Effect of Oral Clonidine and Intrathecal Fentanyl on Tetracaine Spinal Block

Abstract

We studied the effect of oral clonidine and intrathecal (IT) fentanyl on the onset and duration of a hyperbaric tetracaine-induced spinal block. Forty adult males undergoing elective surgery were studied according to a randomized, double-blind, placebo-controlled protocol involving four treatment regimens: Group I, placebo per os (PO) + tetracaine 12 mg IT; Group II, placebo PO+tetracaine 12 mg IT+fentanyl 10 micrograms IT; Group III, clonidine 200 micrograms PO+tetracaine 12 mg IT; Group IV, clonidine 200 micrograms PO+tetracaine 12 mg IT+fentanyl 10 micrograms IT. Onset time to highest sensory level was 8.5 +/- 3.1, 8.2 +/- 2.3, 6.1 +/- 1.6, and 6.8 +/- 1.4 min in Groups I, II, III, and IV, respectively. The time required for sensory regression to the L1 dermatome level was 153 +/- 34, 151 +/- 51, 183 +/- 63, and 209 +/- 39 min in Groups I, II, III, and IV, respectively. Similarly, the duration of Grade III motor block was 132 +/- 37, 140 +/- 55, 160 +/- 51, and 189 +/- 52 min in Groups I, II, III, and IV, respectively. IT fentanyl 10 micrograms did not change the onset or duration of tetracaine-induced spinal block. Furthermore, there was no significant interaction between clonidine and fentanyl in Group IV. Episodes of bradycardia and hypotension were more frequent in the clonidine-treated patients (40%-50% vs 10%). We conclude that oral clonidine (200 micrograms) shortened the onset time of tetracaine's sensory block and prolonged the duration of sensory and motor block. However, clonidine premedication increased the risk of hypotension and bradycardia.

Dose related effects of oral clonidine pre-medication on bupivacaine spinal anaesthesia

“…The dose response data suggested that the prolongation of sensory block by oral clonidine seems to plateau at a dose of 150µg because regression to L1 dermatome was increased by 45% with 75µg, 92% with 150µg and 76% with 300µg of oral clonidine respectively. In this study, the result of the comparison of the sensory and motor blocks of the control group to the clonidine groups is similar to other studies mentioned above5,12,17. The result shows a statistical significant increase in duration of sensory and motor blocks in the clonidine groups when compared to the control group (p<0.05).…”

“…Liu et al5 and Harbhej et al17 also found that 200µg of oral clonidine prolonged the duration of lignocaine and tetracaine spinal anaesthesia respectively. The study of Otalet al12 compared the dose-related effects using three different doses of oral clonidine 75µg, 150µg and 300µg on tetracaine spinal anaesthesia.…”

Efficacy of Bilateral Mental Nerve Block with Bupivacaine for Postoperative Pain Control in Mandibular Parasymphysis Fractures

“…They reported high efficiency of combined bupivacaine versus lidocaine. The same results were achieved by Singh and Bhardwaj 17 using continuous mandibular nerve block with bupivacaine for postoperative pain relief of mandibular fracture surgeries. The present study confirms previous investigations.…”

A comparative study on effect of addition of clonidine and fentanyl as adjuvants to local anaesthetics for subarachnoid block in patients undergoing lumbar laminectomies

“…studied the effect of oral clonidine 200 µg and intrathecal fentanyl 10 µg on the onset and duration of hyperbaric tetracaine-induced spinal block. [ 13 ] In their study, intrathecal fentanyl 10 µg did not change the onset or duration of tetracaine-induced spinal block. However, oral clonidine 200 µg shortened the onset time of tetracaine's sensory block and prolonged the duration of sensory and motor block.…”