Patient Positioning and Preparation
- Consent: A clear discussion should take place of the risks, benefits, complications, and alternatives. This is an opportunity to spend time with the patient and family educating them about the reason for the hydrocephalus, the proposed treatment and its alternatives, potential complications of the proposed treatment, the expectations for its success and failure, and the expected long-term outcome with successful management of the hydrocephalus.
- Implant personnel: Given the relatively high rate of complications and their severe implications, there needs to be an appreciation that shunt placement is a demanding surgery that should be performed by an experienced, senior surgical team.
- Operating room traffic: The flow of people into and out of the OR should be minimized.
- Prophylactic antibiotics: Antibiotics are administered intravenously before or during induction of anesthesia so that adequate tissue levels are present at the time of the first incision. Cefazolin, 50 mg/kg IV, is used. In patients with a history of allergy to cephalosporins, clindamycin or vancomycin is the alternative. One or two postoperative doses are allowable.
- Preoperative scrub: The surgical field is prepped with an alcohol-based chlorhexidine solution or a slow-release iodine soap/solution and allowed to dry.
- Adhesive film: Contact with the skin by shunt material should be avoided. The use adhesive film to cover exposed skin after the prep and draping can help minimize direct contact between skin and surgical instruments, surgical gloves, and shunt hardware.
- Exposure of shunt: Shunt hardware is not opened until it is needed for implantation. It may be immersed in antibiotic solution (bacitracin).
- Manometric testing not required: The testing of new shunt equipment’s resistance to flow prior to its implantation is not necessary.
- Important features about surgery: Skin incisions should be planned so that they do not overlie shunt material. The proposed path for tunneling of the shunt’s distal catheter should avoid a tracheostomy, feeding gastrostomy, and other such sites when present. The system’s valve should be secured to the pericranium once implanted to avoid its migration.
- “No-touch” technique: Attempts can be made to handle shunt hardware only with instrumentation and not gloved hands. While this is an ideal, it can be difficult in some circumstances.
Selection of shunt type
- Temporary CSF shunt: Several options are available when only temporary CSF diversion is required. They include external ventricular drainage (EVD), a ventriculosubgaleal shunt, and a ventricular catheter to a subgaleal reservoir.
- Standard, definitive CSF shunt: The types of definitive CSF shunts vary as a function of the recipient cavity to which the distal catheter is run. They include the ventriculoperitoneal shunt, ventriculopleural shunt, and ventriculoatrial shunt. Another category includes shunts that originate in the lumbar CSF space as opposed to the ventricle. The lumboperitoneal shunt is an example.
- Other definitive CSF shunts (not commonly used): Other types of CSF diversion techniques are available. They include the use of a III-IV ventricular catheter (Lapras catheter), lateral ventricle to cisterna magna shunt (Torkildsen shunt), ventricular-gallbladder shunt, and ventricular-ureter shunt.
Selection of bur hole site
|Location||Eponym||Landmarks||Direction and length of insertion|
|Occipital||Frazier’s point||3-4 cm lateral to midline and 6 cm above inion||Perpendicular to cortex. Approx. 4-5 cm|
|Occipital||Dandy’s point||2 cm lateral to midline and 3 cm above inion. In infants this usually matches with lambdoidal suture at the intersection with the midpupillary line.||Perpendicular to cortex, slightly cephalic. Approx. 4-5 cm|
|Frontal||Kocher’s point||2-3 cm lateral to midline (parallel to midpupillary line) and 1 cm anterior to coronal suture||Coronal plane: Towards ipsilateral inner cantus. AP plane: Towards external auditory meatus. Approx. 4-5 cm|
|Parietal||Keen’s point||2.5-3 cm posterior to the ear and 2.5-3 cm above the ear||Perpendicular to cortex. Approx 4-5 cm|
- Pre-set valve if programmable: If a programmable valve has been chosen, set the desired pressure before opening the sterile valve case. In any case, adjustments can be made postoperatively according to the patient’s needs.
- Shape of incision: The incision shape is designed to position the shunt away from the incision (e.g., partial inverted “U” or “C”).
- Depth of incision: The periosteum is left partially intact so the shunt valve can be secured to it.
- Special consideration for infants: Premature infants require meticulous care. Avoid charring delicate skin edges, and use a toothed retractor or a suture to retract the small skin flap.
- Size: The dural opening should be just large enough to admit the catheter to avoid CSF leak. The incision can be either circular or cruciate but should conform to the ventricular catheter to lessen the risk of CSF leakage.
- Technique: The opening can be made with cautery or by using an 11 or 15 scalpel after bipolar coagulation of the dura.
- Ultrasound: Place at the edge of the bur hole if ultrasound is used.
Insertion of ventricular catheter
- General points about insertion: Usually the larger ventricle is chosen as the recipient site for the proximal catheter. A trajectory for the catheter’s insertion is then determined that will guide the catheter’s tip away from choroid plexus.
- Establishing trajectory of catheter: When an occipital bur hole at Dandy’s point is used, an ECG lead can be placed at midline on the forehead at the hairline for an easily palpable target for the catheter trajectory. When a frontal bur hole at Kocher’s point is used, the trajectory to the ventricle will be perpendicular to the skull in all planes.
