To examine whether adolescents and adults might develop different anesthetic 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 who were scheduled for elective surgery to the lower limb and fulfilled the following criteria: age between 13 and 16 yr (Adolescent group, n = 40) or between 25 and 74 yr (Adult group, n = 60); height between 155 and 180 cm; and body mass index between 18 and 32 kg/m(2). Patients in each group were then 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% phenylephrine at the L3-4 interspace. With patients in the supine horizontal position, neural block was assessed by cold, pinprick, and touch sensation and a modified Bromage scale after the injection of the study drug. The 7.5% glucose 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 0.75% 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 those given the heavier solution. We conclude that adolescents may develop an extensive level of blockade more easily and quickly than adults after intrathecal hyperbaric tetracaine, but that the difference may be reduced by using a less heavy solution.
Implications: The influence of age on the characteristics of spinal anesthesia is still controversial. Our results show that adolescents develop blockade more extensively and quickly than adults after spinal anesthesia with 0.5%tetracaine in 7.5% glucose but not after the 0.75% glucose solution.