Background: Perianal surgeries can be conveniently performed under saddle block . We intended to compare intrathecal low dose isobaric and hyperbaric levobupivacaine and study their efficacy in perianal surgeries under saddle block on ambulatory basis.

Methods: In this prospective, randomised controlled, double blind trial involving 20 patients in each group were randomised into two groups, Group I and Group H. Group I received 1ml of 0.5% levobupivacaine(5 mg) + 0.16 ml of Normal Saline ( total volume-1.16 ml) and Group H : 1 ml of 0.5% levobupivacaine (5 mg) + 0.16 ml of 50% dextrose (total volume-1.16 ml). Duration for ambulation being the primary criteria, we also noted maximum cephalic spread, time to reach maximum height of sensory blockade, 2 segment regression, duration of motor and sensory blockade, time for voiding and time for rescue analgesia . Appropriate statistical tests were used for final analysis. P value less than 0.05 was considered statistically significant.

Results: There were no significant differences between the two groups in terms of the maximum height of sensory blockade and 2 segment regression that was achieved and request for first rescue analgesic. Duration of motor blockade, time to full recovery of sensory block and first voiding were all statistically significantly shorter in group H than group I.

Conclusions: We conclude  that hyperbaric levobupivacaine is superior to isobaric form while being closer to ideal choice of anaesthetic agent on ambulatory basis required for perianal anaesthesia while both the concentrations are similar in their safety profile.