Spinal Analgesia with Bupivacaine, Mepivacaine and Tetracaine

Spinal analgesia with bupivacaine, tetracaine and mepivacaine was studied in 103 patients in two studies, one open and one double-blind. Injections were given with the patients sitting and they remained seated for 2 min after the injection. Regardless of the agent used, the mean cephalad spread of analgesia was T6-8 15 min after injection. Mepivacaine 4% (60 mg) in glucose produced analgesia and motor blockade of good quality but of short duration. Bupivacaine 0.5% and 0.75% and tetracaine 1%, all solutions with glucose, produced long-lasting blockades, tetracaine 14 mg having a longer duration of action than 15 mg bupivacaine. When 15 mg of bupivacaine was administered in solutions containing glucose, no difference in sensory blockade was seen, regardless of volume (2 or 3 ml, 0.75% and 0.5%, respectively) injected. 3 ml of bupivacaine 0.75% (22.5 mg) in glucose-free solution produced a very long-lasting blockade with deep motor engagement, particularly suitable for hip surgery of long duration. Bupivacaine 0.75% (3 ml, 22.5 mg) in solution with glucose produced a more marked effect on the blood pressure than the other solutions tested.