Effect of intrathecal fentanyl on dexmedetomidine requirement for sedation during spinal anesthesia: a randomized controlled trial.

Background

Adequate sedation during spinal anesthesia requires careful titration to avoid hemodynamic instability and respiratory complications. We hypothesized that intrathecal fentanyl, used as an adjunct to neuraxial anesthesia, would reduce dexmedetomidine requirements for conscious sedation. This study evaluated the effects of intrathecal fentanyl on the total dose of dexmedetomidine during spinal anesthesia.

Methods

Sixty-four patients undergoing knee or ankle arthroscopy under spinal anesthesia were randomly assigned to two groups. The fentanyl group received 0.5% bupivacaine 10 mg with fentanyl 20 μg, whereas the control group received bupivacaine 10 mg with saline. After confirmation of sensory block, dexmedetomidine was infused at 1 μg/kg over 10 minutes and maintained at 0.1-1 μg/kg/hour to maintain a bispectral index (BIS) of 70 to 80. The primary outcome was the total dose of dexmedetomidine. Secondary outcomes included BIS values, Modified Observer's Assessment of Alertness/Sedation (MOAA/S) scores, mean blood pressure, and heart rate at predefined time points.

Results

The total dose of dexmedetomidine did not differ significantly between the groups. The MOAA/S scores were significantly affected by group, time, and group-by-time interactions (p=0.003, p<0.001, and p=0.007, respectively). The BIS values were influenced by group (p=0.026) and time (p<0.001), but not by group-by-time interactions (p=0.413). Exploratory analyses suggested deeper sedation in the fentanyl group during the early phase of dexmedetomidine infusion. Hemodynamic variables were comparable between the groups.

Conclusion

Intrathecal fentanyl did not significantly reduce dexmedetomidine requirements during spinal anesthesia, although it was associated with deeper sedation at several time points.