A COMPARISON OF EFFICACY AMONG VARIOUS DOSES OF INTRATHECAL HYPERBARIC BUPIVACAINE 0.75% FOR ADULT ANORECTAL SURGERY

Abstract

Objective: To compare the efficacy of various doses of intrathecal hyperbaric bupivacaine 0.75% for adult anorectal surgery.

Study Design: Randomized control trial.

Place and Duration of Study: The study was conducted at the department of Anaesthesia, Intensive Care and Pain medicine, Combined Military Hospital (CMH) Quetta from November 2008 to October 2009.

Material and Methods: 120 adult patients undergoing anorectal surgery were randomly assigned to three groups. Groups A (n=40) was given the lowest dose of 4.5mg intrathecal hyperbaric bupivacaine 0.75%, while group B (n=40) and group C (n=40) were given 6.0mg and 7.5 mg,respectively. Dural puncture at L4/L5 level for drug administration was done in the sitting position and patient was made to lie down after five minutes and block level assessed.Variables to be assessed were level of sensory block indicated by number of dermatomes with pinprick method and extent of motor block by Modified Bromage Score.

Results: Level of sensory block in groups A,B and C was 5.88 ± 0.94, 8.15± 0.83, 10.10 ± 0.78 dermatomes, respectively (F (2, 117) = 245.976; p<0.0001 ANOVA; p<0.0001 group A vs B, group A vs. C and group B vs. C). Extent of motor block was 4.83 according to the Modified Bromage Scale in group A, compared to 2.25 in group B and 1.48 in group C (H (2) = 92.007; p<0.0001; p<0.0001 group A vs. B, group A vs. C and group B vs. C ).

Conclusion: Efficacy of three doses of intrathecal hyperbaric bupivacaine 0.75% was found to be statistically different although all three doses produced adequate anaesthesia for anorectal surgery. The 4.5 mg dose of spinal hyperbaric bupivacaine is recommended since the doses of 6 mg and 7.5 mg result in extensive motor block.