Efficacy of Analgesic Effects of Low Dose Intrathecal Clonidine as Adjuvant to Bupivacaine

Clonidine (alpha-2-adrenergic agonist) has analgesic effect at spinal level mediated by postsynaptically situated alpha-2-adrenoreceptors in dorsal horn of spinal cord. Previous studies have used this drug intrathecally in higher dosages. Sixty adult patients belonging to ASA grade I and II, scheduled for gynaecological surgery under spinal anaesthesia were randomly divided into two groups. Clonidine group received clonidine 1 mg.kg (-1) with 12.5 mg 0.5% bupivacaine and the Control group received an identical volume of saline mixed with 12.5mg0.5% bupivacaine. The maximum dose of clonidine used was70 mg. The meantime from injection to regression of the level of sensory analgesia by two segments was longer in the Clonidine group than in Control group (P<0.001). The duration of motor blockade was longer in Clonidine group than in Control group (P<0.05). There was also a significant difference in the duration of analgesia between the two groups (P<0.001). The rescue analgesia was required earlier in the Control group(mean 223 min) compared to the Clonidine group(mean614 min). The number of injections of diclofenacin24 hours was higher for Control group (mean2.66) than Clonidine group (mean 1.16) (P <0.05). The patients in the Clonidine group had a significant fall in mean arterial pressure and heart rate and were more sedated than those in Control group, however, no therapeutic interventions needed. We concluded that addition of clonidine to bupivacaine in the dose of 1 mu g.kg (-1) significantly increases the duration of spinal analgesia as compared to bupivacaine alone with clinically insignificant influence on haemodynamic parameters and level of sedation.