The acute toxicity of local anesthetics

The optimal concentration of ropivacaine for transversus abdominis plane blocks in elective cesarean section: A protocol for systematic review and meta-analysis

INTRODUCTION

Transversus abdominis plane (TAP) blocks are commonly performed for postoperative analgesia in elective cesarean section. Ropivacaine is the most commonly used local anesthetic for TAP blocks. Currently, the concentration of ropivacaine for TAP blocks is various, and increasing number of randomized controlled trials (RCTs) have compared the effects of different concentration of ropivacaine for TAP blocks in cesarean section. This protocol of a systematic review and meta-analysis aims to identify the optimal concentration of ropivacaine for TAP blocks in elective cesarean section.

METHODS AND ANALYSIS

Databases including PubMed, Web of science, the Cochrane library, and EMBASE will be searched from their inception to May 1, 2024. RCTs that investigated the analgesia of different concentrations of ropivacaine for TAP blocks in elective cesarean section will be identified. The analgesia duration will be the primary outcome. Secondary outcomes will include the analgesics consumption over postoperative 24 hours, postoperative pain scores at rest and movement, and the incidence of adverse effects. RevMan 5.4 software will used for statistical analysis. The evidence quality of synthesized results will be evaluated by the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) approach.

ETHICS AND DISSEMINATION

Ethical approval is not applicable. The results of this study will be published on completion.

TRIAL REGISTRATION

PROSPERO registration number: CRD42024496907.

When Regional Anesthesia Met Pharmacokinetics

Pharmacokinetics of Local Anaesthetic Agents. By Tucker GT, Mather LE. Br J Anaesth 1975; 47(suppl 1):213-24 Information derived from measurements of blood concentrations of local anaesthetics can be extended by the application of pharmacokinetic analysis. A better understanding of quantitative aspects of the disposition and absorption of these drugs should assist the anaesthetist in deciding the optimal agent and dosage for regional block techniques.

Ropivacaine-Loaded Poloxamer Binary Hydrogels for Prolonged Regional Anesthesia: Structural Aspects, Biocompatibility, and Pharmacological Evaluation

This study reports the development of thermosensitive hydrogels for delivering ropivacaine (RVC), a wide clinically used local anesthetic. For this purpose, poloxamer- (PL-) based hydrogels were synthesized for evaluating the influence of polymer concentration, hydrophilic-lipophilic balances, and binary system formation on biopharmaceutical properties and pharmacological performance. Transition temperatures were shifted, and rheological analysis revealed a viscoelastic behavior with enhanced elastic/viscous modulus relationship (G'/G " = 1.8 to 22 times), according to hydrogel composition and RVC incorporation. The RVC release from PL407 and PL407/338 systems followed the Higuchi model (R 2 = 0.923-0.989), indicating the drug diffusion from hydrogels to the medium. RVC-PL hydrogels were potentially biocompatible evoking low cytotoxic effects (in fibroblasts and Schwann cells) and mild/moderate inflammation signs on sciatic nerve nearby histological evaluation. In vivo pharmacological assays demonstrated that PL407 and PL407/338 evoked differential analgesic effects, by prolonging the sensory blockade duration up to ~340 and 250 min., respectively. All those results highlighted PL407 and PL407/338 as promising new strategies for sustaining analgesic effects during the postoperative period.

Topical Application of Lidocaine and Bupivacaine to Disbudding Wounds in Dairy Calves: Safety, Toxicology and Wound Healing

