Buprenorphine Added to the Local Anesthetic for Axillary Brachial Plexus Block Prolongs Postoperative Analgesia:

Pharmacological and clinical implications of local anaesthetic mixtures: a narrative review

Various techniques have been explored to prolong the duration and improve the efficacy of local anaesthetic nerve blocks. Some of these involve mixing local anaesthetics or adding adjuncts. We did a literature review of studies published between 01 May 2011 and 01 May 2021 that studied specific combinations of local anaesthetics and adjuncts. The rationale behind mixing long- and short-acting local anaesthetics to hasten onset and extend duration is flawed on pharmacokinetic principles. Most local anaesthetic adjuncts are not licensed for use in this manner and the consequences of untested admixtures and adjuncts range from making the solution ineffective to potential harm. Pharmaceutical compatibility needs to be established before administration. The compatibility of drugs from the same class cannot be inferred and each admixture requires individual review. Precipitation on mixing (steroids, non-steroidal anti-inflammatory drugs) and subsequent embolisation can lead to serious adverse events, although these are rare. The additive itself or its preservative can have neurotoxic (adrenaline, midazolam) and/or chondrotoxic properties (non-steroidal anti-inflammatory drugs). The prolongation of block may occur at the expense of motor block quality (ketamine) or block onset (magnesium). Adverse effects for some adjuncts appear to be dose-dependent and recommendations concerning optimal dosing are lacking. An important confounding factor is whether studies used systemic administration of the adjunct as a control to accurately identify an additional benefit of perineural administration. The challenge of how best to prolong block duration while minimising adverse events remains a topic of interest with further research required.

Effects of local dexmedetomidine administration on the neurotoxicity of ropivacaine for sciatic nerve block in rats

Dexmedetomidine, used as an adjuvant to local anesthetics (LAs), may prolong the duration of peripheral nerve block. However, the effect of dexmedetomidine on the neurotoxicity of LAs is not completely understood. The present study was designed to investigate the efficacy of two doses of dexmedetomidine as an adjuvant to ropivacaine and its protective effect against the neurotoxicity of LAs. Paw withdrawal thermal latency testing was used to detect the sensory blockade. Extensor postural thrust testing was used to detect the motor blockade. The results demonstrated that the addition of dexmedetomidine to ropivacaine prolonged the duration of sensory and motor blockade in a dose-dependent manner compared with ropivacaine alone. TUNEL staining was performed to examine apoptosis. Western blotting was used to detect the Cleaved caspase-3 expression levels. The results showed that the addition of dexmedetomidine to ropivacaine decreased the rate of apoptosis and caspase-3 expression levels in a dose-dependent manner compared with ropivacaine alone (P<0.05). In addition, the rate of apoptosis and caspase-3 expression levels were significantly lower in the high-dose dexmedetomidine group compared with the low-dose dexmedetomidine group (P<0.05). The results suggested that the addition of dexmedetomidine to ropivacaine for sciatic nerve block in rats not only prolonged the duration of sensory and motor block of the sciatic nerve, but also markedly alleviated ropivacaine-induced neurotoxicity by decreasing caspase-3-dependent sciatic nerve cell apoptosis. Furthermore, the present study indicated that dexmedetomidine was more effective at a dose of 20 µg/kg compared with 6 µg/kg.

Adjuvants in clinical regional anesthesia practice: A comprehensive review

Adjuvants are medications that work synergistically with local anesthetics to help enhance the duration and quality of analgesia in regional techniques. Regional anesthesia has become more prevalent as evidence continues to show efficacy, enhancement of patient care, increased patient satisfaction, and improved patient safety. Practitioners in the perioperative setting need to not only be familiar with regional techniques but also the medications used for them. Some examples of adjuvant medications for regional techniques include dexamethasone, alpha 2 agonists such as clonidine and dexmedetomidine, midazolam, buprenorphine, NMDA antagonists, including ketamine and magnesium, neostigmine, sodium bicarbonate, epinephrine, and non-steroidal anti-inflammatory drugs. The aim of the present investigation, therefore, is to provide a comprehensive review of the most commonly used non-opioid adjuvants in clinical practice today. Regional adjuvants can improve patient safety, increase patient satisfaction, and enhance clinical efficacy. Future studies and best practice techniques can facilitate standardization of regional anesthesia adjuvant dosing when providing nerve blocks in clinical practice.

Effect of addition of buprenorphine or dexamethasone to levobupivacaine on postoperative analgesia in ultrasound guided transversus abdominis plane block in patients undergoing unilateral inguinal hernia repair: a prospective randomized double blind controlled trial

BACKGROUND

The transversus abdominis plane (TAP) block is an effective technique to block the thoracolumbar nerves innervating the anterolateral abdominal wall. This study was conducted to evaluate the analgesic efficacy and opioid consumption with the use of perineural buprenorphine or dexamethasone in TAP blocks after unilateral inguinal hernioplasties.

