Surgical Site Infections Linked to Cerebrospinal Leak and Skin Maceration

Background: Surgical site infections (SSIs) are associated with significant morbidity and mortality in United States healthcare facilities. During October 2007-June 2008 (study period), the neurosurgery department at a large university hospital recorded increasing numbers of SSIs in patients who had undergone craniotomy.  Despite reported adherence to recommended infection control practices and procedures, SSI rates in this patient population continued to rise.  Thus, an investigation was initiated.

Objective: (i) to identify risk factors associated with SSI acquisition following craniotomy; and (ii) implement appropriate control and preventive measures.

Methods: A case-control study was carried out.  A case was defined as any patient who underwent craniotomy during the study period and acquired an SSI per criteria established by the Centers for Disease Control and Prevention. Controls were randomly selected individuals who underwent craniotomy at the same institution and during the same time period, but did not develop SSIs. Cases were ascertained through review of microbiology line listings and patient medical records. Epidemiologic and clinical data were recorded in a standardized questionnaire.  Odds ratio (OR) and 95% confidence intervals (CI) were calculated.

Results: 23 patients met the case definition during the study period; 46 controls were selected.  Case and control-patients were similar, respectively, for median age (55 vs. 51 yr), body mass index (23 vs. 28 kg/m²), pre-operative length of stay, duration of surgery, or timing of pre-operative antimicrobial prophylaxis.  On univariate analysis, cases were significantly more likely to have received enteral nutrition (OR: 3.9, CI:1.1-13.2), mechanical ventilation (OR: 4.1; 1.3-13), or developed cerebrospinal fluid (CSF) leakage (OR: 15.2, CI:1.7-135).  On multivariate analysis, the single independent risk factor for SSIs was postoperative CSF leakage (adjusted OR: 20.6; CI: 1.7-250.6).  Post craniotomy SSIs significantly increased the length of hospital stay (OR: 31.3; CI: 3.9-252.3) or necessitated reoperation (OR: 25; CI: 6.5-97).  Medical chart review confirmed the presence of skin maceration where CSF leakage had occurred among cases.  Of the 23 isolates recovered from cases, 9 (39%) were Staphylococcus aureus, 2 (9%) were Staphylococcus epidermidis, and 5 (22%) were gram-negative microorganisms.

Conclusions: These results indicate that acquisition of post craniotomy SSIs was associated with CSF leakage, which might have been overlooked because of the severity of illness of patients who were also receiving enteral feeding and mechanical ventilation.  Although risk of wound contamination begins during surgery, additional risks persist in the post-operative period.  Thus, post-operative CSF leakage that results in skin maceration following craniotomy may enhance bacterial colonization of the affected site and lead to subsequent wound infection.