Comparison of sensory and motor blocking action of lidocaine and lidocaine-tramadol following brachial plexus block in sheep

The aim of the present study was to evaluate the effect of adding tramadol to lidocaine for brachial plexus block in sheep. Six healthy, adult ewes weighing 41.7 ± 3.82 kg were used. Using an electrical stimulator, brachial plexus block was performed with lidocaine (4 mg/kg) (LID), lidocaine (4 mg/ kg)-tramadol (2 mg/kg) (LTL), and lidocaine (4 mg/kg)-tramadol (4 mg/kg) (LTH). All sheep received the three treatments with one-week interval. The final volume of administered solutions was adjusted to 0.3 mL/kg. Time to the onset and duration of anesthesia as well as changes in heart rate, respiratory rate, and rectal temperature were determined. Time to the onset of sensory blockade and motor blockade was not significantly different among groups. The duration of sensory blockade and motor blockade were significantly longer in LTH (128.3 ± 9.7 and 151.5 ± 21.5 min, respectively) compared with those of LID (88.6 ± 6.5 and 110.5 ± 21 min, respectively) and LTL (51.6 ± 11.8 and 89.6 ± 22.7 min, respectively). Although the onset of sensory blockade was longer than that of motor blockade in the three treatments, the difference was only significant in LTL. No significant differences were observed in heart rate, respiratory rate and rectal temperature among and within treatments. It was concluded that addition of tramadol (4 mg/kg) to lidocaine, without altering the onset, can provide more prolonged anesthesia than that of lidocaine in brachial plexus block in sheep.