Ropivacaine myotoxicity after single intramuscular injection in rats

Subfascial infiltration of 0.5% ropivacaine, but not 0.25% ropivacaine, exacerbates damage and inflammation in surgically incised abdominal muscles of rats

Ropivacaine-induced myotoxicity in surgically incised muscles has not been fully investigated. We evaluated the effects of infiltration anesthesia with ropivacaine on damage, inflammation and regeneration in the incised muscles of rats undergoing laparotomy. Ropivacaine or saline was infiltrated below the muscle fascia over the incised muscles. Pain-related behaviors and histological muscle damage were assessed. Macrophage infiltration at days 2 and 5 and proliferation of satellite cells at day 5 were detected by CD68 and MyoD immunostaining, respectively. Pain-related behaviors were inhibited by 0.25% and 0.5% of ropivacaine for 2 h after surgery. Single infiltration of 0.5% ropivacaine did not induce injury in intact muscles without incision, but single and repeated infiltration of 0.5% ropivacaine significantly augmented laparotomy-induced muscle injury and increased the numbers of CD68-positve macrophages and MyoD-positive cells compared to those in rats with infiltration of saline or 0.25% ropivacaine. In contrast, there were no significant differences in them between rats with saline infusion and rats with 0.25% ropivacaine infiltration. In conclusion, single or repeated subfascial infiltration of 0.25% ropivacaine can be used without exacerbating the damage and inflammation in surgically incised muscles, but the use of 0.5% ropivacaine may be a concern because of potentially increased muscle damage.

An injectable mesoporous silica-based analgesic delivery system prolongs the duration of sciatic nerve block in mice with minimal toxicity

The major limitation of traditional local anesthetics is the finite duration of a single injection. The present study developed two kinds of novel injectable anesthetic nanocomposites based on mesoporous silica, and evaluated their long-lasting analgesic effect and biosafety. The nanoparticulate carriers, mesoporous silica nanoparticles (MSNs) and mesoporous silica-coated gold nanorods (GNR@MSN), were firstly constructed using the oil-water biphase reaction approach and then ropivacaine (RPC), a local anesthetic, was loaded into the mesoporous carriers by vacuum suction. Transmission electron microscopic images showed the well-ordered mesoporous structure for drug loading. RPC-loaded MSNs and RPC-loaded GNR@MSN exhibited a sustained-release pattern in vitro, and the latter also showed a controlled-release manner triggered by near-infrared (NIR) irradiation. RPC-loaded MSNs and RPC-loaded GNR@MSN caused an initial sensory blockade in mice that lasted for 6 h, almost 2.5 folds of that from free RPC solution. Furthermore, upon NIR irradiation, the latter induced three additional periods of the blockade. Neither of them showed motor nerve block, which may be due to the sustained release manner. The low myotoxicity and low neurotoxicity of the two nanocomposites were presented both in vitro and in vivo. These results demonstrate the potential of the mesoporous silica-based analgesic nanocomposites in effectively controlling postoperative pain, maybe RPC-loaded MSNs for moderate pain and RPC-loaded GNR@MSN for severe pain. STATEMENT OF SIGNIFICANCE: Adequate postoperative analgesia helps early functional exercise after surgery and accelerates rapid recovery, while uncontrolled postoperative pain probably develops chronic post-surgical pain that impacts the life quality of patients for a long time. However, postoperative pain management is still a challenge. The current treatment drugs are always accompanied by some side effects due to their systemic effect. Opioids have risks of addiction and respiratory depression, and nonsteroidal anti-inflammatory drugs can lead to gastrointestinal reaction. Therefore, the long-lasting local anesthetic formulation with good biocompatibility is the most promising solution to manage post-surgical pain. The present study developed novel injectable anesthetic nanocomposites based on mesoporous silica, providing long-lasting pain relief in mice with minimal toxicity.

Change in muscle hardness after trigger point injection and physiotherapy for myofascial pain syndrome

Assessment and treatment of masticatory myofascial pain syndrome (MPS) are not standardized and remain controversial. We examined whether muscle hardness was useful for evaluating masticatory MPS and analyzed the effectiveness of treatments such as stretching and massage (SM) and trigger point injection (TPI). Twenty healthy volunteers and 20 MPS patients were enrolled. MPS patients were divided into TPI and SM treatment groups. Hardness of masticatory muscle with a taut band (TB) and change in hardness were evaluated after SM and TPI treatments. Hardness values were significantly higher in muscle including a TB (TB point) than in the muscle of healthy controls. Visual analogue scale scores were significantly lower after SM and TPI treatments, and hardness of the TB point was significantly lower after SM but not after TPI. These results suggest that measurement of muscle hardness, including the TB, is useful for evaluating masticatory MPS. However, TPI analgesia might not be caused by change in muscle hardness. The mechanisms underlying the effects of SM and TPI on reducing pain in MPS may differ and thus warrant further research.

