SPINAL-ANESTHESIA WITH TETRACAINE IN 0.75-PERCENT GLUCOSE - INFLUENCEOF THE VERTEBRAL INTERSPACE USED FOR INJECTION

Background and Objectives. The anesthetic behavior and hemodynamic con sequences of spinal anesthesia with marginally hyperbaric tetracaine c ontaining a low concentration of glucose injected at two different int erspaces were examined and compared with those of conventionally hyper baric solution. Methods. One-hundred twenty ASA Physical Status I or I I patients scheduled for elective surgery to the lower limb were seque ntially assigned to one of three equal groups to receive spinal anesth esia: Group 1 received 0.5% tetracaine in 0.75% glucose with 0.125% ph enylephrine at the L2-L3 interspace; group 2 0.5% tetracaine in 0.75% glucose with 0.125% phenylephrine at the L3-L4 interspace; group 3 0.5 % tetracaine in 7.5% glucose with 0.125% phenylephrine at the L3-L4 in terspace. Neural block was assessed in a double-blinded manner by cold , pinprick, and touch sensation, and a modified Bromage scale after th e injection of the study drug. Results. Injection at the L2-L3 intersp ace produced significantly higher spread of analgesia [median T7 (10th , 90th percentiles T10, T4)] than injection at L3-L4 interspace [T10 ( L1, T5)] when using the solution in 0.75% glucose. There were no signi ficant differences in peak dermatomal levels between groups 1 and 3, b ut the number of patients who required ephedrine for the treatment of hypotension was larger in group 3. Conclusions. A marginally hyperbari c tetracaine solution injected at the L2-L3 interspace with the patien t in the lateral position produced greater extent of cephalad spread t han that at the L3-L4 interspace. When compared to a conventionally hy perbaric tetracaine solution injected at the L3-L4 interspace, the mar ginally hyperbaric solution injected at the L2-L3 interspace caused le ss hemodynamic variability despite similar levels of maximum sensory b lock.