# Patterns of care and outcomes following external ventricular drain placement: Insights from the England HES administrative data set

## TL;DR

This study analyzed outcomes of patients who had external ventricular drain (EVD) procedures in England, finding that grouping all EVD cases together can lead to misleading comparisons between hospitals.

## Contribution

The study introduces a method for distinguishing between EVD procedures performed alone versus with other surgeries, improving benchmarking accuracy.

## Key findings

- EVD performed alone had higher mortality (43.2%) compared to EVD with an index procedure (19.7%).
- Mortality increased with age, comorbidities, and emergency admission.
- Risk-adjusted models reduced apparent variation in outcomes between hospitals.

## Abstract

To evaluate the outcomes of patients undergoing external ventricular drain (EVD) insertion in England, focusing on the timing of EVD relative to index neurosurgical procedures, and to assess the implications for benchmarking and performance monitoring between neurosurgical centres.

We conducted a retrospective cohort study using Hospital Episode Statistics. Adult patients (≥16 years) undergoing EVD insertion between April 2013 and March 2020. Outcomes included 90-day mortality, length of stay (LOS), and emergency readmission within 30 days. Multivariable logistic regression was used for mortality and readmission, with adjustment for age, admission method, comorbidity (RCS Charlson index), and neurosurgical clinical category. A quantile regression model was performed with LOS as the outcome.

The cohort comprised 10,239 patients. Crude 90-day mortality was 26.7 % overall, highest in the EVD-only group (43.2 %) and lowest when EVD was performed with an index procedure (19.7 %). Mortality rose with age, comorbidity, emergency admission, and was highest in Oncology, Vascular, and General & Trauma categories. The final risk-adjustment model showed good discrimination (AUC 0.71) and reduced apparent inter-unit variation in mortality.

Our findings demonstrate that treating all EVD insertions as a single cohort obscures clinically meaningful differences in patient trajectories and leads to misleading comparisons of outcomes. Although the absence of detailed severity markers in administrative data means that conclusions about quality of care must be interpreted cautiously, this study illustrates how carefully constructed, clinically meaningful cohorts can transform the interpretation of common neurosurgical procedures.

•National cohort study of 10,239 patients undergoing EVD insertion in England.•Mortality (26.7 %) and outcomes varied substantially by EVD timing and Neurosurgical clinical category.•Distinct care patterns identified for “EVD only” and “EVD after index procedure”.•Risk-adjusted models and funnel plots demonstrate inter-unit outcome variation.•Findings support nuanced cohorting of common procedures for audit and benchmarking.

National cohort study of 10,239 patients undergoing EVD insertion in England.

Mortality (26.7 %) and outcomes varied substantially by EVD timing and Neurosurgical clinical category.

Distinct care patterns identified for “EVD only” and “EVD after index procedure”.

Risk-adjusted models and funnel plots demonstrate inter-unit outcome variation.

Findings support nuanced cohorting of common procedures for audit and benchmarking.