Standardized Incidence Rates of Surgical Site Infection: a Multicenter Study in Thailand
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Standardized incidence rates of surgical site infection: A multicenter study in Thailand Nongyao Kasatpibal, RN, MNS,a Silom Jamulitrat, MD,b and Virasakdi Chongsuvivatwong, MD, PhD,a for The Surgical Site Infection Study Group Hat Yai, Songkhla, Thailand Background: No previous multicenter data regarding the incidence of surgical site infection (SSI) are available in Thailand. The magnitude of the problem resulting from SSI at the national level could not be assessed. The purpose of this study was to estimate the incidence of SSI in 9 hospitals, together with patterns of surgical antibiotic prophylaxis, risk factors for SSI, and common causative pathogens. Methods: A prospective data collection among patients undergoing surgery in 9 hospitals in Thailand was conducted. The National Nosocomial Infection Surveillance (NNIS) system criteria and method were used for identifying and diagnosing SSI. The SSI rates were benchmarked with the NNIS report by means of indirect standardization and reported in terms of standardized infection ratio (SIR). Antibiotic prophylaxis was categorized into preoperative, intraoperative, and postoperative. Risk factors for SSI were evaluated using multiple logistic regression models. Results: From July 1, 2003, to February 29, 2004, the study included 8764 patients with 8854 major operations and identified 127 SSIs, yielding an SSI rate of 1.4 infections/100 operations and a corresponding SIR of 0.6 (95% CI: 0.5-0.8). Of these, 35 SSIs (27.6%) were detected postdischarge. The 3 most common operative procedures were cesarean section, appendectomy, and hysterectomy. The 3 most common pathogens isolated were Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa, which accounted for 15.3%, 8.5%, and 6.8% of infections, respectively. The 3 most common antibiotics used for prophylaxis were ampicillin/amoxicillin, cefazolin, and gentamicin. The proportion of types of antibiotic prophylaxis administered were 51.6% preoperative, 24.3% intraoperative, and 24.1% postoperative. Factors significantly associated with SSI were high degree of wound contamination, prolonged preoperative hospital stay, emergency operation, and prolonged duration of operation. Conclusion: Overall SSI rates were less than the average NNIS rates. The causative pathogens of SSI were different from those of other reports. There was a crucial proportion of operations that did not comply with the antibiotic guidelines. The risk factors for SSI identified in this study were consistent with most other reports. (Am J Infect Control 2005;33:587-94.) Surgical site infection (SSI) is a common postoper- From the Epidemiology Unita and the Department of Community Medicine,b Faculty of Medicine, Prince of Songkla University, Hat Yai, ative complication and causes significant morbidity Songkhla, Thailand. and mortality, increases antibiotic usage, prolongs The Surgical Site Infection Study Group: Chiangkham Hospital: Wanpen hospital stay, adds cost, and decreases patients’ quality Boonprasert, RN, MSc (team leader); Saraburi Hospital: Srisuree of life.1-3 The challenge of hospitals is to improve the Aurjirapongpan, RN, MNS (team leader); Thammasat University quality of care delivered to patients during surgery in a Hospital: Prisana Patoomanunt, RN, MSc (team leader); Bhumibol Adulyadej Hospital: Achara Nawajamtrakul, RN, BNS (team leader); cost-effective manner through system redesign using Vachira Phuket Hospital: Wilailuk Wongchunlachat, RN, MNS (team proven, evidence-based practices. leader); Naradhiwas Rajanagarindra Hospital: Doungporn Nukoonruk, Effective surveillance system and appropriate pro- RN, MNS (team leader); Rayong Hospital: Uraiwan Hirunroj, RN, MNS phylactic antibiotics have been described as a preven- (team leader); Chumphon Khet Udomsakdi Hospital: Benjawan Nakornpat, RN, BNS (team leader); Udonthani Hospital: Jutarat tive measure for reducing SSI. The landmark Study on Kraisriwatana, RN, BNS (team leader). the Efficacy of Nosocomial Infection Control (SENIC) Supported by The Royal Golden Jubilee PhD Program of the Thailand project demonstrated that, to be effective, nosocomial Research Fund. infection programs must include the following com- This article is a part of Nongyao Kasatpibal thesis to fulfill the ponents: (1) organized surveillance and control activ- requirements for a PhD degree in Epidemiology at Prince of Songkla ities, (2) an adequate number of trained infection University. control staff, and (3) a system for reporting SSI rates to Reprint requests: Nongyao Kasatpibal, RN, MNS, Epidemiology Unit, surgeons. The study showed that these strategies could Faculty of Medicine, Prince of Songkla University, Hat Yai, Songkhla, reduce approximately one third of SSI.4 An estimated Thailand. E-mail: [email protected]. 