Background and aims Mixing opioids and hyperbaric bupivacaine in a single syringe may alter the density of hyperbaric solution, affecting the spread in intrathecal space. To assess the efficacy of premixed versus succedent administration of fentanyl and hyperbaric bupivacaine in subarachnoid block for lower limb surgeries in terms of:

1. Time taken to reach T₁₀ sensory level and modified bromage score 3 for motor block and the duration of sensory and motor block

2. Incidence of hypotension

3. Patient and surgeon satisfaction score

Methods 120 patients aged 18–70 years ASA grade I, II and III scheduled for unilateral lower limb surgery were enrolled in this prospective randomized study. Patients were randomly allocated to 3 groups.

• Group a patients recieved premixed 0.5% hyperbaric bupivacaine 2.5 ml (12.5 mg) and 0.5 ml (25 mcg) of fentanyl in a single 3.0 ml syringe

• Group B patients first received 0.5 ml (25 mcg) of fentanyl in a 3.0 ml syringe followed by 0.5% hyperbaric bupivacaine 2.5 ml (12.5 mg) in a 3.0 ml syringe

• Group C patients received 0.5% hyperbaric bupivacaine 2.5 ml (12.5 mg) in a 3 ml syringe followed by 0.5 ml (25 mcg) of fentanyl in a 3 ml syringe

Results Difference in mean time to attain T10 sensory level and modified bromage score of 3 was statistically significant among groups a and B (p value <0.05), groups a and C (p value <0.05) and groups B and C (p value <0.05).

Conclusions Administering hyperbaric bupivacaine first followed by fentanyl (i.e. succedent) leads to an early onset and prolonged duration of sensory and motor block.