The influence of baricity on differential blockade with 0.5% bupivacaine spinal anesthesia

We evaluated the influence of baricity on differential blockade during spinal anesthesia using isobaric or hyperbaric 0.5% bupivacaine. Forty ASA-PS I-II patients scheduled for elective surgery (orthopedic, lower abdominal and urologic) were divided into two groups; group H, using hyperbaric 0.5% bupivacaine, and group I, using isobaric 0.5% bupivacaine. Spinal anesthesia was performed in lateral decubitus position, using a 25-gauge Quincke needle at L2-3 interspace, and 0.5% bupivacaine 2.0 ml was injected for 10 seconds. Patients were turned to supine position soon after the spinal anesthesia and the block levels were examined every 5 min for 30 min. Sympathetic blockade was detected by observer's hand, the loss of cold sensation by alcohol sponge and the loss of pain sensation by pinprick. Complete motor blockade was detected by modified Bromage scale. Significant higher sensory blockade and large number of complete motor block were observed in group H. Differential blockade between sympathetic and sensory was significant and lasted 30 min in group I, but lasted only 15 min in group H.