Simple Summary

Disbudding is a common, but painful procedure performed on calves to prevent horn growth. Tri-Solfen^® is a combination local anaesthetic and antiseptic formulation which, applied topically to the disbudding wound, is reported to reduce calf pain. Applied in this manner, the local anaesthetics in Tri-Solfen^®, lidocaine and bupivacaine, are reported to be poorly absorbed, resulting in low risk of neurological or cardiotoxic effects. The potential impacts on other blood, urine and tissue parameters and on wound healing when used in this manner, and/or accidental overdose situations are unknown, however. We performed experiments investigating (i) the safety of Tri-Solfen^® (including overdose situations) and (ii) the impact of Tri-Solfen^® on disbudding wound healing under field conditions. No adverse health effects were observed in Tri-Solfen^®-treated animals, even those receiving 5× the recommended dose, with no clinically significant differences in measured parameters between placebo and Tri-Solfen^® groups. No negative impacts on wound healing were noted. Conversely, lower levels of bacterial wound colonisation were evident, and there was reduced incidence of abnormal wounds at days 11–12 in Tri-Solfen^®-treated animals.

Abstract

Tri-Solfen^® is a combination topical anaesthetic and antiseptic solution containing lidocaine, bupivacaine, adrenaline and cetrimide. Applied to wounds, it is reported to reduce the pain experienced by calves following thermocautery disbudding. While lidocaine and bupivacaine are widely used in medicine, conflicting data exist on the impact of these compounds when applied directly to the surgical wound. To investigate the safety of Tri-Solfen^® applied to thermocautery disbudding wounds of calves, experiments were performed to measure (i) the safety of Tri-Solfen^® (including in overdose situations); and (ii) the impact of Tri-Solfen^® application at recommended doses on disbudding wound healing under field conditions. Haematological, biochemical and urinalysis parameters did not show clinically significant differences between placebo and Tri-Solfen^® groups (1×, 3× and 5× dose). No adverse health impacts were reported. Histopathological analysis of wounds noted a reduction in bacterial colonies in Tri-Solfen^®-treated wounds. Under field conditions, no negative impacts on wound healing were noted. Conversely, there was reduced incidence of abnormal wounds, with an associated trend toward improved average daily gain at days 11–12 in Tri-Solfen^®-treated animals. These data are considered to support the safety of topical anaesthesia, as formulated in Tri-Solfen^®, to the thermocautery disbudding wound in calves.

Comparison of periarticular multidrug infiltration and epidural catheter use in total knee arthroplasty: A prospective randomized controlled study

PURPOSE

The purpose of this study was to assess the effectiveness of periarticular multidrug infiltration (PMDI) and compare it with that of epidural catheter use.

METHODS

Fifty-eight patients (58 joints) who underwent total knee arthroplasty were included in this single-center, prospective, parallel, randomized, controlled trial. Preoperatively, patients were randomly categorized into the PMDI and epidural catheter groups. We evaluated postoperative pain (visual analog scale (VAS) and narcotic consumption), functional outcomes (range of motion (ROM) of knee flexion, the day patients could perform the straight-leg raising (SLR) test, and day of starting cane use), and laboratory data (white blood cell (WBC) and C-reactive protein (CRP)).

RESULTS

There was no significant difference in the VAS score, ROM of knee flexion, the day patients could do SLR, and the day of starting cane use between the PMDI and epidural catheter groups. However, the PMDI group could perform SLR on a postoperative day (POD) 1 (p < 0.05). WBC level on POD 1 was significantly higher in the PMDI group (p < 0.05), whereas the CRP levels on POD 1 (p < 0.01), 3 (p < 0.01), and 5 (p < 0.01) were significantly lower in the PMDI group than in the epidural catheter group. The frequency of side effects was not significantly different between the groups.

CONCLUSION

PMDI was as effective as epidural catheter use for pain control. A higher percentage of patients who underwent PMDI could perform SLR on POD 1; therefore, the functional recovery was earlier in the PMDI group than in the epidural catheter group. PMDI may suppress inflammation in the whole body because of steroids.

