Abstract
This prospective study aimed to determine the surgical site infection (SSI) rate and associated risk factors was carried in a general surgical ward at Liaquat University Hospital Jamshoro. A total of 460 patients requiring elective general surgery from July 2005 to June 2006 were included in this study. All four surgical wound categories were included. Primary closure was employed in all cases. Patients were followed up to 30th day postoperatively. All cases were evaluated for postoperative fever, redness, swelling of wound margins and collection of pus. Cultures were taken from all the cases with any of the above finding. Mean ± SD age of the patients was 38·8 ± 17·4 years with male to female ratio of 1·5:1. The overall rate of surgical site infection was 13·0%. The rate of wound infection was 5·3% in clean operations, 12·4% in clean‐contaminated, 36·3% in contaminated and 40% in dirt‐infected cases. Age, use of surgical drain, duration of operation and wound class were significant risk factors for increased surgical site infection (P < 0·05). Postoperative hospital stay was double in cases who had surgical site infection. Sex, haemoglobin level and diabetes were not statistically significant risk factors (P > 0·05). In conclusion, surgical site infection causes considerable morbidity and economic burden. The routine reporting of SSI rates stratified by potential risk factors associated with increased risk of infection is highly recommended.
Keywords: Elective surgery, Risk factors, Surgical Site Infection, Wound healing
Introduction
Surgical site infections (SSIs) cause an important share of hospital‐acquired infections among surgical patients (1) accounting for 14–16% of all nosocomial infections among hospitalised patients (2). Patients who develop wound infections have longer hospital stay, expensive hospitalisation and increased mortality to double fold 3, 4. In developing countries, estimation of the cost of SSIs has not been made, but a review of the incidence and economic burden of SSIs in Europe estimated that additional hospital stay attributable to SSIs was 9·8 days, at an average cost per day of €325 (5). Surveillance programmes and feed back of surgeon‐specific rates to surgeons can lead to reduction in SSIs rates of 35–50% (6). SSIs are therefore an important outcome measure for surgical procedures and a priority for documentation of infection rates and surveillance. Many studies have shown different variables to affect risk of SSI such as old age, smoking, malnutrition, diabetes, immune deficiency, length of surgery and malignancy (7). A better understanding and documentation of various independent factors associated with SSI will help us to reduce the nosocomial infections in general surgical patients by various preventive strategies. In most of the developing countries including Pakistan, surgical wound infection rates are not observed routinely. There are very few studies about SSIs in Pakistan; therefore, this prospective study was conducted in a general surgical ward of a public sector medical university hospital to document the rate of SSIs and risk factors for SSI.
Material and methods
This prospective study was conducted in a general surgical ward of a 350‐bedded hospital affiliated to the Liaquat University of Medical and Health Sciences (LUMHS) Jamshoro, a public sector medical university in Pakistan. All 460 elective surgical interventions performed between 1 July 2005 and 30 June 2006 were included with the exception of operations, where prosthesis or metallic implants were used. Patients above the age of 12 years of both sexes were included in the study. Detailed information was collected and recorded by two trained surgical residents from patients on first day of their admission. Surgical site was inspected daily by surgical residents who were blinded for operating surgeon during the hospital stay and twice a week up to 14 days postoperatively. Patients of clean wound surgery and those who were discharged earlier were instructed to attend outpatient department twice a week for 14 days for inspection of wound and those who failed to attend there postdischarge appointment, a surgical resident made a home visit to inspect the wound. Surveillance period was, however, extended up to 30 days after hospital discharge to record any other complication. When there was clinical suspicion of wound infection [defined according to centres for disease control and prevention (CDC) criteria] (8). A sample was taken for culture and sensitivity and sent to Pathology department of LUMHS Jamshoro. Wound class was defined according to CDC criteria as clean, clean contaminated, contaminated and dirty (9). Information on variables associated with surgery like type of surgical wound or duration of operation was also recorded. Informed consent was obtained from every study subject. Data were recorded on a standardised data collection form.
Statistical analysis
Data were analysed using SPSS version 10.0 computer software. Mean ± SD was calculated for age, Hb%, duration of operation and postoperative hospital stay. P value was calculated by applying chi‐squared test for significance of two groups regarding age, sex, diabetes, drain, haemoglobin, duration of operation, hospital stay and wound class. In all statistical analysis, only P < 0·05 was considered significant.
