To provide adequate preoperative thoracic epidural analgesia, it is important to determine the appropriate initial dosage of local anesthetics. To determine the proper initial dose, current study evaluated the effects of three different dosages of 1.5% lidocaine, injected in a low thoracic epidural space, on the spread of analgesic segments and on hemodynamic variables.

The subjects were 117 patients between 18 and 80 years of age with ASA physical status I-II. Using an epidural catheter placed a site among T6-11 intervertebral space, 1.5% lidocaine was injected as follows: Group 1 (n = 39), 0.1 ml/kg Group 2 (n = 39), 0.2 ml/kg and Group 3 (n = 39), 0.3 ml/kg. Sensory analgesia, motor blockade, and hemodynamic variables were evaluated every 5 min for 15 min after the injection.

The number of analgesic segment were 8.1, 10.8, and 12.3 in Group 1, Group 2 and Group 3, respectively. Tripling the volume of 1.5% lidocaine increased the number of analgesic segments by 4.2; on doubling from 0.1 to 0.2 ml/kg, the increase was 2.7. No motor block was observed in any patient. The incidence of hypotension was higher in Groups 2 (25.6%) and 3 (35.9%) than in Group 1 (0%) (P = 0.001).

To establish the proper preoperative low thoracic epidural analgesia with less hemodynamic changes, it is recommended to use 0.1 ml/kg of 1.5% lidocaine.