METHODS

This prospective, randomized, double-blinded, placebo-controlled study enrolled 93 patients scheduled for unilateral inguinal hernioplasty, followed by an ultrasound-guided TAP block. The participants were randomized into 3 groups (31 patients each). Group L received 20 ml 0.25% levobupivacaine + 1 ml normal saline (NS); group LB, 20 ml 0.25% levobupivacaine + 0.3 mg (1 ml) buprenorphine; and group LD, 20 ml 0.25% levobupivacaine + 4 mg (1 ml) dexamethasone. The patients were observed postoperatively for 24 h for first rescue analgesic requirement, total rescue analgesic consumption, and pain scores on the numeric rating scale (NRS).

RESULTS

The time to first rescue analgesic requirement was significantly longer in Group LB than in groups LD and L (688.87 ± 36.11 min, 601.45 ± 39.85 min, and 383.06 ± 36.21 min, respectively; P < 0.001). The mean total tramadol consumption in the first 24 h was the lowest in group LB (P < 0.001, L vs. LB / LD). Groups LB and LD displayed significantly lower NRS scores than group L (P < 0.001 both).

CONCLUSIONS

Levobupivacaine with perineural buprenorphine in a TAP block after unilateral open inguinal hernioplasty facilitates prolonged analgesia and reduced requirement for rescue analgesics compared to perineural dexamethasone, without significant side effects.

A Fixed-Dose Combination, QXOH/Levobupivacaine, Produces Long-Acting Local Anesthesia in Rats Without Additional Toxicity

QXOH, a QX314 derivative with longer duration and lesser local toxicity, is a novel local anesthetic in preclinical drug development. Previous studies demonstrated that bupivacaine can prolong the effects of QX314. So, we attempted to combine QXOH with levobupivacaine to shorten the onset time and lengthen the duration. In this study, we investigated the efficacy, local and systemic toxicity in rats. In subcutaneous infiltration anesthesia, the inhibition of cutaneous trunci muscle reflex for QXOH-LB was greater than QXOH and levobupivacaine in the first 8 h (QXOH-LB vs. QXOH, P = 0.004; QXOH-LB vs. LB, P = 0.004). The completely recovery time for QXOH-LB (17.5 ± 2.5 h) was significantly longer than levobupivacaine (9.0 ± 1.3 h, P = 0.034) and QXOH (9.8 ± 0.9 h, P = 0.049). In sciatic nerve block, QXOH-LB produced a rapid onset time, which was obviously shorter than QXOH. For sensory, the time to recovery for QXOH-LB was 17.3 ± 2.6 h, which was statistically longer than 6.0 ± 1.8 h for QXOH (P = 0.027), and 4 h for levobupivacaine (P = 0.001). Meanwhile, the time to motor recovery for QXOH-LB was 7.9 ± 2.8 h, significantly longer than 4 h for levobupivacaine (P = 0.003) but similar to 6.0 ± 1.7 h for QXOH (P = 0.061). In local toxicity, there was no significant difference of histological score regarding muscle and sciatic nerve in QXOH-LB, QXOH, levobupivacaine and saline (P < 0.01). In the combination, the interaction index of LD₅₀ was 1.39, indicating antagonistic interaction between QXOH and levobupivacaine in terms of systemic toxicity. In this study, we demonstrated that QXOH-LB produced cutaneous anesthesia which was 2-fold greater than that produced by QXOH or LB alone, and elicited sciatic nerve block with a potency that was 5- and 3-fold that of LB and QXOH, respectively. Local tissue inflammation by QXOH-LB was mild, similar to that induced by LB. This fixed-dose combination led to an antagonistic interaction between QXOH and LB in terms of systemic toxicity. These results suggested that QXOH-LB induced a long-lasting local anesthesia, likely, avoiding clinically important local and systemic toxicities.

Inhibition of Voltage-Gated Na+ Channels by Bupivacaine Is Enhanced by the Adjuvants Buprenorphine, Ketamine, and Clonidine

BACKGROUND AND OBJECTIVES

Regional anesthesia includes application of local anesthetics (LAs) into the vicinity of peripheral nerves. Prolongation or improvement of nerve blocks with LAs can be accomplished by coapplication with adjuvants, including buprenorphine, ketamine, and clonidine. While the mechanisms mediating prolonged or improved LA-induced effects by adjuvants are poorly understood, we hypothesized that they are likely to increase LA-induced block of voltage-gated Na channels. In this study, we investigated the inhibitory effects of the LA bupivacaine alone and in combination with the adjuvants on neuronal Na channels.

METHODS

Effects of bupivacaine, buprenorphine, ketamine, and clonidine on endogenous Na channels in ND7/23 neuroblastoma cells were investigated with whole-cell patch clamp.

RESULTS

Bupivacaine, buprenorphine, ketamine, and clonidine are concentration- and state-dependent inhibitors of Na currents in ND7/23 cells. Tonic block of resting channels revealed an order of potency of bupivacaine (half-maximal inhibitory concentration [IC50] 178 ± 8 μM) > buprenorphine (IC50 172 ± 25) > clonidine (IC50 824 ± 55 μM) > ketamine (IC50 1377 ± 92 μM). Bupivacaine and buprenorphine, but not clonidine and ketamine, induced a strong use-dependent block at 10 Hz. Except for clonidine, all substances enhanced fast and slow inactivation. The combination of bupivacaine with one of the adjuvants resulted in a concentration-dependent potentiation bupivacaine-induced block.