Results
Age range of patients was from 12 to 75 years. Mean ± SD age was 38·8 ± 17·4 years. The overall cumulative rate of SSI was 13·0%. Of the 460 patients, 60 patients developed wound infection (Table 1). The rate was 5·3% for clean (n = 149), 12·4% for clean‐contaminated (n = 258), 36·3% for contaminated (n = 33) and 40% for dirt‐infected wounds (n = 20) (Table 2). In all the patients who developed SSI, the time of onset for manifestations of SSI was between 4 and 10 days postoperatively.
Table 1.
Overall SSI rate
| Variable | No. of patients (%) |
|---|---|
| SSI | 60 (13·0) |
| No SSI | 400 (87·0) |
SSI, surgical site infection.
Table 2.
Association of selected variables and SSI
| Variable | No SSI | SSI | P value |
|---|---|---|---|
| n (%) | n (%) | ||
| Age | |||
| <50 years | 298 (91·1) | 29 (8·8) | <0·001 |
| ≥50 years | 102 (76·6) | 31 (23·3) | |
| Sex | |||
| Female | 165 (89·1) | 20 (10·8) | >0·05 |
| Male | 235 (85·4) | 40 (14·5) | |
| Haemoglobin% | |||
| <10 mg/dl | 47 (79·6) | 12 (20·3) | >0·05 |
| ≥10 mg/dl | 353 (88·0) | 48 (11·9) | |
| Diabetes | |||
| No | 376 (87·0) | 56 (12·9) | >0·05 |
| Yes | 24 (85·7) | 4 (14·2) | |
| Drain | |||
| No | 274 (89·8) | 31 (10·1) | <0·05 |
| Yes | 126 (81·2) | 29 (18·7) | |
| Wound class | |||
| Clean | 141 (94·6) | 8 (5·3) | <0·001 |
| Clean contaminated | 226 (87·6) | 32 (12·4) | |
| Contaminated | 21 (63·6) | 12 (36·3) | |
| Dirty | 12 (60·0) | 8 (40·0) | |
There were statistically significant differences in duration of operation and postoperative hospital stay in patients with SSI and without developing SSIs (P ≤ 0·001 each). Age, wound class and use of drain were significantly associated with development of SSIs among patient characteristics, while sex, haemoglobin and diabetes were not associated with statistically significant differences. Risk factors independently associated with SSI are summarised in Table 2.
Discussion
The routine reporting of SSI rates stratified by potential factors associated with increased risk of infection is highly recommended. The results of this study were higher as compared with studies measuring the SSIs in developing countries and consistent with many studies in underdeveloping countries. The overall proportion of SSIs in patients who underwent elective surgery in our study was 13·0%. This figure is quite higher keeping in mind that this is a study on elective surgery, although comparison is difficult as the patient populations and methods of collecting data may vary. In the USA, the SSI rate is 2·8% (10). Surveillance reports in English countries report an incidence of SSI of 4·2% (11). One review on many studies has concluded that in European countries the average rate of SSI lies in the range of 2·5% (12). They also suggest that the actual range of rate of SSI lies between 15% and 20% depending mainly on the type of surgical procedure and the wound classification. In Iran, rate of SSI according to one study was found to be 9·9% (13), and in another study it was 8·4% (14). Reported rates of SSI from African countries ranges from 16·4% to 38% (15), while estimated rates of SSI in Vietnam and Japan are 10·7% and 7·6% respectively 16, 17. Although the rate of 13·0%, which we found in our study, is slightly higher as compared with results from developed countries, it is similar to other less developed countries and better compared with African countries. By comparison, our results are not discouraging, keeping in mind the substandard operation theatre conditions in public sector hospitals in Pakistan.
