[Epinephrine in spinal anesthesia].

Isobaric bupivacaine for spinal anesthesia has frequently proved advantageous because of its long and safe analgesia, good motor blockade and low incidence of side-effects. Significant prolongation of analgesia is possible with an epinephrine concentration of as low as 1:200,000 added to bupivacain 0.5%, while optimal prolongation can be achieved by a concentration of 1:100,000. The addition of 1:50,000 epinephrine, however, does not induce any further enhancement. These results are contrary to those of Chambers and Scott, whose short durations of action were possibly due to relative overdosage of epinephrine with a paradoxical reduction of action. The latency period until complete blockade is achieved can be reduced by high epinephrine concentrations (beginning with 1:50,000), a fact which is possibly due to a direct, receptor-induced mechanism of epinephrine. The motor blockade of ankle and toe joints beginning from a concentration of 1:100,000 epinephrine is also prolonged significantly. With all epinephrine concentrations, the overall duration of analgesia could be prolonged significantly, in contrast to the overall duration of motor blockade. Only with free bupivacaine solution did motor and sensory function return at more or less the same time. The period between the beginning and the end of regression for both sensation and motor function was influenced only by the highest epinephrine concentration (1:50,000).(ABSTRACT TRUNCATED AT 250 WORDS)