Sedation and Anesthesia of Pediatric Patients for External Beam Radiotherapy

Abstract

Along with surgery, chemotherapy, and nutrition, radiationtherapy is a cornerstone in the multimodal managementof pediatric cancer. Children with brain tumors,sarcomas of bone and soft tissues, neuroblastoma, Wilmstumor, and Hodgkin lymphoma are commonly treatedwith radiation therapy. The aim of radiation therapy is to deliver tumoricidaldoses of radiation to areas of overt and microscopic tumorwhile limiting damage to adjacent normal tissues. Radiationused for cancer treatment is called ionizing radiationbecause it forms ions in the tissues it passes through,causing damage to cellular DNA. External beam radiotherapy(XRT or EBRT) is the most commonly usedtype of radiation therapy.A linear accelerator accelerateselectrons within a vacuum. The electrons are forced tocollide with a material such as tungsten, which releasesenergy in the form of X-rays. The linear acceleratorfocuses this energy to target the tumor or the whole body(total body irradiation) in one or many directions. Theenergy is measured in gray (Gy). Althoughpainless, there is a requirement for the child to lie still by themselves in the radiationtreatment room, for multiple daily or twice daily treatments for up to 6 weeks. General anesthesiaor sedation is usually necessary to achieve this in younger children.In children older than age 7or 8 years, it is often possible to perform radiotherapywithout sedation. This may be accomplished in youngerchildren with behavioral rehearsal and distraction techniques. Children requiring radiation therapy can experience considerableanxiety. This is related to the unfamiliar andpotentially frightening radiation equipment andim-mobilization devices, particularly the plastic immobilizationcast of the head, which fits tightly over theface.Children have often undergone a rangeof procedures prior to their radiotherapy treatment, andmay be suitably suspicious of strangers.The child has tobe alone in the treatment vault during the treatments,and must lie completely still. Before the first radiation therapy treatment session, childrenundergo a simulation session. This involves CTimaging, multiple measurements, and marking of pointson the child’s body to allow the radiation oncologist toplan the treatment. An immobilization device is oftenmade during the simulation session. Therisks of proceeding with anesthesia should be balancedwith the benefits of the radiation therapy and risks ofpostponing this therapy. If a child develops a serious issuewhich affects the anesthesia during the course of radiationtreatment, it is important to discuss the need forcancellation with the radiation oncologist and parents.Children are kept nil by mouth for 6 h for milk and solidsand for 2 h for clear fluids. Children on concurrent chemotherapymay be dehydrated from vomiting, and mayrequire a bolus of intravenous fluid prior to induction.Most children having radiation therapy have central venous access in place. It is important to follow strict aseptic techniquewhen accessing these lines and handling drugs to preventcentral line-associated bloodstream infection. Many anesthesia techniques and agents have been usedover the years to sedate or anesthetize children duringradiation therapy. Agents such as ketamine, midazolam,chloral hydrate, dexmedetomidine, propofol or a combinationwere often used for sedation. General anesthesia withinhalational agents (halothane, sevoflurane) has been also used, but often requiresan airway device of some kind (endotracheal tube, laryngeal mask). The anesthesiologist must have proper knowledge of the doses, indications, contraindications, side effects and complications of the different drugs used in sedation or anesthesia. Radiation treatmentstake between 10 and 45 minutes. Total body irradiation takes longer and involves prone positioning for nearlyhalf the treatment. The same anesthetic technique is used with the necessity of endotracheal intubation.In the prone position the patient’s face rests ona foam cushion with a circular holeon a board. Sedation of pediatric patients has serious associatedrisks, such as hypoventilation, apnea, airway obstruction,laryngospasm, and cardiopulmonary impairment.These adverse responses during and after sedation may be decreased, but not completely eliminated, by acareful pre-procedural review of the patient’s underlyingmedical conditions and consideration of how the sedationprocess might affect or be affected by these conditions.