This patient's unexplained fever prompted a fever workup and his injury, with skull fracture, predisposed him to bacterial infections. Prophylaxis and preoperative prevention are key in preventing postoperative infection.29,30 Although the rates of infection are fairly low in neurosurgery, surgical techniques for minimizing infection should be used and patients should be given antibiotics with gram-positive and gram-negative coverage in the brief preoperative, intraoperative, and postoperative periods to minimize risk of infection.29 Skin flora are the most common culprits in postoperative infections. A suitable regimen for broad-spectrum prophylactic operative coverage is:
For "clean" operations: Cefazolin and cefoperazone/sulbactam have been shown to be equally effective for preoperative prophlaxis.31
For "dirty" operations: Vancomycin 1.5 g/day and ceftazidime 6 g/day for 72 hours after the operation.30
Patients with an external ventricular drain (EVD) or other invasive devices, especially if the device remains for an extended period of time, may contribute to a higher risk of infection—EVD management is covered in Chapter 22 of this textbook.32-34 In addition, neurosurgical patients should be monitored for nonoperative infections, including urinary tract infections, pneumonia, and infections of various catheters.25 (See Section 10 of this book for detailed nonoperative infection management.) Although neurosurgery is generally associated with low rates of postoperative infection, the following complications are possible:
Management of each infection should begin with a broad-spectrum regimen (Figure 24-5), and once the organism has been identified, an antibiotic regimen should be tailored accordingly.
Broad-spectrum infection management.
Wound infections occur in an estimate of 0% to 5.8% of cases.29,31 Clinical symptoms including swelling and tenderness at the surgical site take at least 48 hours, possibly many days or weeks, to develop.35 Once detected, wound infections should be treated immediately to prevent cranial osteomyelitis or meningitis, which can result from unrecognized and untreated wound infections.36 Skull films, or CT with bony windows, may be helpful for comparison with later films in case osteomyelitis develops. Culture of the wound site will determine the specific antibiotic regimen needed. Because gram-positive cocci are the most common causes of wound infection (Figure 24-6), first-generation cephalosporins, such as cefazolin, are a good choice for initial broad-spectrum therapy.
Most common organisms in wound infections.
If repeat skull films or CT scans reveal spread to the underlying bone, excision of the infected bone flap or plate, with antibiotic treatment and drainage of the area, is critical.
Nosocomial meningitis may be very difficult to detect and often presents differently than community-acquired meningitis. The most common symptoms are fever and an altered level of consciousness, but these are nonspecific and easily mistaken for normal postoperative recovery.36 Meningismus may be present in less than 50% of patients.37 Lumbar puncture with analysis of the cell count, protein, glucose, Gram stain, and culture of the CSF are critical. However, Gram stain and cell count have low sensitivity in neurosurgical patients, and cell count may have low sensitivity, especially in patients who have had intracerebral hemorrhage.37 In cases of diagnostic uncertainty, lactate levels of the CSF may prove helpful. A lactate level of over 4 mmol/L in the CSF has a high sensitivity and specificity for bacterial meningitis.38 Patients should be treated with the antibiotics listed in Table 24-6.39
Table 24-6.Intravenous Antibiotic Regimen for Postoperative Bacterial Meningitis39 ||Download (.pdf) Table 24-6. Intravenous Antibiotic Regimen for Postoperative Bacterial Meningitis39
Aseptic meningitis from surgical trauma or immune reaction to blood in the central nervous system may account for up to 70% of postoperative meningitic findings. If repeated CSF analysis yields negative findings and the patient is determined to have aseptic meningitis, antibiotics can be safely discontinued.40
Subdural empyema (SDE) is fortunately a rare complication of craniotomy, but it is a surgical emergency and must be detected and treated immediately. Patients with subdural bacterial collections may pre-sent with fever, headache, seizures, periorbital edema, and various focal neurologic deficits.41 As with postoperative bacterial meningitis, patients with postoperative SDE tend to present with more subtle symptoms and a more insidious onset than typical SDE patients.42 An urgent CT scan in a patient with postoperative SDE may reveal a hypodense or isodense subdural collection with rim enhancement.41
Surgical evacuation of the abscess is critical and removal of the underlying bone flap may be necessary. Patients should be treated with postoperative medications listed in Table 24-7.41
Table 24-7.Postoperative Medication for Subdural Empyema ||Download (.pdf) Table 24-7. Postoperative Medication for Subdural Empyema
|Antibiotics: 2 wk IV, then 4 wk oral of either |
|Penicillin ||100,000 units/kg/6 h |
|Chloramphenicol ||15 mg/kg/6 h |
|Metronidazole ||7.5 mg/kg/8 h |
Phenytoin, phenobarbitone, etc.
A brain abscess, like subdural empyema, is a life-threatening, rare complication that requires immediate attention. The time course of a bacterial abscess is similar to that of SDE. Symptoms may be subtle. The most common symptoms are headache and alteration in mental status.43 CT has 95% to 99% sensitivity in detecting brain abscess.44 However, the ring-enhancing lesion can be easily mistaken for other pathologic processes, including malignancy, infarction, and hematoma.43 Upon diagnosis of an abscess, broad-spectrum antibiotic therapy should be as shown in Table 24-8.43
Table 24-8.Postoperative Medication for Brain Abscess43 ||Download (.pdf) Table 24-8. Postoperative Medication for Brain Abscess43
|Antibiotics: 4–6 wk, followed by prolonged oral therapy |
|Antistaphylococcal penicillin → oxacillin, nafcillin |
|Third-generation cephalosporin → cefotaxime, ceftriaxone, ceftizoxime |
|High-dose penicillin |
|For patients with sinusitis or chronic lung infections (risk of Bacteroides species) → metronidazole |
Brain abscesses must be either surgically aspirated or resected, and the organism detected will determine the antibiotic therapy that is required.
A 59-year-old woman with a history of well-controlled type II diabetes mellitus underwent an elective surgery to remove a 2.5-cm acoustic neuroma. A retrosigmoid craniotomy was performed and her tumor was more than 95% resected. The patient's intraoperative course was uneventful and she was transferred to the neurologic intensive care unit (NICU, Neuro-ICU) for postoperative management. Her neurologic status remained excellent. Two days after her operation, clear drainage from the wound site was noted, with no warmth or erythema. The drainage was monitored, with the presumptive diagnosis of cerebrospinal fluid (CSF) leak for 6 days, when a spinal drain was put in. Eight days after her operation, fluid drainage persisted. Two weeks after the operation, the patient returned to the OR for repair of her CSF leak. The deficit was repaired and she had an uneventful recovery.