Comparison of the Analgesic Duration of Clonidine and Epinephrine Mixture with Tetracaine on Saddle Block

Cho, Sung Kang

Abstract

Clonidine, a2 adrenergic agonist, has a vasoconstrictive property like epinephrine when injected into the subarachoid space. Thus duration of anesthesia would be prolonged in regional block. Besides this effects clonidine also produces direct analgesic effect at spinal cord level and potentiates the effect of local anesthetics injected into intrathecal space. In this study saddle blocks were induced in sitting position by the intrathecal injection of tetracaine for the perianal procedures. 45 patients were classified randomly into three groups. In group I (control) 0.5% tetracaine 4 mg (0.8 ml) and normal saline 0.2 ml was injected intrathecally at L4-5 interspace. In group II (epinephrine) epinephrine 0.2 mg (0.2 ml) was added to 0.5% tetracaine 4 mg and in group III (clonidine) clonidine 30 ug (0.2 ml) was added to tetracaine 4 mg. After intrathecal injections, sensory block level and motor impairment was checked at 5 min and 50 min, The duration of analgesia was defined by the patients who complain the postoperative pain at the incision site. The results in each group were as follows. Sensory block level was Sl (control), L51 (epinephrine) and L5+/-1 (clonidine) at 50 min after injections. The duration of analgesia was significantly prolonged in epinephrine group (369.6+/-64.1 min) and clonidine group (297.9+/-33.8 min) compared with control group (194.3+/-18.2 min). The number of patients with motor block was 12 in epinephrine group, 4 in clonidine group and 1 in control group. In conclusion, tetracaine plus clonidine 30 ug to prolong the duration of analgesia is considered as adequate and safe dosage without significant adverse effects in saddle block.