Adequate sedation with single-dose dexmedetomidine in patients undergoing transurethral resection of the prostate with spinal anaesthesia: a dose–response study by age group

BACKGROUND: Dexmedetomidine (DMT), a highly selective α2-adrenoceptor agonist, has been used safely as a sedative in patients under regional anesthesia. The purpose of this study was to determine the 50% effective dose (ED(50)) of single-dose DMT to induce adequate light sedation in elderly patients in comparison with younger patients undergoing transurethral resection of the prostate (TURP) with spinal anesthesia. METHODS: Forty-two male patients were recruited. The young age group (Group Y) included patients 45 to 64 years old and the old age group (Group O) included patients 65 to 78 years old. After the spinal anesthesia was performed, a pre-calculated dose of DMT was administered for 10 min. The Observer’s Assessment of Alertness/Sedation (OAA/S) scale, bispectral index score (BIS) were assessed then at 2-min intervals for 20 min. A modified Dixon’s up-and-down method was used to determine the ED(50) of the drug for light sedation (OAA/S score 3/4). In the recovery room, regression times of the motor and sensory blocks were recorded. RESULTS: The ED(50) of DMT was 0.25 (95% C.I. 0.15-0.35) μg/kg in Group O and 0.35 (95% C.I. 0.35-0.45) μg/kg in Group Y (p = 0.002). The ED(95) was 33% lower in Group O compare with Group Y (0.38 (95% C.I. 0.29-0.39) μg/kg vs. 0.57 (95% C.I. 0.49-0.59) μg/kg). The regression time of sensory block was longer in Group O than in Group Y (109.0 ± 40.2 min vs. 80.0 ± 31.6 min) (p = 0.014). CONCLUSION: The single-dose of DMT for light sedation was lower by 21% in Group O compare with Group Y underwent TURP with spinal anesthesia. TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT01665586. Registered July 31, 2012.