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REGIONAL ANESTHESIA

Small-Dose Intrathecal Clonidine and Isobaric Bupivacaine for Orthopedic Surgery: A Dose-Response Study

Stephan Strebel, MD^*, Jürg A. Gurzeler, MD, Markus C. Schneider, MD^*, Armin Aeschbach, MD^*, and Christoph H. Kindler, MD^*

*Department of Anesthesia, University Clinics, Kantonsspital, Basel; and Department of Surgery, Kantonsspital Luzern, Luzern, Switzerland

Address correspondence and reprint requests to Christoph H. Kindler, MD, Department of Anesthesia, University Clinics Basel, Kantonsspital, CH-4031 Basel, Switzerland. Address e-mail to ckindler{at}uhbs.ch

We examined the dose-response relationship of intrathecal clonidine at small doses (150 µg) with respect to prolonging bupivacaine spinal anesthesia. We aimed for establishing doses of intrathecal clonidine that would produce clinically relevant prolongation of spinal anesthesia and pain relief without significant side effects. Eighty orthopedic patients were randomly assigned to intrathecally receive isobaric 0.5% bupivacaine, 18 mg, plus saline (Group 1), clonidine 37.5 µg (Group 2), clonidine 75 µg (Group 3), and clonidine 150 µg (Group 4). Duration of the sensory block (regression below level L1) was increased in patients receiving intrathecal clonidine: 288 ± 62 min (Group 1, control), 311 ± 101 min in Group 2 (+8%), 325 ± 69 min in Group 3 (+13%), and 337 ± 78 min in Group 4 (+17%) (estimated parameter for dose 0.23 [95% confidence interval –0.05–0.50]). Duration of pain relief from intrathecal clonidine administration until the first request for supplemental analgesia was significantly prolonged: 295 ± 80 min (Group 1, control), 343 ± 75 min in Group 2 (+16%), 381 ± 117 min in Group 3 (+29%), and 445 ± 136 min in Group 4 (+51%) (estimated parameter for dose 1.02 [95% confidence interval 0.59–1.45]). Relative hemodynamic stability was maintained and there were no between-group differences in the sedation score. We conclude that small doses of intrathecal clonidine (150 µg) significantly prolong the anesthetic and analgesic effects of bupivacaine in a dose-dependent manner and that 150 µg of clonidine seems to be the preferred dose, in terms of effect versus unwarranted side effects, when prolongation of spinal anesthesia is desired.

IMPLICATIONS: Small doses of intrathecal clonidine (150 µg) coadministered to isobaric bupivacaine provide dose-dependent and clinically significant prolongation of spinal anesthesia and pain relief while preserving hemodynamic stability and causing no sedation. In contrast to other approaches to prolong spinal anesthesia (combined spinal-epidural technique) or to relieve postoperative pain (intrathecal opioids), intrathecal clonidine 150 µg does not cause an additional technical challenge or unpredictable pharmacological risk.

Anesthesia & Analgesia® is published for the International Anesthesia Research Society® by Lippincott Williams & Wilkins with the assistance of Stanford University Libraries' HighWire Press®. Copyright 2006 by the International Anesthesia Research Society. Online ISSN: 1526-7598   Print ISSN: 0003-2999