Risk Factors for Surgical Site Infection (SSI) after Urological Surgery: Incisional and Deep-organ/space Experience at Anjo Hospital

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1 J Rural Med 2009; 4(2): Original article Risk Factors for Surgical Site Infection (SSI) after Urological Surgery: Incisional and Deep-organ/space Experience at Anjo Hospital Jun Sawai 1, Takehiko Okamura 1, 2, Taku Naiki 2, Yasuhiro Hijikata 1, Hideyuki Oe 1, Masashi Sawa 1, Miyuki Hyodo 1, Rie Inatomi 1, Masami Okudaira 1, Atsushi Naito 1 and Kazuhisa Inuzuka 1 1 Infectious Control Team, Anjo Kosei Hospital, Anjo, Japan 2 Department of Urology, Anjo Kosei Hospital, Anjo, Japan Abstract Objective: In urological operations, many endourological procedures and pre-existing urinary tract infections may cause surgical complications. It is essential to identify the risk factors for surgical site infections (SSI) and determine additional influences. Patients and Methods: In the present retrospective investigation, a total of 324 patients who underwent open urological surgery between January 2003 and December 2007 at Anjo-Kosei Hospital were assessed for SSI along with possible associated factors. Results: Forty-four cases (13.6%) proved positive for SSIs during the surveillance period. Among these, 31 demonstrated incisional SSI and 13 demonstrated deep/organ space SSI. Greater age and body mass index, low preoperative haemoglobin levels, long preoperative hospital stay, prolonged operation time and increased blood loss during surgery were all positively associated with SSI in general. For the deep/organ space SSI cases, advanced age, low preoperative haemoglobin levels, long preoperative hospital stay and prolonged operation time were significant factors. Conclusion: This study identified several independent predictors of SSI in general, as well as deep/organ space infection, for urological open surgery at our hospital. The results provided a basis for urologists to decrease the incidence of urological SSI. Key words: incisional surgical site infection, deep/organ space surgical site infection, urological open surgery (J Rural Med 2009; 4(2): 59 63) Correspondence to: Takehiko Okamura Department of Urology, J.A. Aichi Anjo Kosei Hospital, 28 Higashihirokute, Anjo-cho, Anjo , Japan hiko2546@sf.commufa.jp Introduction Surgical site infection (SSI) is one of the most common post-operative complications associated with longer hospital stay, higher treatment costs and significant related morbidity and mortality 1 3). In the Centers for Disease Control and Prevention (CDC) Guidelines for Prevention of Surgical Site Infection, 1999, risk factors for SSI are divided into two groups, patient and environmental 4). Patient factors included coincident remote site infections or colonization, diabetes, cigarette smoking, systemic steroid use, obesity, extreme age, poor nutritional status and perioperative transfusion of certain blood products. Environment risk factors are typically short duration of surgical scrub, inappropriate skin antisepsis and antimicrobial prophylaxis, preoperative shaving, inappropriate skin preparation, prolonged surgery, poor operating room ventilation, inadequate sterilization of instruments, foreign material use in the surgical site, inadequate surgical drains and poor surgical technique 4). It should be stressed that deep/organ space SSI is associated with greater morbidity and mortality than superficial infections, and recently Haridas, et al. focused on specific factors like hypoalbuminemia, low hemoglobin, and a history of previous operations in general surgery cases 5). In regard to urological operations, many endourological procedures may be performed before surgery, such as insertion of indwelling urinary catheters, cystoscopy and retrograde pyelography. Furthermore, bacterial infection with urolithiasis or malignant tumor development may be a complicating feature. Therefore, it is necessary to be aware of risk factors for SSI particularly in the urological field. A number of retrospective studies of SSI after urological surgery have been published, but only few reports of specific risk factors for 2009 The Japanese Association of Rural Medicine