Propofol protects human cardiac cells against chemical hypoxiainduced injury by regulating the JNK signaling pathways

Propofol is a widely used intravenous anesthetic shown to exert a cardioprotective role against oxidative stress and ischemia/reperfusion injury in rat cardiac H9c2 cells. However, the regulatory mechanisms and functions of propofol in human cardiomyocytes remain unknown. The present study chemically induced hypoxia with cobalt chloride (CoCl₂) to mimic cardiomyocyte ischemic injury in human cardiac AC16 and HCM cells. To investigate its underlying mechanisms, propofol was added to the cells before the chemical hypoxia phase. The present results suggested that, in response to hypoxia, mitochondrial membrane potential was lost, and cardiomyocyte viability and superoxide dismutase levels decreased. However, the present results showed that reactive oxygen species and malondialdehyde levels increased. The present results suggested that these effects were significantly reversed following propofol treatment. Additionally, the present results suggested that the protective effect of propofol against CoCl₂-induced injury may be inhibited by the activation of the JNK signaling pathways. The present results indicated that propofol pre-treatment inhibited CoCl₂-induced myocardial injury by preventing mitochondrial dysfunction, which may be partially due to the activation of the JNK signaling pathways. Therefore, propofol may exert anti-oxidative effects in human cardiac cells. The present results suggested that propofol may be used as a treatment for oxidative stress-related cardiac disorders.

Lipid-based carriers for the delivery of local anesthetics

INTRODUCTION

There is a clinical need for pharmaceutical dosage forms devised to prolong the acting time of local anesthetic (LA) agents or to reduce their toxicity. Encapsulation of LA in drug delivery systems (DDSs) can provide long-term anesthesia for inpatients (e.g. in immediate postsurgical pain control, avoiding the side effects from systemic analgesia) and diminished systemic toxicity for outpatients (in ambulatory/dentistry procedures). The lipid-based formulations described here, such as liposomes, microemulsions, and lipid nanoparticles, have provided several nanotechnological advances and therapeutic alternatives despite some inherent limitations associated with the fabrication processes, costs, and preclinical evaluation models.

AREAS COVERED

A description of the currently promising lipid-based carriers, including liposomes, microemulsions, and nanostructured lipid carriers, followed by a systematic review of the existing lipid-based formulations proposed for LA. Trends in the research of these LA-in-DDS are then exposed, from the point of view of administration route and alternatives for non-traditionally administered LA molecules.

EXPERT OPINION

Considering the current state and potential future developments in the field, we discuss the reasons for why dozens of formulations published every year fail to reach clinical trials; only one lipid-based formulation for the delivery of local anesthetic (Exparel®) has been approved so far.

Capsazepine prolongation of the duration of lidocaine block of sensory transmission in mice may be mediated by modulation of HCN channel currents

Background and objectives

Hyperpolarization-activation cyclic nucleotide-gated (HCN) channels contribute to the effects of lidocaine. Capsazepine (CPZ), a competitive inhibitor of capsaicin of transient receptor potential vanilloid-1 channel, has also been found to inhibit HCN channel currents (I _h). This study was designed to investigate whether CPZ could prolong durations of lidocaine in regional anesthesia.

Methods

Mouse HCN1 and HCN2 channels were expressed in human embryonic kidney 293 (HEK 293) cells. The effect of CPZ on I _h was measured by whole-cell patch-clamping recording. Sciatic nerve block model in mice was used for the study in vivo. The mice were randomly divided into seven groups, respectively, receiving lidocaine, CPZ, ZD7288 (HCN channel blocker), CPZ + lidocaine, ZD7288 + lidocaine, ZD7288 + CPZ + lidocaine, forskolin (an activator of adenylyl cyclase) + CPZ + lidocaine. Regional anesthetic durations of lidocaine were determined. Voltage-gated sodium channel currents (I _Na) and I _h were recorded in dorsal root ganglion neurons of mice. The effects of CPZ on I _Na and I _h with or without Cyclic adenosine monophosphate (cAMP) were assessed. Isolated mice sciatic nerve was prepared to evaluate the effect of CPZ on the compound action potentials (CAP).

