Depth and Location of Surgical Site Infections (SSIs) Following 7 Major Procedure Categories

Depth and location of Surgical Site Infections (SSIs) following 7 major procedure categories

Background:

No standard method for public reporting of SSIs exists.  Rates of SSIs differ widely depending on factors such as reporting of superficial-incisional SSIs and inclusion of SSIs diagnosed in the outpatient setting.

Objective:

The objective of this study was to determine the rates of SSIs for 7 categories of major surgery based on depth of infection and clinical setting at the time of diagnosis (inpatient vs. outpatient).  

Methods:

We conducted a cohort study of all surgical procedures performed at 24 community hospitals in the Duke Infection Control Outreach Network (DICON) from 7/2007 to 12/2008.  Clinical and microbiologic data were prospectively collected from standardized surveillance databases. We specifically analyzed 7 categories of procedures selected by the Surgical Care Improvement Project (SCIP), including the following NNIS codes: Cardiac surgeries (CAGB, CARD, OCVS), COLO, HPRO, KPRO, HYST, VHYS, and Vascular surgeries (AAA, PVBY and VS). The inpatient setting included the original admission or readmission.  Standard definitions for SSI types were used.  Deep-incisional and organ/space SSIs were collectively defined as “complex”.

Results:

852 SSIs occurred following 45,872 SCIP procedures identified during the study period. (overall rate, 1.86 SSIs/100 procedures).  Complex SSIs accounted for 63.4% of SSIs.   76.3% of all complex SSIs were diagnosed in the inpatient setting, while 36.6% of superficial incisional SSIs were diagnosed in inpatient settings (overall RR=1.73).  Table 1 summarizes the type of SSIs stratified by location of diagnosis and procedure type. Type of SSI and location of SSI diagnosis varied between procedures. Complex SSIs that were diagnosed in inpatient settings varied between the ranges of 43-64%.  Type of procedure was an effect measure modifier on type and location of SSI (Mantel-Haenszel adjusted RR was 1.25 (95% CI 1.10-1.41), p<0.001).

Conclusions:

The type of SSI and the healthcare setting of SSI diagnosis vary substantially among different SCIP procedures. Complex SSIs comprised the majority of reportable SSIs among procedures in our study. Reporting of complex SSIs detected in inpatient settings is reliable and valid. Furthermore, reporting of superficial-incisional SSIs has poor sensitivity, as there is currently no standard method for post-discharge surveillance.  Thus, we believe publicly reported rates of SSIs for major surgical categories should be limited to complex SSIs diagnosed in inpatient settings.