CSF External Drainage Devices 

Cerebrospinal fluid (CSF) drainage devices are used for draining CSF and monitoring CSF flow from the ventricular system in order to control and reduce intracranial pressure (ICP), evaluate CSF cytology and chemistry, and to provide temporary CSF egress in patients with malfunctioning or infected CSF shunts.

Category

CSF external drainage devices, CSF drainage devices

Device details

Available CSF drainage devices include the following:

• Medtronic Becker External Drainage and Monitoring System and Duet External Drainage and Monitoring System (see the image below)Medtronic Duet External Drainage and Monitoring System. Image used with permission from Medtronic.
• Codman EDS 3 CSF External Drainage System (see the image below)Codman EDS 3 CSF External Drainage System.
• Integra LifeSciences AccuDrain External CSF Drainage System

Ventricular catheters feature fenestrations along the distal portion to minimize obstruction caused by choroid within the ventricles. In addition, ventricular catheters are now manufactured in different sizes, with a typical lumen of approximately 1.5 mm. Smaller catheters are available for neonatal patients, and larger lumen catheters are available for certain settings, such as intraventricular hemorrhage.

Antibiotic-impregnated catheters are widely available, although they may be contraindicated in patients with antibiotic allergy. Most manufacturers package the catheter with a stylet that allows for insertion, as well as a trochar to tunnel the catheter away from the incision.

The Becker External Drainage and Monitoring (EDM) System's 20-cm ventricular catheter, 24-cm lumbar catheter, and 80-cm lumbar catheter, available separately, include a catheter Luer-Lok connector with an integral molded plug. This plug may be used to plug the catheter before connection to the patient line.

The EDM 35-cm ventricular catheter includes a separate end plug to allow temporary closure. EDM catheters with BioGlide include a separate end plug.

The EDS3 CSF External Drainage System has the following features:

• Splash-free valve for air filter protection
• Drip chamber with an antireflux valve (inlet), 100-mL capacity, a funnel bottom, and a sampling site (outlet)
• High-visibility pressure scales in both mm Hg (-3 to 20) and cm H₂ O (-5 to 27)
• Leveling device incorporating a reusable bubble level with a class 2 laser lamp
• Latex-free injection/sampling port

The AccuDrain External CSF Drainage System has the following features:

• Dual-action lever that allows the system to be easily and quickly attached to an intravenous (IV) pole
• Unique squeeze-lock mechanism for quick and secure adjustment of the burette drip chamber
• Very large numerals on the graduated pressure scale, designed to be easily read from across a room and in low light
• Several incorporated safety features, including needleless sampling sites to address sharps safety issues and an antimicrobial and hydrophobic filter that allows the system to be disconnected and laid on its side during patient transport
• Ability to be safely used in proximity to magnetic resonance imaging (MRI) equipment

Goals for draining and monitoring of cerebrospinal fluid (CSF) flow from the ventricular system include the following:

• Control and reduction of intracranial pressure (ICP)
• Evaluation of CSF cytology and chemistry and monitoring of trends
• Provision of temporary CSF egress in patients with malfunctioning or infected CSF shunts

External ventricular drain (EVD) placement is appropriate for patients who require temporary continuous diversion of CSF. An additional function of most EVD systems is the ability to monitor ICP. Both ICP monitors and EVDs allow for ICP monitoring, but only an EVD can allow CSF diversion. Common clinical conditions that require EVD placement include severe head trauma, subarachnoid hemorrhage, intraventricular hemorrhage, and acute hydrocephalus of any other etiology.

Indications for monitoring of ICP include the following:

• Severe head injury
• Hydrocephalus
• Intracranial hemorrhage
• Certain encephalopathies, such as Reye syndrome
• Higher-grade subarachnoid hemorrhage
• Preoperative and postoperative use in patients undergoing resection of space-occupying lesions (especially patients maintained on sedation)

Contraindications for CSF external drainage devices are as follows:

• Current anticoagulant therapy or bleeding diathesis
• Infection of the scalp, subcutaneous tissue, bone, or epidural space at or near the projected site of placement
• Unavailability of continuous close supervision
• Noncommunicating hydrocephalus (in cases in which lumbar puncture is contraindicated)
• Presence of a large intracranial mass lesion, hematoma, or cysts
• Blockage of CSF flow to the subarachnoid space as a consequence of trauma, hematoma, fracture, or tumor

Nuances in the use of external ventricular catheters are the subject of investigation. Recently, prospective randomized trials comparing antibiotic-impregnated catheters to non–antibiotic-impregnated catheters have suggested a statistically significant reduction in infection rates with antibiotic-impregnated catheter use.^{[1, 2]} In addition, there may be utility in prophylactic antibiotic dosing for the insertion of the catheter.^[2] Owing to the heterogeneity of the patient population, a valid comparison between ICP monitors and EVDs is not realistically feasible for most indications.

