Objective  To observe the clinical effects of lumbar anesthesia with small-dose isobaric solution in controlling different blocking planes for anorectal surgery.

  Methods  A total of 120 patients treated by anorectal surgeries were randomly divided into group C (conventional lumbar anesthesia, n=60) and group L (low-plan lumbar anesthesia, n=60). At left lateral position, the patients in group C were injected with bupivacaine at an equal proportion of 5 mg 0.375% and normal speed to the head, and the anesthetic plane was at the level of T₁₂. Group L was slowly injected by bupivacaine to the tail direction with the same lower dose at the same position, with anesthetic plane of L₅. The duration of analgesia, recovery time of spontaneous urination, block condition of lower limb movement and incidence of complications such as urinary retention were compared between the two groups.

  Results  The operations were successfully completed in both groups. Compared with group C, the duration of analgesia in group L was longer and motor block for lower limb was less (P < 0.05). There were no significant differences in incidence of complications in two groups (P>0.05).

  Conclusion  Small-dose isobaric solution in controlling lower blocking planes for anorectal surgery has better efficacy, which can maintain lower limb movement function, and improve patients′comfort degree.