A double-blind study of motor blockade in the lower limbs. Studies during spinal anaesthesia with hyperbaric and glucose-free 0.5% bupivacaine.

Sensory and motor blockade were studied double-blind during spinal anaesthesia in 20 urology patients who received 0.5% bupivacaine solution 4 ml with or without glucose. Using a new method for determining muscle strength, motor blockade during anaesthesia was recorded quantitatively for flexion of the hip, extension of the knee and plantar flexion of the big toe. Movements of the lower part of the thoracic cage were recorded at the same time. Complete motor blockade of longer duration was observed for all three movements following the administration of the glucose-free solution compared with the solution containing glucose. During the regression phase, the muscle strength returned significantly later (knee extension and hip flexion) when glucose-free bupivacaine solution was given. There was no significant difference between the two anaesthetic solutions regarding plantar flexion of the big toe during this phase. For hip flexion (L1-L3) there was no noteworthy difference between the levels of analgesia and the motor blockade, whereas for plantar flexion of the big toe (L5-S2) the level of analgesia was 2-3 segments higher than the level of motor blockade. Thoracic movements (maximal inspiration to normal expiration) did not appear to be notably influenced by the level of analgesia. Complete regression of motor blockade was not observed for any of the movements at grade O of a modified Bromage scale. Not until 1.5-2 h after the attainment of this grade was the muscle strength of all movements restored (90% of control value).