Overall, we found that in patients with ICH and IVH, EVD placement was independently associated with lower mortality, but not with better 90-day neurologic outcome. Other factors associated with 90-day mortality and outcome included age, ICH and IVH volume, ICH location, and initial GCS score.
We noted several factors associated with IVH incidence. These included a past medical history of hypertension and diabetes, higher initial systolic blood pressure, larger ICH volume, basal ganglia location, and lower initial GCS score. Other authors have found similar findings8,11, however some have also found older age to be associated with IVH11. We are unaware of prior findings suggesting a linkage between diabetes and IVH. We also confirmed prior findings that IVH predicts poor outcome 5,6,10,17.
Few other studies have examined the link between EVD placement and other clinical markers of ICH and outcome. Herrick et al, 2014, found that EVD placement is primarily in patients with greater IVH volumes, younger age, lower admission GCS score, and basal ganglia location10. Similarly, we found that EVDs are placed in those with smaller ICH volume, larger IVH volume, basal ganglia location, higher initial blood pressure, and lower initial GCS. Not surprisingly, those with withdrawal of care were less likely to undergo EVD placement.
Our finding that EVD placement was associated with worse neurologic outcome in univariate analysis, but not after multivariate analysis, suggests that its use is preferentially directed towards the most severely injured patients. We note that Nieukamp et al, 2014, reached similar conclusions from their metanalyses of published literature17. We can thus infer that some of the findings on univariate analysis may be due to confounding by indication. The fact that controlling for disease severity reverses this finding suggests that clinical providers may be appropriately targeting those patients for EVD placement who are likely to truly benefit. Overall, our data suggest that the current use of EVD in clinical practice is justified and likely lowering mortality.
Whether lowering mortality leads to an increase in “good” neurologic outcome is unclear. Other clinical trials of surgical therapy have found reductions in mortality, without a corresponding improvement in neurologic outcome7,8,14,22, suggesting that some interventions may save lives but with severe associated morbidity, rather than leading to “good” recovery. Another study has similarly found that EVD subjects exhibited lower mortality but worse outcome13. It is not clear whether EVD placement falls into this category, or whether any benefit from its use comes from bundling it with multiple other interventions.
While previous projects have examined EVD placement and outcome, this analysis includes a substantially larger cohort than prior efforts2,10,12, lending more power to adjust for multiple factors related to clinical outcome. Other papers previously examining EVD on large populations have focused on assessing EVD placement and complications but have not looked directly at clinical outcome11. We also investigated variables related to EVD placement such as timing of EVD placement and early presence of hydrocephalus. Hydrocephalus was positively associated with 90-day mortality, meaning that presence of hydrocephalus on the first CT was correlated with a higher likelihood of death within 90 days. Time to EVD placement was negatively associated with 90-day mortality, meaning that the later an EVD was placed, the more likely patients were to survive past 90 days. This may mean that acute EVD places additional stressors on patients with intracerebral hemorrhages, but it could also indicate that the most severe cases are given priority for EVD placement as a final measure to attempt to improve outcome.
There were several limitations to the scope of this study. First, as this was an observational study, EVD placement was at the direction of clinical providers, and there may have been confounding by indication. Clinicians may have selected those patients most likely to have good outcome to undergo EVD placement. We attempted to control for this with multivariable analysis, but unmeasured confounders may still have been present. Second, we did not directly assess hydrocephalus, the expansion of fluid in the ventricles that is thought to cause many of the problems associated with IVH. We also did not assess the position of EVD placement, the experience of the neurosurgeon involved, or the actual amount of CSF drainage, all of which may have an impact on its efficacy. The EVD placement decision was made by individual clinicians, raising the risk of confounding by indication. Many patients did not have 3-month functional outcome available; as a result, poor outcome may be overrepresented as those who died were more likely to have available outcomes (Social Security Death Index) than those who did not. We were also unable to control for thrombolytic treatments received. Finally, as this was a retrospective single-center study, the results may not be generalizable to other institutions with different patient populations or practice patterns.