Choice of Antibiotics in the prophylaxis and Treatment of

Common Neurosurgical Problems Chayooth Thanapornsangsuth

Fifth year medical student

Invasive potential of bacteria or other pathogens that are inoculated into wound during surgery that exceeds the capability of local and systemic host defense

>105 Increase potential of SSI Presence of foreign material (ex. VP shunt)

decrease size of minimal inoculation Gram positive bacteria biofilms shield

pathogen, inhibit action of antibiotics Primary reservoir=flora colonizing the skin

and paranasal sinuses

Pathogenesis of surgical site infection

Patients characteristics associated with surgical site of infection

1. Concomitant remote site infection eg. pneumonia, UTIs

2. DM 3. Cigarette smoking 4. Prolonged use of systemic corticosteroids 5. Obesity 6. Extreme age 7. Poor nutritional status 8. Others eg. U/D malignancies, use of

immunosuppressive agents in organ transplant patients

Risk Factors

Predict degree of microbial contamination at a surgical site and likelihood of developing a surgical site of infection(SSI)

Classification of wounds and predictors of surgical site infection

Wound Classification

Definition Examples

Clean An uninfected woundRespiratory, GI, GU tract not encounteredWound closed primarilyMay be drained with closed drainage system

Lumbar diskectomyTemporal lobectomy

Clean contaminated Respiratory, GI, GU tract entered under controlled conditionsNo usual contamination

Transsphenoidal pituitaryRetromastoid craniectomy for microvascular decompressionAcute open depressed skull fracture

Contaminated-open Acute accidental woundsMajor violation of sterile techniqueGross contamination from GI tractNonpurulent inflammation may present

Dirty/infected-old Traumatic wounds with retained devitalized tissuePurulent tissue encounteredPerforation of major viscera

Classification of surgical wounds

1. Intraabdominal procedure 2. Operation greater than 2 hours 3. Wound classified as contaminated or dirty 4. Operation performed on patients having

greater than three discharge diagnoses

Independent risk factors associated with development of surgical site infection(SSI) <SENIC project>

Definition 1. Prophylaxis- ATB administration for

procedures with minimal contamination of surgical site anticipated

2. Therapy- ATB administration for procedures with significant contamination

Antimicrobial prophylaxis

Techniques for surgical prophylaxis CDC Recommendations for Prevention of SSI

Category Definition

IA Strongly recommended for all hospitals and strongly supported by well-designed experimental or epidemiological studies

IB Strongly recommended for all hospitals and viewed as effective by experts in field and a consensus of Hospital Infection Control Practices Advisory Committee (HICPAC) based on strong rationale and suggestive evidence, even though definitive scientific studies may not have been done

II Suggested for implementation in many hospitalsRecommendations may be supported by suggestive clinical recommendations or epidemiological studies, a strong theoretical rationale, or definitive studies applicable to some but not all hospitals.

No recommendation; unresolved issue

Practices for which insufficient evidence or no consensus regarding efficacy exists

The prophylactic antimicrobial agent should be efficacious against the most common pathogens causing SSI for a specific operation(IA); for neurosurgery, this mandate excellent gram positive coverage against most common skin contaminants such as staphylococcal species and attention to the organism predominant in the surgeon institution

CDC Guidelines for the use of Prophylactic ATB

The ATB should ideally be administered intravenous within 30 minutes but not longer than 2 hours before the initial incision(IA)

Administer of the prophylactic antimicrobial agent as close as possible to the time of induction of anesthesia(II)

Prophylaxis should not be extended to the time of postoperative period(IB)

CDC Guidelines for the use of Prophylactic ATB

Additional intraoperative doses should be considered (a) during procedures whose duration exceeds the estimated half-life of the drug, (b) during operations associated with major blood loss, (c) during operations on morbidly obese patients (IB)

