PLACEMENT OF VENTRICULAR DRAINS - KOCHER, FRAZIER, AND PAINE's POINTS

 

The placement of external ventricular drains (EVDs) is a fundamental and early part of neurosurgical training. In order, from highest to lowest frequency of placement sites are Kocher's point (frontal), Frazier's point (parieto-occipital) and Paine's point/modified Paine's point (intraoperative, periSylvian).

As always, informed consent or emergency consent should be obtained and documented. Regarding emergency consent, i.e., in the setting of a cognitively impaired or obtunded patient requiring EVD placement, the operator should follow his/her hospital's consent policy, although the author of the Webpage recommends that in an emergency consent situation for an EVD or any invasive procedure, the process should involve discussion and signatures of two treating physicians and a discussion with the next-of-kin documenting approval to proceed if the patient is unable to.

Although regarded as a minor invasive procedure, the technique carries its own set of risks including infection/ventriculitis, tract haematoma, drain misplacement requiring re-positioning, and (particularly with Frazier point EVD placement in the absence of stereotactic guidance) the risk of new neurological deficit from e.g., inadvertent cannulation of the internal capsule/basal ganglia region.

A combined serious risk quotation of <= 2% is usually appropriate, but the exact % varies according to the clinical circumstance.

Make sure you have checked the coagulation status and platelet count and correct abnormalities accordingly.

FRONTAL DRAIN @ KOCHER's POINT:

 

Notes regarding EVD placement at Kocher's point:

• Location: Kocher's point (KP) is located 3 centimetres from the midline & 1 cm anterior to the coronal suture (CS). It lies approximately along the mid-pupillary line (MPL).
  • Note: In an adult, the junction between the sagittal and coronal sutures (bregma) is found in the midline approximately 12 cm from the nasion (Nn, i.e., 12 cm back along the scalp from the junction of where the bridge of the nose meets the forehead). The suture sweeps slightly forward as you move away from the midline, as drawn above. In trauma patients, the scalp may be swollen and the suture may be difficult to palpate. The above measurements are helpful, but another good way of finding the bregma is by drawing an imaginary line between each ear's tragus (Tg). Where that inter-tragal line crosses the midline is the bregma.
• Patient position: Supine; head and neck neutral; nose pointing straight up. This is the ideal position because it's intuitive anatomically.
• Before you put on your gown and gloves and before you prep and drape....Landmarks: Make precise measurements with a permanent/surgical marking pen. Mark the region on the skin that is Kocher's point based on the information above. Shave the skin and remove loose hairs from the field in order to allow enough room to create a 2.5 cm subcutaneous tunnel and to place a clear-sticky dressing (e.g., Tagaderm) over a loop of the skin-anchored drain at the completion of the procedure.
• Preparation: The patient is unconscious and intubated. You may need to place the drain in the ICU or in the OR. You will have a standard equipment tray including a drill (manual twist drill in the ICU or an electric/pneumatic in the OR), drapes and dressings, antiseptic solutions, needles, and suture materials. There is a separate kit containing the ventricular catheter and the drainage burette and bag. Have an assistant with you. Be meticulous in your aseptic technique from start to finish. Wear a mask, faceshield/glasses, and gown, in addition to sterile gloves (which the Author recommends you change prior to ventricular catheter handling; see below). A standard dose of IV antibiotic should be administered prior to the skin incision. Allow the antiseptic skin prep about 3 minutes to dry in order to be effective. No local anaesthetic is required as the patient is intubated and sedated.
• Incision: A small linear stab-incision (incision A, above) is okay for the placement of a frontal EVD (E). A curved incision (incision B, above) is good for the placement of an EVD (E) that may later be changed over to a fresh ventriculo-peritoneal shunt system. The latter incision is good because the tubing of the current and future ventricular catheters (VC) and future shunt valve (SV) will be placed remote from the incision itself. Tubing running directly under or crossing incisions is likely to put such systems at higher risk of infection, as is tubing that eminates directly out of the skin in the absence of a small subcutaneous tunnel (of min. length 2.5 cm).
• The bur hole: Make it wide enough to (i) accommodate the catheter (a Bactiseal or equivalent antibiotic-impregnated catheter is preferred by the Author), and (ii) allow for minor directional changes in your trajectory and parenchymal tract. When using the hand twist-drill, rotate the handle at a regular speed without plunging (use a depth-stop if available on the drill-bit). There will be an initial "catch" as the skull's outer table is traversed and later a second "catch" as the inner table is traversed. After the second catch, blunt-probe the bur hole, hopefully, your probe is bouncing on the dura. The Author recommends sterile saline irrigation of the hole at this point to remove bone debris.
• NOW: Before you touch the ventricular catheter immediately prior to its placement...aseptically change your gloves to a new pair of sterile gloves. This step may decrease the rate of ventriculitis/shunt infection over and above other useful measures such as using a Bactiseal catheter or equivalent.
• Catheter trajectory and depth: The rule-of-thumb to follow for your trajectory is: "perpendicular to the skull at the point of insertion". At Kocher's point, the tip of the plastic catheter (with its metal stylet in situ) is advanced towards the junction of a line extending directly backwards from the ipsilateral medial canthus and a line extending coronally from the ipsilateral tragus. As the operator's experience with EVD placement increases, a subtle "popping" sensation is felt as the catheter penetrates the ependyma. This usually occurs at a depth of about 4-5 cm from the skull's outer table. At this depth, advance a few more millimetres and then remove the metal stylet and check for CSF egress. If successful, and now without the stylet, advance the plastic tubing 1 cm more to a maximum depth of 6 cm from the skull's outer table. This should put the tip close to the foramen of Monro in this anterior approach.
• Securing the catheter: Secure the base of the catheter to the skin using a firm but non-occlusive suture and during this maneuver ensure that the depth of the catheter is unaltered from your original intended depth. The Author recommends that prior to this anchoring step, a 2.5 cm subcutaneous tunnel is trochared. Also recommended is the placement of a clear-sticky dressing (e.g., Tagaderm) over a loop of the skin-anchored drain at the completion of the procedure. The Author places Betatine paste over the skin exit point of the catheter prior to placing the Tagaderm aseptically.
• Trouble shooting: Common reasons for EVD failure are the use of inappropriate landmarks or an incorrect advancement trajectory. Difficulty might be compounded by narrower ventricles, brain shift, or non-neutral/non-intuitive head position. If you are following the above recommendations, and have not encountered CSF return at a depth of 5-6 cm from the skull's outer table, you may be "skiving" the lateral margin of the ventricle, so remove the catheter and with the stylet in place change to a trajectory that is slightly more medial. Do not continue to blindly advance the catheter beyond 6 cm from the skull's outer table.
• Post-placement: A brain CT scan should be obtained after EVD placement to verify correct localation and serve as a radiological baseline.