Clonidine as an Adjuvant to Local Anesthetics for Peripheral Nerve and Plexus Blocks

Abstract

The effect of adding clonidine to local anesthetics for nerve or plexus blocks remains unclear. The authors searched for randomized placebo-controlled trials testing the impact of adding clonidine to local anesthetics for peripheral single-injection nerve or plexus blocks in adults undergoing any surgery (except eye) without general anesthesia. Twenty trials (1,054 patients, 573 received clonidine) published 1992-2006 tested plexus (14 brachial, 1 cervical) and nerve blocks (2 sciatic/femoral, 1 midhumeral, 1 ilioinguinal/iliohypogastric, 1 ankle). Clonidine doses ranged from 30 to 300 microg; most patients received 150 microg. Clonidine prolonged the duration of postoperative analgesia (weighted mean difference 122 min; 95% confidence interval [CI] 74-169), sensory block (weighted mean difference 74 min; 95% CI 37-111), and motor block (weighted mean difference 141 min; 95% CI 82-199). In a subgroup of patients receiving an axillary plexus block, these effects were independent of whether clonidine was added to an intermediate or a long-acting local anesthetic. Clonidine increased the risk of arterial hypotension (odds ratio 3.61; 95% CI 1.52-8.55; number-needed-to-harm 11), orthostatic hypotension or fainting (odds ratio 5.07; 95% CI 1.20-21.4; number-needed-to-harm 10), bradycardia (odds ratio 3.09; 95% CI 1.10-8.64; number-needed-to-harm 13), and sedation (odds ratio 2.28; 95% CI 1.15-4.51; number-needed-to-harm 5). There was a lack of evidence of dose-responsiveness for beneficial or harmful effects. Clonidine added to intermediate or long-acting local anesthetics for single-shot peripheral nerve or plexus blocks prolongs duration of analgesia and motor block by about 2 h. The increased risk of hypotension, fainting, and sedation may limit its usefulness. Dose-responsiveness remains unclear.

Magnesium added to bupivacaine prolongs the duration of analgesia after interscalene nerve block

“…Whereas the effectiveness in the analgesic duration may be similar for perineural adjuvants regardless of type of local anesthetic, the relative increase in the duration of analgesia is far more pronounced with intermediate-acting local anesthetics than with long-acting local anesthetics. 2 Although magnesium is likely to prolong the analgesic duration without reference to any local anesthetics, the clinical relevance of adding magnesium to a long-acting local anesthetic may be questioned because the relative gain will be minimal. Furthermore, mixed epinephrine to bupivacaine could have masked any pharmacodynamic effect of perineural magnesium, similar to the report in which clonidine failed to prolong the analgesic duration of ropivacaine and bupivacaine with epinephrine.…”

“…However, the increased risk of hypotension, fainting, and sedation may limit its usefulness. 2 The addition of dexamethasone to bupivacaine and clonidine has been shown to prolong the analgesic duration of brachial plexus blocks. This effect may be secondary to a local action of dexamethasone on nociceptive C-fibre mediated via glucocorticoid receptors and anti-inflammatory action.…”

Eficacia analgésica de una dosis única de dexametasona perineural en el bloqueo ecoguiado del nervio femoral en cirugía de prótesis total de rodilla

“…Respecto a los coadyuvantes se ha visto que los agonistas de los receptores alfa-2 adrenérgicos 20,21 (clonidina y dexmetomidina) prolongan de forma significativa la analgesia postoperatoria (122 minutos) de bloqueos realizados sobre el miembro superior, pero producen importantes efectos adversos como sedación e hipotensión. Estudios realizados en cirugía de PTR donde se han utilizado los agonistas alfa-2 (clonidina y efedrina) como coadyuvantes, no han demostrado mayor eficacia o analgesia del bloqueo femoral, por tanto no están recomendados actualmente para su uso como coadyuvantes a los AL en el bloqueo femoral en PTR (recomendación A, evidencia 1) 110 .…”

“…Se han realizado diversos estudios que tenían como objetivo prolongar la duración de los bloqueos locorregionales añadiendo a los AL coadyuvantes [18][19][20] como adrenalina, opioides, ketamina o midazolam, obteniéndose una efectividad limitada. Los agonistas de los receptores alfa-2 adrenérgicos (clonidina 20 y dexmetomidina 21 ) sí han demostrado prolongar de forma significativa la analgesia pero con importantes efectos adversos.…”

Anesthesia, cytokines and cancer recurrence

“…Dexmedetomidine is a α2 -adrenoceptor agonist, which induces sedative state similar to physiological sleep [78,79]. Several studies have shown that propofol impairs neutrophil, monocyte and macrophage functions.…”