid colectomy wounds generally contain E coli and Bacteroides fragilis as microbial contaminants. Elective intestinal resection, pulmonary resection, gynecologic procedures, and head-neck cancer operations that involve the oropharynx are examples of clean-contaminated procedures. Infection rates for these procedures are in the range of 4% to 10% and can be optimized with specific preventive strategies.
3. 污染傷口﹝Contaminated Wounds﹞
   • 開放性的、新的、意外性的傷口。
   • 腸胃道內容物有明顯溢出、手術過程有明顯的污染者。
   • 有急性發炎，但未化濃。
   
   Contaminated Wounds:Contaminated procedures occur when gross contamination is present at the surgical site in the absence of obvious infection. Laparotomy for penetrating injury with intestinal spillage and elective intestinal procedures with gross contamination of the surgical site are examples of contaminated procedures. As with clean-contaminated procedures, the contaminants are the bacteria that are introduced by gross soilage of the surgical field. Infection rates will be greater than 10% for this classification of wound, even with preventive antibiotics and other strategies
4. 髒或己感染的傷口﹝Dirty or Infected Wounds﹞
   • 有壞死組織的舊的外傷傷口。
   • 內臟穿孔。
   • 己有感染的傷口。
   
   Dirty Wounds:Surgical procedures performed when active infection is already present are considered dirty wounds. Abdominal exploration for acute bacterial peritonitis and intra-abdominal abscess are examples of this class of surgical site. Pathogens to be expected are the pathogens of the active infection that is encountered. Unusual pathogens are often encountered in dirty wounds, especially if the infection has occurred in a hospital or nursing home setting, or in patients receiving prior antibiotic therapy.

NNIS SSI Risk Index

To further allow comparison of infection rates between institutions and analyses of SSI rates within a given institution over time, the US Centers for Disease Control and Prevention (CDC) developed the NNIS Risk Index system, by which member hospitals report cumulative wound infection data. The risk index includes the traditional wound classification system defined above and additional variables.

This simplified risk index has a range from 0 to 3 points. A point is added to the patient's risk index for each of the following 3 variables:

• the patient has an operation that is classified as either contaminated or dirty.
• the patient has an American Society of Anesthesiologists (ASA) preoperative assessment score of 3, 4, or 5 (Table 1)
• the duration of the operation exceeds the 75th percentile where a standard T point (75% percentile) was determined from the NNIS database (Table 2); the T point is defined as the length of time in hours that represents the 75th percentile of procedures reported in the NNIS survey (Table 2)

The NNIS Risk Index has the advantage of using the ASA preoperative assessment score as an estimate of the patient's overall health at the time of the operation. The duration of the procedure becomes a surrogate marker for procedures of unusual complexity. The NNIS Risk Index has become a standard format for presenting SSI data by many institutions and is largely replacing the older wound classification system, while still using the older system as part of its methodology (Table 3).

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