Contemporary Approaches to Preventing and Treating Infections of Novel Intrathecal Neurostimulation Devices.

INTRODUCTION: Contemporary approaches to surgical site infections have evolved significantly over the last several decades in response to the economic pressures of soaring health care costs and increasing patient expectations of safety. Neurosurgeons face multiple unique challenges when striving to avoid as well as manage surgical implant infections. The tissue compartment, organ system, or joint is characterized by biological factors and physical forces that may not be universally relevant. Such implants, once rare, are now routine. Although the prevention, diagnosis, and treatment of surgical site infections involving neural implants has advanced, guidelines are ever changing, and the incidence still exceeds acceptable levels. We assess the impact of these factors on a new class of implantable neuromodulation devices. METHODS: The available evidence along with practice patterns were examined and organized to establish relevant groupings for continuing evaluation and to propose justifiable recommendations for the treatment of infections that might arise in the case of intradural spinal cord stimulators. RESULTS: Few studies in the modern era have systematically evaluated preventive behaviors that were applied to intradural neural implants alone. We anticipate that future efforts will focus even more on the investigation of modifiable factors along a continuum from bacterially repellant implants to weight management. Early diagnosis could offer the best hope for device salvage but to date has been largely understudied. CONCLUSIONS: Historically, prevention is the cornerstone to infection mitigation. However, immediate diagnosis and hardware salvage have not received the attention deserved, and that approach may be especially important for intradural devices.

Pharmacodynamics of ceftazidime and meropenem in cerebrospinal fluid: results of population pharmacokinetic modelling and Monte Carlo simulation.

BACKGROUND: Ceftazidime and meropenem are frequently used in the empirical treatment of hospital-acquired cerebrospinal fluid (CSF) infections. Although their dispositions in CSF have been described, the ability of these agents to achieve critical pharmacodynamic targets against the array of nosocomial CSF Gram-negative bacteria encountered in practice has not been reported. METHODS: Serum and CSF pharmacokinetic data were obtained from hospital patients with external ventricular drains and who received ceftazidime or meropenem. Concentration-time profiles in serum and CSF were modelled using a three-compartment model with zero-order infusion and first-order elimination and transfer. The model parameters were identified using population pharmacokinetic analysis [Big Non-Parametric Adaptive Grid (BigNPAG)]. A Monte Carlo simulation (9999 subjects) estimated the probability of target attainment (PTA) for total drug CSF concentrations at 50% and 100% T(>MIC) for ceftazidime 2 g intravenously every 8 h and meropenem 2 g intravenously every 8 h. The Gram-negative infection isolates of the seven most prevalent Gram-negative bacilli from the Meropenem Yearly Susceptibility Test Information Collection Program were used as a measure of contemporary MIC distribution. RESULTS: Post-Bayesian measures of bias and precision, observed-predicted plots and R(2) values were highly acceptable for both drugs. Although the PTA in CSF was approximately one dilution higher for ceftazidime compared with meropenem at a given MIC value, the cumulative fraction of response (CFR) in CSF against all Gram-negatives was markedly higher for meropenem when compared with ceftazidime secondary to the higher occurrence of lower MIC values for meropenem. Both agents had a low CFR against Pseudomonas aeruginosa. CONCLUSIONS: The pharmacodynamics of meropenem was superior to that of ceftazidime against Gram-negative pathogens in the CSF.

The efficacy and cost of prophylactic and perioprocedural antibiotics in patients with external ventricular drains.

OBJECTIVE: Prophylactic antibiotics are routinely administered to patients with external ventricular drains (EVDs); however, no conclusive evidence supports this practice. This study compared the efficacy and cost of prophylactic and periprocedural antibiotics in patients with EVDs. METHODS: We reviewed the charts of 308 patients who had an EVD in place for 3 or more days between January 1996 and June 1997. Patients with EVDs placed for shunt infections or meningitis were excluded. A standard protocol was used to insert and monitor EVDs. Catheters were left in place as long as clinically indicated and changed only if they malfunctioned. Cerebrospinal fluid cultures were obtained twice weekly. Prophylactic antibiotics were used at the discretion of the attending neurosurgeon. Patients were divided into two groups: Group A comprised 209 patients who received prophylactic antibiotics for the duration of the EVD (intravenously administered cefuroxime, 1.5 g every 8 h); Group B comprised 99 patients who received only periprocedural antibiotics (intravenously administered cefuroxime, 1.5 g every 8 h, three or less doses). RESULTS: Although there were significantly more males in Group A than in Group B, the two groups were otherwise well matched, with no significant differences in age, indications, or duration of EVD placement. The overall rate of ventriculitis was 3.9%. The infection rates for Group A (3.8%) and Group B (4.0%) were almost identical. CONCLUSION: Prophylactic antibiotics did not significantly reduce the rate of ventriculitis in patients with EVDs, and they may select for resistant organisms. Discontinuing the use of prophylactic antibiotics for EVDs at the authors' institution would save approximately $80,000 per year in direct drug costs.