The chondrotoxic and apoptotic effects of levobupivacaine and bupivacaine on the rabbit knee joint

Background

A single dose injection or continuous infusion of local anesthetics into the joint space is considered to be a well-defined analgesia technique. The aim of this study was to investigate the chondrotoxic and apoptotic effects of single-dose intra-articular injection of levobupivacaine and bupivacaine on rabbit knee joint tissues.

Materials and methods

The animals were allocated into two groups each containing 20 rabbits. 0.5% levobupivacaine (Group L) and 0.5% bupivacaine (Group B) were applied intra-articularly to the left posterior joints of rabbits. At the same time, normal saline was applied to the right posterior leg knee joints of rabbits in both groups and used as a control (Group S). At the end of the 7th and 28th days after the intraarticular injections, ten randomly chosen rabbits in each group were killed by applying intraperitoneal thiopental. Sections of cartilage tissue samples were stained for light microscopic examinations and the TUNEL method was used to investigate apoptotic cells.

Results

As a result of immunofluorescence microscopic examination, the number of apoptotic cells in Group B at day 7 and day 28 were both significantly higher than Group L and S (p < 0.05). Also, the number of apoptotic cells in Group L at day 7 and day 28 were both significantly higher than Group S (p < 0.05).

Conclusions

We found that bupivacaine is more chondrotoxic than other anesthetic agent and increases the number of apoptotic cells. These results indicated that bupivacaine caused high chondrotoxic damage and it led to more apoptotic activation than levobupivacaine.

Subacromial Local Anesthetics Do Not Interfere With Rotator Cuff Healing After Arthroscopic Repair

BACKGROUND

Subacromial pain pumps are used for analgesia after arthroscopic rotator cuff surgery. However, there is controversy about myotoxic or tendinotoxic effects of local anesthetics.

HYPOTHESIS

Ropivacaine administered via a subacromial pain pump would have no adverse effect on rotator cuff tendon healing, fatty degeneration, strength, or functional outcomes after arthroscopic repair.

STUDY DESIGN

Cohort study; Level of evidence, 3.

METHODS

This study continues follow-up of patients enrolled in the authors' 3 published prospective studies regarding pain control after arthroscopic rotator cuff repair. In total, 118 patients who underwent rotator cuff repair and returned for evaluation at least 1 year postoperatively were divided into 3 groups: patients who received continuous subacromial ropivacaine infusion (group 1, n = 33), those who received patient-controlled subacromial ropivacaine infusion (group 2, n = 30), and those who received other pain control modalities (intravenous patient-controlled analgesia and/or interscalene block; group 3, n = 55). At least 1 year postoperatively, tendon healing and changes in global fatty degeneration index (GFDI) were estimated through computed tomographic arthrography, magnetic resonance imaging, or ultrasonography. Changes in isokinetic muscle performance test (IMPT) were calculated and functional outcomes evaluated, including visual analog scales (VASs) for pain and satisfaction, American Shoulder and Elbow Surgeons score, and Constant score.

RESULTS

At final follow-up, there were no differences in pain VAS (group 1, 1.1 ± 2.3; group 2, 1.3 ± 1.9; group 3, 0.9 ± 1.7; P = .88), satisfaction VAS (group 1, 8.3 ± 2.4; group 2, 8.7 ± 1.5; group 3, 8.0 ± 2.1; P = .64), American Shoulder and Elbow Surgeons score (group 1, 79.5 ± 10.5; group 2, 81.1 ± 6.9; group 3, 75.7 ± 7.6; P = .34), or Constant score (group 1, 81.8 ± 8.7; group 2, 77.6 ± 9.3; group 3, 78.2 ± 8.4; P = .31). Among the 3 groups, there were no significant differences in healing rates (group 1, 72.7%; group 2, 73.3%; group 3, 70.9%; P = .83) and no differences in changes of GFDI (group 1, 0.45; group 2, 0.62; group 3, 0.41; P = .79), and IMPT (abduction: group 1, 113.0%; group 2, 121.5%; group 3, 120.1%; P = .73; external rotation: group 1, 112.1%; group 2, 121.6%; group 3, 111.7%; P = .71; internal rotation: group 1, 118.2%; group 2, 118.0%; group 3, 118.1%; P = .95). When data were reanalyzed with 2 groups (group 1 + 2 vs group 3), there were no significant differences in functional scores, healing rates, or changes in GFDI and IMPT ( P > .05).

