Published online Dec 26, 2018. doi: 10.12998/wjcc.v6.i16.1136
Peer-review started: September 10, 2018
First decision: October 11, 2018
Revised: October 17, 2018
Accepted: November 7, 2018
Article in press: November 7, 2018
Published online: December 26, 2018
To investigate the effect of clonidine on the cutaneous silent period (CSP) during spinal anesthesia.
A total of 67 adult patients were included in this randomized, prospective, single-center, double-blind trial. They did not have neurological disorders and were scheduled for inguinal hernia repair surgery. This trial was registered on ClinicalTrials.gov (NTC03121261). The patients were randomized into two groups with regards to the intrathecally administered solution: (1) 15 mg of 0.5% levobupivacaine with 50 µg of 0.015% clonidine, or (2) 15 mg of 0.5% levobupivacaine alone. There were 34 patients in the levobupivacaine-clonidine (LC) group and 33 patients in the levobupivacaine (L) group. CSP and its latency were measured four times: prior to the subarachnoid block (SAB), after motor block regression to the 0 level of the Bromage scale, with ongoing sensory blockade, and both 6 and 24 h after SAB.
Only data from 30 patients in each group were analyzed. There were no significant differences between the groups investigated preoperatively and after 24 h. The CSP of the L group at the time point when the Bromage scale was 0 was 44.8 ± 8.1 ms, while in the LC group it measured 40.2 ± 3.8 ms (P = 0.007). The latency in the L group at the time point when the Bromage scale was 0 was 130.3 ± 10.2 ms, and in the LC group it was 144.7 ± 8.3 ms (P < 0.001). The CSP of the L group after 6 h was 59.6 ± 9.8 ms, while in the LC group it was 44.5 ± 5.0 ms (P < 0.001). The latency in the L group after 6 h was 110.4 ± 10.6 ms, while in LC group it was 132.3 ± 9.7 ms (P < 0.001).
Intrathecal addition of clonidine to levobupivacaine for SAB in comparison with levobupivacaine alone results in a diminished inhibitory tonus and shortened CSP.
Core tip: Cutaneous silent period (CSP) is an oligosynaptic spinal inhibitory reflex. The results of our study show that intrathecal administration of levobupivacaine with added clonidine, in comparison to levobupivacaine alone, yields a significantly shorter CSP and a significantly longer CSP latency during block regression following subarachnoid block (SAB) application. Accordingly, we can conclude that during SAB regression, a small dose of intrathecally administered clonidine ameliorates the inhibitory tonus and accelerates the conduction in the oligosynaptic spinal circuit.