Anorectal manometry requires that the patient be able to respond to command and not receive any medications which could alter muscle tone or motility. In the pediatric population, anorectal manometry can be psychologically challenging to parents and their child, as it is traditionally performed without adjuvant sedation or anesthesia. Sedatives and anesthesia can alter motility and smooth muscle activity, as well as render it difficult or impossible for the child to follow commands required of the study. Patient or parent non-compliance, inability to follow commands or to tolerate the procedure often renders the study invalid or impossible to complete. Dexmedetomidine is a sedative who's effect on anorectal musculature has not been studied nor determined. It would be important to determine whether it spares smooth muscle function, as it would provide a viable option to provide sedation to children while still preserving their ability to respond to command. The primary objective of this study is to examine the effects of dexmedetomidine on gastrointestinal smooth muscle by observing changes in anorectal manometry before and after dexmedetomdine administration.

Primary objective:

To examine the effects of dexmedetomidine on intra-anal pressure and the dose response curve to balloon distention by comparing the baseline measurements with those after dexmedetomidine administration.

Dexmedetomidine is an alpha-2 agonist that is considered to be a smooth muscle relaxant. It's a potential use as a sedative for endoscopies has been considered. It is important to know whether or not it has effect on smooth muscle tone and would affect manometry studies in those patients who could receive it. The investigator hypothesizes that dexmedetomidine will have minimal effects in the dosing that is being administered.

Background:

Anorectal manometry requires that the patient be able to respond to command and not receive any medications which could alter muscle tone or motility. These patients typically have the manometry performed without any adjuvant sedatives, anesthetics or medications. In the pediatric population, anorectal manometry can be psychologically challenging to parents and their child, particularly without adjuvant sedation or anesthesia. There are some exceptional circumstances which require sedation/anesthesia administration for these procedures, either because the children are young (< 5 years), they have behavioral issues (like autism) or because they have severe anxiety. In those patients with severe issues even general anesthesia may be needed. The risk of administering any medication to these patients is that they can alter motility and smooth muscle activity, consequently artificially altering the results of the anal manometry. It is important to know which medications can be administered without affecting anal muscle tone. Dexmedetomidine is a newer sedative and anxiolytic. It could be valuable for anxiolysis for anal manometry. It's effect on anal smooth muscle, however, has never been studied. It would be important to determine whether it spares smooth muscle function, as it would provide a viable option to provide sedation to children while still preserving their ability to respond to command.

Dexmedetomidine is one of the standard drugs administered for sedation in children who require sedation for diagnostic (gastroendoscopic upper and lower procedures) and radiologic diagnostic imaging studies (MRI, CT and Nuclear Medicine). Over 17,000 infants, children and developmentally compromised young adults have been sedated with dexmedetomidine at Boston Children's Hospital without a cardiac or respiratory arrest, or a need to provide positive pressure assisted ventilation.

Methods:

Patients will undergo the usual anal manometry study, with no adjuvant medications, per routine practice currently in the gastrointestinal unit. Following completion of manometry, 0.5 mcg/kg DEX will be administered over 1 minute followed by an infusion of 0.15 mcg/kg/hr. Manometry measurements will be followed for 15 minutes in response to DEX.

Definition of Primary Endpoint:

Primary outcome: To examine the effects of dexmedetomidine on intra-anal pressure and the dose response curve to balloon distention by comparing the baseline measurements with those after dexmedetomidine administration. The pressure measurements will be recorded by the research team member who will be present, every 30 seconds starting from 5 minutes prior to DEX to 15 minutes following DEX administration.

Data Analysis Plan:

Data will be analyzed after the completion of the study. The manometry measurements will be done blindly by one of the investigators.

The following endpoints will be analyzed at the completion of the study: time to meet modified Aldrete discharge criteria, adverse events, need for unplanned airway interventions, intravenous anesthetic duration of sedation, presence of agitation/delirium (PAED score), and time of BIS score to return to baseline (pre-sedation level).

Statistical Power and Sample Considerations:

The study was powered and sample size calculated assuming a mean intra-anal pressure of 90 mmHg, with a mean reduction to 65 mmHg, and a standard deviation of 32. With a significance level of 0.05, it would require approximately 15 subjects to achieve power of 80.3%.

Inclusion Criteria:

• Ages 3-18 years who are scheduled to have an anorectal manometry followed by an upper or lower endoscopic procedures at Boston Children's Hospital
• Patients are cooperative to do the anorectal manometry without sedation (besides pre-med midazolam)
• Anticipates to receive standard sedation with dexmedetomidine and propofol for a gastrointestinal procedure in the Gastroenterology Procedure Unit (GPU)
• Provides written consent to participate in the research study
• In females of reproductive age, pregnancy testing

Exclusion Criteria:

• Do not meet established sedation criteria
• Patients who require sedation prior to their anal manometry testing
• History of allergy, intolerance, or reaction to dexmedetomidine
• Current, repaired or risk of Moya-Moya disease
• Recent stroke (cerebrovascular accident) within past 6 months
• Uncontrolled hypertension
• Concomitant use of opioids, beta antagonist, alpha 2 agonist or calcium channel blocker
• BMI greater than 30 or weight above 110th percentile
• Refuses insertion of intravenous catheter while awake
• Currently receiving pharmacologic agents for hypertension or cardiac disease
• Currently receiving or has received digoxin within the past 3 months
• Active, uncontrolled gastroesophageal reflux (an aspiration risk), requiring endotracheal intubation.
• Current (or within past 3 months) history of apnea requiring an apnea monitor
• Unstable cardiac status (life threatening arrhythmias, abnormal cardiac anatomy, significant cardiac dysfunction)
• Craniofacial anomaly, which could make it difficult to effectively establish a mask airway for positive pressure ventilation if needed
• Active, current respiratory issues that are different from the baseline status (pneumonia, exacerbation of asthma, bronchiolitis, respiratory syncytial virus).

Adverse event data were collected on the day of the procedure, during study involvement and immediately following in the post-anesthesia care unit. Subjects were monitored for AEs for 1 day.