Age has been associated with increased risk of wound infection 14, 18, 19; our study was inconsistent with these studies showing that age significantly increase the risk of SSIs in patients older than 50 years. Some studies have correlated male sex with increased risk of SSI (20); in our study there was slight increase in rate of SSI in male patients, however it was not significant. Clinical data regarding the effect of anaemia on wound healing is mixed. Low haemoglobin level has been found to be a risk factor in some studies (21). This study has also shown similar results with slightly higher SSI rate in patients having haemoglobin level below 10 gm/dl but statistically the difference was not significant (P > 0·05). Previous studies have documented diabetes mellitus associated with increased risk for SSIs 22, 23. Malone et al. (24) in their study showed that patients with diabetes are 1·5 times more likely to develop SSIs, while other study from Iran (14) showed that patients with diabetes mellitus were at a 4·9‐fold increased risk for SSI. Our present study was in contradiction to all the above studies showing no significant difference between rate of SSI and diabetes mellitus. This contradiction may be the because of difference in methodology, because in this study blood sugar level was brought to the level of <200 mg% preoperatively. The use of surgical drains has been shown to be a risk factor for higher rates of SSI 14, 25. This finding was supported by our study, which showed surgical drain to be a significant risk factor for SSI. The risk of SSI has repeatedly been shown to be proportional to the duration of operative procedures (26). This is in agreement with our finding as it can be seen from Table 3, that the rate of SSI was higher in patients who had longer duration of operation. Mean ± SD duration of postoperative hospital stay was 6·3 ± 4·4 days in patients who had no SSI, and 16·2 ± 7·2 days who had SSI. This finding shows almost more than twofold postoperative hospital stay in infected cases, and these findings were consistent with local as well as studies in other countries 4, 27, 28. Increased rate of surgical site infection with increasing wound class according to traditional wound classification has been attributed as a significant risk factor by many studies (20). Our study is in agreement with this fact as can be seen from Table 2, which shows wound contamination as a statistically significant risk factor for development of surgical site infection.
Table 3.
Comparison of selected variables between patients with and without SSI
| Variable | SSI (mean ± SD) | No SSI (mean ± SD) | P value |
|---|---|---|---|
| Duration of operation (minutes) | 102·8 ± 56·4 | 76·6 ± 38·3 | <0·001 |
| Postoperative hospital stay (days) | 16·2 ± 7·2 | 6·3 ± 4·4 | <0·001 |
SSI, surgical site infection.
References
- 1. Mangram AJ, Horan TC, Pearson ML, Silver LC, Jarvis WR. Guideline for prevention of surgical site infection, 1999: Hospital Infection Control Practices Advisory Committee. Infect Control Hosp Epidemiol 1999;20:250–80. [DOI] [PubMed] [Google Scholar]
- 2. Emori TG, Gaynes RP. An overview of nosocomial infections, including the role of microbiology laboratory. Clin Microbiol Rev 1993;6:428–42. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 3. Kirkland KB, Briggs JP, Trivette SL, Willkinson WE, Sexton DJ. The impact of surgical‐site infections in the 1990s: attributable mortality, access length of hospitalization, and extra cost. Infect Control Hosp Epidemiol 2000;20:725–30. [DOI] [PubMed] [Google Scholar]
- 4. Kirkland KB, Briggs JP, Trivette SL, Willkinson WE, Sexton DJ. The impact of surgical‐site infections in the 1990s: attributable mortality, access length of hospitalization, and extra cost. Infect Control Hosp Epidemiol 1999;20:725–30. [DOI] [PubMed] [Google Scholar]
- 5. DiPiro JT, Martindale RG, Bakst A, Vacani PF, Watson P, Miller MT. Infection in surgical patients: effects on mortality, hospitalization, and postdischarge care. Am J Health Syst Pharm 1998;55:777–81. [DOI] [PubMed] [Google Scholar]
- 6. Haley RW, Culver DH, Morgan WM, White JW, Emori TG, Hooton TM. Identifying patients at high risk of surgical wound infection: a simple multivariate index of patient susceptibility and wound contamination. Am J Epidemiol 1985;121:206–15. [DOI] [PubMed] [Google Scholar]
- 7. Nandi PL, Soundara Rajan S, Mak KC, Chan SC, So YP. Surgical wound infection. Hong Kong Med J 1999;5:82–6. [PubMed] [Google Scholar]
- 8. Horan TC, Gaynes RP, Martone WJ, Jarvis WR, Emori TG. CDC definitions of nosocomial surgical site infections, 1992: a modification of CDC definitions of surgical wound infections. Infect Control Hosp Epidemiol 1992;1:606–8. [PubMed] [Google Scholar]
- 9. Simmons BP. CDC guidelines on infection control. Infect Control 1982;3:187–96. [DOI] [PubMed] [Google Scholar]
- 10. Nichols RL. Surveillance of the surgical wound. Infect Control Hosp Epidemiol 1990;11:513–4. [DOI] [PubMed] [Google Scholar]
- 11. National Institute for Clinical Excellence . Surgical site infection – final scope. URL http://www.nice.org.uk/download.aspx?0=225954 (accessed 6th August 2007).
