[Application of sedation with a low dose of dexmedetomidine during intrathecal anesthesia in elderly patients].

ABSTRACT

OBJECTIVE: To explore the feasibility and safety of sedation with a low dose of dexmedetomidine (DEX) during intrathecal anesthesia in the elderly patients. METHODS: Thirty elderly patients were randomly divided into the DEX group (n = 15) and the control group (n = 15). There were 13 males and 17 females with a mean age of 77 years old (range 65 - 89 years old). After an induction of intrathecal anesthesia, the patients in the DEX group received an infusion of 0.4 µg×kg(-1)×h(-1) for 10 min. Then the infusion speed was adjusted between 0.2 and 0.4 µg×kg(-1)×h(-1) to maintain the values of bispectral index (BIS) at around 80. An equivalent volume of normal saline was administered in the control group. Blood pressure, heart rate, respiratory rate, pulse oxygen saturation (SpO2), end-tidal carbon dioxide partial pressure (P(ET)CO(2)) and BIS were recorded at the beginning of DEX infusion, 10, 20, 30 and 60 min after DEX infusion beginning and at the end of surgery. The observer's assessment of alertness/sedation (OAA/S) scores and the clinical responses were also recorded. A statistical analysis was performed. RESULTS: All intraoperative hemodynamic and respiratory parameters were within the normal range in both groups. Compared with the beginning after infusion, blood pressure at the point of 10 min after infusion decreased about 10% - 15% (P < 0.05) in the DEX group. But there was no such change in the control group. The values of BIS also decreased significantly at each time point after 10 min infusion versus the beginning of administration (P < 0.05); as compared with the control group, the values of BIS also decreased significantly at 30, 60 min and the end of infusion (P < 0.05). The 95%confidence interval (CI) of BIS values were 70 - 95 in the DEX group and 80 - 100 in the control group (P < 0.05). In the DEX group, the OAA/S scores were significantly lower at the points of 20, 30, 60 min and the end of infusion versus the beginning after infusion. And it was also lower in the DEX group than that in the control group (95%CI 3 - 4 vs 4 - 5, P < 0.05). No bradycardia occurred in the DEX group. Two of three patients with concurrent atrial fibrillation were converted to sinus rhythm after the administration of DEX. Patients with severe lung diseases (pulmonary fibrosis, asthma or chronic obstructive pulmonary disease) maintained normal cardiopulmonary functions in the DEX group. DEX showed a good sedation effect in 1 patient with mental diseases. CONCLUSION: Sedation with a small dose of DEX during intrathecal anesthesia in elderly patients is both feasible and efficacious. But studies of larger sample sizes are warranted to confirm its safety.