40% to 60% of SSIs are preventable with appropriate 0196-6553/$30.00 use of prophylactic antibiotics.5-8 However, overuse, Copyright ª 2005 by the Association for Professionals in Infection underuse, improper use, and misuse of antibiotics Control and Epidemiology, Inc. occurs in 25% to 50% of operations.9-13 Inappropriate doi:10.1016/j.ajic.2004.11.012 use of broad spectrum antibiotics, or prolonged 587 588 Vol. 33 No. 10 Kasatpibal, Jamulitrat, and Chongsuvivatwong courses of prophylactic antibiotics, puts all patients at All participating hospitals had at least 100 beds; even greater infection risk because of the development 1 infection control nurse (ICN) per 250 beds (ICN of antibiotic-resistant pathogens.14 Reducing surgical responsible for the whole hospital); 1 infection control infections while minimizing antibiotic resistance re- ward nurse (ICWN) per ward (ICWN responsible for mains a challenge to hospitals. each ward); undertook surveillance by using prospec- In Thailand, no prospective study concerning inci- tive surveillance methods with an efficiency of at least dence SSI on a national level has been published. The 60%; and had a computer in the infection control unit, previous prevalence studies in 1988 and in 1992 a hospital computer database, and adequate clinical revealed that SSI was the second and third ranked of and laboratory information for diagnosis of SSI. Par- all nosocomial infections in Thai hospitals, accounting ticipation was voluntary, and the hospitals were as- for 19.6% and 16.6%, respectively.15,16 Traditionally, sured of confidentiality of their data. The participating SSI surveillance in Thailand has been stratified by only hospitals would receive their own standardized and the degree of wound contamination. The major limi- stratified infection rates quarterly to compare their tation of the system is its failure to capture the other own data with pooled data from all participating intrinsic important patient risks of SSI, which is re- hospitals. Once a year, a meeting of these hospitals quired before meaningful comparisons for mixed was organized for discussion of methodologic points cases can be made. and exchange of participants’ experience using such Adjustment for variables known to confound rate data for surveillance and infection control practices. estimates is critical for valid comparisons of SSI rates. During the SENIC project, a simplified index was Data collection developed.17 Despite improved performance over the traditional wound classification scheme, limitations in From July 2003 to February 2004, a prospective the SENIC index were still noted. Recently, the National multicenter study was conducted in the 9 hospitals. The Nosocomial Infections Surveillance (NNIS) System de- surveillance of SSI concentrated on 28 NNIS operative veloped the SSI risk index to provide a satisfactory procedure categories. However, each participating hos- risk-adjusted SSI rate across a diversity of operative pital selected its own major operative procedures of procedures.18,19 The NNIS risk index has proven to interest (at least 5 operative procedures/hospital), such have significantly better discriminatory power than the as high infection rate, high volume of procedures, or SENIC index.20 high cost, for data collection. After a 1-day training Standardized infection ratio (SIR) is one of the session in data collection and diagnosis criteria, infec- proven measures for interpretation of SSI rate. This tion control nurses in each hospital prospectively measure is used in many countries such as Spain and collected the pertinent data and recorded the data on United States. Monge Jodra et al explained the use of the preprinted data collection forms. The collected data the SIR to benchmark their SSI rates to SSI rates included patient’s demographic data, diagnosis, opera- reported by the NNIS System.21 Gustafson stated that tion, antibiotics administered, clinical signs and symp- there were several advantages of using the SIR: (1) It is toms of infection, laboratory results including adjusted for known variations in patient risk levels, and microbiology and serology results, and imaging results. (2) any reported standard could be used as a bench- The log book in the operative theater was reviewed mark.22 A study in Thailand proclaimed that use of the every day for operations that met the inclusion criteria, SIR enabled a single comparison of rates, adjusted for which were as follows: procedure performed in an risk category, instead of multiple comparisons specific operating room (OR), a surgeon made a skin or mucous to procedure and risk category with small numbers.23 membrane incision and primarily closed it before the This study was conducted with the primary inten- patient