Catheter occlusions are one of the most frustrating challenges in external ventricular drainage and have the potential to increase intracranial pressure (ICP) to dangerous levels. In the study “Visualizing the pressure and time burden of intracranial hypertension in adult and pediatric traumatic brain injury,” researchers measured minute-by-minute intracranial pressure and mean arterial blood pressure data of 261 adult patients and found that it takes 37 minutes for patients’ ICP to rise to levels that are linked to poor clinical outcomes. In pediatric patients, that critical timeframe drops to just 8 minutes.

The neuro care team must act fast to address catheter occlusions, which are often a build-up of blood clots and tissue fragments. If initial approaches of saline irrigation cannot clear the clog, the occluded catheter can be flushed with more active agents to break up the block or replaced with a new catheter.

The time-sensitive nature of addressing occlusions adds a burden on the care team as does how often they occur. A 2016 study by Fargen et. al of 131 catheters and 1,076 catheter days found that 41% developed at least one temporary occlusion, requiring an average of 2.4 irrigations per patient. In the same study, 19% of the ventriculostomy catheters developed a permanent occlusion, which required at least one catheter replacement if not more.


What Increases the Risk of EVD Catheter Occlusion?

Several studies have found that patients who present with bloody CSF at the time of the EVD procedure are more likely to be at risk for occlusion. This is because the catheter surface can become coated with plasma and CSF proteins, leading to platelet adhesion and activation and thus thrombus accumulation. Conformational changes of adsorbed fibrinogen have been thought to play a role in platelet accumulation on EVD catheters, as they can encourage platelet adhesion to the catheter surface.

Even if bloody CSF is not present, each EVD placement carries its own risk of bleeding, which could contribute to occlusion. The Fargen study found that intracranial hemorrhage occurred in 28% of patients after the first EVD placement and in 62% of patients after one replacement.

Likewise, in a 2020 article in World Neurosurgery, Aten et. al found that up to 42% of catheters placed can cause a new hemorrhage. Additionally, following EVD placement, there is a 19.1% chance of subarachnoid hemorrhage and 14.9% chance of intracranial hemorrhage, both of which have a strong correlation to secondary IVH.

However, EVD catheter occlusions can also be caused by other factors as well. The diameter of the catheter has been found to play a role in the prevalence of occlusions. Small lumen catheters (1.5 mm) have been linked to higher rates of occlusions, due to the principles outlined in Poiseullie’s law. Fargen et al found that 25.5% of small catheters can become permanently occluded, while this occurred in only 10.9% of large catheters in a study of 101 patients undergoing EVD placement. Misplacement or migration of the EVD catheter into the parenchyma could also play a role in whether a catheter will occlude.

Click here to read Integra’s special report, “Finally, Advances in the Standard of External Ventricular Drains.”



Aten, Q, Killeffer J, Seaver C, Reier, L. Causes, Complications, and Costs Associated with External Ventricular Drainage Catheter Obstruction. World Neurosurg. 2020; 134:501-506.

Fargen KM, Hoh BL, Neal D, O’Connor T, Rivera-Zengotita M, Murad GJA. The burden and risk factors of ventriculostomy occlusion in a high- volume cerebrovascular practice: results of an ongoing prospective database. J Neurosurg. 2016; 124:1805-1812.

Güiza, F., Depreitere, B., Piper, I. et al. Visualizing the pressure and time burden of intracranial hypertension in adult and paediatric traumatic brain injury. Intensive Care Med 41, 1067–1076 (2015).

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