Ventriculostomy

Anatomy and Physiology

Herophilus and Erasistratus were the first to provide the anatomical depiction of the ventricular system inside the brain. Later, Domenico Felice Antonio Cotugno described the presence of cerebrospinal fluid (CSF) within this interconnecting system.[4]

The ventricular system develops from the cavities within the developing brain vesicles. The cavity of the rhombencephalon later forms the fourth ventricle, whereas the cavity of the diencephalon forms the third ventricle, and those of the telencephalon develop into the lateral ventricles. The cavity within the mesencephalon forms the aqueduct connecting the third to the fourth ventricles.[4]

Indications

A summary of indications for performing ventriculostomy is as follows:

1. Acute symptomatic hydrocephalus - following subarachnoid hemorrhage (SAH), strokes, meningitis
2. Intracranial pressure (ICP) monitoring
3. Adjunct management for malfunctioning or infected ventriculoperitoneal shunts
4. As a panacea for brain relaxation during intraoperative brain edema
5. Planning therapeutic interventions- thrombolytics, antibiotics, for managing vasospasms[5][6]

Contraindications

The contraindications for ventriculostomy include:

1. Concurrent use of anticoagulant drugs
2. Bleeding disorders
3. Scalp infection
4. Brain abscess[7]

Equipment

Basic equipment sets should include the following:

1. Non-sterile gloves, soap, brush, hand towel, razor, and a marker pen for parts preparation and marking of the site of placement of monitor devices.
2. For the procedure itself, face mask, sterile gown and gloves, an antiseptic solution, a drape, a local anesthetic agent, a 5-ml syringe, a 15 or 11 number surgical blade, and an ICP-monitoring kit. A drill with a drill bit, a bolt, an ICP sensor, and a transducer as per the methods utilized.  A suture material and a sterile dressing.[7]

Personnel

A composite healthcare team comprised of:

• A neurosurgeon
• A qualified assistant
• An attending nurse
• An anesthetist
• A general duty assistant (GDA)[7]

Preparation

The patient and next of kin/relatives should receive a thorough explanation regarding the indication for the procedure and the risks involved before the procedure, and written consent should be obtained.[7]

Strict adherence to aseptic guidelines is a cornerstone in preventing the risk of infection, and prophylactic antibiotic needs to be administered just at the beginning of the procedure.[8]

The meticulous technique is pivotal in minimizing procedure-related complications. The patient should be well sedated, assuring patency of his airway, and a local anesthetic administered at the allocated point of ventriculostomy.

Technique or Treatment

The insertion of the device is aided by the placement of either a burr hole or a twist drill technique. Kocher's point is the choice for the ventriculostomy. Other points of ventricular puncture include[4]:

1. Keen’s point: -2.5 to 3 cm posterior and 2.5 to 3 cm above the pinna of the ear
2. Kocher’s point: This point is 1 to 2 cm anterior to the coronal suture in the mid pupillary line, or 11 cm posterior from the glabella and 3 to 4 cm lateral from midline ipsilateral medial canthus and a line extending coronally from the ipsilateral tragus
3. Dandy’s point: 3 cm above and 2 cm lateral to the inion
4. Frazier’s point: 6 cm above and 4 cm lateral to the inion
5. Paine’s point-  the apex of an isosceles triangle, whose base is 3.5 cm and lies along the Sylvian's veins, and each of the two limbs is 2.5 cm.
6. Tubbs’ point- a point just medial to the midpapillary point through the roof of the orbit - the trajectory aims 45 degrees from a horizontal line and 15 to 20 degrees medial to a vertical line.

