Local anesthetics

Peripheral Regional Anesthesia Using Local Anesthetics: Old Wine in New Bottles?

During the past decade, numerous efforts were undertaken aiming at prolonging the analgesic effect of regional anesthesia. With the development of extended-release formulations and enhanced selectivity for nociceptive sensory neurons, a very promising contribution to the development of pain medications has been achieved. At present, liposomal bupivacaine is the most popular, non-opioid, controlled drug delivery system, but its duration of action, which is still controversially discussed, and its expensiveness have decreased initial enthusiasm. Continuous techniques can be seen as an elegant alternative for providing a prolonged duration of analgesia, but for logistic or anatomical reasons, they are not always the best choice. Therefore, focus has been directed towards the perineural and/or intravenous addition of old and established substances. As for perineural application, most of these so-called 'adjuvants' are used outside their indication, and their pharmacological efficacy is often not or only poorly understood. This review aims to summarize the recent developments for prolonging the duration of regional anesthesia. It will also discuss the potential harmful interactions and side effects of frequently used analgesic mixtures.

Junctional rhythm with severe hypotension following infiltration of lidocaine containing epinephrine during dental surgery

We experienced an unusual case of accelerated junctional rhythm with severe hypotension after infiltration of lidocaine containing epinephrine during dental surgery under general anesthesia. The patient's electrocardiogram exhibited retrograde P-waves following the QRS complex, which could be misinterpreted as ST-segment depression. As a temporary measure, administration of ephedrine restored the patient's blood pressure to normal levels. The importance of this case lies in its demonstration of an unexpected and serious side effect of commonly used epinephrine infiltration. This case also highlights the need for accurate interpretation of the electrocardiogram and comprehensive understanding of best practices for patient management.

Mepivacaine reduces calcium transients in isolated murine ventricular cardiomyocytes

Background

The potential mechanism of mepivacaine’s myocardial depressant effect observed in papillary muscle has not yet been investigated at cellular level. Therefore, we evaluated mepivacaine’s effects on Ca²⁺ transient in isolated adult mouse cardiomyocytes.

Methods

Single ventricular myocytes were enzymatically isolated from wild-type C57Bl/6 mice and loaded with 10 μM fluorescent Ca²⁺ indicator Fluo-4-AM to record intracellular Ca²⁺ transients upon electrical stimulation. The mepivacaine effects at half-maximal inhibitory concentration (IC₅₀) was determined on calibrated cardiomyocytes’ Ca²⁺ transients by non-parametric statistical analyses on biophysical parameters. Combination of mepivacaine with NCX blockers ORM-10103 or NiCl₂ were used to test a possible mechanism to explain mepivacaine-induced Ca²⁺ transients’ reduction.

Results

A significant inhibition at mepivacaine’s IC₅₀ (50 μM) on Ca²⁺ transients was measured in biophysical parameters such as peak (control: 528.6 ± 73.61 nM vs mepivacaine: 130.9 ± 15.63 nM; p < 0.05), peak area (control: 401.7 ± 63.09 nM*s vs mepivacaine: 72.14 ± 10.46 nM*s; p < 0.05), slope (control: 7699 ± 1110 nM/s vs mepivacaine: 1686 ± 226.6 nM/s; p < 0.05), time to peak (control: 107.9 ± 8.967 ms vs mepivacaine: 83.61 ± 7.650 ms; p < 0.05) and D₅₀ (control: 457.1 ± 47.16 ms vs mepivacaine: 284.5 ± 22.71 ms; p < 0.05). Combination of mepivacaine with NCX blockers ORM-10103 or NiCl₂ showed a significant increase in the baseline of [Ca²⁺] and arrhythmic activity upon electrical stimulation.

Conclusion

At cellular level, mepivacaine blocks Na⁺ channels, enhancing the reverse mode activity of NCX, leading to a significant reduction of Ca²⁺ transients. These results suggest a new mechanism for the mepivacaine-reduction contractility effect.

Safety of local anesthetics

Local anesthetics are essential medications for the conduction of dermatological procedures. They stop the depolarization of nerve fibers and are divided into two main categories, the amide and ester types. Systemic toxicity with reflex on the central nervous and cardiovascular systems is their most feared adverse reactions, and the anaphylactic reaction is the most concerning one. Although potentially fatal, these events are extremely rare, so local anesthetics are considered safe for use in in-office procedures.

Lidocaine Allergy: Do Positive Patch Results Restrict Future Use?

BACKGROUND

Adverse reactions from lidocaine are commonly reported. When allergy is suspected, patients may be referred for specific skin testing to confirm the association of their clinical findings.

OBJECTIVE

We aimed to investigate 13 cases of suspected lidocaine allergy to analyze if positive patch results restricted future use as an injectable local anesthetic.

METHODS

A prospective study was conducted from March 2013 to September 2014 at 2 academic hospital-based patch test clinics in Toronto. Patients were tested to the North American Contact Dermatitis Group standard series (Smart Practice, Phoenix, AZ) and, if suspicion for lidocaine allergy was high, a local anesthetic series (Chemotechnique Diagnostics, Malmö, Sweden) was added. Intradermal skin testing to local anesthetics below irritant concentrations was subsequently conducted in lidocaine-positive patients. If negative, a subcutaneous challenge with 1% lidocaine was done.

RESULTS

Thirteen of 756 patients patch tested were positive to lidocaine. Seven patients had relevant reactions to over-the-counter products containing lidocaine, 2 reacted to subcutaneous lidocaine, and 4 had incidental findings. There were no patients with positive results to intradermal testing. Three patients had delayed reactions to the subcutaneous challenge.

CONCLUSIONS

Patients with positive patch tests to lidocaine and negative results to intradermal testing and subcutaneous challenge may be safe to use lidocaine as an injectable local anesthetic in the future.

The effects and side effects of lidocaine tetracaine peel off on laser-assisted hair removal

Background:

Lidocaine 7%-tetracaine 7% is one of the combinations recently offered for performing laser-assisted hair removal. The aim of this study was to compare the effects of this combination with placebo on the side effects of laser-assisted hair removal.

Materials and Methods:

This clinical trial was carried out on 110 women who referred to Isfahan Spadana laser clinic for laser-assisted hair removal. Lidocaine 7%-tetracaine 7% was applied on one-half of the face, whereas placebo was applied on the other side to create local anesthesia, and after 30 min, the place was cleaned and investigated for complications (edema, erythema, and pallor); then laser therapy was begun. At the end of the therapy, the patients’ pain was estimated using Visual Analog Scale (VAS). The data were analyzed using SPSS software by Chi-square and paired t-tests.

Results:

The mean age of patients was 27.74 ± 10.8 years. Average levels of anesthesia at 30 min after using lidocaine 7%-tetracaine 7% and placebo based on VAS were 3.6 ± 1.4 and 8.4 ± 1.5, respectively (P = 0.001). In other words, patients felt less pain by using lidocaine 7%-tetracaine 7%. The frequency of complications in patients was not significantly different between the two groups.

Conclusion:

Considering the better effect of lidocaine 7%-tetracaine 7% compared to placebo and its minimal side effects, we can use it before performing laser-assisted hair removal.

A double-blind randomized controlled trial showing the analgesic and anesthetic properties of lidocaine E to be equivalent to those of ropivicaine and bupivacaine in carpal tunnel release surgery

