Introduction and Indications
An external ventricular drain (EVD) is a catheter that is passed into the lateral ventricles of the brain. It is most commonly placed "at the bedside" by a trained neurosurgeon through a small burr hole drilled into the skull.
Once placed, the EVD provides real time information about intracranial pressure, and perhaps more importantly, can be used to relieve abnormal pressure via the drainage of cerebrospinal fluid.
Common indications for the placement of an external ventricular drain include subarachnoid hemorrhage after aneurysm rupture, traumatic brain injury, and hydrocephalus. Once an EVD is placed, the patient is monitored in an intensive care unit.
- Ventriculostomy kit (usually in its own rectangular box)
- Cranial access kit. Most kits contain at least the following things:
- Drill bit
- Small scalp retractor
- Multiple needles and syringes
- Sharp metal trochar
- 3 sets of sterile blue towels
- Half drape
- Sterile gloves
- Sterile gown(s)
- Hair bonnet(s)
- Face mask(s)
- Duraprep™ sticks (a mixture of iodine and alcohol)
- Hair clippers
- Lidocaine with epinephrine
- 10 mL syringe
- 22 gauge needle
- 25 gauge needle
- Durapore tape
These steps may not be done in this exact order, and quite frankly, some steps may be completely ignored, altered, or changed depending on the circumstance. This is meant to serve only as a guide to the placement of an EVD.
- Get consent from patient or next of kin.
- Order cefazolin (vancomycin if patient is allergic to penicillins) to be given prior to incision.
- Check the patient's coagulation parameters (INR should be less than or equal to 1.3). Give fresh frozen plasma or vitamin K (usually 10mg IV if urgent correction is needed) as indicated.
- Check patient's platelets (goal should be greater than 100,000).
- Clip the patient's hair where placement of ventriculostomy will be. Most are placed on the right side at Kocher's point (see discussion below).
- Mark the location of Kocher's point. This is usually found 10.5 to 11.0 cm back from the nasion and 2.5 to 3.0 cm lateral to the midline, which usually corresponds to the mid-pupillary line. An alternative method is to feel for the coronal suture and mark a spot one centimeter anterior (ie: towards the face) on the mid-pupillary line.
- Duraprep™ the area and wait for solution to dry. Alternatively, you may use another iodine based cleaning solution. Do not fan or blow the area dry.
- Draw up your lidocaine with epinephrine using the 10 mL syringe and 22 gauge needle. Change the needle over to the 25 gauge size.
- Inject the lidocaine with epinephrine down to skull where you marked Kocher's point. Do this before you make everything sterile because it will give the epinephrine time to "seed" the location, which will aid in hemostasis during the procedure.
- Also inject lidocaine along the path you will tunnel your intraventricular catheter. The location/direction of the tunneling can vary depending on the operator and situation.
- Open up the cranial access kit using sterile technique. This will be your "sterile field" that you can open your remaining supplies on.
- Open up a sterile half drape onto the cranial access kit.
- Open up the packs of sterile blue operating room towels on to the cranial access kit.
- Open ventricular catheter and place on sterile field.
- Open additional syringe and needles onto kit (these can be used if more lidocaine is needed).
- Take some sterile solution and poor a little into any plastic reservoir, which is usually present in the access kit. The sterile solution can be used to flush the ventriculostomy catheter if multiple passes are needed and the tip gets clotted with blood/debris.
- Open a pair of sterile gloves, but do not put them on yet!
- Get into a sterile gown. Learn how to do this without help. This is trickier said than done! Practice makes perfect!
- Put on the sterile gloves making sure that the rest of the gown remains sterile. Again doing this alone is tricky.
- Using the blue towels (opened onto sterile cranial access kit) place one towel to cover the contralateral (ie: opposite) skull. Place towel line directly along the midline of the patient's skull. Then place multiple other towels, but ensure that you can still see appropriate anatomical land marks.
- You can use the half drape to form a sterile field for the rest of the patient's body if needed.
- Re-identify Kocher's point using both your mark (which was unfortunately probably washed away during re-prepping and distorted during epinephrine injection!) and anatomical landmarks (see discussion above).
- Attach the drill bit to the drill.
- Ensure that the patient is appropriately anesthetized and sedated. Medications such as fentanyl, propofol, and midazolam are commonly used. If the patient is not intubated it is important not to "snow" the patient too much to cause them to stop breathing. If the patient is not intubated you can also perform a supra-orbital nerve block, which will anesthetize the appropriate area. If intubated you may be more aggressive with your intravenous sedation and analgesia since the patient has a "secured" airway.
