| Abstract: | The influence of variations in the volume of injectate when maintaining an identical dose of a hyperbaric local anesthetic has not previously been investigated when performing spinal anesthesia. This study compares spinal anesthesia of 5 mg of lyophilized tetracaine diluted in 1 ml, 2 ml or 4 ml of 10% glucose in 45 elderly patients undergoing elective hip surgery. While supine and horizontal, each patient received double–blind one of the three solutions through a catheter inserted 4 cm into the intrathecal space at the L2–L3 or L3–L4 interspace. No difference in the anesthetic effects was found between the three groups. The median value of the maximal sensory level was T6 (range T3–L2), T4 (range T3–T9) and T5 (range T3–T11) in the 1–ml, 2–ml, and 4–ml groups, respectively. The number of patients with a motor blockade of grade 2 or 3 was 12/ 15, 14/15 and 13/15, and the time from the initial dose to the need for the first top–up dose (mean ± s.d.) was 88 ± 35 min, 75±15 min and 68 ±x 15 min for the 1–ml, 2–ml and 4–ml groups, respectively. Hemodynamic changes were also comparable between the three groups. The authors conclude that in elderly patients, undergoing spinal anesthesia while supine and horizontal, variations in volume from 1 to 4 ml do not influence the characteristics of hyperbaric spinal anesthesia while injecting an identical dose of local anesthetic. |
