ideal administration rate for local anesthetics

36In our analysis, a majority of comparisons reported on a significantly prolonged duration of postoperative analgesia with clonidine. 35When injected concomitantly with lidocaine for intravenous regional anesthesia, clonidine decreased the incidence of tourniquet pain.

On the isolated vagus nerve, clonidine intensified the conduction block induced by LAs. Laboratory and clinical data on clonidine as an adjuvant to LAs for peripheral nerve blocks are more convincing. 34Thus, data from clinical and experimental trials testing the effect of peripheral clonidine alone have remained inconclusive.

33However, in another clinical study, clonidine alone failed to produce analgesia when injected into the axillary brachial plexus sheath. 32Similarly, in healthy volunteers, sensory and motor block were significantly prolonged when clonidine alone was administered into the axillary plexus sheath. 2In one study, clonidine without LA given through an interscalene catheter provided better analgesia compared with the systemic administration of the same dose. Specific peripheral effects of clonidine appear less obvious because α 2adrenoreceptors are not present on the axon of the normal peripheral nerve. The large expression of α 2receptors in the central nervous system, i.e., loecus coeruleus and dorsal horn of the spinal cord, has eventually focused the interest of that drug on centrally mediated sedation and analgesia. Materials and MethodsĬlonidine, an α 2adrenergic agonist, was initially used for its antihypertensive properties. Our meta-analysis was designed to address these issues. Finally, it remained unclear from these analyses whether there was dose-responsiveness and what the optimal dose of clonidine was. These analyses did not provide quantitative estimates of analgesic efficacy (for instance, duration of postoperative analgesia) or adverse effects (for instance, arterial hypotension, sedation, delay of discharge to home). 3They concluded that clonidine was beneficial only when added to intermediate-acting LAs. reviewed 27 studies (1,385 patients) that all tested clonidine as an adjuvant to LAs for a variety of peripheral nerve blocks. 4On the basis of data from six trials (349 patients), they concluded that clonidine in doses up to 150 μg increased the duration of postoperative analgesia with minimal adverse effects. analyzed randomized trials that investigated the usefulness of a variety of adjuvants, including clonidine added to LAs for brachial plexus block. 1,2The benefit of adding clonidine to LAs for peripheral nerve blocks is less clear, although it is widely believed that clonidine improves quality and duration of a LA block. The analgesic properties of clonidine when administered intrathecally or epidurally have been demonstrated they seem to be attributable to its α 2agonist properties. Dose-responsiveness remains unclear.ĬLONIDINE is a frequently used adjuvant to local anesthetics (LA). The increased risk of hypotension, fainting, and sedation may limit its usefulness. 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. There was a lack of evidence of dose-responsiveness for beneficial or harmful effects. 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). 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 prolonged the duration of postoperative analgesia (weighted mean difference 122 min 95% confidence interval 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). Clonidine doses ranged from 30 to 300 microg most patients received 150 microg. 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). 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. The effect of adding clonidine to local anesthetics for nerve or plexus blocks remains unclear.

Ideal administration rate for local anesthetics