Antimicrobial effects of local anaesthetics

Review of intra-articular local anaesthetic administration in horses: Clinical indications, cytotoxicity, and outcomes

Equine practitioners frequently inject local anaesthetics (LA) intra-articularly in both diagnosis of lameness and for pain management intra- or post-operatively with synovial endoscopy. Recent reviews of the human and veterinary literature support the concept that chondrotoxicity of LA on joint tissues depends on the type of drug, dose administered, and duration of exposure. The purpose of this review is to summarise the current literature describing intra-articular local anaesthetic use, including both in vitro and in vivo studies, and to draw some comparisons to literature from other species where potential toxicity and duration of effect have been evaluated with the goal of advancing the field's understanding of intra-articular local anaesthetic use in horses, and indicating future directions for the field. The aggregate data available from all species, while generally sparse for horses, indicate that LA are rapidly cleared from the synovial fluid after injection, often within 30 min. In vitro data strongly suggest that lidocaine and bupivacaine are likely more chondrotoxic than other LA, although to what extent is still unknown, and cytotoxicity of LA may be mitigated through concurrent injection with HA, PRP, and drug combinations including nonsteroidal anti-inflammatories and opioids. The current body of in vitro research is not reflective of the in vivo environment, and further in vitro work, if performed, should focus on mimicking the native joint environment, utilising PK data and joint/injection volumes to replicate the native environment more accurately within the joint and the expected exposures to LA.

Repurposing of dibucaine and niflumic acid as antimicrobial agents in combination with antibiotics against Staphylococcus aureus

The versatile human commensal bacteria and pathogen Staphylococcus aureus cause several community and hospital-acquired illnesses associated with significant morbidity and death. Antibiotic therapy for S. aureus infections has grown increasingly difficult as the organism has developed a wide spectrum of antibiotic resistance mechanisms. This situation emphasizes the significance of developing and advocating new antimicrobials for preventative and therapeutic measures. Our study aimed to identify and evaluate new therapeutic options against S. aureus. We investigated the efficacy of two drugs, dibucaine, and niflumic acid, as potential adjuvant for anti-staphylococcal therapeutics. Dibucaine and niflumic acid found to have bactericidal activity against S. aureus. These drugs acted synergistically with antibiotics reducing the required dose of antibiotics up to 4 times. In combination with antibiotics, they were effectively and synergistically inhibited the formation of biofilms of S. aureus. The best synergistic partner of dibucaine was with kanamycin and tetracycline, whereas niflumic acid was with streptomycin and ampicillin. Both the drugs showed significant efflux inhibition in the bacteria. Moreover, the drugs are found to be safe at synergistic doses. Our findings suggest that dibucaine and niflumic acid could be potential adjuvant with antibiotics for the treatment of S. aureus infections. Their ability to significantly enhance the efficacy of antibiotics highlights their potential clinical significance as adjunct therapies.

Effect of pre-incisional and peritoneal local anesthetics administration on colon anastomosis and wound healing

BACKGROUND

Previous research has shown that levobupivacaine is as effective as bupivacaine but carries a lower risk of cardiac and central nervous system toxicity. This study explores whether levobupivacaine and bupivacaine are preferable for all patients, includ-ing those with comorbidities, particularly focusing on their effects on colonic anastomosis. The primary objective is to examine the influence of levobupivacaine and bupivacaine on colonic anastomosis. Additionally, the study will assess their impact on wound healing and their anti-adhesive properties.

METHODS

Conducted between July 28, 2022, to August 4, 2022, at the Hamidiye Animal Experiments Laboratory, this study was approved by the University Science Health, Hamidiye Animal Experiments Local Ethics Committee. This study was conducted using 21 male Sprague rats aged 16-20 weeks. The rats were allocated into three equal groups of seven each: Group C: pre-incisional isotonic; Group B: pre-incisional bupivacaine; and Group L: pre-incisional levobupivacaine. Macroscopic adhesion scores (MAS) were recorded during laparotomy and tissue samples were taken for histopathological examination and hydroxyproline levels measurement. Wound tensile strength along the middle incision line and anastomotic burst pressure were also assessed.

RESULTS

MAS was statistically significantly lower in Groups B and L compared to Group C (p<0.001). The wound histopathology score (WHS) was significantly higher in Group L than in Group B (p=0.021). Colon histopathology scores (CHSs) were also signifi-cantly higher in Group L compared to Group C (p=0.011).