Vancomycin should not be administered routinely for category IB

CDC Guidelines for the use of Prophylactic ATB

1. Prophylactic ATB is not risk free -Vancomycin hypotensive episodes or

flushing -Aminoglycosides Ototoxicity -Penicillin 8% of patient suffer adverse

reactions 2. Costs

Considerations

1. Clean neurosurgical procedures 2. Foreign body implantation 3. Timing and duration of prophylaxis 4. Prophylactic ATB in patient with basilar

skull fractures 5. Prophylactic ATB for external ventricular

drains

Clinical Data regarding antimicrobial prophylaxis

Clean procedures Efficacy established Clean contaminated General surgical

procedures have clearly been shown to benefit from preoperative ATB

Dirty and contaminated cases Therapeutic rather than prophylactic

Clean neurosurgical procedures

For CSF shunt, the higher the baseline infection rate of CSF procedure, the more protective prophylactic ATB appeared to be. If the baseline infection rate <5% use other method of infection control such as rigorous aseptic technique

Foreign body implantation

Other foreign bodies eg. Intrathecal catheter, synthetic cranioplasties, deep brain and spinal cord electrodes, no controlled trial regarding the efficacy of prophylactic antibiotics.

Foreign body implantation

Timing- with in 2 hours of incision time Duration- procedures whose length exceeds

the half life of the prophylactic ATB repeat dose

Timing and duration of prophylaxis

No convincing data that supports the prophylactic use of ATB

1. Routine use of ATB will lead to resistance of more virulent organism than would otherwise be encountered

2. CSF analysis may fail to identify organism 3. Problem relating toxicity

Prophylactic ATB in patient with basilar skull fractures

External ventricular drains are used to monitor intracranial pressure and therapeutic drainage of CSF

Lumbar subarachnoid drains management of CSF leaks + administration of intrathecal medications

Prophylactic ATB for external ventricular drains

No clear evidence that this is beneficial Other than prophylactic ATP, other steps

that are important are strict aseptic technique during placement, tunneling of catheter away from insertion site, minimal entry into the system, changing catheter at specified interval.

Prophylactic ATB for external ventricular drains

1. Posttraumatic and postoperative bacterial meningitis

2. Post operative bone flap infection, cranial epidural abscess, and subdural emphysemas

3. Bacterial Brain abscess

Antibiotic Therapy of Neurosurgical Infections

Majority is caused by secondary complication of basilar skull fracture and CSF fistulae

Fracture of skull base + tearing of dura direct communication with paranasal sinuses, mastoid air cels bacteria ingress to subarachnoid space

Strep. pnemoniae + other Strep.spp about three-quarters of cases

Secondary bacterial meningitis Same ATB treatment with that occurs spontaneously

Posttraumatic and postoperative bacterial meningitis

Post operative bone flap infection- uncommon

-diagnosis- fever, pain, tenderness, erythema, swelling, fluctuance, drainage of purulent material from the incision

-risk factors- procedure of long duration, reoperation, trauma, exposure involving the air sinuses, poor irradiation of the scalp, use of foreign body drain, immunosuppression, excessive traffic in and out of the surgical suite.

Post operative bone flap infection, cranial epidural abscess, and subdural emphysemas

Treatment - if not ill-appearing or toxic wait until

cultures are obtained - appears ill or manifest systemic signs of

toxicity ATB start without delay Staphylococcus aureus accounts for most

cases

Post operative bone flap infection, cranial epidural abscess, and subdural emphysemas

Stapphylococci account for most postoperative infection

Many other organisms can be encounted with CEA

Initial empiric therapy should be broad spectrum

Parenteral ATB should be given 4-6 weeks

Cranial epidural abscess

ATB similar to as above In infants complication of bacterial

meningitis most commonly due to Haemophilus influenzae. In such case ampicillin or cefuroxime can be used with third generation cephalosporins as alternative agents

Subdural Empyema

1. Empiric therapy should be based on a thorough understanding of the microbiological flora that is anticipated based on individual clinical situation

2. Treatment should be adequate 3. Therapy should be adjusted as necessary

based on cultures

Bacterial Brain abscess