Results

Capsazepine non-selectively inhibited transfected mHCN1 and mHCN2 channel currents in HEK 293 cells. In sciatic nerve block in vivo, compared to lidocaine alone, adding CPZ extended the durations of lidocaine for noxious sensory block (35.1 ± 3.3 vs. 20.3 ± 1.7 min), tactile sensory block (25.5 ± 4.4 vs. 20.0 ± 3.7 min), thermal sensory block (39.6 ± 6.6 vs. 26.8 ± 5.5 min), and motor function block (28.6 ± 4.1 vs. 20.9 ± 4.2 min). Duration of thermal sensory block was longer in CPZ + lidocaine group than that of ZD7288 + lidocaine group (39.6 ± 6.6 vs. 33.4 ± 4.5 min). Forskolin reversed the prolongation by CPZ on lidocaine durations. CPZ or ZD7288 alone did not produce typical regional anesthetic effects. Increased intracellular concentration of cAMP reversed the inhibition of CPZ on I _h. Although CPZ alone inhibited I _Na at the concentration more than 30 μM, it did not inhibit the CAP amplitudes in isolated sciatic nerves. CPZ dose-dependently enhanced the inhibitory effect of 1% lidocaine on the CAP amplitudes.

Conclusions

Capsazepine may prolong durations of lidocaine in peripheral nerve block by modulation of HCN channel currents.

A 96-hour continuous wound infiltration with ropivacaine reduces analgesic consumption after liver resection: A randomized, double-blind, controlled trial

BACKGROUND

Continuous wound infiltration (CWI) with local anesthetics to reduce morphine consumption in postoperative pain management after open liver resection in patients with cancer.

METHODS

This single-center randomized double-blind study allocated patients requiring resection of liver metastases to receive a 3.75 mg/mL ropivacaine (ROP) infiltration, followed by a 2 mg/mL ROP CWI, or placebo (P) for 96 hours. Postoperative analgesia included acetaminophen and patient-controlled analgesia morphine pump. The primary endpoint was to investigate the reduction of total morphine consumption (mg/kg) over the first 96 postoperative hours.

RESULTS

Eighty-five patients were recruited, and randomized (ROP: 42, P: 43) between 2009 and 2014. The median morphine consumption significantly decreased in the ROP arm in the first 96 postoperative hours (ROP: 1.0, P: 1.5 mg/kg; P = 0.026). Twenty-three (27%) patients had grade 3 adverse events (ROP: 14, P: 9) and four experienced grade 3 treatment-related adverse events (ROP: mental confusion [n = 1], hallucinations [n = 2], P: hematoma [n = 1]). Two (5%) patients showed a wound inflammation (ROP: 1, P: 1). Nine (11%) patients experienced at least one serious adverse event (ROP: 6, P: 3); none related to treatment.

CONCLUSION

Preperitoneal CWI of 2 mg/mL ROP significantly reduces intravenous morphine consumption during the 96 postoperative hours resulting in an absolute reduction of 0.5 mg/kg.

Ropivacaine regulates the expression and function of heme oxygenase-1

As a new generation of amide-type local anesthetics (LAs), ropivacaine has been widely used for pain management in clinical settings. Increasing evidence has shown that administration of ropivacaine causes cytotoxic effects and apoptosis. However, the underlying molecular mechanisms still need to be elucidated. In the current study, our results indicated that ropivacaine treatment caused a significant induction of heme oxygenase-1 (HO-1) at both the mRNA and protein levels in human SHSY5Y cells. Levels of HO-1 mRNA and protein peaked at 1 h and 18 h, respectively, in response to ropivacaine treatment. Additionally, ropivacaine treatment enhanced HO-1 activity in a dose-dependent manner. Interestingly, we found that ropivacaine treatment induced phosphorylation of p38. Blockage of p38 phosphorylation with its specific inhibitor SB203580 or by transfection with p38 siRNA restrained ropivacaine-stimulated HO-1 expression. Additionally, we found that ropivacaine treatment promoted nuclear translocation of Nrf2 and amplified ARE promoter activity. Silencing of Nrf2 abolished ropivacaine-induced HO-1 expression. Notably, we found that inhibition of HO-1 activity promoted ropivacaine-induced production of reactive oxygen species (ROS), deletion of reduced glutathione (GSH), and release of lactate dehydrogenase (LDH), suggesting that induction of HO-1 by ropivacaine acted as a compensatory survival response against ropivacaine.

Low-level laser therapy (LLLT) accelerates the sternomastoid muscle regeneration process after myonecrosis due to bupivacaine

BACKGROUND

Because of its long-lasting analgesic action, bupivacaine is an anesthetic used for peripheral nerve block and relief of postoperative pain. Muscle degeneration and neurotoxicity are its main limitations. There is strong evidence that low-level laser therapy (LLLT) assists in muscle and nerve repair. The authors evaluated the effects of a Gallium Arsenide laser (GaAs), on the regeneration of muscle fibers of the sternomastoid muscle and accessory nerve after injection of bupivacaine.

METHODS

In total, 30 Wistar adult rats were divided into 2 groups: control group (C: n=15) and laser group (L: n=15). The groups were subdivided by antimere, with 0.5% bupivacaine injected on the right and 0.9% sodium chloride on the left. LLLT (GaAs 904nm, 0,05W, 2.8J per point) was administered for 5 consecutive days, starting 24h after injection of the solutions. Seven days after the trial period, blood samples were collected for determination of creatine kinase (CK). The sternomastoid nerve was removed for morphological and morphometric analyses; the surface portion of the sternomastoid muscle was used for histopathological and ultrastructural analyses. Muscle CK and TNFα protein levels were measured.

RESULTS

The anesthetic promoted myonecrosis and increased muscle CK without neurotoxic effects. The LLLT reduced myonecrosis, characterized by a decrease in muscle CK levels, inflammation, necrosis, and atrophy, as well as the number of central nuclei in the muscle fibers and the percentage of collagen. TNFα values remained constant.

CONCLUSIONS

LLLT, at the dose used, reduced fibrosis and myonecrosis in the sternomastoid muscle triggered by bupivacaine, accelerating the muscle regeneration process.

Comparison of local infiltration and epidural analgesia for postoperative pain control in total knee arthroplasty and total hip arthroplasty: A systematic review and meta-analysis

Pain management after total knee arthroplasty (TKA) and total hip arthroplasty should permit early mobilization with minimal pain. Local infiltration analgesia (LIA) is a new popular method for decreasing postoperative pain. The goal of this meta-analysis is to evaluate the efficacy of LIA in comparison with epidural analgesia. A literature search was performed in PubMed, EMBASE, the OVID database, Web of Science, and the Cochrane Library databases. The risk of bias was assessed using the Cochrane collaboration tool. Outcomes of interest included visual analog scale score, range of flexion, length of stay, and complications. Nine trials involving 537 patients met the inclusion criteria. LIA provides better pain relief and larger range of motion in TKA patients compared to epidural analgesia at the late postoperative period. No significant difference was observed in regard to the length of stay and complications. The current evidence shows that the use of local infiltration is effective for postoperative pain management in TKA patients. More high-quality randomized controlled trials with long-term follow-up are required for examining the long-term efficacy and safety of local infiltration.

Electrophysiological, haemodynamic, and mitochondrial alterations induced by levobupivacaine during myocardial ischemia in a pig model: protection by lipid emulsions?