In a three-phase trial, the anesthetic properties of lidocaine, bupivacaine and ropivicaine were compared in carpal tunnel release surgery. In phase I, two groups of 25 sequential patients were injected with either lidocaine plain 2% or lidocaine 2% with adrenaline 1:100,000 (E), as the local anesthetic for outpatient carpal tunnel release surgery. Subjective injection pain, postoperative pain at 2 h increments and the number of analgesic pills taken were recorded. During the first postoperative hours, outcome measures were superior in the lidocaine E group. In phase II, a double-blind randomized design compared 42 patients injected with either lidocaine E or a combination of lidocaine E and bupivacaine. Postoperative pain scores and analgesic pills taken were compared using nonparametric statistical tests. During the first 4 h there was a slight benefit in the duration of the anesthetic and fewer pain pills were used in the bupivacaine group. Phase III was a randomized double-blind comparison of ropivicaine and lidocaine E 2% in 72 patients. There was a slight decrease in pain scores and fewer analgesic pills required during the first 6 h in the ropivicaine group. Lidocaine plain 2% provided significantly inferior analgesic and anesthetic properties compared with lidocaine E 2%, bupivacaine or ropivicaine. Sequential randomized comparisons between lidocaine E and bupivacaine and ropivicaine showed clinical equivalence. The present study showed lidocaine E 2% to be a satisfactory and comparatively cost-effective anesthetic for outpatient carpal tunnel surgery.

[Local anesthetic procedures in dermatology: Part 1: principles]

Most dermatologic surgery is performed under local anesthesia. The choice of the type of anesthesia depends on the age, ability to cooperate and comorbidities of the patient. Anesthetics of the amide type are generally preferred for local infiltration. A solid anatomic background is required to perform effective peripheral nerve blocks. If the methods of action, toxic effects and potential drug interactions are considered, then local anesthetics have a low risk of complications. One must also not overlook the need for regular training in managing anesthetic emergencies for the entire operating room team, especially with the increasing age of our patients.

ATP synthase and the actions of inhibitors utilized to study its roles in human health, disease, and other scientific areas

ATP synthase, a double-motor enzyme, plays various roles in the cell, participating not only in ATP synthesis but in ATP hydrolysis-dependent processes and in the regulation of a proton gradient across some membrane-dependent systems. Recent studies of ATP synthase as a potential molecular target for the treatment of some human diseases have displayed promising results, and this enzyme is now emerging as an attractive molecular target for the development of new therapies for a variety of diseases. Significantly, ATP synthase, because of its complex structure, is inhibited by a number of different inhibitors and provides diverse possibilities in the development of new ATP synthase-directed agents. In this review, we classify over 250 natural and synthetic inhibitors of ATP synthase reported to date and present their inhibitory sites and their known or proposed modes of action. The rich source of ATP synthase inhibitors and their known or purported sites of action presented in this review should provide valuable insights into their applications as potential scaffolds for new therapeutics for human and animal diseases as well as for the discovery of new pesticides and herbicides to help protect the world's food supply. Finally, as ATP synthase is now known to consist of two unique nanomotors involved in making ATP from ADP and P(i), the information provided in this review may greatly assist those investigators entering the emerging field of nanotechnology.

Slow injection of local anaesthetic will decrease pain during dorsal penile nerve block

PURPOSE

To evaluate whether a very slow injection of local anaesthetics during dorsal penile nerve block for circumcision causes less pain than a more rapid injection.

METHODS

In a prospective, double-blind, randomized study, 75 patients aged 15 to 53 yr (mean +/- SD = 22 +/- 8.4 yr) were randomized into two groups. A solution of 2% lidocaine, 1 mg.kg-1, and 0.5% bupivacaine, 0.5 mg.kg-1 without epinephrine to a maximum dose of 10 ml was injected using either a very slow rate (injection time 100 to 150 s, Group A) or a faster rate (injection time 40 to 80 s, Group B). Patients were questioned regarding pain by a physician who was blinded to the mode of therapy. Pain was rated as 1) mild (negligible), 2) moderate (non-negligible, but easily endurable), 3) intense (but endurable) and 4) total refusal to continue.

RESULTS

A significant pain score difference was found between Groups A and B (median = 1 vs. 2, P = 0.0006) as well as a significant correlation between pain score and the rate of infiltration (rs = -0.394, P < 0.0001).

CONCLUSIONS

Slow injection is an important factor in reducing pain during penile block.