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Indications for Surgery
- Treatment is necessary: Problematic hydrocephalus must be proven prior to considering treatment. Macrocrania, accelerated head growth, and/or signs of elevated ICP in a child can be due to reasons other than hydrocephalus.
- Better treatments not indicated: Alternative treatments for enlarged CSF spaces are available (ETV, fenestration of trapped spaces to the subarachnoid or normal ventricular spaces, treatment of causative factors such as tumors, hematomas, and infections including temporary CSF diversion) and should be considered before settling on the use of a shunt.
- No contraindications for shunt: The patient should be free from infection, and there should be no foreign body along the proposed path for the shunt. Assessment of nutritional status is also advisable, as well as control of other comorbidities.
- Progressive neurological decline needs timely intervention: If the patient’s clinical course of hydrocephalus is rapidly progressive, an intervention should be performed to relieve ICP and prevent neurological deterioration before other diagnostic studies are obtained or the cause is treated. Alternatives include temporary CSF diversions.
- Communicating hydrocephalus: A shunt may be indicated when there is intracranial hypertension, neurological compromise, accelerated increase of head circumference, lethargy, seizures, and confirmed increase in ventricular size by ultrasound (when fontanelle is patent), plain CT, or MRI.
- Obstructive hydrocephalus: A shunt is used to treat obstructive hydrocephalus when a ETV is not indicated, not feasible, or has failed to manage the hydrocephalus adequately.
- Normal pressure hydrocephalus: When normal pressure hydrocephalus is confirmed by the clinical picture, images, and lumbar puncture, a shunt may be used to treat the condition..
- Complex hydrocephalus: A shunt system may be indicated to complement endoscopic fenestration of the septum pellucidum and/or intraventricular septi when managing a patient with complex hydrocephalus.
- NPO orders: Avoid prolonged fasting. Many institutions practice age-specific NPO guidelines. General recommendations are: a 4-hour fast from milk and solids for infants younger than 6 months of age, a 6-hour fast from milk and solids for children 6–36 months of age, and an 8-hour fast from milk and solids for children older than 36 months of age.
- IVF rate: Fluid replacement should be started according to patient’s weight and fasting time prior to surgery.
- Steroids: Steroids are not specifically indicated for hydrocephalus. If steroids were indicated to treat an underlying condition, they should be continued during the perioperative period.
- Antibiotics: Prophylactic antibiotics should be administered before or during induction of anesthesia. According to specific institutional protocols, antibiotics can be used as a single perioperative dose or be continued for 24 hours. A longer period is neither necessary nor recommended.
- Clamp time for CSF drain: A period of 6–12 hours prior to surgery is recommended for clamping of external CSF drainage systems, under strict monitoring of vital signs and neurological status to detect clinical deterioration or raised ICP.
- Surgical site scrub: Chlorhexidine body wash and shampoo is an alternative the night before and morning of surgery.
Comorbidities to be considered
- Prematurity: Premature infants are more prone to shunt complications. Consider a temporary CSF diversion until patient has reached a minimum weight of 2000–2500 g, skin conditions are optimal, and other comorbidities have been treated.
- Malnutrition: A proper assessment of nutritional status and correction of malnutrition (if present) is advisable for patients who will have a shunt insertion, in order to decrease the risk of infection, wound dehiscence, and shunt exposure.
- Coagulopathy and platelet disorders: Coagulation and platelet disorders must be corrected before surgery to avoid hemorrhagic complications such as intraparenchymal or intraventricular hemorrhage.
- Remote sepsis: Systemic infections must be completely treated before placing a shunt.
- Seizures: Anti-epileptic medications must be continued on regular dosage during the perioperative period.
Scheduling of surgery
- First case: Consider scheduling as the first procedure of the day.
- Limit room traffic: Consider restricting the number of people in the OR to the minimum necessary.
Devices to be Implanted
- Ventricular catheter: Most ventricular catheters are made of silicone rubber and come straight or preshaped with angular fashion. They vary in terms of length, diameter, stiffness, shape, tip configuration, and radiopaque markings.
- Distal catheter: Distal catheters (peritoneal, cardiac or vascular, pleural) are shunt tubings of different lengths, mostly made of silicone rubber that may be open-ended or closed with distal slit valves. They can come as separate pieces or preassembled with the valve (unitized).
Valves are a fundamental component of shunt systems. Their main function is to regulate the flow of CSF passage to a distal site. Most valves are placed either proximally or distally, although theoretically, a valve can be placed anywhere along the course of the shunt line. At this time, no particular shunt system’s valve or device has been scientifically proven to be superior to any other (19). Nevertheless, thought should be given to the design of the shunt assembly to be used on a patient prior to the surgery. Valves can be classified as standard differential pressure valves, externally adjustable (or programmable) differential pressure valves, flow control valves, or gravity-actuated siphon reducing devices. It is always important to take into account the following considerations:
- Patient-specific valves: The special characteristics of a patient may influence valve selection, although data to support this consideration are weak.
- Standard valve: For most patients, a fixed medium-pressure valve that drains CSF in a range of 70–100 mm Hg is a reasonable choice.
- Large ventricles: Older patients with very large ventricles and thin cortex have a higher risk of subdural collections. A variable flow valve (e.g., Orbis-Sigma valve), gravity-actuated valve, or a programmable valve may prevent subdural collections. The programmable valve will also allow for nonoperative change in the drainage parameters of the system. A high-pressure valve is another possibility.
- Slit ventricles: Adding an antisiphon device, using a programmable valve (80) or an Orbis-Sigma valve (81) are useful alternatives in patients with a history or risk of slit ventricle syndrome
- Premature infants: In premature infants, low-pressure valves may promote ventricular decompression. Small contour valves reduce stress on the very thin overlying skin.
- Other devices: Accessory devices include introducers, connectors (straight, “Y” shaped), tapping reservoirs, antisiphoning devices and others. The need for these devices should be defined by the surgical team before starting the procedure.
In general, shunt placement does not require specialized equipment in addition to surgical instruments. In some cases, ancillary equipment may be useful:
- Intraoperative ultrasound guidance: Intraoperative ultrasound has been shown to be effective for increasing accuracy in ventricular catheter insertion, especially in children with small- or medium-size ventricles (see Intervention below) (20).
- Neuroendoscopic guidance: Use of endoscopes is helpful for placement of ventricular catheters in the presence of loculated ventricles or complex hydrocephalus.
- Laparoscopic guidance: Laparoscopy may be indicated if the patient has had an abdominal infection or previous abdominal surgeries due to the increased risk for adhesions..
- Neuronavigation: Computer-assisted stereotactic guidance is also available whenever it is necessary to increase accuracy of shunt insertions or technical difficulties are expected with conventional techniques.