We measured the formation of
methemoglobin in vitro in a whole blood culture system of 8 healthy individuals 30, 60, and 360 min after the addition of different concentrations of
o-toluidine (0.5, 5, 50 micrograms/ml) with and without addition of
ascorbic acid (0.5 and 5 mg/ml). In a prospective randomized clinical study, a total of 72 patients of ASA risk I-III were investigated. The 3 groups of 24 patients received either an axillary, an infraclavicular vertical brachial plexus, or a combined femoral and ischiadic blockade. In each plexus
anesthesia group, 12 patients were given 2,000 mg
ascorbic acid intravenously before applying the
local anesthetics. For surgery of the upper limb the patients received 40 ml 1%
prilocaine and 10 ml 0.5%
bupivacaine, for surgery of the lower limb they received 60 ml 1%
prilocaine and 0.25 mg
adrenaline. Blood samples for measurement of
methemoglobin concentrations were taken before and 30, 60, 120, 180 and 360 min after the injection of the regional
anesthetic. A p < 0.05 was considered to be significant.
RESULTS: CONCLUSIONS: