Risk Factors of Surgical Site Infection in Hospital A, Bangkok, August – September 2011

Abstract

Background: On 4 November 2011, Hospital A reported that surgical site infection (SSI) rate had increased from baseline 2% to 6.8% during August-September 2011. The investigation was conducted to determine the etiology, evaluate risk factors and establish control measures.
Methods: We conducted case-control study with a 1:5 ratio of cases to controls between July 1- Sep 30, 2011 using CDC’s case definition for SSI. We did active case finding and used simple randomization to select control group. We abstracted data including about infection site and microbiology, clinical and demographic information and OR staff and logistics by medical record review. Environmental survey was performed. All factors found to have p value < 0.20 or known SSI risk factors were included in multiple logistic regression analysis.
Results: Fifteen (3.7%) of 406 patients developed SSI. The median incubation period was 7 days (range, 0-58 days). Five SSI patients had microorganisms identified by culture; each patient had an organism cultured; all organisms were different. Compared with 74 controls, 1 nurse (aOR 8.36, 95% CI: 1.26-55.32) was significantly associated with SSI. Risk factors not quite significantly associated with SSI included receiving operation from 1 surgeon and BMI > 28.5 kg/m2 (aOR 5.02, 95% CI: 0.84-26.88 and aOR 6.66, 95% CI: 0.87-50.87, respectively). Environment included several potential sources of infection, including spray from aircon onto operative field and unlimited staff in OR.
Conclusion: This study found one nurse strongly associated with SSI, however several environmental factors at risk were found during survey can possibly increase the risk of contamination during the operation. We provided infection control training to OR staff and recommended environmental clean up. In follow up, SSI prevalence decreased after intervention.