What is the role of antibiotics in the management of brain injury?

Antibiotics in Brain Injury

Antibiotics should NOT be used routinely for prophylaxis in closed traumatic brain injury (TBI), but are indicated for specific scenarios including penetrating brain injury, open skull fractures, CSF leakage, and bacterial meningitis where they must be administered as soon as possible.

Closed Traumatic Brain Injury (Non-Penetrating)

Prophylactic antibiotics are not recommended for routine use in closed TBI, even when intracranial pressure monitors are placed 1.

• A study of severe closed head injuries demonstrated that prophylactic antibiotics for ICP monitor duration resulted in significantly higher septic morbidity (78.6% vs 31.3%) and pneumonia rates (57.1% vs 18.8%) compared to no prophylaxis 1.
• No central nervous system infections related to the monitors occurred in either group 1.
• If antibiotics are considered at all for ICP monitor placement, they should be limited to the immediate perioperative period only, not continued for the duration of monitoring 1.

Key Caveat

The French Society of Anaesthesia guidelines emphasize that sedation and correction of secondary brain insults are the primary management strategies for intracranial hypertension in closed TBI, not antibiotic prophylaxis 2.

Penetrating Traumatic Brain Injury (pTBI)

For penetrating brain injuries, prophylactic antibiotics should be administered immediately to reduce CNS infection risk 3, 4.

Evidence Supporting Use:

• In a single-center series, all 4 patients (100%) who did not receive prophylactic antibiotics developed infections (3 CNS infections, 1 wound infection), compared to only 2 of 17 patients (12%) who received prophylaxis 3.
• Another institutional study showed zero documented CNS infections when prophylactic antibiotics were used, with median duration of 24 hours 4.
• The most common mechanism is gunshot wounds (94% of cases) 4.

Recommended Regimen:

• First-line: Single dose of cefazolin (first-generation cephalosporin) for cases without organic debris 3, 4.
• For contamination with organic debris: Add coverage for anaerobes and gram-negative organisms (e.g., ceftriaxone plus metronidazole) 3, 4.
• Duration: 24 hours to 5 days depending on contamination severity, with most evidence supporting shorter courses (24-72 hours) 3, 4.

Timing Critical:

• Median time to administration should be under 60 minutes 4.
• Delay beyond 3 hours significantly increases infection risk 2.

Open Skull Fractures

Prophylactic antibiotics are indicated for open displaced skull fractures requiring surgical closure 2.

• These are classified as contaminated wounds requiring therapeutic rather than prophylactic dosing 2.
• First-generation cephalosporin (cefazolin) provides coverage for Staphylococcus aureus and streptococci 2.
• Duration should be 3-5 days depending on wound severity and contamination 2.

CSF Leakage (Traumatic or Post-Neurosurgery)

For traumatic CSF leakage (rhinorrhea/otorrhea), antibiotics are NOT routinely recommended for prophylaxis unless bacterial meningitis develops 2.

• The UK Joint Specialist Societies guidelines do not recommend prophylactic antibiotics for CSF leaks alone 2.
• Investigations (CT/MRI) to identify the leak source are warranted 2.
• If bacterial meningitis develops, immediate empiric therapy is required (see below) 2.

Bacterial Meningitis (Post-Traumatic or Spontaneous)

Bacterial meningitis is a neurologic emergency requiring immediate antibiotic administration as soon as the diagnosis is suspected 2.

Empiric Therapy:

• Adults: Vancomycin PLUS ceftriaxone or cefotaxime 2.
• Infants/children: Same combination (vancomycin plus ceftriaxone/cefotaxime) 2.
• Therapy should be initiated even before lumbar puncture if the procedure is delayed (e.g., awaiting head CT) 2.

Timing:

• Early administration reduces mortality and improves neurologic outcomes 2.
• Patients who received antibiotics before Glasgow Coma Scale deteriorated to ≤10 had better survival and neurologic outcomes 2.
• Administration should occur as soon as possible, potentially even before hospital admission 2.

Adjunctive Therapy:

• Dexamethasone should be considered as adjunctive therapy to attenuate the inflammatory response that contributes to cerebral edema, increased intracranial pressure, and neuronal injury 2.

Common Pitfalls to Avoid

• Do not use prolonged prophylactic antibiotics for closed TBI or ICP monitors - this increases septic complications without preventing CNS infections 1.
• Do not delay antibiotics in penetrating brain injury - all patients without prophylaxis in one series developed infections 3.
• Do not use prophylactic dosing for contaminated wounds - therapeutic dosing is required for open fractures and penetrating injuries 2.
• Do not extend antibiotics beyond 24 hours for closed procedures without documented infection - this promotes antibiotic resistance 2.
• Do not delay antibiotics beyond 3 hours post-injury in penetrating trauma or open fractures - infection risk increases significantly 2, 4.