Parodi et al found that Enterobacter species are increasingly a cause of nosocomial meningitis among neurosurgery patients, although risk factors for these infections are not well defined.^[3] The investigators identified 15 postneurosurgical cases of Enterobacter meningitis over an 8-year period, 14 of which were cured. They concluded that external cerebrospinal fluid (CSF) drainage devices were an independent risk factor for this infection.

Abla et al, comparing the efficacy of 2 different antibiotic-impregnated external ventricular drain (EVD) catheters in preventing CSF infections, found that the antibiotic-impregnated catheters carried an extremely low risk of CSF infection compared with standard EVD catheters.^[4] .

Of the 129 patients studied, 65 received clindamycin/rifampin-impregnated (C/R) catheters, and 64 received minocycline/rifampin-impregnated (M/R) catheters.^[4] The most common indication was subarachnoid hemorrhage (48.1%), followed by spontaneous intraparenchymal bleeding (13.2%). The mean duration of drainage was 11.8 days in the C/R group and 12.7 days in the M/R group.

Kwok et al, reviewing the clinical records of 107 cases of EVDs, found that the most common indication for an EVD was spontaneous intracerebral/intraventricular hemorrhage (36%) and that only 35% of patients needed a permanent shunt.^[5] Of the complications, EVD infection was the most common and carried the greatest significance. Of the 107 patients, 8.4% had a positive CSF culture. Of the coexisting conditions, chest infection was the most common (50%), followed by urinary tract infection (20%).

Because each external cerebrospinal fluid (CSF) drainage device has its own special features, only a general idea of the clinical implementation is provided here.

System setup

The system should be prepared about half an hour before placement of the CSF catheter under sterile conditions. The pack should be checked to confirm that all of the components are assembled and free of damage. An electronic pressure monitoring system may be attached to the transducer adapter on the patient's line.

The system should be mounted in such a way that the main stopcock is at the level of the foramen of Monro or at the level of the lumbar catheter. This point is taken as the zero reference level, and it is vital for accurate measurement of pressure. The foramen of Monro can be approximated as the external auditory meatus.

The next step is to remove the air from the system. Via either a 20-mL syringe fitted with a needle or a needleless injection port, the tubes and the system are prefilled with preservative- free sterile saline before being connected to the patient. The fluid should freely drain from the flow chamber into the drainage bag. Check for any residual air bubbles, and aspirate via the needle at the injection site on the patient's line.

Ventricular catheter insertion

Insertion can occur at the bedside or in the operating room. The ventricular catheter is inserted into the patient's ventricles. This is most commonly accomplished via a frontal ventriculostomy, although other sites may also be used. Sterile conditions are maintained. The scalp is prepared and draped in the usual manner. Kocher's point is then identified (for a frontal ventriculostomy), located about 2-3 cm lateral to the midline and 1-2 cm anterior to the coronal suture. A 2-cm incision is made down to the bone with a scalpel.

Landmarks have traditionally guided catheter placement, although adjuncts such as frameless stereotaxy and hand-held guides have recently become available.^{[6, 7]}

The periosteum is dissected off the bone, and the twist drill is used to make a burr hole at that site. The dura is then punctured with a small needle. The catheter, after having been irrigated with preservative-free saline, is inserted along a tract aimed perpendicular to the skull, toward the ipsilateral medial canthus. After the catheter has been advanced about 5-6 cm, adequate flow of CSF is typically obtained. Caution is excercised not to place the catheter too deeply.

The catheter is then tunneled to a distal exiting site. After the catheter has been properly placed, the appropriate connector is inserted into the catheter. Care should be taken to allow only a minimal amount of CSF to escape.

System control and calibration

To obtain an accurate pressure head, the tubing from the patient to the flow chamber drip should be completely fluid-filled. If the tubing is not completely fluid-filled, the pressure head (in cm H₂ O) is equal to the height of the meniscus of the fluid in the tubing, as referenced to the zero level of the system. The system should be calibrated before being connected to the patient. The best way of calibrating the system is to set the transducer on either of the stopcocks to the atmospheric pressure to zero the transducer.

The flow chamber connection line may be used as a manometer tube. The transducer is then referenced to the saline-filled connection line. A scale is located adjacent to the flow chamber slide on the mounting panel. A pressure setting of 20 mm Hg is recommended for transducer calibration.

For the CSF to flow from the drainage catheter to the flow chamber, the patient line and system stopcocks are opened, and the slide clamps are opened to allow the fluid to drain into the bag. The fluid drained depends on the pressure head adjustment (where the drainage chamber entry point of the catheter is placed in relation to the patient's external auditory meatus, which is an approximation of the level of the foramen of Monro).