CONCLUSIONS

We demonstrate that buprenorphine, ketamine, and clonidine directly inhibit Na channels and that they potentiate the blocking efficacy of bupivacaine on Na channels. These data indicate that block of Na channels may account for the additive effects of adjuvants used for regional anesthesia.

The quaternary lidocaine derivative QX-314 in combination with bupivacaine for long-lasting nerve block: Efficacy, toxicity, and the optimal formulation in rats

OBJECTIVE

The quaternary lidocaine derivative (QX-314) in combination with bupivacaine can produce long-lasting nerve blocks in vivo, indicating potential clinical application. The aim of the study was to investigate the efficacy, safety, and the optimal formulation of this combination.

METHODS

QX-314 and bupivacaine at different concentration ratios were injected in the vicinity of the sciatic nerve in rats; bupivacaine and saline served as controls (n = 6~10). Rats were inspected for durations of effective sensory and motor nerve blocks, systemic adverse effects, and histological changes of local tissues. Mathematical models were established to reveal drug-interaction, concentration-effect relationships, and the optimal ratio of QX-314 to bupivacaine.

RESULTS

0.2~1.5% QX-314 with 0.03~0.5% bupivacaine produced 5.8~23.8 h of effective nerve block; while 0.5% bupivacaine alone was effective for 4 h. No systemic side effects were observed; local tissue reactions were similar to those caused by 0.5% bupivacaine if QX-314 were used < 1.2%. The weighted modification model was successfully established, which revealed that QX-314 was the main active ingredient while bupivacaine was the synergist. The formulation, 0.9% QX-314 plus 0.5% bupivacaine, resulted in 10.1 ± 0.8 h of effective sensory and motor nerve blocks.

CONCLUSION

The combination of QX-314 and bupivacaine facilitated prolonged sciatic nerve block in rats with a satisfactory safety profile, maximizing the duration of nerve block without clinically important systemic and local tissue toxicity. It may emerge as an alternative approach to post-operative pain treatment.

Adjuvant Agents in Regional Anesthesia in the Ambulatory Setting

PURPOSE OF REVIEW

A majority of surgical practice has involved ambulatory centers with the number of outpatient operations in the USA doubling to 26.8 million per year. Local anesthesia delivery provides numerous benefits, including increased satisfaction, earlier discharge, and reduction in unplanned hospital admission. Further, with the epidemic of opioid mediated overdoses, local anesthesia can be a key tool in providing an opportunity to reduce the need for other analgesics postoperatively.

RECENT FINDINGS

Adjuvants such as epinephrine and clonidine enhance local anesthetic clinical utility. Further, dexmedetomidine prolongs regional blockade duration effects. There has also been a significant interest recently in the use of dexamethasone. Studies have demonstrated a significant prolongation in motor and sensory block with perineural dexamethasone. Findings are conflicting as to whether intravenous dexamethasone has similar beneficial effects. However, considering the possible neurotoxicity effects, which perineural dexamethasone may present, it would be prudent not to consider intravenously administered dexamethasone to prolong regional block duration. Many studies have also demonstrated neurotoxicity from intrathecally administered midazolam. Therefore, midazolam as an adjuvant is not recommended. Magnesium prolongs regional block duration but related to paucity of studies as of yet, cannot be recommended. Tramadol yields inconsistent results and ketamine is associated with psychotomimetic adverse effects. Buprenorphine consistently increases regional block duration and reduce opioid requirements by a significant amount. Future studies are warranted to define best practice strategies for these adjuvant agents. The present review focuses on the many roles of local anesthetics in current ambulatory practice.

Efficacy of buprenorphine added to 2% lignocaine plus adrenaline 1:80,000 in providing postoperative analgesia after lower third molar surgery

A number of trials have examined the peripheral analgesic effect of opioids, known to have an anti-nociceptive effect at the central and/or spinal cord level. This study aimed to evaluate the efficacy of buprenorphine added to 2% lignocaine with adrenaline 1:80,000 in providing postoperative analgesia after lower third molar surgery. Sixty patients were randomized to three groups: group A received lignocaine 2% with adrenaline 1:80,000 for inferior alveolar nerve block (IANB), along with intramuscular (IM) injection of 1ml saline; group B received buprenorphine mixed with lignocaine 2% with adrenaline 1:80,000 for IANB (0.01mg buprenorphine/ml lignocaine with adrenaline), along with 1ml saline IM; group C received lignocaine 2% with adrenaline 1:80,000 for IANB, along with 0.03mg buprenorphine IM. Mean postoperative pain scores (visual analogue scale; when the patient first felt pain) were 6.0 for group A, 1.0 for group B, and 4.4 for group C. The mean duration of postoperative analgesia was 3.5h in groups A and C and 12h in group B. The mean number of postoperative analgesics consumed was 5.8 in groups A and C and 3.9 in group B. The addition of buprenorphine (0.03mg) to 2% lignocaine with adrenaline 1:80,000 significantly reduced the severity of postoperative pain and prolonged the duration of analgesia, thereby decreasing the need for postoperative analgesics.