Accidental intravascular or high-dose injection of local anesthetics (LA) can result in serious, potentially life-threatening complications. Indeed, adequate supportive measures and the administration of lipid emulsions are required in such complications. The study's objectives were threefold: (i) evaluate the myocardial toxicity of levobupivacaine when administered intravenously; (ii) investigate levobupivacaine toxicity on cardiomyocytes mitochondrial functions and cellular structure; (iii) assess the protective effects of a lipid emulsion in the presence or absence of myocardial ischemia. Domestic pigs randomized into two groups of 24 animals each, with either preserved coronary circulation or experimental myocardial ischemia. Six animals from each group received either: (i) single IV injection of saline, (ii) lipid emulsion (Intralipid(®) ), (iii) levobupivacaine, (iv) combination levobupivacaine-Intralipid(®) . Serially measured endpoints included: heart rate, duration of the monophasic action potentials (dMAP), mean arterial pressure, and peak of the time derivative of left ventricular pressure (LV dP/dtmax ). In addition, the following cardiomyocytes mitochondrial functions were measured: reactive oxygen species (ROS) production, oxidative phosphorylation, and calcium retention capacity (CRC) as well as the consequences of ROS production on lipids, proteins, and DNA. IV injection of levobupivacaine induced sinus bradycardia and reduced dMAP and LV dP/dtmax . At the mitochondrial level, oxygen consumption and CRC were decreased. In contrast, ROS production was increased leading to enhanced lipid peroxidation and structural alterations of proteins and DNA. Myocardial ischemia was associated with global worsening of all changes. Intralipid(®) quickly improved haemodynamics. However, beneficial effects of Intralipid(®) were less clear after myocardial ischemia.

Dexmedetomidine Dose-Dependently Attenuates Ropivacaine-Induced Seizures and Negative Emotions Via Inhibiting Phosphorylation of Amygdala Extracellular Signal-Regulated Kinase in Mice

Ropivacaine (Ropi), one of the newest and safest amino amide local anesthetics, is linked to toxicity, including the potential for seizures, changes in behavior, and even cardiovascular collapse. Dexmedetomidine (Dex), an α2-adrenergic receptor agonist, has been widely used in anesthesia and critical care practice. To date, the underlying mechanisms of the effects of Dex premedication on Ropi-induced toxicity have not been clearly identified. In the current study, we investigated the effects of increasing doses of Dex premedication on 50% convulsive dose (CD50) of Ropi. With increasing doses of intraperitoneal (i.p.) Dex 10 min prior to each i.p. RopiCD50, the latency and duration of seizure activity were recorded. Open-field (OF) and elevated plus maze (EPM) test were used to measure negative behavioral emotions such as depression and anxiety. Immunohistochemistry and Western blot were utilized to investigate phosphorylation-extracellular regulated protein kinases (p-ERK) expression in the basolateral amygdala (BLA) on 2 h and in the central amygdala (CeA) on 24 h after convulsion in mice. The results of our investigation demonstrated that Dex dose-dependently increased RopiCD50, prolonged the latency and shortened the duration of each RopiCD50-induced seizure, improved the negative emotions revealed by both OF and EPM test, and inhibited p-ERK expression in the BLA and the CeA.

Efficacy of periarticular injection applied trough knee other than posterior capsule in simultaneous bilateral total knee arthroplasty

BACKGROUND

We aimed to evaluate periarticular multimodal drug injection (PMDI) in bilateral total knee arthroplasty.

METHODS

In 154 knees of 77 patients, PMDI was administered intraoperatively through the regions other than posterior capsule to one knee; other knee was control.

RESULTS

Drug-injected knees had lower visual analog scale scores and higher passive range of motion postoperatively (p < 0.05). The active straight leg raise was higher in drug-injected knees (47 [61%] vs 19 [24.7%], p = 0.001).

CONCLUSIONS

PMDI is a safe and effective method of early postoperative pain management in total knee arthroplasty when applied through regions other than posterior capsule.

Periarticular multimodal drug injection in total knee arthroplasty

PURPOSE

A systematic review and meta-analysis based on randomized controlled trials (RCTs) were conducted to evaluate the efficiency and safety of periarticular multimodal drug injection in total knee arthroplasty (TKA).

