gms | German Medical Science

Objectives: Risk index (RI) for Surgical Site Infection (SSI) was introduced in 1992 for the National Nosocomial Infection Surveillance System (NNISS). Since, 2010 the National Healthcare Safety Network (NHSN) developed a more specific and simple indicator to estimate the reduction in SSI rate with patient- and hospital-specific variables by univariate analysis. The objective of this study was to quantify the impact of prevention strategies for SSI associated at hip replacement surgery (HRS) through the estimation of the Standardized Infection Ratio (SIR).

Methods: A multi-disciplinary effort to prevent SSI was applied in a University hospital since January 2014 as part of a quality improvement program. The impact of the following pre-operative measures were assessed: preoperative screening and topical decolonization for Staphylococcus aureus, chlorhexidine whole-body bath once daily for five days before surgery, surgical skin preparation with chlorhexidine gluconate alcohol-based solution and combined prophylactic antibiotic (cephalothin plus gentamycin).For the comparison we retrospective review the register of HRS performed at the hospital between January 2010 and December 2014. The SIR value of the pre-intervention period (Jan 2010-Dec 2013) was compared with that of the intervention-protocol period (Jan 2014-Dec 2014) through two different standards for SSI, the RI of NNISS (American Society of Anesthesiologists (ASA) score, wound classification and procedure duration), and the MRI of NHSN (anesthesia, gender, trauma, ASA score, wound class, bed size, age, duration, total/primary/partial/revision), the latter is a stepwise logistic regression for HRS. The standardized infection ratio (SIR) is calculated by dividing the observed number of infections by the expected number of infections over a particular period. A value greater than 1 indicates an excess of infections compared with an international benchmark, oppositely a value less than 1 is a reliable indicator of reduction in SSI incidence (95% confidence interval were estimated for each indicator).

Results and Conclusion: 15 SSI cases were identified during the study period in 467 patients for a total incidence rate of 3,21% (CI95% 1,87%-5,36%), 3,56% (13/365) and 1,96% (2/102) in the pre- and post-intervention period respectively. Using the NNISS RI model the SIR value was 1,35 (CI95% 0,62-2,08) and 0,75 (CI95% 0,00-1,79) in the pre- and post-intervention period respectively (not significantly different from 1). SIR value adjusted by NHSN RI was 2,88 (CI95% 1,32-4,45, p< 0,001) and 1,73 (CI95% 0,00-4,13 p >0.05) in the pre- and post-intervention period respectively. The SIR is a useful surveillance tool to verify the impact of preventive measures since many risk factors can be adjusted by a single value. Composed by patient- and non-patient weighted factors, the NHSN MRI assess the impact of preventive measures with more reliability than the traditional NNISS index which serve as guides for internal quality improvement efforts.