Pathophysiology and Management of Surgical and Chronic Oral Pain in Dogs and Cats

Pain involves a myriad of physiochemical responses leading to the perception of an unpleasant sensation arising from tissue damage. An understanding of the terminology and basic neurophysiology involved with the pain process is helpful in preventing and treating discomfort in our patients. A general understanding of the concepts of nociception, peripheral sensitization, and central sensitization will allow decisions to be made on the choices of analgesic agents in each individual patient based upon the type, duration, and severity of the pain. Using preemptive pain management with a multimodal approach provides the most consistent and predictable results. Analgesic protocols should be closely scrutinized on an individual basis with careful patient pain assessment during the postoperative period. Chronic pain mechanisms, particularly significant in cancer pain and stomatitis, require aggressive and perhaps unique approaches to ensure maximum patient comfort.

Addition of Dexamethasone and Buprenorphine to Bupivacaine Sciatic Nerve Block: A Randomized Controlled Trial

BACKGROUND AND OBJECTIVES

Sciatic nerve block provides analgesia after foot and ankle surgery, but block duration may be insufficient. We hypothesized that perineural dexamethasone and buprenorphine would reduce pain scores at 24 hours.

METHODS

Ninety patients received ultrasound-guided sciatic (25 mL 0.25% bupivacaine) and adductor canal (10 mL 0.25% bupivacaine) blockade, with random assignment into 3 groups (30 patients per group): control blocks + intravenous (IV) dexamethasone (4 mg) (control); control blocks + IV buprenorphine (150 μg) + IV dexamethasone (IV buprenorphine); and nerve blocks containing buprenorphine + dexamethasone (perineural). Patients received mepivacaine neuraxial anesthesia and postoperative oxycodone/acetaminophen, meloxicam, pregabalin, and ondansetron. Patients and assessors were blinded to group assignment. The primary outcome was pain with movement at 24 hours.

RESULTS

There was no difference in pain with movement at 24 hours (median score, 0). However, the perineural group had longer block duration versus control (45.6 vs 30.0 hours). Perineural patients had lower scores for "worst pain" versus control (median, 0 vs 2). Both IV buprenorphine and perineural groups were less likely to use opioids on the day after surgery versus control (28.6%, 28.6%, and 60.7%, respectively). Nausea after IV buprenorphine (but not perineural buprenorphine) was severe, frequent, and bothersome.

CONCLUSIONS

Pain scores were very low at 24 hours after surgery in the context of multimodal analgesia and were not improved by additives. However, perineural buprenorphine and dexamethasone prolonged block duration, reduced the worst pain experienced, and reduced opioid use. Intravenous buprenorphine caused troubling nausea and vomiting. Future research is needed to confirm and extend these observations.

Buprenorphine, Clonidine, Dexamethasone, and Ropivacaine for Interscalene Nerve Blockade: A Prospective, Randomized, Blinded, Ropivacaine Dose-Response Study

OBJECTIVE

This study investigated interscalene block for shoulder arthroplasty with various ropivacaine concentrations in the presence of clonidine, dexamethasone, and buprenorphine. The goal was prolonged analgesia with minimal motor blockade.

DESIGN

Prospective, double-blind, randomized controlled trial.

SETTING

University-affiliated orthopedic hospital.

METHODS

Patients (20/group) received acetaminophen, ketorolac, pregabalin, opioids, and "Control"; interscalene block, 0.375% ropivacaine, intravenous additives (buprenorphine, clonidine, dexamethasone); "High Dose"; 0.375% ropivacaine, perineural additives; "Medium Dose"; 0.2% ropivacaine, perineural additives; and "Low Dose"; 0.1% ropivacaine, perineural additives.

RESULTS

Pain with movement at 24 hours was 4.9 ± 2.5 (mean ± standard deviation [SD]) (Control), 4.5 ± 3.0 (High Dose), 3.4 ± 1.8 (Medium Dose), 4.2 ± 2.4 (Low Dose). The difference between Medium Dose and Control was -1.5 (95% CI: -2.9, -0.1) (P = 0.040). Median time until need for opioids was 16.1 hours (Control) vs 23.7 hours (High Dose); hazard ratio 0.37 [95% CI: 0.17, 0.79]. High Dose had less pain with movement the morning after surgery, vs Control; 2.9 ± 2.5 vs 4.9 ± 2.7; P = 0.027. Pain with movement in the Post-Anesthesia Care Unit was higher in Low Dose, vs Control; 0.9 ± 1.4 vs 0 ± 0, P = 0.009. Low Dose had superior hand strength in the Post-Anesthesia Care Unit (mean ± SD of pre-operative strength: 44.0 ± 20.3%) compared to Control (27.5 ± 24.5%) (P = 0.031).

