Isobaric levobupivacaine and fentanyl with isobaric ropivacaine and fentanyl: Effects on heart rate and blood pressure

Abstract

Most local anaesthetics block the unmyelinated C and myelinated Aδ fibres that transmit pain impulses at the same rate. However the rate of blockade of Aα and Aβ (that carry motor impulses) depends on the physicochemical properties, pKa and lipid solubility of the individual local anaesthetic drugs. As ropivacaine is less lipid soluble when compared to bupivacaine, the blockade of Aα and Aβ is slow and hence produce less motor blockade than bupivacaine. In this study, 30 males in each group (group R and group L) satisfying the inclusion criteria. Group R: 2.6 cc of 0.75% isobaric ropivacaine (19.5mg) with 0.4cc of fentanyl (20 microgram).Group L: 2.6 cc of 0.5% isobaric levobupivacaine (13 mg) with 0.4cc of fentanyl (20 microgram). There is no statistically significant difference in systolic blood pressure between both the two groups at various intervals. There is no statistically significant difference in mean arterial pressure between the two groups. Ten patients in ropivacaine 0.75% group and seven patients in levobupivacaine 0.5% group developed hypotension which was managed by inj. mephentermine 6 mg IV.