559 Benzocaine-Lidocaine-Tetracaine (BLT) Cream Adverse Effects in Burn Patients: A Case Report and Literature Review

Introduction Historically, BLT cream has been used at our burn center in laser procedures and tattoo removal with 6–8% lidocaine to improve tolerance of outpatient procedures. Recently, the laser BLT formulation (8%) has been trialed as an opioid-sparing alternative for managing pain during inpatient microneedling procedures. When utilizing this formulation for microneedling, the high percentage of lidocaine absorption may correlate with adverse central nervous system (CNS) effects. Methods A literature evaluation and retrospective chart review of burn patients receiving BLT cream for inpatient microneedling was performed. Results From January to June 2020, two elderly females (77 and 78 years old) received several doses of BLT cream during inpatient microneedling procedures with no documented adverse events attributed to the medication. A 68 year old male with a total body surface area (TBSA) of 8% reported dizziness shortly after he received BLT cream. Vitals were normal, but the patient was unable to focus his eyes or communicate clearly. Neurological exam revealed sluggish, pinpoint pupils. Patient remained disoriented with gargling and tongue thrusting though vitals remained stable. At this time, the remainder of the BLT cream was removed from the wound and his mentation returned to baseline within 90 minutes. No residual neurologic deficits occurred. No other potential causes were identified. Literature review revealed topical lidocaine can be absorbed systemically and cause CNS depression, confusion, and disorientation. Based on limited published data in healthy patients, it is recommended to use no more than 5% of topical lidocaine in large quantities, especially over raw surfaces or blistered areas. The amount of lidocaine systemically absorbed is linked to both the duration of application and the surface area over which it is applied. Using study data from lidocaine/prilocaine 2.5% cream and lidocaine patches, we explored a safer BLT formulation for burn patients as published data do not exist for this group. Conclusions Based on our review, we determined 2% to be the maximum lidocaine concentration to apply to a burn wound, 5% TBSA as the maximum surface area involved, and total exposure time limited to 30 minutes or less to reduce incidence of adverse effects. Specifically, formulations with a higher lidocaine concentration applied to a burn wound have the potential to result in untoward neurological deficits.

Efficacy of Topical Anesthetics in Pain Perception During Mini-implant Insertion: Systematic Review of Controlled Clinical Trials

The focus of this systematic review is to assess the efficacy of several commonly utilized anesthetic techniques for reducing pain during the placement of mini-implants. An electronic search was conducted in the databases PubMed, Scopus, Web of Science, Medline Complete, Cochrane, Trials Central, and Clinical Trials, without limitations on year of publication or language. Randomized controlled trials (RCTs) and controlled clinical trials (CCTs) were considered. Two reviewers of articles independently evaluated the results of the study, and the risk of bias of included articles was evaluated according to the Cochrane Scale. Five eligible articles (3 RCTs and 2 CCTs) were included. The quality of the body of evidence was considered low because of the presence of multiple methodological problems, high risks of bias, and heterogeneity in the articles included. There was evidence that the efficacy of the analgesia of infiltrative anesthesia was most effective in promoting a lower perception of pain compared to the other anesthetic agents, although an injection was required. Among topical anesthetics, compound topical anesthetics with 20% lidocaine were more effective than compound topical anesthetics with low lidocaine concentration and conventional topical anesthetic with 20% benzocaine.

Cardiovascular, respiratory, gastrointestinal and behavioral effects of intravenous lidocaine in healthy, conscious horses and evaluation of the relationship with lidocaine and monoethylglycinexylidide serum concentrations

This study aimed to evaluate the relationship between the serum concentrations of lidocaine/ monoethylglycinexylidide (MEGX) and their effects on several systems in horses. Five healthy, conscious horses received a two-hour placebo intravenous infusion followed by a two-hour lidocaine infusion (bolus of 1.3 mg/kg over ten minutes followed by a continuous rate infusion of 0.05 mg/kg/min). Lidocaine and MEGX serum concentrations were sampled every ten to fifteen minutes during the experiment, and the presence of muscle fasciculations and loss of balance as well as the respiratory, digestive and cardiovascular systems of the five horses were evaluated by means of different non-invasive methods. During the lidocaine infusion, the mean (± SD) lidocaine and MEGX concentrations were respectively 768.88 ± 93.32ng/ml and 163.08 ± 108.98 ng/ml. The infusion of lidocaine significantly influenced the presence of fasciculations, caused a statistically but non-clinically significant decrease of systolic and diastolic blood pressures, which were both correlated with lidocaine and MEGX serum concentrations, and it increased the duodenal contractions frequency, which was correlated with the serum lidocaine concentration. In this study, mild hypotensive and prokinetic effects of short-term lidocaine infusion were observed.