CONCLUSIONS

For maximum pain reduction, combining perineural additives with ropivacaine 0.375% or 0.2% is suggested. To minimize motor blockade, perineural additives can be combined with ropivacaine, 0.1%.

Local Anesthetic Peripheral Nerve Block Adjuvants for Prolongation of Analgesia: A Systematic Qualitative Review

Background

The use of peripheral nerve blocks for anesthesia and postoperative analgesia has increased significantly in recent years. Adjuvants are frequently added to local anesthetics to prolong analgesia following peripheral nerve blockade. Numerous randomized controlled trials and meta-analyses have examined the pros and cons of the use of various individual adjuvants.

Objectives

To systematically review adjuvant-related randomized controlled trials and meta-analyses and provide clinical recommendations for the use of adjuvants in peripheral nerve blocks.

Methods

Randomized controlled trials and meta-analyses that were published between 1990 and 2014 were included in the initial bibliographic search, which was conducted using Medline/PubMed, Cochrane Central Register of Controlled Trials, and EMBASE. Only studies that were published in English and listed block analgesic duration as an outcome were included. Trials that had already been published in the identified meta-analyses and included adjuvants not in widespread use and published without an Investigational New Drug application or equivalent status were excluded.

Results

Sixty one novel clinical trials and meta-analyses were identified and included in this review. The clinical trials reported analgesic duration data for the following adjuvants: buprenorphine (6), morphine (6), fentanyl (10), epinephrine (3), clonidine (7), dexmedetomidine (7), dexamethasone (7), tramadol (8), and magnesium (4). Studies of perineural buprenorphine, clonidine, dexamethasone, dexmedetomidine, and magnesium most consistently demonstrated prolongation of peripheral nerve blocks.

Conclusions

Buprenorphine, clonidine, dexamethasone, magnesium, and dexmedetomidine are promising agents for use in prolongation of local anesthetic peripheral nerve blocks, and further studies of safety and efficacy are merited. However, caution is recommended with use of any perineural adjuvant, as none have Food and Drug Administration approval, and concerns for side effects and potential toxicity persist.

Additives to local anesthetics for peripheral nerve blocks or local anesthesia: a review of the literature

SUMMARY 

A multitude of studies have focused on individual additives to local anesthetics and their effect on quality, onset, duration, spread and selectivity, as well as the potential toxic effects of their use. This review aims to give a broad overview of the current evidence in this developing field, based on beneficial and adverse effects of these drugs. We discuss the limitations of the available data and hope to convey implications and future perspectives for clinicians and researchers alike.

Buprenorphine added to bupivacaine prolongs femoral nerve block duration and improves analgesia in patients undergoing primary total knee arthroplasty-a randomised prospective double-blind study

The aim of the study was to determine whether the addition the long-acting opioid buprenorphine as an adjuvant to the local anaesthetic agent would improve quality and prolong duration of femoral nerve blockade in post-operative analgesia following primary total knee arthroplasty. The study involved 48 patients. The femoral nerve was anaesthetised with a 0.25% solution of bupivacaine with adrenaline or with the addition of 0.3mg of buprenorphine. The duration of the sensory block and analgesic effect was assessed according to NRS scale at 12, 24, 36, 48, 60 and 72 hours post-surgery. Patients who received buprenorphine as an adjuvant to the local anaesthetic had significantly longer sensory blockade and lower NRS-rated pain intensity with the difference reaching statistical significance at 12 hours post-surgery.

Role of regional anesthesia in orthopedic trauma

Regional anesthesia plays a key role in the treatment of patients with orthopedic trauma. Trauma-induced pain can be in multiple locations, severe, and can predispose the patient to other morbidities. Additional complications as a result of the overdependence on opioids as a primary pain therapy that can be minimized or avoided with the use of regional anesthesia. Both neuraxial and peripheral regional techniques in patients with orthopedic trauma should be incorporated into the patient care plan and recognized as an essential therapeutic intervention in the overall treatment of this unique patient population.

Setting up an acute pain management service

Successful implementation of an acute pain management service involves a team approach in which team members have clearly defined roles. Clinical protocols are designed to help address common problems and prevent errors. As the complexity of surgery and patients' diseases continues to increase, current knowledge of new analgesic medications, acute pain literature, and skills in regional anesthesia techniques is imperative. Emphasizing a multimodal approach can improve analgesia and decrease opioid-related side effects.

Facilitatory effects of perineural dexmedetomidine on neuraxial and peripheral nerve block: a systematic review and meta-analysis

Nerve blocks improve postoperative analgesia, but their benefits may be short-lived. This quantitative review examines whether perineural dexmedetomidine as a local anaesthetic (LA) adjuvant for neuraxial and peripheral nerve blocks can prolong the duration of analgesia compared with LA alone. All randomized controlled trials (RCTs) comparing the effect of dexmedetomidine as an LA adjuvant to LA alone on neuraxial and peripheral nerve blocks were reviewed. Sensory block duration, motor block duration, block onset times, analgesic consumption, time to first analgesic request, and side-effects were analysed.

