[Isobaric spinal anaesthesia with bupivacaine and tetracaine (author's transl)]

4 ml 0.5% solutions of bupivacaine and tetracaine without the addition of a vasoconstrictor, approximately isobaric, were used for spinal anaesthesia on patients in the sitting position. The sensory and motor block due to the two local anesthetics was tested and compared. The mean time on onset of complete analgesia was the same for both local anaesthetics (9 and 11 min), as was also the highest level of analgesia (T10). The duration of maximal extension of analgesia was on an average 45 min longer due to tetracaine (bupivacaine 105 min, tetracaine 150 min). The duration of maximal spread of the blocked sensation of pain, temperature, pressure and touch was similar for each of both local anesthetics. The regression of these sensory qualities, blocked in a dissoaciated manner, took a parallel course. With tetracaine the motor block of the lower extremities developed faster and lasted longer (Bromage 3 for bupivacaine 192 min, for tetracaine 220 min). Motor function and proprioception normalized in a synchronized manner. Isobaric spinal anaesthesia with these two solutions of local anaesthetics was found to be reliable and controllable, especially when administered to the sitting patient. Tetracaine is a good alternative to bupivacaine, currently controversial for intrathecal use.