Age and the spread of local anesthetic solutions in the epidural space

Sensory level of anesthesia following the injection of 20 ml of 1.5% lidocaine with epinephrine (1:200,000) in 238 adult males averaged T7.7, T5.6, and T5.1 at 10, 20, and 30 minutes, respectively. Patient age had no significant effect on local anesthetic requirements per spinal segment per unit height until age 40 years, which age the calculated amount of local anesthetic decreased significantly to 0.62 ml from 0.69 ml/segment/meter of height. Above age 40 there was no further decrease in epidural anesthetic requirement with advancing age. Patient height was inversely related to sensory level (p < 0.001). Time required for anesthesia ro recede to T12 averaged 164 minutes and was slightly but significantly (p < 0.05) prolonged with advancing age.