RESULTS

were combined using random-effects modelling. A total of 516 patients were analysed from nine RCTs. Five trials investigated dexmedetomidine as part of spinal anaesthesia and four as part of a brachial plexus (BP) block. Sensory block duration was prolonged by 150 min [95% confidence interval (CI): 96, 205, P<0.00001] with intrathecal dexmedetomidine. Perineural dexmedetomidine used in BP block may prolong the mean duration of sensory block by 284 min (95% CI: 1, 566, P=0.05), but this difference did not reach statistical significance. Motor block duration and time to first analgesic request were prolonged for both intrathecal and BP block. Dexmedetomidine produced reversible bradycardia in 7% of BP block patients, but no effect on the incidence of hypotension. No patients experienced respiratory depression. Dexmedetomidine is a potential LA adjuvant that can exhibit a facilitatory effect when administered intrathecally as part of spinal anaesthesia or peripherally as part of a BP block. However, there are presently insufficient safety data to support perineural dexmedetomidine use in the clinical setting.

Buprenorphine added to levobupivacaine enhances postoperative analgesia of middle interscalene brachial plexus block

PURPOSE

The aim of this study was to assess whether addition of epineural buprenorphine prolonged postoperative analgesia of middle interscalene brachial plexus block (MIB) with levobupivacaine.

METHODS

One hundred and fifty consenting adult patients, scheduled for shoulder arthroscopic surgery for a rotator cuff tear under MIB with 29.5 ml of 0.75 % levobupivacaine, were randomized to receive additionally either saline or intramuscular buprenorphine 0.15 mg or epineural buprenorphine 0.15 mg. Onset of sensory and motor blocks, duration of postoperative analgesia, and consumption of postoperative analgesics were compared among the groups.

RESULTS

There were significant (P < 0.05) differences in the onset and the duration of the sensory block and in the duration of postoperative analgesia. Duration of both sensory block and postoperative analgesia was longer (P < 0.05) in patients who had received epineural buprenorphine (856.1 ± 215.2 and 1,049.7 ± 242.2 min) than in patients who had received intramuscular buprenorphine (693.6 ± 143.4 and 820.3 ± 335.3 min) or saline (488.3 ± 137.6 and 637.5 ± 72.1 min). Requirement of postoperative rescue analgesics was lower in the epineural buprenorphine group than in the other two groups. Few complications occurred from MIB (<1 %) and none from buprenorphine.

CONCLUSIONS

Epineural buprenorphine prolonged postoperative analgesia of MIB more effectively than intramuscular buprenorphine, which suggests that buprenorphine acts at a peripheral nervous system site of action.

Efficacy of buprenorphine added 2 % lignocaine 1:80000 in postoperative analgesia after minor oral surgery

PURPOSE

Recent studies have demonstrated that opioid analgesia cannot be exclusively attributed to effects within central nervous system. Peripheral opioid receptors exist that can be activated by locally applied opioid agonists which mediate analgesic effects that are particularly prominent in painful inflammatory conditions. Patients who present themselves with conditions requiring minor surgery in the maxillo-facial region usually have associated ongoing inflammatory process. The aim of our study was to apply the concept of peripheral opioid analgesia in minor oral surgery and evaluate its effectiveness in managing postoperative pain. The present study was designed to evaluate the efficacy of buprenorphine added lignocaine 2 % in providing postoperative analgesia after minor oral surgery.

MATERIALS AND METHODS

Hundred consenting adult patients who were scheduled to undergo various minor oral surgeries were enrolled in this double blinded study. Patients were randomly assigned into one of the two groups based on whether they received buprenorphine added 2 % lignocaine 1:80000 (Group I) or (Group II) lignocaine 2 % with adrenaline 1:80000 alone. Visual analog scale method was used for evaluation of the postoperative analgesia.

RESULTS

The duration of analgesia in Group I was found to be 36 ± 1.5 h and the average consumption of NSAIDs was found to be 1.86 as compared to Group II mean value of 4.4 (P < 0.0001).

CONCLUSION

Addition of small amounts of buprenorphine to 30 ml lignocaine with adrenaline 1:80000 for minor oral surgery results in significant improvement in postoperative analgesia up to 36 h and markedly reduces the need for excessive analgesic intake. Thus reducing the adverse effects associated with excessive use of NSAIDs.

Neurotoxicity of adjuvants used in perineural anesthesia and analgesia in comparison with ropivacaine

BACKGROUND AND OBJECTIVES

Clonidine, buprenorphine, dexamethasone, and midazolam (C, B, D, M) have been used to prolong perineural local anesthesia in the absence of data on the influence of these adjuvants on local anesthetic-induced neurotoxicity. Therefore, the impact of these adjuvants on ropivacaine (R)-induced death of isolated sensory neurons was assessed.

METHODS

The trypan blue exclusion assay was used to assess death of sensory neurons isolated from adult male Sprague-Dawley rats. Drugs were applied, alone or in combination, for 2 or 24 hrs at 37°C.

