Comparative evaluation of two different loading doses of dexmedetomidine with midazolam-fentanyl for sedation in vitreoretinal surgery under peribulbar anaesthesia.

BACKGROUND AND AIMS: Midazolam-fentanyl (MDZ:FEN) combination has been routinely used for intravenous sedation in ophthalmic surgeries. Dexmedetomidine (DEX), a recent α2 adrenoreceptor agonist indicated for sedation for ophthalmic use at a loading dose of 0.5 μg/kg over 10 min, can cause deeper plane of sedation and surgeon dissatisfaction. Therefore, we proposed to evaluate the efficacy and safety of two different loading doses of DEX.

METHODS: In a prospective study, 60 patients aged 50-70 years, scheduled for retinal surgery under peribulbar block were divided equally to receive either MDZ:FEN or DEX 0.5 μg/kg (DEX full) or DEX 0.25 μg/kg (DEX half) loading dose over 10 min followed by titrated maintenance dose of DEX 0.25-0.4 μg/kg/h. Vital parameters, level of sedation (Ramsay Sedation Scale 1-6), effect on respiration and surgeon satisfaction were assessed at regular intervals. Surgeon satisfaction score (0-3) was noted.

RESULTS: 'DEX half' group patients had predominantly stable haemodynamics, level 3 sedation and surgeon satisfaction score of 2-3 (good to excellent operating conditions). This group had no vomiting and no respiratory depression. 'DEX full' group had a higher incidence of bradycardia, hypotension, level 4 sedation (Ramsay Sedation Scale) and lower surgeon satisfaction. Incidence of nausea and vomiting was higher in MDZ:FEN group compared to other two groups.

CONCLUSION: DEX 0.25 μg/kg loading dose over 10 min followed by titrated maintenance dose is an effective alternative to MDZ:FEN and provides controlled (level 3) sedation and stable haemodynamics maximising surgeon satisfaction. Avoiding narcotic analgesics with its associated post-operative nausea and vomiting is an additional benefit.