Comparison of bupivacaine and alkalinized bupivacaine in brachial plexus anesthesia

To define the effect of alkalinization of bupivacaine 0.5% in subclavian perivascular brachial plexus blockade, the time to onset, time to peak effect, and 6-hour regression of sensory and motor blockade were determined. Sixty physical status ASA I and II patients were randomly allocated to one of two groups and a double-blind design was used: group I (n = 30) received bupivacaine 0.5% (pH, 5.5) 3 mg/kg, while group II (n = 30) received alkalinized bupivacaine 0.5% (pH, 7.05-7.15) 3 mg/kg. Onset and regression of sensory blockade were determined by pinprick in the C4-T2 skin dermatomes, while motor blockade was assessed using a scheme of proximal to distal muscle group paralysis. Time to onset of sensory blockade (group I, 4.0 +/- 1.2 min; group II, 3.6 +/- 0.9 min) and time to peak sensory effect (group I, 17.7 +/- 1.8 min; group II, 16.3 +/- 1.8 min) did not differ significantly between the groups. Similarly, no difference in time to onset of motor blockade (group I, 6.9 +/- 1.7 min; group II, 6.3 +/- 1.5 min) or time to peak motor effect (group I, 18.1 +/- 1.9 min; group II, 15.1 +/- 1.9 min) was observed. Regression of postoperative sensory and motor blockade was similar in both groups. It is concluded that alkalinization of bupivacaine 0.5% solutions does not confer any added clinical advantage in subclavian perivascular brachial plexus blockade when compared with commercially available bupivacaine.