It is often difficult to obtain an adequate computed tomographic (CT) scan in small children who may be frightened by the procedure. Chloral hydrate, midazolam and ketamine are frequently used for sedation, but each has drawbacks. Chloral hydrate lasts a variable length of time, midazolam may not be effective enough to render the child motionless and ketamine requires an injection. Pomeranz and associates conducted a study of the safety and efficacy of methohexital (MXT) administered rectally. MXT is currently used as preinduction anesthesia in pediatric patients, but its use has not been studied in an outpatient setting.
Children between three and 60 months of age were included in the study if they were stable, needed a CT scan, were judged to be unable to be still without sedation for the scan and their parent or guardian consented to enrollment. Patients were excluded if they had a history of a seizure disorder or a previous reaction to a barbiturate, or were medically unstable. Vital signs, pulse oximetry and cardiorespiratory status were monitored throughout the procedure. Each child received a dose of MXT of 25 mg per kg (maximum: 500 mg) administered rectally through a no. 8 French feeding tube. The medication was administered 15 minutes before the CT scan was to begin. Lack of sedation within 20 minutes was defined as treatment failure. Alternative sedation methods were then available at the discretion of the physician. Side effects were recorded, as was parental satisfaction with the sedation.
One hundred patients were evaluated during the study. The average weight was 12.3 kg (23 lb) and the average age was 24 months. Sixty-three percent of the CT scans were performed for closed head injuries. Full sedation took an average of 8.2 minutes (standard deviation: 3.9 minutes). Average recovery time (defined as the time from sedation to a state judged as safe enough for discharge) was 79.3 minutes. Most (93 percent) of the patients achieved adequate sedation after a single rectal infusion of MXT; three patients required mild restraint in addition to the MXT. The failure rate was just less than 5 percent. Scan images were adequate in 98 percent of patients. Side effects (hiccups or hypersalivation) were generally mild. Six percent of the patients experienced slight oxygen desaturation. Intubation was not required in any patient. Most (90 percent) of the parents reported that they would like the same sedation used for their child should it be needed in the future.
The authors conclude that rectally administered MXT is a safe, effective sedative for pediatric patients requiring CT scanning. Use of this medication seems to avoid some of the problems experienced with other routinely used sedative agents, such as chloral hydrate and midazolam. Comparative studies are needed.