Short review of randomized controlled trials for Surgical Neurology International: Part II - drain-associated cerebrospinal fluid infections

INTRODUCTION

Two methodologically sound randomized controlled trials (RCTs) were published in the third and fourth quarters of 2018 dealing with drain-associated cerebrospinal fluid (CSF) infections. Both RCTs offer significant scientific findings which may be of interest to readers of Surgical Neurology International.

Infectious diseases society of America’s 2017 clinical infectious disease guidelines for external ventricular drains

Drain-associated CSF infections have a pooled incidence rate of about 11.4/1000 catheter days.[10] The Infectious Diseases Society of America’s 2017 Clinical Infectious Disease Guidelines for external ventricular drains are listed in Table 1.[10]

Table 1: Infectious Diseases Society of America’s 2017 Clinical Infectious Disease guidelines for external ventricular drains.

Lumbar drain protocol

All patients had lumbar drains placed for an average of 4 days (range 1–10 days). Daily inspection of puncture sites was accompanied by routine CSF sampling on the day of drain placement and every 2^nd day until drains were removed. Here, drain-associated CSF infection was defined as a confirmed cultured organism or clinical sign suggestive of meningitis. Patients in the silver-impregnated lumbar drain group experienced significantly fewer catheter-related complications [Table 2]. Fewer patients (1 in the study group versus 4 in the control group, not statistically significant) experienced drain-associated CSF infections, diagnosed after 7 days of drain placement (range of 6–9 days). For the five patients with CSF infections, 14 CSF samples confirmed the growth of microorganisms (13 CSF cultures grew Staphylococcus species, one Gram-negative Escherichia coli, and one candida species). Ten of 14 Gram-positive CSF cultures showed significantly reduced bacterial growth when cultured in the presence of silver-impregnated catheters.

Table 2: Results from the SiLuDrain trial.

Culture from the scalp

Sampling of scalp at drain exit sites was performed at the time of procedure for a skin area of 12 cm², with dressing changes every 5 days. Those with silver-impregnated ventriculostomies placed for an average of 8 days (range 5–12 days), utilizing the chlorhexidine protocol, exhibited significantly less bacterial growth versus those with uncoated dressings [Table 3]. More virulent Gram-positive cocci were detected for those with uncoated dressings. Given the small study cohort sizes, both groups showed nonsignificant differences in bacterial colonization of subcutaneous catheter segments, catheter tips, and ventriculostomy-associated infections.

Table 3: Results from the EVDAI study.

DISCUSSION

The SiLuDrain trial and EVDAI study offer insight regarding the prevention of drain-associated infections. The SiLuDrain trial demonstrated that silver-impregnated lumbar drains are well tolerated with fewer Gram-positive bacterial infections. Findings from this study are consistent with prior meta-analysis of prospective studies demonstrating the effectiveness of silver-coated ventricular drains in preventing ventriculostomy-associated infections.[2,5-7] Silver-coated catheters contain combinations of metallic silver and insoluble luminal silver salts with demonstrated patient safety profiles and antimicrobial properties.[4,5,10] Silver-coated drains may not be as effective as antibiotic-impregnated drains in preventing Gram-negative bacterial colonization. Dependent on the silver particle size, the positive charge of silver ions may be mitigated by negative charges of bacterial cell wall proteins as the duration of drain placement increases.[1]

Most drain-associated infections are caused by bacteria introduced at the time of drain insertion and subsequent catheter colonization, possibly as a result of scalp bacterial growth. The EVDAI study demonstrated reduced scalp bacterial growth, including fewer virulent Gram-positive strains, with the use of chlorhexidine wound dressings.[9] Despite this trial’s small sample size, it was methodologically well designed using silver-coated ventriculostomies as an effort to control for potential confounders associated with CSF infections.

Protocols for drain insertion and care can raise awareness of drain-associated CSF infection risk factors. Management of these risk factors, including multiple drain exchanges, frequent CSF samplings, and catheter duration, is essential to decrease patient morbidity and health-care-related costs associated with CSF infections and long-term likelihood of requiring permanent CSF diversion.

CONCLUSIONS

Two 2018 RCTs demonstrated that silver-coated drains were effective in decreasing Gram-positive bacterial adherence to catheter tips and subsequent colonization. They may not be as effective as antibiotic-impregnated drains in preventing Gram-negative bacterial colonization. Furthermore, antimicrobial-coated chlorhexidine dressings appear to be effective in suppressing scalp bacterial growth.