CONCLUSION

TThe study found that bupivacaine and levobupivacaine did not significantly enhance wound healing, although le-vobupivacaine significantly improved WHS relative to bupivacaine. According to the findings of this study, levobupivacaine can enhance clinical practice by being used in patients undergoing colon anastomosis. It contributes significantly to the durability of colon anasto-mosis, has a more positive effect on wound healing compared to bupivacaine, and exhibits anti-adhesive properties. Additional clinical trials are necessary to validate these results further.

The effect of local anesthetics against planktonic forms and film formation of S. aureus strains and its dependence on antiseptics activity

Today surgical site infections (SSIs) remain the second among hospital acquired infections in Europe and the USA. Staphylococcus aureus as a pathogen of nosocomial infections occur more frequently in surgical hospitals. The work was aimed to establish the effect of local anesthetics against planktonic forms and biofilm-formation of S. aureus clinical strains and the relationship between the sensitivity of S. aureus strains to local anesthetics and antiseptics in vitro. The antimicrobial activity of local anesthetics (0.5%, bupivacaine, 2.0% lidocaine, 0.375% ropivacaine) and antiseptics (decamethoxine 0.02%, chlorhexidine 0.05%) against clinical strains of S. aureus was observed and studied their ability to produce biofilms. The antimicrobial effect of local anesthetics was lower compared to antiseptics, but we observed inhibition of growth and reproduction of S. aureus in their presence. The ropivacaine solution and the lidocaine solution demonstrated almost the same activity against the studied microorganism isolates. Along with this, bupivacaine solution had the highest activity against the studied microorganisms. The minimal inhibitory concentration of bupivacaine for S. aureus was 2.2 times lower than the minimal inhibitory concentration of lidocaine and 2.1 times lower than the minimal inhibitory concentration of ropivacaine significantly (p < 0.05). Scientific research on various aspects of the formation of bacterial biofilms is a relevant area that will change approaches to the prophylaxis and treatment of a number of infections, including SSIs.

Evaluation of primary wound healing and potential complications after perioperative infiltration with lidocaine without adrenaline in surgical incisions in dogs and cats

BACKGROUND

Pre-emptive local analgesia with the use of lidocaine is practised increasingly in veterinary medicine as part of applied multimodal analgesia, despite its controversial impact on wound healing. The purpose of this prospective, randomised, double-blinded, placebo-controlled clinical study was to evaluate if preoperative subcutaneous infiltration of lidocaine has a negative impact on primary wound healing of surgical incisions. Fifty-two companion animals (3 cats and 49 dogs) were enrolled in the study. The inclusion criteria were as follows: American Society of Anaesthesiologists (ASA) score I or II, a minimum body weight of 5 kg, and a planned incisional length of at least 4 cm. Surgical incisions were infiltrated subcutaneously with lidocaine without adrenaline or NaCl (placebo). Follow-up questionnaires for owners and veterinarians and thermography of the surgical wound were used to assess wound healing. Antimicrobial use was documented.

RESULTS

There was no significant difference in either the total score or the individual assessment points between the treatment and the placebo group on the owner or the veterinary questionnaires in regard to primary wound healing (P > 0.05 for all comparisons). No significant difference was found between the thermography results of the treatment and placebo group (P = 0.78), and there was no significant correlation between the total score from the veterinary protocol and thermography results (Spearman's correlation coefficient - 0.10, P = 0.51). Surgical site infections developed in 5/53 (9.4%) surgeries and its occurrence varied significantly between the treatment and the placebo group as all cases of infection were in the placebo group (P = 0.05).

CONCLUSION

The results of this study indicate that lidocaine used as a local anaesthetic did not affect wound healing in patients with ASA scores I-II. The results suggest that lidocaine infiltration in surgical incisions can be safely used to reduce pain.

[Antimicrobial effects of fentanyl and bupivacaine]

STUDY OBJECTIVE

In this study, we aimed to compare the antimicrobial effects of bupivacaine and fentanyl citrate and to reveal the impact on antimicrobial effect potential in the case of combined use.

DESIGN

In vitro prospective study.

SETTING

University Clinical Microbiology Laboratory.

