Additive risk of surgical site infection from more than one risk factor following craniotomy for tumor.

PURPOSE: This study seeks to expound upon risk factor etiologies for surgical site infection (SSI) and investigate their combinatorial effects on infection rate following craniotomy for neuro-oncologic pathology.

METHODS: Patients who underwent neuro-oncologic craniotomy between 2006 and 2020 were included. Medical records were reviewed to identify the occurrence of wound infection at ≤ 3 months postoperatively. Potential risk factors for infection included tumor pathology, location, anesthesia type, indication, ventricular entry, foreign body, brachytherapy, lumbar drain, prior operation, prior cranial radiation, prior infection, bevacizumab, and medical comorbidities (hypertension, obesity, diabetes, hyperlipidemia, other cancer, cirrhosis). Logistic regression was implemented to determine risk factors for SSI. Chi-square tests were used to assess whether the number of risk factors (e.g., 0, ≥ 1, ≥2, ≥ 3, ≥4) increases the risk of SSI compared to patients with fewer risk factors. The relative increase with each additional risk factor was also evaluated.

RESULTS: A total of 1209 patients were included. SSI occurred in 42 patients (3.5%) by 90 days after surgery. Significant risk factors on multivariate logistic regression were bevacizumab (OR 40.84; p < 0.001), cirrhosis (OR 14.20, p = 0.03), foreign body placement (OR 4.06; P < 0.0001), prior radiation (OR 2.20; p = 0.03), and prior operation (OR 1.92; p = 0.04). Infection rates in the combinatorial analysis were as follows: ≥1 risk factor = 5.9% (OR 2.74; p = 0.001), ≥ 2 = 6.7% (OR 2.28; p = 0.01), ≥ 3 = 19.0% (OR 6.5; p < 0.0001), ≥ 4 = 100% (OR 30.2; p < 0.0001).

CONCLUSIONS: Risk factors in aggregate incrementally increase the risk of postoperative SSI after craniotomy for tumor.