CONCLUSION

Current data suggest that myotoxicity of subacromial ropivacaine administered via pain pump may be reversible or may not be so severe as to interfere with tendon healing and cause muscle degeneration and thus may not affect postoperative function.

Effect of bloodletting therapy at local myofascial trigger points and acupuncture at Jiaji (EX-B 2) points on upper back myofascial pain syndrome: a randomized controlled trial

OBJECTIVE

To observe the clinical efficacy of bloodletting therapy and acupuncture at Jiaji points for treating upper back myofascial pain syndrome (MPS), and compare this with lidocaine block therapy.

METHODS

A total of 66 upper back MPS patients were randomly assigned to either the treatment group or the control group in a 1: 1 ratio. The treatment group (n = 33) were treated with bloodletting therapy at local myofascial trigger points and acupuncture at Jiaji (EX-B 2) points; one treatment course consisted of five, single 20-min-treatments with a 2-day break between each treatment. The control group (n = 33) were treated with a lidocaine block at trigger points; one treatment course consisted of five sessions of lidocaine block therapy with a 2-day break between each session. The simplified McGill Scale (SF-MPQ) and tenderness threshold determination were used to assess pain before and after a course of treatment.

RESULTS

After the third and fifth treatment, the SF-MPQ values were significantly decreased (P < 0.01) and the tenderness thresholds were significantly increased (P < 0.01) in both groups compared with before treatment. There were no significant differences in pain assessments between the two groups after three and five treatments (P > 0.05). There were five cases with minor adverse reactions reported in the control patients, while no adverse reactions were reported in the treatment group.

CONCLUSION

Bloodletting therapy at local myofascial trigger points and acupuncture at Jiaji points was effective in treating upper back MPS. Clinically, bloodletting and acupuncture therapy had the same efficacy as the lidocaine block therapy, with fewer adverse reactions.

Pathophysiology and Etiology of Nerve Injury Following Peripheral Nerve Blockade

This review synthesizes anatomical, anesthetic, surgical, and patient factors that may contribute to neurologic complications associated with peripheral nerve blockade. Peripheral nerves have anatomical features unique to a given location that may influence risk of injury. Peripheral nerve blockade-related peripheral nerve injury (PNI) is most severe with intrafascicular injection. Surgery and its associated requirements such as positioning and tourniquet have specific risks. Patients with preexisting neuropathy may be at an increased risk of postoperative neurologic dysfunction. Distinguishing potential causes of PNI require clinical assessment and investigation; a definitive diagnosis, however, is not always possible. Fortunately, most postoperative neurologic dysfunction appears to resolve with time, and the incidence of serious long-term nerve injury directly attributable to peripheral nerve blockade is relatively uncommon. Nonetheless, despite the use of ultrasound guidance, the risk of block-related PNI remains unchanged.

WHAT'S NEW

Since the 2008 Practice Advisory, new information has been published, furthering our understanding of the microanatomy of peripheral nerves, mechanisms of peripheral nerve injection injury, toxicity of local anesthetics, the etiology of and monitoring methods, and technologies that may decrease the risk of nerve block-related peripheral nerve injury.

Time course of mitochondrial metabolism alterations to repeated injections of bupivacaine in rat muscle

PURPOSE

Bupivacaine-induced myotoxicity is associated with mitochondrial bioenergetic alterations. The impact of the duration of bupivacaine treatment on mitochondrial energy production remains undetermined. Here, we assessed, in vivo, the alteration of mitochondrial metabolism following different durations of bupivacaine exposure (40, 56, or 112 hr) that correspond to 5, 7, or 14 repeated injections of 0.25% bupivacaine, respectively.

METHODS

Rats were divided randomly into seven different groups: one control group (no catheter); three groups with normal saline injections (1 mL x kg(-1)) every eight hours via a femoral nerve catheter for 40, 56, and 112 hr, respectively; and three groups with 0.25% bupivacaine injections (1 mL x kg(-1)) every eight hours via a femoral nerve catheter for 40, 56, and 112 hr. Psoas and gracilis muscle samples located within the bupivacaine infusion-diffusion space were investigated. To estimate mitochondrial respiratory capacity, the protein content of the mitochondrial respiratory chain apparatus was evaluated by measuring citrate synthase activity. To measure mitochondrial respiratory function, adenosine diphosphate-stimulated oxygen consumption was measured by polarography in saponin-skinned muscle fibres using glutamate-malate or succinate as energy substrates.

