Remifentanil requirements for preventing motor response to skin incision in healthy women anesthetized with combinations of propofol and dexmedetomidine titrated to similar Bispectral Index (BIS) values.

BACKGROUND: It is unclear whether the sedative, analgesic or sympatholytic effects of adjunctive dexmedetomidine contribute to reduced analgesic requirements in general anesthesia. This study aimed to assess the analgesic effect of dexmedetomidine on intraoperative opioid requirements using body movement as observation indicator at similar BIS-guided sedative depth in propofol anesthesia.

METHODS: Ninety patients were randomly divided into three groups to receive administration of saline, and dexmedetomidine at 0.5 and 1.0 µg kg(-1) over 10 min, followed by saline and dexmedetomidine at infusion rates of 0.17 and 0.33 µg kg(-1) h(-1), respectively. After dexmedetomidine and saline bolus administration, propofol was titrated to maintain the BIS values at 45-55. When BIS values reached the predetermined range, remifentanil was administered by target-controlled infusion. Five minutes following remifentanil treatment, skin was incised and the motor response observed. Then, the concentration of remifentanil blunting the motor response in 50% of patients (Ce50) was determined using a modified Dixon's sequential 'up-and-down' method.

RESULTS: Dexmedetomidine significantly decreased effect-site concentrations of propofol for maintaining the preset BIS range (P < 0.01). The Ce50 (95% CI) of remifentanil were 0.93 (0.82-1.03), 1.03 (0.89-1.17) and 0.91 (0.77-1.06) ng ml(-1) in the 0 (saline), 0.5 and 1.0 µg kg(-1) dexmedetomidine groups, respectively, indicating non-statistically significant differences among groups (P > 0.0167).

CONCLUSIONS: Propofol and its combination with dexmedetomidine have similar opioid requirements for preventing motor response to skin incision when titrated to similar BIS values. These findings indicate that adjunctive dexmedetomidine for general anesthesia has sedative but no opioid sparing effects.