RESULTS

Neuronal viability was halved by 24-hr exposure to R (2.5 mg/mL), far exceeding the neurotoxicity of C, B, D, or M (at 2-100 times estimated clinical concentrations). Plain M at twice the estimated clinical concentration produced a small but significant increase in neurotoxicity at 24 hrs. After 2-hr exposure, high concentrations of B, C, and M increased the neurotoxicity of R; the combination of R + M killed more than 90% of neurons. Estimated clinical concentrations of C + B (plus 66 μg/mL D) had no influence on (i) R-induced neurotoxicity, (ii) the increased neurotoxicity associated with the combination of R + M, or (iii) the neurotoxicity associated with estimated clinical concentrations of M. There was increased neurotoxicity with 133 μg/mL D combined with R + C + B.

CONCLUSIONS

Results with R reaffirm the need to identify ways to mitigate local anesthetic-induced neurotoxicity. While having no protective effect on R-induced neurotoxicity in vitro, future research with adjuvants should address if the C + B + D combination can enable reducing R concentrations needed to achieve equianalgesia (and/or provide equal or superior duration, in preclinical in vivo models).

Buprenorphine in postoperative pain management

Several decades ago, the analgesic properties of buprenorphine were discovered. Its approval for the use as an agent for the treatment of opioid abuse has led to increasing numbers of patients presenting for surgery on buprenorphine. This article describes the challenges, advantages, and disadvantages of the use of buprenorphine as an analgesic for postoperative pain in patients with and without preoperative maintenance therapy.

Functional deficits after intraneural injection during interscalene block

OBJECTIVE

We present an occurrence of a severe but transient neurologic complication after intraneural injection during an ultrasound-guided interscalene block.

CASE REPORT

A 36-year-old man underwent ultrasound-guided interscalene nerve blockade before shoulder incision and drainage. On postoperative day 1, he exhibited new-onset arm weakness with dysesthesias. Intraneural injection was recognized based on a retrospective review of the recorded ultrasound imaging. The symptoms persisted for more than 2 weeks and completely resolved by 6 weeks.

CONCLUSIONS

Our report suggests that intraneural injection during ultrasound-guided interscalene block carries a risk of neurologic complications.

Local anaesthetic adjuvants: neuraxial versus peripheral nerve block

PURPOSE OF REVIEW

To present a review of the literature on the importance and the clinical characteristics relevant to adjuvants added to local anaesthetics in neuraxial and peripheral nerve blocks.

RECENT FINDINGS

In neuraxial anaesthesia, both opioids and alpha-2 receptor agonists have beneficial effects. Intrathecally, fentanyl and sufentanil not only improve the postoperative analgesia but also make it possible to allow a decrease in the local anaesthetic dose. When clonidine or dexmedetomidine was added to intrathecal local anaesthetics, the regression of sensory, motor block increased dose-dependently and postoperative analgesia was prolonged. The potency of intrathecal clonidine: dexmedetomidine seems to be 10: 1. In peripheral nerve block, when opioid was combined with local anaesthetics, no increased improvement in analgesia was reported in comparison with systemic controls in most of the studies, except buprenorphine. Also clonidine is controversial as an analgesic adjuvant. Special factors, such as type of local anaesthetics, block of upper or lower limb, are important for its the beneficial effect. Other adjuvants, except neuraxial low-dose neostigmine, are of minor importance.

SUMMARY

Opioids and alpha-2 receptor agonists are important as neuraxial adjuvants to improve the quality of peroperative and postoperative analgesia in high-risk patients and in ambulatory procedures. In peripheral nerve blocks, however, some benefit is found only when clonidine is added to local anaesthetics under certain circumstances.

Upper extremity regional anesthesia: essentials of our current understanding, 2008

Brachial plexus blockade is the cornerstone of the peripheral nerve regional anesthesia practice of most anesthesiologists. As part of the American Society of Regional Anesthesia and Pain Medicine's commitment to providing intensive evidence-based education related to regional anesthesia and analgesia, this article is a complete update of our 2002 comprehensive review of upper extremity anesthesia. The text of the review focuses on (1) pertinent anatomy, (2) approaches to the brachial plexus and techniques that optimize block quality, (4) local anesthetic and adjuvant pharmacology, (5) complications, (6) perioperative issues, and (6) challenges for future research.

Peripheral nerve blocks for anaesthesia and postoperative analgesia

PURPOSE OF REVIEW

Perioperative analgesia is a major concern for the patient and for the anesthesiologist, whose task is to avoid pain and all related complications on immediate outcome and healing. Regional anesthesia, alone or combined with general anesthesia, is becoming a preferred technique in a variety of surgical procedures. There is increasing interest in peripheral nerve blocks, single or continuous, mainly for perioperative treatment of unilateral surgery. Specificity of analgesic area combined with decreased complications, including spinal or epidural hematoma, urinary retention, or hemodynamic alterations, are advantages of the peripheral nerve block over more central neural blocks.

