Discharge Readiness After Propofol With or Without Dexmedetomidine for Colonoscopy

A Randomized Controlled Trial

Leonard U. Edokpolo, M.D.; Daniel J. Mastriano, M.D.; Joanna Serafin, Ph.D.; Jeremy C. Weedon, Ph.D.; Maryam T. Siddiqui, M.D.; Dennis P. Dimaculangan, M.D.


Anesthesiology. 2019;131(2):279-286. 

In This Article

Materials and Methods

This study was approved by the State University of New York Downstate Medical Center Institutional Review Board (no. 932304) and the protocol registered at ClinicalTrials.gov (NCT03139279; registered May 3, 2017, principal investigator Dr. Dimaculangan). The trial was conducted from May 2017 to March 2018 at State University of New York Downstate Medical Center. The article was prepared in accordance with the Consolidated Standards of Reporting Trials guidelines.

After written, informed consent was obtained from patients, we prospectively randomized, in a noninferiority, double-blind design, American Society of Anesthesiologists (ASA) physical classification status I to III patients (aged 18 to 75 yr) having ambulatory elective colonoscopies at State University of New York Downstate Medical Center. The exclusion criteria were as follows: pregnancy, inability to ambulate without assistance, metabolic equivalents less than four per self-report during preoperative assessment, inability to read or understand English, preexisting clinical diagnosis of cognitive impairment in medical history, body weight greater than 135 kg, allergies to constituents of propofol, soy or glycerol, a previous adverse reaction to dexmedetomidine, preexisting diagnosis of acute or chronic renal function impairment (or glomerular filtration rate less than 60 ml/min if preoperative chemistries were available), significant hepatic impairment causing ascites, cirrhosis, or decreased synthetic function with international normalized ratio greater than 1.5 (as documented in medical records or reported by the patient), and use of benzodiazepine or opioid medications within 24 h of the colonoscopy procedure.

A computerized randomization table in a block of 126 subjects was generated, in a 1:1 ratio of propofol–dexmedetomidine to propofol–placebo, using an online randomization tool.[18] This table was maintained by the research pharmacist who allocated a group assignment for each recruited subject. The clinical pharmacist dispensed premade, numbered syringes containing either saline (placebo) or dexmedetomidine, 4 μg/ml, according to the table. This procedure ensured that the patient, the investigators, the clinical anesthesiologists, and nursing staff were blinded to the actual content of each syringe and to each subject's group assignment. Only the research and clinical pharmacists knew each subject's group assignment.

Demographic information, including race, sex, weight, and body mass index, was obtained from the medical records. Baseline blood pressure and heart rate were documented in the preoperative holding area. During the procedure subjects were monitored with standard ASA monitors plus a Bispectral Index (BIS) monitor (BIS VISTA; Aspect Medical Systems, Inc., USA). The propofol–dexmedetomidine group received an initial IV bolus dose of 0.3 μg/kg dexmedetomidine (Precedex; Hospira/Pfizer Inc., USA) followed by propofol, 1 mg/kg, to allow initial passage of the endoscope. While the propofol group received saline (placebo) followed by propofol, 1 mg/kg. The clinical anesthesiologist was instructed not to view the BIS monitor until after the first dose of propofol was administered and the endoscope had been introduced. This ensured that the anesthesiologist was not provided with information regarding which study arm the patient was randomized to. Additional doses of propofol were administered at the discretion of the anesthesiologist to maintain a BIS value of approximately 60, for the purposes of standardizing the sedation/anesthesia in our study.

We chose the BIS target value of 60 in order to target levels of anesthesia depth that could be considered both moderate sedation and general anesthesia.[19] As there is no standardized target sedation level during colonoscopy, many centers use moderate sedation and general anesthesia without a secure airway.[20] For purposes of comparison, the total propofol administered to each patient was normalized to the patient's body weight and the length of time of the procedure (μg · kg−1 · min−1). Bolus dosing rather than an infusion of propofol was chosen so that the study protocol would be similar to how propofol is typically administered for colonoscopy procedures in clinical practice at many centers in the community and at our institution. Episodes of sustained bradycardia (heart rate less than 50 beats/min for 5 min or more), apnea (requiring bag mask ventilation), and the largest decrease in mean arterial pressure (MAP) from baseline to lowest value observed during the procedure for each subject, were documented. The timing of study drugs and propofol administration, and the duration of the procedure, were recorded. Episodes of sustained bradycardia associated with hypotension (MAP less than 60 mmHg) were treated with ephedrine, 5 to 10 mg, or glycopyrrolate, 0.2 mg, via IV boluses, at the discretion of the anesthesiologist. We used a cutoff of less than 50 bpm to define bradycardia in this study.

End-of-procedure recovery in the endoscopy suite was assessed using the Modified Aldrete Score (Aldrete score).[21] Transport time from the endoscopy suite to the postanesthesia care unit (PACU) was noted. A second Aldrete score was obtained upon arrival in the PACU. Discharge readiness was assessed every 10 min, using the Modified Post Anesthetic Discharge Scoring System scale, from the procedure end time until recovery criteria were met.[17] Discharge readiness was defined by a score greater than or equal to 9 on the Modified Post Anesthetic Discharge Scoring System scale.

The primary outcome was the percentage of patients in each group who were ready for discharge within 30 min of procedure end time (as assessed by the Modified Post Anesthetic Discharge Scoring System scale). Secondary outcomes were: extent of recovery from anesthesia on PACU arrival (assessed by the Aldrete score); total propofol consumption normalized to body weight and time of procedure; largest decrease in MAP from baseline value; incidence of sustained bradycardia; incidence of apnea requiring positive pressure ventilation.