Proton beam radiation therapy

Proton beam radiation therapy is used to treat arteriovenous malformations, pituitary tumors, retinoblastomas, and an expanding number of other tumors. Irradiation is painless, but planning sessions and creation of molds may take many hours, while each individual therapy session is much shorter. During irradiation, the target area must remain in a fixed position using a stereotactic frame locked to a positioning device.

1. In adults, placement of small pins or screws in the skull can be performed under local anesthesia with 2% lidocaine with epinephrine. If “ear bars” are used, a satisfactory ear block can be performed by subcutaneous injection of 3 mL of 2% lidocaine with epinephrine in the outer ear canal. Sedation is usually not recommended because patient cooperation is required.
2. For children, a general anesthetic is usually administered. The procedure typically is performed daily for about 4 weeks; a propofol induction (2 to 4 mg/kg IV) and maintenance infusion (~75 to 300 μg/kg/min) through an implanted Broviac or Hickman catheter is a suitable technique. Spontaneous ventilation should be permitted whenever possible. The patient's head is placed in a sniffing position, and a plaster mold is formed that maintains the head in the correct position for treatment. Nasal prongs or a facemask can provide supplemental oxygen; a sidestream sampling line will provide qualitative assessment of ventilation. LMA is considered if a natural airway cannot be maintained. Standard monitoring is used, and patients are monitored and viewed via closed-circuit television because the anesthetist must leave the room during the brief period of radiation.