RESULTS

In psoas and gracilis muscles, saline solution had no effect on the two mitochondrial parameters. Bupivacaine induced a significant decrease in the citrate synthase activity in psoas (r(2) = 0.74; P < 0.001) and gracilis muscle (r(2) = 0.52; P < 0.001), and there was a significant decrease in the adenosine diphosphate-stimulated oxygen consumption using glutamate or succinate as substrates in both muscles (P < 0.001).

CONCLUSIONS

The severity of bupivacaine-induced myotoxicity is closely linked to the duration of bupivacaine exposure in the muscle fibres located close to the catheter tip.

Safety of amide local anesthetics: new trends

IMPORTANCE OF THE FIELD

Local anesthetics have become one of the most common drugs used in daily practice worldwide. Neurologic and cardiovascular events are the most frequent adverse reactions related to local anesthetics use. Recently, new trends have been developed on this topic.

AREAS COVERED IN THIS REVIEW

We performed an overview of the data available so far on local anesthetics adverse reactions. Relevant literature was identified using PubMed search of articles published up to November 2009, including experimental studies, case reports or clinical studies when available. Search terms included: 'local anaesthetics', 'adverse drug reaction', 'pharmacovigilance' and 'complication'.

WHAT THE READER WILL GAIN

Neurologic, cardiovascular and allergic reactions remain the most frequent adverse drug reactions related to local anesthetics in the literature. Studies based on pharmacovigilance systems have highlighted the frequency of adverse reactions little known until now, such as failure of block. Lipid emulsions are included into algorithm for cardiac resuscitation. Recent studies have demonstrated the myotoxicity and chondrotoxic effects of long-acting local anesthetics.

TAKE HOME MESSAGE

Physicians must keep in mind all these adverse reactions to better prevent their occurrence and give the most appropriate treatment.

Pharmacological and local toxicity studies of a liposomal formulation for the novel local anaesthetic ropivacaine

This study reports an investigation of the pharmacological activity, cytotoxicity and local effects of a liposomal formulation of the novel local anaesthetic ropivacaine (RVC) compared with its plain solution. RVC was encapsulated into large unilamellar vesicles (LUVs) composed of egg phosphatidylcholine, cholesterol and α-tocopherol (4:3:0.07, mole%). Particle size, partition coefficient determination and in-vitro release studies were used to characterize the encapsulation process. Cytotoxicity was evaluated by the tetrazolium reduction test using sciatic nerve Schwann cells in culture. Local anaesthetic activity was assessed by mouse sciatic and rat infraorbital nerve blockades. Histological analysis was performed to verify the myotoxic effects evoked by RVC formulations. Plain (RVCPLAIN) and liposomal RVC (RVCLUV) samples were tested at 0.125%, 0.25% and 0.5% concentrations. Vesicle size distribution showed liposomal populations of 370 and 130 nm (85 and 15%, respectively), without changes after RVC encapsulation. The partition coefficient value was 132 ± 26 and in-vitro release assays revealed a decrease in RVC release rate (1.5 fold, P &lt; 0.001) from liposomes. RVCLUV presented reduced cytotoxicity (P &lt; 0.001) when compared with RVCPLAIN. Treatment with RVCLUV increased the duration (P &lt; 0.001) and intensity of the analgesic effects either on sciatic nerve blockade (1.4–1.6 fold) and infraorbital nerve blockade tests (1.5 fold), in relation to RVCPLAIN. Regarding histological analysis, no morphological tissue changes were detected in the area of injection and sparse inflammatory cells were observed in only one of the animals treated with RVCPLAIN or RVCluv at 0.5%. Despite the differences between these preclinical studies and clinical conditions, we suggest RVCLUV as a potential new formulation, since RVC is a new and safe local anaesthetic agent.

Acupuncture needling versus lidocaine injection of trigger points in myofascial pain syndrome in elderly patients--a randomised trial

AIM

To compare the efficacy of acupuncture needling and 0.5% lidocaine injection of trigger points in myofascial pain syndrome of elderly patients.

METHODS

Thirty nine participants with myofascial pain syndrome of one or both upper trapezius muscles were randomised to treatment with either acupuncture needling (n=18) or 0.5% lidocaine injection (n=21) at all the trigger points on days 0, 7 and 14, in a single-blinded study. Pain scores, range of neck movement, pressure pain intensity and depression were measured up to four weeks from the first treatment.

RESULTS

Local twitch responses were elicited at least once in 94.9% of all subjects. Both groups improved, but there was no significant difference in reduction of pain in the two groups at any time point up to one month. Overall, the range of cervical movement improved in both groups, apart from extension in the acupuncture needling group. Changes in depression showed only trends.

CONCLUSION

There was no significant difference between acupuncture needling and 0.5% lidocaine injection of trigger points for treating myofascial pain syndrome in elderly patients.