[Effect of drug volume on spinal anesthesia with isobaric tetracaine]

The effects of drug volume on spinal anesthesia with 10 mg tetracaine in 1 ml or 2 ml isobaric solution were studied in 100 demographically compatible patients in a randomized double-blind manner. Identical technique was used for every patient in the study except for the volume of anesthetic solutions. Drugs were administered in a lateral decubitus position and patients remained horizontal during the study. Hoghest cephalad spread of analgesia varied from T12-T3, with a median sensory level of T7 in those who received 2 ml solutions, compared with T12-T5 and a median level of T10 in those who received 1 ml solutions. The time for maximum spread was longer in 2 ml--group (7.54 +/- 1.76 min vs 4.85 +/- 1.54 min). The 2-segment regression times were 180 +/- 53.44 min (mean) with a range of 75-270 min, and 219 +/- 34.11 min (mean) with a range of 150-300 min respectively for the 2 ml--group and the 1 ml--group. The differences were statistically significant. Complete motor blockade of the lower extremities as assessed by the modified Bromage scale was achieved in 35 out of 50 patients given 2 ml solutions, while all those who received 1 ml solutions achieved complete motor blockade. The onset times of maximum blockade were 5.42 +/- 1.59 min (mean) with a range of 2-10 min, and 5.98 +/- 1.79 min (mean) with a range of 2-12 min respectively. The difference between the degree of maximum motor blockade was also statistically significant but was insignificant regarding the time to maximum motor blockade.(ABSTRACT TRUNCATED AT 250 WORDS)