Spinal anesthesia with tetracaine in 7.5% or 0.75% glucose in adolescents and adults

To examine whether adolescents and adults might develop different anestheti c distribution and hemodynamic consequences after spinal injection of 0.5% tetracaine in 7.5% or 0.75% glucose, we studied 100 ASA I or II patients wh o were scheduled for elective surgery to the lower limb and fulfilled the f ollowing criteria: age between 13 and 16 yr (Adolescent group, n = 40) or b etween 25 and 74 yr (Adult group, n = 60); height between 155 and 180 cm; a nd body mass index between 18 and 32 kg/m(2). Patients in each group were t hen randomly divided into two equal subgroups to receive spinal anesthesia with 0.5% tetracaine in either 7.5% or 0.75% glucose with 0.125% phenylephr ine at the L3-4 interspace. With patients in the supine horizontal position , neural block was assessed by cold, pinprick, and touch sensation and a mo dified Bromage scale after the injection of the study drug. The 7.5% glucos e solution produced a significantly higher and faster spread of blockade in adolescents than in adults. In contrast, there were no differences in the levels of three sensory modalities between the two age groups after the 0.7 5% glucose solution, which produced a lower spread of blockade than the 7.5 % glucose solution in either age group. Adolescents given the 0.75% glucose solution developed a smaller maximum decrease in systolic pressure than th ose given the heavier solution. We conclude that adolescents may develop an extensive level of blockade more easily and quickly than adults after intr athecal hyperbaric tetracaine, but that the difference may be reduced by us ing a less heavy solution.