MEASUREMENTS

In our study, in vitro antimicrobial effect of 0.05 mg.mL-1 fentanyl citrate, 5 mg.mL-1 bupivacaine were tested against Staphylococcus aureus American Type Culture Collection (ATCC) 29213, Pseudomonas aeruginosa ATCC 27853, Klebsiella pneumoniae ATCC 13883, Escherichia coli ATCC 25922 and Candida albicans ATCC 10231 as Group F (Fentanyl Citrate) and Group B (Bupivacaine), respectively. S. aureus ATCC 29213, P. aeruginosa ATCC 27853, Klebsiella pneumoniae ATCC 13883 and Escherichia coli ATCC 25922 were cultured onto Mueller Hinton agar (Oxoid, UK) plates and Candida albicans ATCC 10231 were cultured onto Sabouraud dextrose agar (Oxoid, UK) plates for 18−24 hours at 37 °C.

MAIN RESULTS

In terms of inhibition zone diameters, S. Aureus ATCC 29213, P. aeruginosa ATCC 27853, and C. albicans ATCC10231 values obtained after 12 and 24 hours of incubation ​​were significantly higher in Group F than Group B (p <  0.001). In terms of inhibition zone diameters, E. coli ATCC 25922, and K. pneumomiae ATCC 13883 values obtained after 12 and 24 hours of incubation ​​were significantly higher in Group B than Group F (p <  0.001, E. coli 12ª hour p  = 0.005).

CONCLUSIONS

Addition of fentanyl to Local Anesthetics (LAs) is often preferred in regional anesthesia applications in today's practice owing especially to its effect on decreasing the local anesthetic dose and increasing analgesia quality and patient satisfaction. However, when the fact that fentanyl antagonized the antimicrobial effects of LAs in the studies is taken into account, it might be though that it contributes to an increase in infection complications. When the fact that fentanyl citrate which was used in our study and included hydrochloric acid and sodium hydroxide as protective agents, broadened the antimicrobial effect spectrum of LAs, had no antagonistic effect and showed a synergistic antimicrobial effect against E. Coli is considered, we are of the opinion that the addition of fentanyl to LAs would contribute significantly in preventing the increasing regional anesthesia infection complications.

Antibacterial effects of lidocaine and adrenaline

The most commonly used local anaesthetics (LAs) for postoperative analgesia and surgical anaesthesia are lidocaine and bupivacaine. Adrenaline is a vasopressor agent, which is widely used in anaesthesia for many purposes. This study aims to determine the antibacterial efficacy of lidocaine, mupirocin, adrenaline, and lidocaine + adrenaline combination. In our study, the in vitro antimicrobial effect of 1 mL of sterile saline, 20 mg/mL mupirocin, 20 mg/mL lidocaine, 1 mg/mL adrenaline, and 20 mg/mL lidocaine and adrenaline were tested against Staphylococcus aureus American-type culture collection (ATCC) 29213, Pseudomonas aeruginosa ATCC 27853, and Escherichia coli ATCC 25922, classified as Group C (control), Group M (mupirocin), Group L (lidocaine), Group A (adrenaline), and Group LA (lidocaine+adrenaline), respectively. S. aureus ATCC 29213, P. aeruginosa ATCC 27853, and E. coli ATCC 25922 were cultured on Mueller-Hinton agar (Oxoid, UK) plates for 18 to 24 hours at 37°C. Colonies from these plates were suspended in sterile saline, and a 0.5 McFarland turbidity standard suspension (corresponding to 1.5 × 10⁸ CFU/mL) of each isolate was prepared. In terms of inhibition zone diameters, S. aureus ATCC 29213 values obtained after 12 and 24 hours of incubation were significantly different between groups (P < .001). According to inhibition zone diameters, Group M > Group LA > Group L > Group C = Group A. P. Aeruginosa ATCC 27853 values obtained after 12 and 24 hours of incubation were significantly different between groups (P < .001). According to inhibition zone diameters, Group M > Group LA > Group L = Group C = Group A. E. coli ATCC 25922 values obtained after 12 and 24 hours of incubation were significantly different between groups (P < .001). According to inhibition zone diameters, Group M > Group LA > Group L > Group C = Group A. It is known that LAs have antimicrobial effect potential in addition to their anaesthetic, analgesic, antiarrhythmic, and anti-inflammatory effects. There are also studies showing the antimicrobial effects of vasopressor agents, which are frequently used, particularly in intensive care unit (ICUs). However, it has been observed in the present study that adrenaline alone did not have any antimicrobial effect. Adrenaline, when used in combination with lidocaine, provides a stronger and broad-spectrum antimicrobial activity, suggesting that its combined use in proper indications will be clinically significant. Because the prevention and treatment of wound infections make a positive contribution to wound healing, the potential of antimicrobial effect of LAs can provide successful results in the prevention and treatment of ICU and wound infections. Thus, an important contribution can be made in terms of reducing the costs of antibacterial treatment and reducing morbidity.