2 60 deep/organ space SSI are available 6 8). In the present article, we document an investigation of risk factors for developing SSI in general, and deep organ/space SSI in particular, for urological open surgery performed in our hospital. Patients and Methods This retrospective study covered all 324 patients who underwent open urological surgery between January 2003 and December 2007 at Anjo-Kosei Hospital. Clinical data during hospitalization were obtained from the medical history charts. Wound conditions were evaluated for 30 days after each operation. Surgical site infections (SSI) were diagnosed based on the CDC guidelines and classified incisional and deep/organ space SSI 4). In all cases, perioperative patient and surgical factors were assessed for possible association with positive findings for SSI. Included patient factors were age, body mass index, tobacco use, existence of diabetes mellitus, history of previous surgery, state of nutrition (evaluated with reference to serum total protein and albumin), preoperative hemoglobin level and preoperative hospital stay. Surgical factors were duration of surgery and amount of blood loss. Operative procedures included total cystectomy, prostatectomy, partial nephrectomy, total nephrectomy, total nephroureterectomy and others. Total cystectomy was classified on the basis of 3 types of urinary diversion: ureterocutaneostomy, ileal conduit diversion, and neobladder construction. The χ 2 t and unpaired, 2-tailed Student t tests were employed for statistical analysis, with p<0.05 considered as statistically significant. Results Table 1 Patient background data are shown in Table 1. Men accounted for 86.7% of the total of 324 studied patients. The mean age was 63.2 years, and the mean preoperative and total hospital stays were 7.7 and 34.1 days, respectively. Thirty-four of the patients underwent total cystectomy; ureterocutaneostomy was conducted for 13 patients, ileal conduit diversion was conducted for 16 patients and neobladder construction was conducted for 5 patients. Retropubic radical prostatectomy was performed for 153 patients, partial nephrectomy was conducted for 4 patients, total nephrectomy was conducted for 32 patients, and total nephroureterectomy was conducted for 74 patients. Forty-four cases of SSI were detected during the surveillance period. Among them, 31 were incisional alone, and 13 involved a deep/organ space. The patient and surgical factors that appeared to contribute to development of SSI are listed in Table 2. High body mass index (p<0.01), low preoperative haemoglobin level (p<0.01), long preoperative hospital stay (p<0.01), prolonged operation time (p<0.01) and increased blood loss during surgery (p<0.01) were associated with SSI in general. For deep/organ space SSI, advanced age (p<0.05), low preoperative haemoglobin level (p<0.01), long preoperative hospital stay (p<0.05) and prolonged operation time (p<0.05) were significant (Table 3). The pathogens isolated from the SSIs are listed in Figure 1. Coagulase-negative staphylococci (CNS) were the most frequently isolated pathogens followed by Methicillin-resistant Staphylococcus aureus (MRSA). There were no significant differences in the isolated pathogen types between the incisional and deep/organ space SSI cases. Discussion Backgrounds of patients Number of patients 324 Sex (male/female) 281/43 Mean age, years (SD) 63.2 (11.8) Mean preoperative hospital stay, days (SD) 7.7 (11.3) Mean total hospital stay, days (SD) 34.1 (29.6) Total cystectomy 34 Ureterocutaneous fistula (%) 13 (38.2) Ileal conduit diversion (%) 16 (47.1) Neobladder (%) 5 (14.7) Prostatectomy 153 Partial nephrectomy 4 Total nephrectomy 32 Total nephroureterectomy 74 Others 27 In the present study, obesity, low preoperative haemoglobin level, long preoperative hospital stay, prolonged operative time and a large amount of blood loss were established as major risk factors for development of SSI. All but obesity were also linked to deep organ/space SSI. Although malnutrition and diabetes mellitus are considered to be common risk factors for SSI, they did not prove to have any significant influence in our series. This may have been because the affected individuals underwent treatment before their operations after hospitalization, thereby increasing their preoperative hospital stay. Prolonged preoperative hospital stay has been frequently suggested as a patient characteristic associated with SSI risk 9, 10). However, it depends on the severity of illness, and comorbidity conditions requiring inpatient workup and/or therapy before operations can be safely performed. Further investigations are needed to clarify this point. SSI is one of the most common nosocomial infection