- Make an approximately 1-inch (2.54 cm) incision down to the skull at Kocher's point. There is no need to be ginger with this step; allow your scalpel blade to cut all the way to the bone. If adequate lidocaine with epinephrine was used bleeding should be minimal at this point.
- Some cranial access kits will have a small retractor that can be used to provide better visualization. You can use this to help "open up" your incision.
- At a 90 degree angle to the skull place a burr hole using the catch guide on the drill to prevent puncture of the dura with the bit. The key at this step is to use very gentle pressure while spinning the drill bit very fast. Once through the first layer of compact bone you'll feel the bit "fall" into the cancellous bone, where drilling will be easier. Then you'll reach the second layer of compact bone. Continue to spin the drill quickly but lighten up on the pressure because at this point you are close to the dura.
- Use a pair of forceps to remove any bone dust or chips as these can get passed into the brain tissue during catheter insertion.
- Once the burr hole is made, use a needle (I prefer a spinal needle) to puncture the dura. You'll want to "push" away dural leaflets so that you do not create a potential epidural space.
- Take your trochar, and using the sharp end, tunnel your access path out below the galeal layer of the scalp and "pop" out at a site two or three inches away from your burr hole site. Be careful to avoid sticking yourself with the trochar tip. You can use forceps as a fulcrum to aid you with this step. Leave the catheter attachment side near the burr hole (ie: the trochar should remain buried underneath the scalp with one tip at the burr hole site and one tip sticking out of the skin).
- Recap the trochar tip carefully. These are super sharp!
- Now take the ventricular catheter with the guide wire in place, and using your left hand as a stabilizing device advance slowly but steadily into the parenchyma. The trajectory should be towards the ipsilateral medial canthus of the eye, and the catheter should be orthogonal (ie: exactly perpendicular) to the skull itself.
- Advance the catheter 6.0 to 7.0 cm at the most! Do not be tempted to go further than this.
- Pull the stylet and assess for cerebrospinal fluid (CSF) pulsations in the catheter.
- If no CSF is seen, pull the catheter out and re-place the stylet after washing down the tip of catheter with sterile solution. This will remove any "debris" in the tip of the catheter that may prevent flow.
- Re-pass the cathter. In general, a maximum of three attempts should be tried. If no CSF is obtained the patient is either not under pressure or the catheter is not in the ventricle. At this point you can either abort the mission entirely, or suture the catheter in place (see steps below) and get a head CT to see where the catheter is.
- Once CSF is obtained place the extracranial end of the catheter onto the trochar tip. Be careful not to pull the catheter out of the ventricle inadvertently!
- Using blunt forceps "pinch" the catheter at the skull with your non-dominant hand. Then using your other hand pull the trochar through the tunneled pathway. If the catheter was secured appropriately it should hold onto the trochar and exit the skin.
- The ventriculostomy catheter should "sit" firmly down as you pull the other end through the scalp.
- Cut the catheter off of the end of the trochar (do not attempt to pull it off!!!).
- Place the included capping device on the end of the catheter to prevent CSF from leaking everywhere.
- Then using 3-O nylon or prolene sutures place a drain stitch at the point where the catheter exits the scalp. Be careful to not place a stitch through the catheter itself!
- Close the incision with 3 or 4 interrupted sutures. Attempt to close the galeal layer, but again be careful not to put a stitch through the catheter.
- Gently wrap the catheter along the head (see image), and place 3 more securing stitches onto the scalp along the course of the catheter.
- While still sterile have the nurse/assistant hold up the connection tubing. This is usually flushed with saline prior to being connected.
- Remove the stop cock device from the tip of the catheter and connect the end of the catheter to the tubing. There is usually a small V-shaped cylinder in the ventriculostomy set that allows you to connect the catheter to the tubing directly.
- Place and tie a silk ligature around the area where the tip of the tubing connects to the catheter to prevent it from becoming dislodged accidentally.
- At this point it is OK to break sterility.
- Clean up all your sharp instruments and place them in the appropriate receptacles.
- Provide the nurse with an ICP monitoring order. Usually the initial settings are to place the level at approximately 15 cmH20 above the tragus of the ear. However, more intense drainage (done by decreasing the level) may be necessary depending on the patients disease process.
Ventriculostomy catheters (aka: external ventricular drains or "ventrics") provide real time information about intracranial pressure. They also provide a way to treat elevated intracranial pressure. Common indications for EVD placement include subarachnoid hemorrhage, traumatic brain injury, and acute hydrocephalus.
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