Bicarbonate-buffered ropivacaine-mepivacaine solution for medial caruncle anaesthesia

Crystallization of mixtures of local anesthetics with and without select adjuvants: a semiquantitative light microscopy analysis

INTRODUCTION

Injecting mixtures of local anesthetics with or without adjuvants is a common practise in regional and particularly obstetric anesthesia to decrease block onset time and/or augment epidural analgesia for cesarean section. While evidence on the efficacy of this practise is equivocal, little is known about its safety in terms of the pharmacologic compatibility of local anesthetics.

METHODS

We assessed the grade of crystallization in individual mixtures of seven local anesthetics (bupivacaine, ropivacaine, lidocaine, procaine, chloroprocaine, mepivacaine, prilocaine) with or without four adjuvants (sodium bicarbonate, dexamethasone, clonidine, fentanyl) using a semiquantitative light microscopy scale (ranging from 0 to 5), repeatedly for up to 60 min and performed correlation analysis between grade of crystallization and initial solution pH.

RESULTS

Of the 50 mixtures tested, 26 showed grades of crystallization ≥4 at admixture and 41 showed grades of crystallization ≥4 after 60 min. The addition of adjuvants to local anesthetic mixtures did not substantially change the grades of crystallization. Bupivacaine has a slightly lower precipitation tendency, compared with ropivacaine. A moderate relationship was found between initial pH and grade of crystallization after 15 min for the adjuvant mixtures (R=0.33, p=0.04), but not at other time points.

DISCUSSION

The preparation of local anesthetic (±adjuvant) mixtures leads to high grades of crystallization, which increase over 60 min and appear independent of solution pH. The risk of mixing medications with unknown physical or chemical compatibility profiles in regional anesthesia should be critically appraised and its clinical significance elucidated in future translational research.

Effect of ropivacaine, mepivacaine or the combination of ropivacaine and mepivacaine for epidural anaesthesia on the postoperative recovery in patients undergoing caesarean section: a randomized, prospective, double-blind study

BACKGROUND

Anaesthetic methods and drugs with rapid onset, rapid recovery and better postoperative analgesia are more suitable for rapid recovery in obstetric anaesthesia. We formulated the following hypothesis: a combination of mepivacaine and ropivacaine could provide a longer analgesic effect and have more advantages in terms of rapid-recovery indicators.

METHODS

A total of 180 pregnant women scheduled to undergo elective caesarean sections were randomly assigned to three surgical groups, which received 2% mepivacaine (Group M), 2% mepivacaine + 0.75% ropivacaine (Group MR) (Volume 1:1) or 0.75% ropivacaine (Group R) through an epidural catheter. The situation of postoperative analgesia and other indicators of rapid recovery were recorded.

RESULTS

One hundred and fifty patients were included in the final analysis. Their demographic data were similar. The visual analogue scale (VAS) scores of Group MR and Group R were lower than Group M at 1 and 2 h after surgery both at rest and with movement (P < 0.05), and the time to first ambulation in Group MR (17.38 ± 2.06 h) and Group M (17.20 ± 2.09 h) was shorter than that in Group R (22.18 ± 1.74 h) (P < 0.05).

CONCLUSION

Application of 2% mepivacaine combined with 0.75% ropivacaine for epidural anaesthesia can provide longer postoperative analgesia and earlier ambulation, these effect may be more suitable than that of 2% mepivacaine or 0.75% ropivacaine alone for caesarean section.

TRIAL REGISTRATION

This study was registered at Chinese Clinical Trial Registry (Registration number: ChiCTR 2300078288; date of registration: 04/12/2023).

Ropivacaine-loaded, hydroxypropyl chitin thermo-sensitive hydrogel combined with hyaluronan: an injectable, sustained-release system for providing long-lasting local anesthesia in rats

BACKGROUND AND OBJECTIVE

Ropivacaine hydrochloride is a commonly used local anesthetic in clinics. However, local injection or continuous infusion of ropivacaine has been associated with several disadvantages. Accordingly, it is important to develop a new controlled release system for local administration of ropivacaine to achieve a prolong anesthetic effect, improve efficacy, and minimize the side effects.

METHODS

We developed injectable hydroxypropyl chitin thermo-sensitive hydrogel (HPCH) combined with hyaluronan (HA), which was used to synthesize a ropivacaine (R)-loaded controlled release system. We then conducted drug release test and cytotoxicity assay in vitro. Importantly, we examined the analgesic effects and biocompatibility of this system in vivo by injecting different concentrations of R-HPCH-HA (7.5, 15, 22.5 mg/mL), ropivacaine hydrochloride (R_HCL, 7.5 mg/mL), or saline (all in 0.5 mL) near the sciatic nerve in rats.

RESULTS

R-HPCH-HA induced concentration-dependent thermal-sensory blockade and motor blockade in vivo. In hot plate test, R-HPCH-HA (22.5 mg/mL) induced a significant longer thermal-sensory blockade (17.7±0.7 hours), as compared with R_HCL (7.5 mg/mL, 5.7±0.8 hours, n=6/group, p<0.05). It also produced a more prolonged motor blockade (6.8±0.8 hours) than R_HCL (3.5±0.8 hours, p<0.05). R-HPCH-HA caused less cytotoxicity than R_HCL, as indicated by the higher cell viability in vitro (n=8/group).

CONCLUSION

Our findings in a sciatic nerve block model demonstrated that the injectable, ropivacaine-loaded controlled release system effectively prolonged the local analgesic effect in rats without notable side effects.

Do buffered local anesthetics provide more successful anesthesia than nonbuffered solutions in patients with pulpally involved teeth requiring dental therapy?: A systematic review

BACKGROUND

The authors conducted a systematic review that addresses the following population, intervention, comparison, outcome question: "In adults requiring dental therapy with pulpally involved teeth, what is the comparative efficacy of buffered local anesthetics (LAs) compared with that of nonbuffered LAs in achieving anesthetic success?"

TYPES OF STUDIES REVIEWED

The authors searched MEDLINE, Scopus, Cochrane Library, ClinicalTrials.gov, World Health Organization International Trials Registry Platform, OpenGrey, Google Scholar Beta, and 2 textbooks to identify double-blinded randomized controlled trials in which researchers directly compared the efficacy of buffered and nonbuffered LAs in adult participants, as well as any associated side effects. Furthermore, they checked the reference lists of all included and excluded studies to identify any further trials. Weighted anesthesia success rates were estimated and compared by using a random-effects model.

RESULTS

A total of 14,011 studies were initially identified from the search; 5 double-blinded randomized clinical trials met inclusion criteria. Buffered LAs were more likely to achieve successful anesthesia than nonbuffered LAs (odds ratio, 2.29; 95% confidence interval, 1.11 to 4.71; P = .0232; I² = 66%).

CONCLUSIONS AND PRACTICAL IMPLICATIONS

This investigation revealed that buffered LAs are more effective than nonbuffered LAs when used for mandibular or maxillary anesthesia in pulpally involved teeth. Buffering of LAs has 2.29 times greater likelihood of achieving successful anesthesia.