Neuro ICU Procedure Atlas (eBook)

1 External Ventricular Drain

David F. Slottje, Nitesh V. Patel, and Ira Goldstein

Abstract

External ventricular drains (EVDs) are a common and useful tool in the Neuro-ICU. Here the following topics related to insertion of an EVD are discussed in detail: relevant anatomy and physiology, indications/contraindications, equipment, technique, complications, and expert suggestions.

Keywords: ventricular drain, external ventricular drain, ventriculostomy, cerebrospinal fluid, hydrocephalus, intracranial pressure

1.1 Introduction

An external ventricular drain (EVD) is a catheter, inserted via a cranial opening, through the dura and brain parenchyma, into the ventricular system. Cerebrospinal fluid (CSF) flows through the catheter into an external collection burette. The CSF column height in the catheter tubing reflects the intracranial pressure (ICP). Typically, a transducer is connected to the tubing to measure and record the ICP. The pressure is reported in cm H2O or mm Hg. The tubing system contains a valve stopcock which can be occluded or opened to allow egress of CSF into the burette. When the stopcock is open, the height of the burette can be adjusted to regulate the flow of CSF. CSF will drain into the burette when the ICP exceeds the height of the burette (see ▶ Fig. 1.1).

1.2 Relevant Anatomy and Physiology

Cerebrospinal fluid is produced by the choroid plexus. Prominent tufts of choroid plexus are most commonly located in the atria of the lateral ventricles, within the third ventricle, and at the foramina of Monro and Luschka. CSF flows from the lateral ventricles, through the foramina of Monro, into the third ventricle, through the Sylvian aqueduct, into the fourth ventricle, through the foramina of Luschka and Magendie, and into the subarachnoid cisternal spaces around the brain, spinal cord, and spinal nerves. The CSF is resorbed from the subarachnoid space into the superior sagittal sinus via the arachnoid granulations (see ▶ Fig. 1.2).

In an adult, the central nervous system contains roughly 150 cc of CSF at any given time. Under normal conditions, the ventricles only contain 25 cc of CSF, with the remainder being located in the subarachnoid spaces. The majority of subarachnoid CSF lies within the lumbar cistern. The CSF is replaced roughly three times daily, with a typical adult generating 450 cc of CSF per day.

Imbalance of CSF cycling can be due to overproduction, or more commonly impeded resorption. Overproduction of CSF is encountered rarely in the setting of choroid plexus papillomas. Disruption of CSF resorption can be classified as obstructive or nonobstructive.

Obstructive hydrocephalus results from any macroscopic blockage of CSF flow at any point in the CSF pathway. This may be due to a blood clot, tumor, other mass lesion, or cerebral edema. Common scenarios resulting in obstructive hydrocephalus include subarachnoid/ventricular hemorrhage obstructing the third ventricle or Sylvian aqueduct, posterior fossa lesions (i.e., tumors, intraparenchymal hemorrhages, cytotoxic edema from cerebellar stroke) obstructing the fourth ventricle, or intraventricular lesions such as a colloid cyst which may act as a “ball valve” intermittently obstructing the third ventricle (see ▶ Fig. 1.3).

Nonobstructive hydrocephalus results from congestion or scaring of the arachnoid granulations, preventing the resorption of CSF into the bloodstream (see ▶ Fig. 1.4). Nonobstructive hydrocephalus is commonly seen in the aftermath of bacterial meningitis or following subarachnoid hemorrhage. Less commonly, certain tumors, such as pineocytomas, may cause nonobstructive hydrocephalus by shedding large amounts of proteinaceous debris.

1.3 Indications

The indications for insertion of a ventricular drain fall into three broad categories—ICP monitoring, CSF diversion, and intrathecal access. In many disease states, the ventricular drain may serve multiple purposes concurrently.

1.3.1 ICP Monitoring

A ventricular drain allows for direct measurement of ICP by establishing a mobile fluid column in continuity with the CSF space. Measurement of the ICP may be desirable to direct therapy in patients with intracranial hypertension, to monitor for the development of intracranial hypertension in comatose patients, or to diagnose various disease states when there is clinical suspicion for intracranial hypertension. Of note, when ICP monitoring is the only anticipated application for a ventricular drain, a fiber-optic ICP monitor may be preferred, given the lower risk of infection and less invasive nature of this procedure (see Chapter 5).

1.3.2 CSF Diversion

By allowing for external drainage of CSF, a ventricular drain can relieve build-up of CSF and reduce ICP. This function of a ventricular drain is especially useful and potentially life-saving in the setting of acute hydrocephalus. It may also be useful to afford modest ICP reduction in cases of global brain injury even with relatively normal CSF circulation. Additionally, CSF diversion can be used to clear the ventricular system of debris (i.e., blood or proteinacious material) that is anticipated to clog the arachnoid granulations and would otherwise result in hydrocephalus. Lastly, CSF diversion may be used to relieve pressure on a CSF fistula to prevent CSF leak and promote healing and closure of the fistula.

1.3.3 Intrathecal Access

A ventricular drain can be used to administer medications directly into the intrathecal space, or to obtain a sample of CSF for analysis. Ventricular drains are rarely placed primarily for intrathecal access, but they are frequently used for this purpose when placed for other indications.

1.4 Contraindications

The following are relative contraindications to insertion of a ventricular drain:

•Coagulopathy

•Thrombocytopenia

•Recent antiplatelet therapy

•Uremic platelet dysfunction

•Recent thrombolytic therapy

•Mass lesion obstructing catheter trajectory

•Scalp infection

1.4.1 Special Situations

Periventricular pyogenic abscesses pose significant risk during ventricular drain insertion given that rupture of such lesions through the ependyma may cause ventriculitis, rapid neurologic decline, and death. Similarly, the approach vector of a ventricular catheter should avoid peri- or intraventricular neurocysticercosis cysts as puncture of these lesions prior to steroid administration will generate a potentially fatal inflammatory response.

1.5 Equipment

The majority of equipment needed for ventricular drain insertion is contained in a pre-packaged cranial access kit (see ▶ Fig. 1.5). Below is a list of the necessary equipment:

•Ventriculostomy catheter, trochar

•Twist drill

•CSF collection system burette

•#15 or #10 blade scalpel

•Lidocaine with epinephrine

•Cap, mask, gown, sterile gloves (× 2), perforated sterile drape, chuck

•Shaver, shaver head, alcohol or betadine skin prep, marking pen, ruler, gauze

•2–0 vicryl (10-pack), 3–0 monocryl (× 2), dermabond, 2–0 silk (× 1)

•Sterile flush (× 2), 23-gauge needle, tegaderm with chlorhexidine gluconate, regular tegaderm (× 3)

•Optional: paraffin bee’s wax, cautery

In addition to standard ventriculostomy catheters, there are several ventriculostomy catheters on the market that are impregnated with antibiotics, usually rifampin. Studies have shown decreased risk of infection with these devices.1 Drug allergies should be reviewed prior to use of an antibiotic-impregnated catheter.

1.6 Technique

1.6.1 Preparation

•Measure catheter trajectory, scalp thickness, skull thickness, and distance to the lateral ventricle on computed tomography (CT) of the head. A coronal plane reconstruction is preferred if available (see ▶ Fig. 1.6).