Ghajar first introduced a ventricular catheter guide for optimizing trajectory during ventriculostomy. He advocated a perpendicular trajectory relative to the skull surface.[9]

However, the calvarial slope obviates this trajectory, especially in the coronal plane.[10][11] The accuracy for the ideal placement of the ventricular tip is around 86%. Furthermore, only 3.1% of the catheters were found to be nonfunctional and require a replacement or repositioning.[12] The accuracy can undergo further improvement along with the application of ultrasonogram,[13] endoscopy, neuronavigation,[10] and adjustable Ghajar guide technique.[11]

Kakarla Grading of Catheter Placement[14]

• Grade 1 (optimal)-ipsilateral frontal horn, including the tip of the third ventricle
• Grade 2 (suboptimal and in the non-eloquent area)-contralateral frontal horn, corpus callosum, or interhemispheric fissure
• Grade 3 (suboptimal and in the eloquent area)-basal ganglia, internal capsule, thalamus, brainstem, cerebellum, basal cisterns, and occipital cortex

Complications

The complications include [5]:

1. Intracranial and tract hemorrhage (10%) However, this hemorrhage is usually insignificant and rarely needs surgical intervention.[15]  The use of the antiplatelet within 96 hours of insertion is a significant risk indicator of post-procedural hemorrhage (odds ratio of 13.1).[16] 
2. Ventriculitis (20%)Infection is the most common complication of external ventricular drainage (EVD), with rates ranging from 0 to 45%.
3. Technical failure (failure to tap ventricle or misplacement) (5%) One study revealed that 22.4% of catheter tips were in extraventricular spaces during a freehand placement,  showing ample room for improvement.[17] There is also an association between malpositioned tips with the subsequent risk of shunt occlusion.[10] 
4. The cost for placing an external ventricular drain (EVD) amounts to around $200, with transducers costing an extra $400 to 600.
5. Over-drainage can lead to aneurysmal rebleed and, in cases of hydrocephalus, complicate the upward transtentorial herniation.
6. Kinks and blockage by air, blood, and debris are also frequent, leading to the poor and false recording of the ICP.
7. Inadvertent vascular injury.
8. Pneumocephalus and pneumoventriculi.
9. CSF leak.
10. Accidental fracture
11. Accidental pull
12. Obstruction by choroid plexus, blood clot, or proteinous plug. The anterior entry site lowered the risk of shunt failure compared with the posterior entry site by approximately one-third due to the chandelier effect.[18] Overdrainage can also lead to catheter obstruction due to the formation of ependymal bands.[19]

Various clinical parameters shown to harbinger the risk of infection include:

• CSF leak
• Frequent CSF sampling (each sampling increasing the risk by 8.3%)
• Increased duration of catheter insertion (9.3% with time duration of ≥8 days)
• Frequent changing of the catheter (each increasing the risk by 4-fold)
• The dictum of catheter irrigation.[2][20][21][22]

There have been no significant differences observed in terms of the risk of infection or complications while comparing the EVDs placed either in the operating room or at the bedside. The experience of the surgeons also did not influence the outcome.[1][23] The use of bolt EVDs has minimal risks of CSF leak and tube migration.[3] Absolute risk reduction of around 20% has been reported by applying the antibiotic-coated catheter.[2] The anatomical point of ventriculostomy has not been shown to alter the risk of infection.[2] Rapid weaning within 24 hours has been advocated rather than the training of the EVD (raising the height of the drain until clamping).[20]

Strict adherence to EVD care bundles is of paramount importance in reducing the risk of infection. The most rational strategy is to avoid its insertion whenever possible and implement it only when deemed necessary.[20]

The misplacement rate of the EVD has been reported from 12.3 to 60%.[14][24] A systematic review showed the ipsilateral medial epicanthus as the most favored anatomical trajectory during frontal ventriculostomy. Kakarla grade 1 placement was achieved in 68.58% of procedures, whereas Kakarla grade 3 placement occurred in 10.21% of cases.[25] Suboptimal placements were significantly associated with longer intracranial catheter length.[26] 

Using navigation and augmented reality aids in the appropriate EVD placement and impacts the learning curve.[27][28][29][30]

Clinical Significance

Ventricular catheters represent a “global” ICP with minimal chances of drift and influence from pressure gradients between the parenchyma and ventricular system.