Monitoring

Simultaneous drainage and pressure monitoring should not be performed, because it may result in artifacts in measured pressure. If more accurate pressure monitoring is desired, the system should be temporarily closed to drainage by adjusting the patient line stopcock or the main system stopcock so that the drainage catheter communicates only with the pressure transducer.

The flow must be carefully monitored to prevent complete filling of the chamber; a full chamber will prevent CSF drainage. Fluid accumulation can be recorded by following the graduations on the flow chamber.

Maintenance and uses

The patient’s injection site may be used to flush the system. The fluid is allowed to drain into the drainage bag. When the bag is full, it may be replaced. Before the bag is replaced, the distal drainage line is clamped to prevent retrograde flow. The bag is then removed from the panel. Under sterile conditions, the bag is disconnected from the connection line and discarded according to standard procedure. A new bag is then connected to the line and attached to the mounting panel.

The steps in changing the drainage bag are as follows:

1. Remove the bag from the system mounting panel without disconnecting the drainage bag from the flow chamber connection
2. Disconnect the cap at the top of the bag from the Luer-Lok fitting
3. Avoid contamination of the open Luer-Lok fitting, invert the bag, and empty it
4. Using sterile technique, replace the port cap, and reattach the bag

The injection sites can be used for different purposes. A 25-gauge needle may be inserted through the site after it is cleaned and disinfected and subsequently used to irrigate a clogged ventricular catheter with 0.1 mL of sterile saline. Alternatively, the site may be used to withdraw CSF for laboratory analysis or to inject medication intraventricularly.^[8]

Many patients with an external ventricular drain (EVD) typically require intensive care, although some patients who are neurologically stable and require prolonged external drainage may be appropriately managed in other hospital settings, such as a surgical or pediatric ward. For patients in an intensive care unit setting, routine monitoring consists primarily of recorded CSF output as frequently as every hour. Intracranial pressure (ICP) can be transduced either intermittently or continuously. Some patients will have radiographic evidence of ventriculomegaly, and serial head CT scanning can be performed to monitor the resolution of acute hydrocephalus.

Typically, patients with an EVD will be weaned, with two potential outcomes. The patient will either tolerate removal of the EVD without developing symptomatic hydrocephalus, or they will require permanent CSF diversion, which most commonly requires placement of a ventriculoperitoneal shunt.

To prevent complications, it is essential to monitor and adjust the CSF outflow through the external drainage system so as to avoid underdrainage or overdrainage. Monitoring should be done by experienced intensive care personnel who are familiar with ICP and lumbar pressure monitoring techniques.

ICP monitoring has been associated with intracranial infection, meningitis, and ventriculitis. The factors responsible include frequent opening of the system and extended monitoring of the system. First and foremost, the injection sites should always be cleaned with alcohol and the alcohol allowed to dry before a needle is inserted into them. Second, sterile technique should be employed in setting up the system and in placing the catheter. Third, subgaleal tunneling of the ventricular catheter should extend for approximately 1-2 in.

Ventricular collapse may occur if the CSF is rapidly drained, and such collapse can occlude the catheter and cause injury to the patient, leading to tentorial herniation. Accordingly, drainage maneuvers should be made against a positive pressure head of 20 cm H₂ O.

False pressure readings may occur if the line is clogged or an air bubble is lodged in the system. Thus, a false reading may lead to the provision of inappropriate treatment to the patient. If the waveform begins to dampen out, the entire monitoring system must be examined. This is necessary to ensure that the line to the patient is not kinked and that all air bubbles or blood or other debris are removed from the system.

It is important to determine that the transducer is on the same level as the patient’s ventricular system to ensure the proper reference level in the manometer tube for use in calibration procedures. Pressure monitoring with the manometer may result in overdrainage of the ventricles.

Either the puncture of the ventricle or the opening of the dura may result in an intracranial hemorrhage.^[9]

Complications of external drainage of cerebrospinal fluid (CSF) include the following:

• Infections, particularly meningitis, ventriculitis, and wound infections; limiting the duration of monitoring from a single site to less than 5 days reduces the infection rate
• Intracranial hemorrhage and permanent neurologic deficit caused by overdrainage of CSF
• Intracerebral hemorrhage and edema, leading to a further rise in intracranial pressure (ICP), as a consequence of frequent punctures of the brain to insert the ventricular catheter; minimizing the number of punctures will help prevent this
• Ventricular wall collapse, in small patients, resulting in obstruction of the catheter and predisposing to tentorial herniation; avoiding excessive release of CSF before the system catheter is attached to the patient line is important

The placement of an external ventricular drain can be associated with hemorrhage. A recent meta-analysis approximates the risk of any hemorrhage at 7% and the risk of significant hemorrhage at 0.8%.^[10] Infection is another leading complication associated with external ventricular drainage, with an estimated 11% of patients developing ventriculitis or meningitis.^[11]