An ideal sedative for colonoscopy should have properties that include: rapid onset and offset of action, provide cardiopulmonary stability, have minimal adverse effects, and allow for smooth recovery, and early discharge. Propofol is often used solely because of its rapid onset and short duration of action---a property which is ideal for a fast recovery and early discharge in the ambulatory setting. However, the use of propofol has been associated with undesirable effects such as hypotension, hypoventilation and apnea requiring assisted ventilation.

Balanced anesthesia, using a combination of medications with different mechanisms of action can reduce the total amount of each sedative agent used and minimize their side effects while achieving the desired level of sedation. Dexmedetomidine is one agent that has been used either alone or in combination with propofol for sedation during colonoscopy. While there are many advantages to using dexmedetomidine, there is concern that the use of this agent for sedation during colonoscopy may prolong post-operative recovery time and readiness for discharge home.

No study has definitively assessed whether the use of dexmedetomidine in combination with propofol during ambulatory colonoscopy prolongs post-operative recovery time as determined by the Modified Post Anesthesia Discharge Scoring System (MPADSS).

In this study, investigators plan to prospectively compare in a randomized, controlled, double-blind trial, the sedation technique for colonoscopy between two groups. Group 1: sedation with dexmedetomidine and propopfol versus group 2: sedation with saline placebo and propofol.

The study will have the following outcome measures for each group.

Primary outcome measure:

Readiness-for-discharge (RFD) at 10, 20 and 30 minutes after the colonoscopic procedure. Ready-for-discharge is defined as attainment of MPADSS score of 9-10.

Secondary outcome measures:

1. Total propofol consumption in mg/kg/duration of procedure in minutes;

2. Side effects:

   1. lowest intraoperative percent (%) drop in mean arterial pressure (MAP) from baseline,
   2. incidence of sustained bradycardic episodes (HR<50 for at least 5 minutes) intraoperatively,
   3. incidence of apneic episodes intraoperatively requiring positive pressure ventilation.

Methods:

One hundred patients will be recruited and randomized into two groups. For sedation, Group 1 will receive intravenous dexmedetomidine 0.3 ug/kg bolused at the onset of the procedure followed by titrated doses of propofol. Group 2 will receive a saline placebo bolus at the onset of the procedure followed by titrated doses of propofol. A hospital research pharmacist, based on a randomization table, will allocate to the anesthesia provider giving the sedation, the bolus syringe labelled dexmedetomidine/or saline study agent. The anesthesia provider, gastroenterologist, nurses as well as the subject will be blinded as to the syringe's actual content. A Bispectral Index (BIS) Monitor will be used during sedation. All subjects will be targeted to maintain a BIS score between 60-70. Outcome measures will be evaluated for statistical significance in a non-inferiority assessment.

Investigators hypothesize that there will be no difference in the time to discharge between the two treatment groups.

Inclusion Criteria:

• patients scheduled to undergo colonoscopy at SUNY Downstate Medical Center.

Exclusion Criteria:

• < 18 years old
• > 75 years old
• Cognitively Impaired patients (Cognitively impaired patients are excluded from the study because our primary outcome involves a very strict discharge criteria that requires the patient to respond to and perform tasks on our pre-existing discharge scale checklist. These may be impossible to assess or will be difficult to standardize for patients whom are Cognitively Impaired.)
• Pregnant patients
• Patients who use a wheelchair or ambulates with crutches (Patients using a wheelchair are excluded from the study because our primary outcome involves a very strict discharge criteria that requires the patient to respond to and perform tasks on our pre-existing discharge scale checklist. These may be impossible to assess or will be difficult to standardize for patients whom who use a wheel-chair).
• Limited exercise tolerance (as this could represent active coronary disease)
• Total body weight greater than 105 kg (due to maximal dose of drug available in randomized syringes containing study drug)
• Propofol, soy, glycerol or dexmedetomidine allergy
• Significant renal impairment
• Significant hepatic impairment
• Inability to read or write in English

114 were randomized into the treatment and placebo groups. Seven additional patients in the propofol-dexmedetomidine group and 6 in the propofol-saline group were excluded. Final n = 101

From patient enrollment through discharge from PACU

The definition of adverse event, used to collect adverse event information in the study, did not differ from the clinicaltrials.gov.

Additional information: list of potential adverse events relevant to the study included:

• episodes of sustained bradycardia (greater than 5 minutes) associated with hypotension (MAP < 60 mm Hg) that were unresponsive to treatment. We used a cutoff of < 50 bpm to define bradycardia in this study.
• apnea requiring positive pressure ventilation