Effect of Dexmedetomidine on Recovery Profiles of Elderly Patients

Purpose: The aims of this study were to investigate the recovery characteristics (time to recovery of consciousness (ROC) and recovery, bispectral index (BIS) values at ROC and orientation, and Ricker sedation-agitated scale at the postanesthetic care unit) and safety (vital signs during and after administration of dexmedetomidine) of dexmedetomidine in elderly patients undergoing elective surgery.

Hypothesis: Dexmedetomidine as a adjuvant agent may be a help to smooth emergence from anesthesia in elderly.

Objectives: Patients who are scheduled to undergo elective surgery, American society of anesthesiologist class (ASA) I-II, aged over 65 years, are randomly allocated into six groups.

• Group 1: general anesthesia with sevoflurane only (placebo: normal saline)
• Group 2: general anesthesia with propofol and remifentanil (total intravenous anesthesia) only (placebo: normal saline)
• Group 3: general anesthesia with sevoflurane and adjuvant dexmedetomidine
• Group 4: general anesthesia with propofol and remifentanil (total intravenous anesthesia), and adjuvant dexmedetomidine

Research Method: Once in the operating room, patients were monitored with electrocardiography, non invasive blood pressure, pulse oximetry (Datex-Ohmeda S/5, Planar Systems, Inc., Beaverton, OR, USA) and BIS (Aspect 2000, Aspect Medical Systems, Inc., Newton, MA, USA).

In the group 1 and group 3, anesthesia was induced with propofol (2mg/kg) and followed by administering rocuronium 0.6 mg/kg. After tracheal intubation, the lungs of the patients were then ventilated with oxygen in air (1:2), and the ventilation rate was adjusted to maintain the end-tidal carbon dioxide partial pressure between 35 and 45 mmHg. The concentrations of sevoflurane was adjusted for maintain BIS score between 40 and 45.

In the group 2 and group 4, anesthesia was induced and maintained with total intravenous anesthesia using propofol and remifentanil. Effective site concentration of propofol and remifentanil were adjusted for maintain BIS between 40 and 45 and maintain changes of vital sign between 20% of baseline value.

In the group 3 and group 4, dexmedetomidine was administered (0.4 ug/kg/hr) during surgery. Instead, in the group 1 and group 2, normal saline was administered with same rate as a placebo.

The concentrations of sevoflurane was measured continuously using an infrared anesthetic gas analyzer (Datex-Ohmeda S/5, Planar Systems, Inc., Beaverton, OR, USA) and the effect site concentration of propofol and remifentanil also measured with target controlled infuser (Orchestra® Base Primea, Fresenius-Vial, France) during surgery.

After the end of surgery, all anesthetics or dexmedetomidine was discontinued and the time to recovery BIS score until 60, 70, and 80 were measured. Patients were asked to open their eyes and the time of eye opening were measured. After the eye opening, reversal agent was administered and the patients were transferred to postanesthetic care unit (PACU).

After arrival on PACU, blood pressure, heart rate, and Ricker sedation-agitated scale were measure every 5 minutes. When the Ricker sedation-agitated scale became 4, patients were transferred to ward, and the time of staying in postanesthetic care unit were measured.

The incidence of nausea, vomiting, hypotension, hypertension, bradycardia, and tachycardia was measured during surgery and staying in postanesthetic care unit.

All participants will be followed for the duration of surgery and postanesthetic care unit stay, an expected average of 1 day.

Statistical Analysis: All data are expressed as mean ± standard deviation. Recovery profiles (time to recovery of consciousness (ROC) and recovery, BIS values at ROC and orientation, and Ricker sedation-agitated scale at the postanesthetic care unit) were analyzed by paired t-test. And the incidence of nausea/vomiting, hypotension, hypertension, bradycardia, and tachycardia was analyzed by Chi-square test.