Surveillance of infection associated with external ventricular drains. Proposed methodology and results from a pilot study

Summary Background The insertion of external ventricular drains (EVD) is necessary in some neurosurgical patients but increases the risk of meningitis/ventriculitis. While there are well recognised risk factors, the proportion of patients developing meningitis/ventriculitis varies partly due to differences in definitions. A multi-disciplinary working group was established to agree definitions for EVD-associated meningitis/ventriculitis and a surveillance system was piloted in four centres in the UK and Ireland. Methods Definitions were agreed based on those previously published and on clinical and microbiological criteria. An agreed dataset was developed to monitor patients after the insertion of an EVD and until the EVD was removed and the microbial aetiology was recorded. Findings Four neurosurgical centres participated with between 61 and 564 patients being surveyed in each unit. The vast majority of drains were cranial. Intra-cranial haemorrhage was the most common indication for the EVD insertion. Between 6 and 35% were inserted by consultants compared to junior doctors. The proportion developing meningitis/ventriculitis varied from 3-18% and from 4.8-12.7/1000 EVD days. Coagulase negative staphylococci were the most common microbial causes. Conclusions The routine and on-going monitoring of patients with an EVD in situ to detect meningitis/ventriculitis presents logistical difficulties and few units undertake this. We consider that a national system of surveillance with agreed definitions and a methodology to enable unit-to-unit comparisons of EVD meningitis/ventriculitis, based on this pilot study, is both needed and feasible. This will in turn inform quality improvement processes leading to the minimisation of infection.