Effects of Drug Dose, Volume, and Concentration on the Spinal Anesthesia with Isobaric Tetracaine

Cho, Hyun Sung; Hahm, Tae Soo; Kim, You Hong

Abstract

BACKGROUND
The patient's position cannot be changed in the hyperbaric spinal anesthesia until the anesthesia level is fixed because gravity has an effect on the spread of hyperbaric solutions. The isobaric spinal anesthesia has the advantage that the patient's position can be changed soon after drug is injected into the subarachnoid space because gravity has no effect on the spread of isobaric solutions. Most studies of isobaric spinal anesthesia had been made using plain bupivacaine. In this study, effects of drug dose, volume, and concentration on the spinal anesthesia with isobaric tetracaine were investigated.
METHODS
Eighty patients were randomly allocated to four groups: 1), group 1 received 1% tetracaine 14mg, 1.4ml (N=20), 2), group 2 received 0.74% tetracaine 14mg, 1.9ml (n=20), 3), group 3 received 0.5% tetracaine 14mg, 2.8ml (n=20), 4), group 4 received 1% tetracaine 19mg, 1.9ml (n=20). Drugs were administered in lateral position at L3~4 level. Neural block was assessed by pinprick. Changes of analgesic level were evaluated with time.
RESULTS
Peak analgesic level of group 4 was higher than that of group 2 after 12 minutes and no difference in analgesic level between group 1, 2, and 3 after 18 minutes. Group 4 resulted in longer duration and a higher peak level of sensory block than group 2.
CONCLUSIONS
In spinal anesthesia with isobaric tetracaine, the volume is the major factor affecting initial spread of isobaric tetracaine and the dosage was the major factor affecting peak level. High concentration results in longer duration, and higher peak level.