3 61 Table 2 Comparison of patients with and without SSI Variables SSI (44 patients) No SSI (280 patients) P value Patient factors Mean age, years (SD) 63.2 (12.0) 62.9 (10.0) NSD Mean body mass index, kg/m 2 (SD) 23.5 (3.4) 23.0 (3.7) <0.01 Tobacco use, n (%) 21 (48) 102 (36) NSD Diabetes mellitus, n (%) 8 (18) 26 (9.2) NSD History of previous operation, n (%) 7 (15.9) 87 (31.1) NSD Laboratory data Mean total protein, g/l (SD) 7.1 (0.7) 7.3 (0.6) NSD Mean albumin, g/l (SD) 4.34 (0.43) 4.28 (0.48) NSD Preop haemoglobin, g/dl (SD) 12.8 (1.8) 13.1 (1.7) <0.01 Preoperative stay, days (SD) 12.2 (15.1) 6.9 (10.4) <0.01 Surgical factors Duration of operation, min (SD) (132.7) (106.2) <0.01 Mean amount of blood loss, ml (SD) (2088.0) (1235.4) <0.01 NSD, not significant difference. Table 3 Comparison of patients with Incisional SSI and Organ/Space SSI Variables Incisional SSI Deep/ Organ Space SSI P value (31 patients) (13 patients) Patient factors Mean age, years (SD) 61.2 (11.1) 67.0 (5.4) <0.05 Mean body mass index, kg/m 2 (SD) 23.5 (3.1) 23.6 (4.2) NSD Tobacco use, n (%) 14 (45.2) 9 (69.2) NSD Diabetes mellitus, n (%) 8 (18) 26 (9.2) NSD History of previous operation, n (%) 7 (22.3) 2 (15.4) NSD Laboratory data Mean total protein, g/l (SD) 7.2 (0.7) 6.8 (0.7) NSD Mean albumin, g/l (SD) 4.38 (0.40) 4.05 (0.60) NSD Meam preop haemoglobin, g/dl (SD) 13.3 (1.4) 11.6 (2.1) <0.01 Preoperative stay, days (SD) 8.1 (6.9) 21.8 (23.5) <0.05 Surgical factors Duration of operation, min (SD) (106.9) (153.0) <0.05 Mean amount of blood loss, ml (SD) (1823.6) (2683.5) NSD NSD, not significant difference. conditions, accounting for 38% of all infections. In one series of SSI patients who died after surgery, the infection was a major cause in 77% of the patietns, and the majority of these patients (93%) had serious infections involving organs or spaces accessed during surgery 4). In addition, deep/organ space SSI is associated with longer hospital stays and higher costs than incisional SSI 2, 3). For prevention of SSI, attention should be focused particulary on perioperative care. Matsumoto, et al. presented the Japanese guidelines for prevention of perioperative infection 11). In their summary, they recommended shortening of the preoperative hospital stay, determining and treating urinary tract infections before surgery, and avoiding hair removal as preoperative care. Administration of appropriate antibiotics and performance of appropriate operative procedures are essential as intraoperative care. Appropriate wound management, such as covering wounds with a sterile dressing for hours and early removal of urethral catheters and drainage tubes are also recommended as postoperative care. In addition to these guidelines, we rec-

4 62 Figure 1 Pathogens isolated from SSIs. NSD, not significant difference. ommend treatment of comorbidity conditions, including anemia, malnutrition and diabetes mellitus, on an outpatient basis as much as possible. The association between age and SSI is complex. Some authors have concluded that advanced age is associated with an increased risk for SSI 12 14), but others have considered that it is not an independent risk factor 15 17). Whether or not advanced age is associated with SSI, it is clear that elderly patients with SSI may have worse outcomes than younger patients 4) in line with their relatively diminished host response, many comorbidity diseases, including higherstage malignancies, ischemia at the level of the skin and low fat. Some researchers have argued that certain interventions for elderly patients should be considered before surgery. For example, it has been suggested that adequate levels of oxygen, maintenance of normothermia throughout the procedure, careful surgical techniques to counteract the increased fragility of the dermis and preoperative care, such as nutritional supplementation, more aggressive glucose control and smoking cessation measures should be emphasized 1). Our study suffers from its small sample size, particularly in the subset of patients with deep/organ space SSI, and its retrospective nature. We were unable to collect detailed data on factors such as coexistent infections at remote body sites, patient immune response levels, use of perioperative antimicrobial prophylaxis, method and timing of hair removal and skin preparation 18 20). Although these are limitations, the results do clearly suggest that there are important preoperative risk factors for deep/organ space SSI that should be taken into account when planning open urological surgery. Conclusion Deep/organ space SSI is associated with advanced age, low preoperative haemoglobin level, long preoperative stay and long operative time. Attempts to decrease deep/organ space SSI must be focused on these factors. Precise assessment of elderly patients and appropriate interventions that may decrease the likelihood of deep/organ space SSI are clearly a high priority. The results of this study provide a target base for urologists, but further assessment is still necessary to determine associations in elderly people. References 1. Kaye KS, Schmader KE, Sawyer R. Surgical site infection in the elderly population. Infect Dis 2004; 39; Vegas AA, Jodra VM, García ML. Nosocomial infection in surgery wards: a controlled study of increased duration of hospital stays and direct cost of hospitalization. Eur J Epidemiol 1993; 9: Albers BA, Patka P, Haarman HJ, et al. Cost effectiveness of preventive antibiotic administration for lowering risk of infection by 0.25%. Unfallchirurg 1994; 97:

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