METHODS

Periarticular injection with the use of multimodal drugs is an efficient alternative for postoperative analgesia in TKA. A systematical electronic search was performed to identify the eligible RCTs in the databases of PubMed, Embase, Cochrane Central Register of Controlled Trials, Web of Science and the Chinese Biomedical Literature Database. Two independent reviewers completed data collection and assessment of methodological quality. The quality of evidence of outcomes was judged using GRADE criteria. Meta-analysis was performed for the outcomes of pain, straight leg raise, operating time, hospital stay and complications.

RESULTS

Ten RCTs including eight studies with 1,216 TKAs in 835 patients met the inclusion criteria. Periarticular injection with multimodal drugs in TKA was associated with short-term benefits in terms of pain relief, straight leg raise, narcotic consumption, and the rates of nausea, vomiting, rash and pruritus. There were no statistically significant differences in operating time, hospital stay, wound complications and deep vein thrombosis between both groups.

CONCLUSIONS

The current evidence suggests that periarticular multimodal drug injection in TKA provides short-term advantages in pain relief, straight leg raise and postoperative complications.

The efficacy of periarticular multimodal drug injection for postoperative pain management in total knee or hip arthroplasty

The efficacy of periarticular multimodal drug injection (PMDI) to reduce pain after total knee or hip arthroplasty (TKA or THA) still remains controversial. Our study aimed at evaluating the efficacy of PMDI after TKA or THA. A fully recursive literature search was conducted to identify relevant randomized controlled trials. Ultimately, 21 studies were included in the analysis. Pooled results showed that the PMDI group had better pain relief, less opioid consumption, larger range of motion, and lower rates of nausea and vomiting than the placebo group. No significant difference was seen in regard to the length of hospital stay between the two groups. In conclusion, PMDI should be recommended for the pain management after TKA or THA.

[Single-dose intraincisional levobupivacaine infiltration in caesarean postoperative analgesia: a placebo-controlled double-blind randomized trial]

OBJECTIVES

The efficacy of single-dose intraincisional infiltration with levobupivacaine in postoperative analgesia and chronic pain after caesarean sections is unknown.

STUDY

A placebo-controlled double-blind randomized trial.

PATIENTS AND METHODS

After ethical approval, and written inform consent, 140 women scheduled for a caesarean section were randomly assigned and received 30mL of levobupivacaine 0.5% (L group) or saline (placebo-P group) into their wound. The primary endpoint was morphine consumption (using intravenous morphine patient-controlled analgesia) for the first 24h after surgery. At 1h to 48h, side effects, pain at rest and pain 2months later were recorded.

RESULTS

All included patients had similar demographic and surgical characteristics. The morphine consumption was significantly lower in the L group at h6, h8 and h12 (considering both total intake and each request). At h4, the mean total morphine consumption was 25 (12) mg in the L group versus 31 (14) mg in the P group (P=0.05). Time until discharge and side effects including nausea-vomiting (14 vs 20%), wound scar complications (6 vs 8%) and chronic pain after 2months (25% in both groups complained of small pain, and 75% no pain) were similar between the two groups (P>0.05).

CONCLUSION

Single-dose local infiltration of levobupivacaine 0.5% reduced opioid requirement at 12h, with no difference after 24h. www.clinicaltrials.com, number: NCT00621907.

Intraarticular vs. extraarticular ropivacaine infusion following high-dose local infiltration analgesia after total knee arthroplasty: a randomized double-blind study

BACKGROUND AND PURPOSE

Ropivacaine infusion following high-volume local infiltration analgesia has been shown to be effective after total knee arthroplasty, but the optimum site of administration of ropivacaine has not been evaluated. We compared the effects of intraarticular and extraarticular adminstration of the local anesthetic for postoperative supplementation of high-volume local infiltration analgesia.