- 12. Leaper DJ, Van Goor H, Reilly J, Petrosillo N, Geiss HK, Torres AJ, Berger A. Surgical site infection – a European perspective of incidence and economic burden. Int Wound J 2004;1:247–73. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 13. Askarian M, Gooran NR. National nosocomial infection surveillance system‐based study in Iran: additional hospital stay attributable to nosocomial infections. Am J Infect Control 2003;31:465–8. [DOI] [PubMed] [Google Scholar]
- 14. Arabshahi KS, Koohpayezade J. Investigation of risk factors for surgical wound infection among teaching hospitals in Tehran. Int Wound J 2006;3:59–62. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 15. Kotisso B, Aseffa A. Surgical wound infection in a teaching hospital in Ethiopia. East Afr Med J 1998;75:402–5. [PubMed] [Google Scholar]
- 16. Nguyen D, MacLeod WB, Phung DC, Cong QT, Nguy VH, Van Nguyen H, Hamer DH. Incidence and predictors of surgical‐site infections in Vietnam. Infect Control Hosp Epidemiol 2001;22:485–92. [DOI] [PubMed] [Google Scholar]
- 17. Saito T, Aoki Y, Ebara K, Hirai S, Kitmura Y, Kasaoka Y, Mori Y, Linuma Y, Ichiyama S, Kohi F. Surgical‐site infection surveillance at a small‐scale community hospital. J Infect Chemother 2005;11:204–6. [DOI] [PubMed] [Google Scholar]
- 18. Lizan GM, Garcia CJ, Asensio VA. Risk factors for surgical wound infection in general surgery: a prospective study. Infect Control Hosp Epidemiol 1997;18:310–5. [DOI] [PubMed] [Google Scholar]
- 19. Hanif M, Ijaz A, Niazi UF, Akhtar I, Zaidi AA, Khan MM. Acute wound failure in emergency and elective laparotomies. J Coll Physicians Surg Pak 2001;11:23–6. [Google Scholar]
- 20. Anielski R, Barczynski M. Postoperative wound infection, I. Population data and risk factors. Przegl Lek 1998;55:101–8. [PubMed] [Google Scholar]
- 21. Hopf HW, Hunt TK, West JM, Blomquist P, Goodson WH 3rd, Jensen JA, Jonsson K, Paty PB, Rabkin JM, Upton RA, Von Smitten K, Whitney JD. Wound tissue oxygen tension predicts the risk of wound infection in surgical patients. Arch Surg 1997;132:997–1004. Discussion 1005. [DOI] [PubMed] [Google Scholar]
- 22. Trick WE, Schechler WE, Tokars JI, Jones KC, Smith EM, Reppen ML, Jarvis WR. Risk factors for radial artery harvest site infection following coronary artery bypass graft surgery. Clin Infect Dis 2000;30:270–5. [DOI] [PubMed] [Google Scholar]
- 23. Takoudes TC, Weitzen S, Slocum J, Malee M. Risk of cesarean wound complications in diabetic gestations. Am J Obstet Gynecol 2004;191:958–63. [DOI] [PubMed] [Google Scholar]
- 24. Malone DL, Genuit T, Tracy JK, Gannon C, Napolitano LM. Surgical Site Infections: reanalysis of risk factors. J Surg Res 2002;103:89–95. [DOI] [PubMed] [Google Scholar]
- 25. Soleto L, Pirard M, Boelaert M, Peredo R, Vargas R, Gianella A, Van der Stuyft P. Incidence of surgical‐site infections and the validity of the National Nosocomial Infections Surveillance System risk index in a general ward in Santa Cruz, Bolivia. Infect Control Hosp Epidemiol 2003;24:26–30. [DOI] [PubMed] [Google Scholar]
- 26. Garibaldi RA, Cushing D, Lerer T. Risk factors for postoperative infection. Am J Med 1991;91:158S–63S. [DOI] [PubMed] [Google Scholar]
- 27. Iqbal M, Khan JA, Rehman S, Saleem SM, Mehboob M, Qayyum A, Aybab GR. Comparative study of potentially contaminated wound healing in primarily applied stitches and delayed primary closure. J Coll Physicians Surg Pak 1999;9:480–2. [Google Scholar]
- 28. DiPiro JT, Martindale RG, Bakst A, Vacani PF, Watson P, Miller MT. Infection in surgical patients: effects on mortality, hospitalization, and postdischarge care. Am J Health Syst Pharm 1998;55:777–81. [DOI] [PubMed] [Google Scholar]