It is the most reliable method of achieving maximum accuracy at minimal expense. There are added therapeutic benefits of CSF drainage, instilling medications like antibiotics and thrombolytic agents.

The advantage of the ventricular monitoring device is the facility for egress of CSF in cases of a sustained rise in ICP (greater than or equal to 20 mm Hg for 5 minutes or longer), but the disadvantage is that simultaneous monitoring, as well as CSF drainage, is not possible. The amount of CSF to be drained can be guided as per the recommended target ICP (commonly set as 10 mm Hg) or can be aided with the visual guidance in improving the ICP waveform analysis obtained from the concurrent application of intraparenchymal monitors or through clinical neurological examination. Care always needs to be taken in preventing paradoxical upward transtentorial herniation due to overzealous drainage of CSF.

EVD can be removed once the ICP is normalized with sustained or improved clinical neurology (motor score at least 5) for at least 48 to 72 hours without the use of any interventions by clamping or, more ideally, gradual increment in its height (training of the EVD) is attained to watch for any clinical deterioration in the patient for at least 48 hours.[7]

Strict aseptic precautions and care also need to be implemented during its removal as well. The head end should be lowered to prevent the risk of pneumocephalus and pneumoventriculi. The tip of the catheter can be sent for bacteriological analysis in cases of persisting fever with features of meningitis. The wound is closed in layers to minimize the risk of CSF leak and infection. The patient should receive close monitoring for any signs of clinical deterioration for at least 24 hours with all preparations made for the emergency placement of a new EVD set.[7]

Enhancing Healthcare Team Outcomes

To ensure better clinical outcomes and to prioritize patient safety by minimizing complications, there need to be mandatory patient safety checklists to be implemented by the interprofessional team involved in the process.[7] The following guidelines have to be adhered to:

1. Valid treatment order sheet which has to be signed and dated by the surgeon
2. All reportable limits clearly specified by the clinician
3. Nurses need to be educated in the management of patients with a ventriculostomy and understand the tracing waveform to report abnormalities to the team.
4. EVD drainage point at a prescribed level with the transducer leveled to the tragus of the ear
5. The EVD column is oscillating
6. Monitoring for normal ICP waveform
7. ICP waveform is pulsatile on the monitor
8. No soakage in the wound site or any junctions within the monitor set
9. Judicious assessment of drained CSF volume
10. Stringent evaluation of the neurological status of the patient
11. Strict maintenance of an aseptic environment.

Monitoring intracranial pressure requires an interprofessional team approach, including physicians, specialists, and specialty-trained nurses, all collaborating across disciplines to achieve optimal patient results. Surgically-trained nurses will play a significant role in the procedure, assisting and monitoring the surgeon performing the procedure. Deviation from these standards can result in life-threatening complications. Open communication between the interprofessional team is necessary so that the procedure achieves optimal outcomes safely. [Level 5]

Nursing, Allied Health, and Interprofessional Team Interventions

• Draw CSF for culture
• Assist the surgeon in administering medications
• Monitoring for signs of intracranial hypertension
• Checking for CSF leak
• Ensuring aseptic techniques when manipulating the catheter
• Monitoring the tracing for dampening or lack of pulsation

Nursing, Allied Health, and Interprofessional Team Monitoring

The nurses involved in patient care should monitor the following:

• Monitor hourly CSF drainage
• Ensure CSF oscillation inside the tubes
• Confer no soakage of the wound
• Ensure the correct height of EVD
• Zeroing of the EVD height at the level of the foramen of Monro or tragus of the ear
• Stringent neurological monitoring of the patient
• Monitor hourly ICP[5]

There needs to be a strict provision of the recommended checklists.[5]

Maintaining a sterile environment and stringent monitoring for foreseeing and timely troubleshooting complications are the cornerstones in the care bundle approach to managing these patients.[31]