PATIENTS AND METHODS

In this double-blind study, 36 rheumatic patients aged 51-78 years with physical status ASA 2-3 who were scheduled for total knee arthroplasty were randomized into 2 groups. All patients received wound infiltration at the end of surgery with 300 mg ropivacaine, 30 mg ketorolac, and 0.5 mg epinephrine (total volume 156 mL). A tunneled catheter was randomly placed either extraarticularly or intraarticularly. Continuous infusion of ropivacain (0.5%, 2 mL/h) was started immediately and was maintained during the next 48 h. Pain intensity at rest, on movement, and with mobilization was estimated by the patients and the physiotherapist; rescue morphine consumption was recorded.

RESULTS

As estimated by the patients, ropivacaine administered intraarticularly did not improve analgesia relative to extraarticular infusion, but improved the first mobilization. The incidence of high intensity of pain (VAS 7-10) was less in the group with intraarticular infusion. Analgesic requirements were similar in the 2 groups (47 mg and 49 mg morphine). No complications of postoperative wound healing were seen and there were no toxic side effects.

INTERPRETATION

Continuous infusion of ropivacaine intraarticulary did not improve postoperative analgesia at rest relative to extraarticular administration, but it appeared to reduce the incidence of high pain intensity during first exercises, and could therefore be expected to improve mobilization up to 24 h after total knee arthroplasty.

Safety Evaluation of EXPAREL (DepoFoam Bupivacaine) Administered by Repeated Subcutaneous Injection in Rabbits and Dogs: Species Comparison

EXPAREL (bupivacaine extended-release liposome injection), DepoFoam bupivacaine, is in development for prolonged postsurgical analgesia. Repeat-dose toxicity studies were conducted in rabbits and dogs to compare the potential local and systemic toxicities of EXPAREL and bupivacaine HCl (Bsol), and the reversibility of any effects. Dogs tolerated much larger doses than rabbits. EXPAREL-related minimal-to-moderate granulomatous inflammation was noted at the injection sites. In recovery animals, the granulomatous inflammation was observed less frequently and was characterized by an increased number of multinucleated giant cells. These effects were considered a normal response to liposomes and nonadverse. Rabbits are more sensitive than dogs. In rabbits, convulsions were noted with EXPAREL and more frequently with Bsol; a NOAEL was not identified. In dogs, EXPAREL was well tolerated (NOAEL > 30 mg/kg/dose). The cumulative exposure of EXPAREL in these studies is well in excess of the proposed maximum single-dose exposure that is intended in humans.

Midazolam in rabbits terminates dysrhythmias caused by intracerebroventricular ropivacaine

The current study was designed to investigate the mechanisms by which ropivacaine may act within the central nervous system (CNS) to produce cardiotoxicity. Eighty New Zealand rabbits were divided into four groups randomly. In Group 1, 20 rabbits received intracerebroventricular (icv) saline, and then received icv ropivacaine 30 min later. In Group 2, 20 rabbits received icv ropivacaine. Whenever dysrhythmias continued for more than 5 min, 0.1 ml saline was administered into the left cerebral ventricle. Ten minutes later, 0.1 ml midazolam was given into the left lateral ventricle. In Group 3, 20 rabbits received icv ropivacaine, and once the dysrhythmias developed, the inspired isoflurane concentration was increased from 0.75% to 1.50%. In Group 4, 20 animals received an intravenous (iv) phenylephrine infusion until dysrhythmias occurred. In Group 1, the rabbits did not develop dysrhythmias in response to icv saline, whereas dysrhythmias did develop in these animals after icv ropivacaine. In Group 2, icv saline had no effect on the dysrhythmias; however, icv midazolam terminated cardiac dysrhythmias. In Group 3, an increase in the concentration of the inspired isoflurane had no effect on dysrhythmias. In Group 4, icv midazolam had no effect on dysrhythmias in response to iv phenylephrine. Ropivacaine administered directly into the CNS is capable of producing cardiac dysrhythmias; midazolam terminated dysrhythmias presumably by potentiation of γ-aminobutyric acid (GABA) receptor activity. Our results suggest that ropivacaine produces some of its cardiotoxicity not only by the direct cardiotoxicity of the drug, but also by the CNS effects of ropivacaine.