RECENT FINDINGS

Insertion of catheters near neural plexuses or in the vicinity of single nerves are being continuously developed and improved. The appearance of new techniques and devices is increasing. Percutaneous electrode guidance, ultrasonographic localization of neural structures, and the use of stimulating catheters represent the newest advances in this area. Use of enantiomeric local anesthetic drugs permits a safer and wider range of postoperative treatment, which includes continuous analgesia administered in the patient's home. Use of patient-controlled analgesia, through electronic or elastomeric pumps, is recommended for postoperative pain control. Peripheral nerve block is the standard for anesthesia or analgesia in ambulatory surgery. Complications of the technique have been examined in large clinical studies which have recently been published. Results of such studies highlight the effectiveness and safety of peripheral blocks. These results have given new strength to arguments for regional anesthesia and analgesia and led to the increase in popularity of regional techniques. The articles considered below have, in summary, the main purpose of enhancing safety, as well as dissemination and education regarding regional anesthetic techniques.

SUMMARY

Possibilities afforded by the use of peripheral nerve blocks mainly consist of prolonged analgesia, selective area of action, and fewer collateral effects when compared with general anesthesia or more central neural blockade. Introduction of new devices and new techniques are increasing, as evidenced by the large number of studies which have appeared in the literature during the past year.

Anesthesia and analgesia for small mammals and birds

This article should help the veterinarian to assess pain in small mammals and birds. The focus is on a multimodal approach to anesthesia and analgesia using opioids, nonsteroidal anti-inflammatory drugs, alpha(2)-agonists, dissociatives, and local anesthetics as injectables, constant rate infusions, local blocks, and epidurals. Drugs used for induction, intubation techniques, and inhalant anesthesia are discussed. Protocols for critical patients and doses of common analgesics are covered.

Local anesthetics

Local anesthetics are used broadly to prevent or reverse acute pain and treat symptoms of chronic pain. This chapter, on the analgesic aspects of local anesthetics, reviews their broad actions that affect many different molecular targets and disrupt their functions in pain processing. Application of local anesthetics to peripheral nerve primarily results in the blockade of propagating action potentials, through their inhibition of voltage-gated sodium channels. Such inhibition results from drug binding at a site in the channel's inner pore, accessible from the cytoplasmic opening. Binding of drug molecules to these channels depends on their conformation, with the drugs generally having a higher affinity for the open and inactivated channel states that are induced by membrane depolarization. As a result, the effective potency of these drugs for blocking impulses increases during high-frequency repetitive firing and also under slow depolarization, such as occurs at a region of nerve injury, which is often the locus for generation of abnormal, pain-related ectopic impulses. At distal and central terminals the inhibition of voltage-gated calcium channels by local anesthetics will suppress neurogenic inflammation and the release of neurotransmitters. Actions on receptors that contribute to nociceptive transduction, such as TRPV1 and the bradykinin B2 receptor, provide an independent mode of analgesia. In the spinal cord, where local anesthetics are present during epidural or intrathecal anesthesia, inhibition of inotropic receptors, such as those for glutamate, by local anesthetics further interferes with neuronal transmission. Activation of spinal cord mitogen-activated protein (MAP) kinases, which are essential for the hyperalgesia following injury or incision and occur in both neurons and glia, is inhibited by spinal local anesthetics. Many G protein-coupled receptors are susceptible to local anesthetics, with particular sensitivity of those coupled via the Gq alpha-subunit. Local anesthetics are also infused intravenously to yield plasma concentrations far below those that block normal action potentials, yet that are frequently effective at reversing neuropathic pain. Thus, local anesthetics modify a variety of neuronal membrane channels and receptors, leading to what is probably a synergistic mixture of analgesic mechanisms to achieve effective clinical analgesia.

Peripheral Nerve Blocks and Continuous Catheter Techniques

Peripheral nerve blocks provide intense, site-specific analgesia and are associated with a lower incidence of side effects when compared with many other modalities of postoperative analgesia. Continuous catheter techniques further prolong these benefits. These advantages can facilitate a prompt recovery and discharge and achieve significant perioperative cost savings. This is of tremendous value in a modern health care system that stresses cost-effective use of resources and a continued shift toward shorter hospital stay as well as outpatient surgery.

Regional anaesthesia in ambulatory surgery

PURPOSE OF REVIEW

The purpose of this review is to present recent research into the clinical use of regional anaesthesia techniques in ambulatory surgery. Further, to put into an ambulatory perspective some of the issues recently discussed on the basis and practice of regional anaesthesia in general.

RECENT FINDINGS

Early discharge with long-acting peripheral nerve blockade seems safe, and discharge of patients who have not voided after surgery is possible under specified terms. The spinal anaesthesia technique may be improved in terms of better and faster recovery characteristics if the dose of local anaesthesia is reduced by adding a small dose of opioid.

SUMMARY

Loco-regional techniques are well suited for ambulatory surgery due to less postoperative nausea and pain and possibly less cognitive dysfunction. The different techniques are continuously being refined in order to provide fast discharge readiness, while still maintaining the benefits.