Factors Associated with Surgical Site Infection in Blast-Induced Traumatic Brain Injury

Surgical site infection (SSI) following neurosurgical procedures, though relatively rare, remains a critical complication with significant clinical implications. In the context of blast-induced traumatic brain injury (bTBI), the risk of SSI is compounded by the unique pathophysiology of blast-related trauma, which often involves contaminated wounds, retained foreign bodies, and extensive tissue damage. This study investigates the factors associated with SSI in patients with bTBI, focusing on a cohort from southern Thailand, where ongoing conflicts have resulted in a high incidence of blast injuries.

Background and Clinical Context

Blast-induced traumatic brain injury is characterized by a combination of primary, secondary, and tertiary blast effects. Primary blast injuries result from the direct impact of pressure waves on intracranial structures, while secondary injuries involve penetrating trauma from debris and shrapnel. Tertiary injuries occur when victims are thrown by the blast force, leading to blunt trauma. In southern Thailand, military personnel and civilians exposed to explosive devices frequently present with open scalp wounds, skull fractures, dural tears, and cerebrospinal fluid (CSF) leakage. These injuries create a high-risk environment for microbial contamination, increasing the likelihood of SSI.

SSI rates in neurosurgical populations generally range from 0.5% to 8.0%, with established risk factors including prolonged operative time (>4 hours), CSF leakage, repeated surgeries, and the presence of external drainage devices. However, specific data on SSI in bTBI populations are scarce. This study addresses this gap by analyzing clinical, radiographic, and procedural factors contributing to SSI in a cohort of 80 patients treated for bTBI between 2009 and 2019 at a tertiary trauma center.

Methodology and Patient Characteristics

The retrospective study utilized data from a trauma registry, including patients who underwent neurosurgical intervention for bTBI. Clinical variables such as Glasgow Coma Scale (GCS) scores, presence of hypotension or hypoxia, and blast injury mechanisms were recorded. Radiographic assessments, including computed tomography (CT) scans, evaluated intracranial injuries such as skull fractures, midline shift (>5 mm), cisternal compression, and the presence of retained foreign bodies (metallic, bone, or wooden fragments). Surgical procedures were categorized into craniotomy for clot removal/debridement, decompressive craniectomy, and other interventions.

All patients received prophylactic antibiotics, and SSI was diagnosed according to Centers for Disease Control and Prevention (CDC) criteria, classified as superficial incisional, deep incisional, or organ/space infections. Statistical analysis employed binary logistic regression to identify predictors of SSI, with a focus on univariate and multivariable models.

Key Findings and Risk Factors

Among the 80 patients analyzed, the majority were male (reflecting the predominance of military personnel, 67.5%), with 40% classified as severe TBI (GCS ≤8) and 46.3% as mild TBI (GCS 13–15). Scalp lacerations or contusions were present in 51.3% of cases, while secondary insults such as hypotension (22.5%) and hypoxia (15%) were common. Penetrating blast injuries, characterized by contaminated projectiles and bone fragments, accounted for 53.8% of cases.

Neuroimaging revealed depressed skull fractures in 36.3% of patients and coup contusions in 32.5%. Midline shift exceeding 5 mm and basal cistern obliteration were observed in 20% and 17.5% of cases, respectively. Retained foreign bodies were identified in 30% of patients preoperatively, with metallic fragments (17.5%), bone fragments (11.2%), and wooden fragments (1.2%) being the most common. Postoperatively, 12.5% of patients had retained foreign bodies visible on follow-up CT scans.

SSI occurred in 5% of the cohort (n=4), with all cases classified as organ/space infections (brain abscesses). No instances of meningitis or ventriculitis were reported. Microbiological analysis identified Acinetobacter baumannii and Staphylococcus aureus in 25% of cases each, while 50% of cultures yielded sterile purulent discharge. All SSI cases required surgical abscess evacuation, followed by 12 weeks of intravenous antibiotics.

Statistical Analysis and Predictors of SSI

Univariate logistic regression identified retained foreign bodies as the sole significant predictor of SSI (odds ratio [OR]: 35.0; 95% confidence interval [CI]: 3.13–390.41; p=0.004). Other variables, including GCS severity, operative duration, CSF leakage, and presence of scalp injuries, did not reach statistical significance. Multivariable analysis was not performed due to the limited number of SSI cases and the dominance of retained foreign bodies as a predictor.

Clinical Implications and Recommendations

The study underscores the critical role of foreign body retention in SSI development following bTBI. Blast injuries inherently introduce contaminated materials into intracranial compartments, creating niduses for infection. Despite universal antibiotic prophylaxis, residual fragments—particularly metallic and bone shards—served as persistent sources of microbial colonization. This finding aligns with prior observations in penetrating TBI but highlights the amplified risk in blast scenarios due to the volume and diversity of embedded debris.

Surgical management of bTBI should prioritize thorough debridement and removal of accessible foreign bodies. Intraoperative imaging, such as real-time CT or ultrasonography, may enhance detection of residual fragments. Postoperative surveillance with serial imaging is recommended, especially in cases with incomplete debridement. Prolonged antibiotic regimens, tailored to local microbiological profiles, remain essential given the prevalence of multidrug-resistant organisms like Acinetobacter baumannii.

Limitations and Future Directions

The study’s retrospective design and small sample size limit the generalizability of findings. The predominance of military personnel may also introduce selection bias, as civilian blast injuries might differ in mechanism and severity. Prospective multicenter studies are needed to validate the association between retained foreign bodies and SSI, particularly in diverse demographic and geographic settings.

Conclusion

Retained intracranial foreign bodies are a critical modifiable risk factor for SSI in blast-induced TBI. Aggressive surgical debridement, combined with targeted antimicrobial therapy, can mitigate infection risks and improve outcomes in this vulnerable population.

doi.org/10.1097/CM9.0000000000000470

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