Document Type


Date of Degree

Summer 2012

Degree Name

PhD (Doctor of Philosophy)

Degree In


First Advisor

Loreen A. Herwaldt


Few investigators have used robust analytic methods to assess risk factors and outcomes for surgical site infections (SSIs) after craniotomy and craniectomy (CRANI) procedures. We performed a retrospective study among patients undergoing CRANI procedures between 2006 and 2010 at the University of Iowa Hospitals and Clinics (UIHC) to assess the effect of an intervention (e.g., limiting Gliadel wafer use among patients with malignant brain tumors) on the trend of SSI rates, to identify independent risk factors for SSIs, and to evaluate one-year postoperative patient outcomes associated with these SSIs. We abstracted demographic data and clinical data from medical records or from the UIHC's Health information Management System.

We identified 104 patients with SSIs and selected 312 controls. Of SSIs, 88% were deep incisional or organ space infections, 70% were identified after patients were discharged from their initial hospitalizations, 32% were caused by Staphylococcus aureus alone or in combination with other organisms, and 27% were caused by Gram-negative organisms alone or in combination with other organisms. Significant independent risk factors for SSIs were: previous chemotherapy (odds ratio [OR], 10.0; 95% confidence interval [CI] 1.1, 92.1), preoperative length of stay ≥ 1 day (OR, 2.1; 95% CI 1.3, 3.5), preoperative serum glucose ≥ 100 mg/dL (OR, 1.7; 95% CI, 1.0, 3.0), Gliadel® wafer use (OR, 8.6; 95% CI 3.2, 23.1), and postoperative cerebrospinal fluid leak (OR, 4.0; 95% CI, 1.6, 10.3). Gliadel® wafer use was the strongest risk factor; however, limiting Gliadel® wafer use did not decrease SSI rate significantly among patients with brain tumors. Perioperative ventricular drains or lumbar drains were not independently associated with an increased risk of SSIs, but drains may have clinical significance. An SSI risk index that included the significant preoperative patient-related risk factors had a better predictive power than the National Healthcare Safety Network (NHSN) risk index. After adjusting for preoperative length of stay, age, comorbidity score, severity of illness score, the reason for the procedure, and procedure month, patients with SSIs were hospitalized longer postoperatively than were controls during their readmissions (2.3 days; P < 0.0001). After controlling for the same covariates and treating SSI as a time-varying factor, patients with SSIs were more likely than controls to: die (hazard ratio [HR], 3.3; 95% CI, 1.8, 5.8), be readmitted (HR, 4.1; 95% CI, 2.9, 5.8), and have reoperations (HR, 56.6; 95% CI, 38.1, 84.0).

In conclusion, surgeons could predict patients' risk of SSIs based on their preoperative risk factors and surgeons could modify some processes of care to lower the SSI risk. Preventing SSIs after CRANI procedures could improve patient outcomes and decrease healthcare utilization.


Craniectomy, Craniotomy, Outcome, Risk factor, Surgical site infection


xiii, 223 pages


Includes bibliographical references (pages 214-223).


Copyright 2012 Hsiu-Yin Chiang