- Intracranial guidance: Ultrasound guidance for trajectory and depth can be used in infants when the fontanelle is still open. In older children, an enlarged bur hole that allows an ultrasound head to sound the intracranial space is a feasible, safe, and effective technique for the placement of ventricular catheters (20). Selective use of intra-catheter endoscopic-assisted proximal shunt placement is useful and may be indicated in small or distorted ventricles and in cases when fenestration of an intraventricular membrane or aqueductal web is indicated (78).
- Confirmation of catheter entry into ventricle: A pop or sudden increase and then a decrease in resistance to advancement of the catheter will be felt as it breaches the ependymal wall of the ventricle. A clear flow of CSF will then be seen coming from the catheter’s external end.
- Positioning catheter tip: Once the catheter is in the ventricle, it should be advanced with its stylet removed (a so-called “soft pass”). The goal is to have all of the catheter’s inlets within the ventricle. Since there are inlets spread over the proximal 2 cm of most ventricular catheters, this effectively means that at least 2 cm of the proximal end of the catheter should be within the ventricle.
- Secure and occlude catheter: The catheter is then grasped in a manner that avoids its dislodgement and excessive CSF egress until it is attached to the shunt valve and its position secured.
Tunneling distal catheter
- Timing: The authors usually place the distal catheter before placing the ventricular catheter.
- Direction: The distal catheter can be tunneled from either the scalp or the distal incision.|
- Tunneler: Make a gentle curve at the tip of tunneler to control its passage through the patient’s subcutaneous tissues.
- Precautions: Take extreme care to avoid vital structures, insuring that the tunneler is neither too deep nor superficial during its passage. Awareness of skull defects (e.g., post-fossa craniotomy), intravenous central lines, tracheostomy, and other obstacles along the path is key to avoiding them.
- Obstruction to tunneler: If difficulties arise, make an intervening incision so that the passage can be done in stages.
Subcutaneous pocket for valve
- Timing: Establish a subcutaneous pocket for the shunt valve prior to removing the tunneler.
- Fit testing: Test fit the valve in the pocket prior to connecting the ventricular catheter so that the pocket can be readjusted if needed.
Connection of devices
- Materials: Secure, non-absorbable ties must be used in all connecting points. Silk ties are preferred, since polypropylene sutures can cut silicone catheters or connecting devices.
- Knots position: If possible, knots should lie in the internal surface of the catheter, i.e., as far as possible from the skin to avoid skin erosion, especially in younger patients.
- Shunt fixation: The valve/ventricular catheter junction should be sutured to underlying periosteum to prevent migration.
Confirmation of patency
- Timing: Distal flow of CSF must be confirmed before the catheter is placed into the distal cavity.
- Technique: If the ICP is low, the distal end of the catheter may be dropped below the level of the head to promote drainage. A low- capacity syringe (i.e., 5 ml or less) can also be used to apply gentle aspiration to clear airlocks or debris from the catheter (19, 21).
- Technique: Mini-laparotomy, abdominal trocar, or laparoscopy may be used.
- Location of incision: Typically, a small transverse periumbilical incision is made. A pristine entry site away from gastrostomy tubes and an empty bladder are required.
- Entry into peritoneum: Confirm entry into free peritoneal cavity with a blunt dissector.
- General surgery assistance: Seek the assistance of general surgeons for previous significant abdominal surgery.
- Location: Locate the jugular vein at the anterior triangle of the neck, in front of the sternocleidomastoid.
- Access: Access can be obtained with either a percutaneous introducer or open exposure of facial vein or jugular vein. The subclavian vein constitutes an alternative when jugular vein access is not feasible.
- Technique: Percutaneous: Using a needle, insert a guide wire and vessel dilator into the chosen vein. Open: Make a sharp incision with a scalpel (partial or total vein opening); secure the distal end and tight closure of the proximal end. Introduce the distal catheter into the vein opening.
- Catheter advancement: The distal catheter is advanced under fluoroscopic guidance to the junction of the right atrium and the superior vena cava.
- Securing distal catheter: Tie the distal vein end tight enough to prevent hemorrhage but loose enough not to occlude the catheter.
- Location: Incision is made over the second or third rib, above and lateral to the nipple, between the anterior and mid-axillary line.
- Access: The pleural space is reached by dissecting through intercostal musculature.
- Catheter advancement: The distal catheter is advanced 20–25 cm into the pleural space.
- Lung reinflation: Several positive pressure ventilations help to reinflate the lung and reduce the likelihood of pneumothorax.
- Relevance: Closure is perhaps the most important part of the operation, particularly in infants.
- Technique and materials: Scalp: gentle meticulous apposition of the skin in two layers. Absorbable skin sutures usually provide secure skin closure and avoid the emotional trauma of suture removal in younger children. Abdomen: secure closure of anterior rectus sheath; the peritoneum does not require closure. Neck (ventriculoatrial shunts): secure closure of platysma with absorbable sutures and skin with removable or absorbable sutures; deep layers do not require closure. Chest (ventriculopleural shunts): secure closure of subcutaneous tissue with absorbable sutures and skin with removable or absorbable sutures; pleura and deep layers do not require closure.
- Precautions: Remember to close the intervening incision and inspect the shunt path for any inadvertent skin disruptions.
- Alternatives in damaged skin: For atrophic, radiated, or otherwise compromised skin, nonabsorbable sutures that can be left for weeks are an option.
- Local anesthesia: Injection of local anesthetic into the skin edges may assist with postoperative analgesia.