Indications for Surgery
- Control of CSF pressure: By either CSF diversion or restoration of normal anatomical drainage
- Emergency decompression: For life-threatening elevated ICP from tumor mass or compression of vital structures (including spinal cord or cauda equina)
- Histological diagnosis: Biopsy only or partial resection
- Cytoreductive surgery: Prior to adjuvant chemotherapy
- Curative resection
- Fasting: It is important that the infant is not dehydrated preoperatively by inappropriate fasting. Intravenous fluid replacement may be necessary (see below). Local protocol should be followed. However, a recommended schedule is to discontinue formula milk 6 hours before, breast milk 4 hours before, and clear oral fluids 2 hours before anesthesia.
- Infant – 4 ml/kg/hr: The 4,2,1 rule is a simple formula for calculating baseline fluid requirements for children. The rule states that the total hourly rate of IV fluids for a child is 4 ml/kg/hr for the first 10 kg of body weight, plus 2 ml/kg/hr for the next 10 kg, plus 1 ml/kg/hr for the remainder of body weight. Most infants weigh less than 10 kg.
- Replacement of fluid losses: Volumes included in IV drug preparations and volumes lost by wound or CSF drainage become important factors in this group as a result.
- Steroids: Steroid therapy commenced preoperatively should be continued. If steroids have not been used preoperatively, consideration should be given to commencing steroid administration as part of the procedural medication.
- Antibiotics: Prophylactic antibiotic therapy is recommenced for major neurosurgical procedures and should be administered as per local protocol.
- Clamp time for CSF drain: This will vary with the clinical situation and surgical goals. If a dilated ventricular space is desired, then the system can be clamped for a duration of time based on the previous output history.
- Surgical site preparation: The surgical site is prepared per local protocol.
Given the often labile physiology of infants, the anesthesia team must be experienced in managing patients in this age group. It may be worthwhile to discuss the following specifically:
- Patient positioning: Prone position allowing the abdomen to remain free for ventilation can be challenging depending on the size of the infant. One method is to arrange gel bolsters longitudinally to create a gutter.
- Avoidance of heat loss
- Potential for blood loss
- Potential for CSF loss: CSF loss with ventricular tumor resection can be underestimated with respect to fluid balance calculation in infants. With massive fluid shifts, there can be systemic electrolyte disturbance. This can be minimized by electrolytically comparable irrigation solutions, but as much as possible it is important to avoid surgically decompressing CSF spaces in an uncontrolled fashion.
- Hypothalamic/pituitary axis effects: Tumor resection can be associated with unpredictable pituitary axis effects with DI/SIADH apparent intraoperatively or perioperatively.
- Intraoperative steroid maintenance
- Prophylactic antibiotic
- Role of muscle relaxants: If intraoperative monitoring is to be considered.
Devices to Be Implanted
- CSF catheters: All medical devices planned for implantation during the case should be readily available and sterile. CSF diversion materials such as EVD, shunts, etc., should be preselected to avoid delay during surgery.
- Cranial plating systems: If consideration is given to the use of resorbable skull plating systems, the appropriate implantation instruments should be made available.
- Intraoperative imaging, guidance, monitoring, and resection tools: As previously discussed, the ultrasonic aspirator has proven invaluable for use with these patients, and, similarly, intraoperative ultrasound, image-guidance systems, intraoperative neurophysiology and intraoperative axial scanning systems prepared and scheduled if available (which may involve the assistance of other specialists).