Bacterial inhibition efficiency of prilocaine and bupivacaine

This study aimed to demonstrate the antibacterial effects of bupivacaine and prilocaine on Escherichia coli, Staphylococcus aureus, and Pseudomonas aeruginosa. In our study, the in vitro antimicrobial effects of 20 mg/mL prilocaine and 5 mg/mL bupivacaine were tested against a S. aureus American-type culture collection (ATCC) 29213, P. aeruginosa ATCC 27853, and E. coli ATCC 25922, divided into Group P (Prilocaine) and Group B (Bupivacaine), respectively. S. aureus ATCC 29213, P. aeruginosa ATCC 27853, and E. coli ATCC 25922 were cultured on Mueller Hinton agar (Oxoid, Basingstoke, UK) plates for 18 to 24 hours at 37°C. In terms of inhibition zone diameters, inhibition of S. aureus ATCC 29213 was observed in both groups at the 12th and 24th hours. The 12th- and 24th-hour S. aureus ATCC 29213 value was significantly higher in Group P compared with Group B (P = .008). At the 12th and 24th hours, inhibition of E. coli ATCC 25922 was observed in both groups. The 12th- and 24th-hour E. coli ATCC 25922 value was significantly higher in Group P compared with Group B (P = .008). In our study, it was seen that prilocaine and bupivacaine had an antimicrobial effect on S. aureus and E. coli. In the comparison between these two local anesthetics (LAs), this effect was found to be significantly higher in prilocaine than bupivacaine. Therefore, we are of the opinion that antimicrobial effect potentials should also be taken into account in the selection of an LA agent in order to prevent the complications of an infection that might develop during LA infiltration and might lead to serious morbidity.

Antimicrobial effects of local anaesthetics

After the introduction of cocaine to the medical practice, local anaesthetics (LA) became essential in pain control. LA infiltration along the incision may be used to provide surgical anaesthesia or postoperative analgesia. This study aimed to compare the antimicrobial effects of the topical antimicrobial agent mupirocine with those of the LA lidocaine and the combination of lidocaine and adrenalin. In our study, the in vitro antimicrobial effects of 1 mL sterile saline, 20 mg/mL mupirocine, 20 mg/mL Lidocaine, and 20 mg/mL Lidocaine and Adrenaline were tested against Staphylococcus aureus American type culture collection (ATCC) 29213, Pseudomonas aeruginosa ATCC 27853, and Escherichia coli ATCC 25922 as Group C (Control), Group M (Mupirocine), Group L (Lidocaine), and Group LA (Lidocaine + adrenaline), respectively. S aureus ATCC 29213, P aeruginosa ATCC 27853, and E coli ATCC 25922 were cultured onto Mueller-Hinton agar (Oxoid, UK) plates for 18 to 24 hours at 37°C. Colonies from these plates were suspended in sterile saline and a 0.5 McFarland turbidity standard suspension (corresponding to 1.5 × 10⁸  CFU/mL) of each isolate was prepared. S Aureus ATCC 29213 inhibition zone diameter values of Group M, Group LA, and Group L were significantly higher compared with the group C (P ˂ 0.05). P aeruginosa ATCC 27853 inhibition zone diameter values of Group M and Group LA were significantly higher compared with the group C (P ˂ 0.05). E coli ATCC 25922 inhibition zone diameter values of Group M, Group LA, and Group L were significantly higher compared to the group C (P ˂ 0.05). LA infiltration along the incision may be used to provide surgical anaesthesia or postoperative analgesia. Considering that LAs show antimicrobial effects besides their analgesic effects, they may contribute to preventing the development and reducing the rate of surgical infections, decreasing the requirement to administer antibiotics. However, caution should be exercised not to antagonise the effective treatment of surgical infections, remembering that controversy on the antimicrobial effects of LAs remains in the literature. Therefore, further comprehensive studies with larger patient populations are warranted to demonstrate the antimicrobial effects of LAs.