The Effect of Dexmedetomidine on Oral Mucosal Blood Flow and the Absorption of Lidocaine

Dexmedetomidine (DEX) is a sedative and analgesic agent that acts via the alpha-2 adrenoreceptor and is associated with reduced anesthetic requirements, as well as attenuated blood pressure and heart rate in response to stressful events. A previous study reported that cat gingival blood flow was controlled via sympathetic alpha-adrenergic fibers involved in vasoconstriction. In the present study, experiment 1 focused on the relationship between the effects of DEX on alpha adrenoreceptors and vasoconstriction in the tissues of the oral cavity and compared the palatal mucosal blood flow (PMBF) in rabbits between general anesthesia with sevoflurane and sedation with DEX. We found that the PMBF was decreased by DEX presumably because of the vasoconstriction of oral mucosal vessels following alpha-2 adrenoreceptor stimulation by DEX. To assess if this vasoconstriction would allow decreased use of locally administered epinephrine during DEX infusion, experiment 2 in the present study monitored the serum lidocaine concentration in rabbits to compare the absorption of lidocaine without epinephrine during general anesthesia with sevoflurane and sedation with DEX. The depression of PMBF by DEX did not affect the absorption of lidocaine. We hypothesize that this is because lidocaine dilates the blood vessels, counteracting the effects of DEX. In conclusion, despite decreased palatal blood flow with DEX infusion, local anesthetics with vasoconstrictors should be used in implant and oral surgery even with administered DEX.

Effect of Injection Pressure of Infiltration Anesthesia to the Jawbone

To obtain effective infiltration anesthesia in the jawbone, high concentrations of local anesthetic are needed. However, to reduce pain experienced by patients during local anesthetic administration, low-pressure injection is recommended for subperiosteal infiltration anesthesia. Currently, there are no studies regarding the effect of injection pressure on infiltration anesthesia, and a standard injection pressure has not been clearly determined. Hence, the effect of injection pressure of subperiosteal infiltration anesthesia on local anesthetic infiltration to the jawbone was considered by directly measuring lidocaine concentration in the jawbone. Japanese white male rabbits were used as test animals. After inducing general anesthesia with oxygen and sevoflurane, cannulation to the femoral artery was performed and arterial pressure was continuously recorded. Subperiosteal infiltration anesthesia was performed by injecting 0.5 mL of 2% lidocaine containing 1/80,000 adrenaline, and injection pressure was monitored by a pressure transducer for 40 seconds. After specified time intervals (10, 20, 30, 40, 50, and 60 minutes), jawbone and blood samples were collected, and the concentration of lidocaine at each time interval was measured. The mean injection pressure was divided into 4 groups (100 ± 50 mm Hg, 200 ± 50 mm Hg, 300 ± 50 mm Hg, and 400 ± 50 mm Hg), and comparison statistical analysis between these 4 groups was performed. No significant change in blood pressure during infiltration anesthesia was observed in any of the 4 groups. Lidocaine concentration in the blood and jawbone were highest 10 minutes after the infiltration anesthesia in all 4 groups and decreased thereafter. Lidocaine concentration in the jawbone increased as injection pressure increased, while serum lidocaine concentration was significantly lower. This suggests that when injection pressure of subperiosteal infiltration anesthesia is low, infiltration of local anesthetic to the jawbone may be reduced, while transfer to oral mucosa and blood may be increased.

Lidocaine Concentration in Oral Tissue by the Addition of Epinephrine

The vasoconstrictive effect due to the addition of epinephrine to local anesthetic has been clearly shown by measuring blood-flow volume or blood anesthetic concentration in oral mucosal tissue. However, there are no reports on the measurement of anesthetic concentration using samples directly taken from the jawbone and oral mucosal tissue. Consequently, in this study, the effect of lidocaine concentration in the jawbone and oral mucosal tissue by the addition of epinephrine to the local anesthetic lidocaine was considered by quantitatively measuring lidocaine concentration within the tissue. Japanese white male rabbits (n = 96) were used as test animals. General anesthesia was induced by sevoflurane and oxygen, and then cannulation to the femoral artery was performed while arterial pressure was constantly recorded. Infiltration anesthesia was achieved by 0.5 mL of 2% lidocaine containing 1 : 80,000 epinephrine in the upper jawbone (E+) and 0.5 mL of 2% of epinephrine additive–free lidocaine (E0) under the periosteum. At specified time increments (10, 20, 30, 40, 50, and 60 minutes), samples from the jawbone, oral mucosa, and blood were collected, and lidocaine concentration was directly measured by high-performance liquid chromatography. No significant differences in the change in blood pressure were observed either in E+ or E0. In both E+ and E0 groups, the serum lidocaine concentration peaked 10 minutes after local anesthesia and decreased thereafter. At all time increments, serum lidocaine concentration in E+ was significantly lower than that in E0. There were no significant differences in measured lidocaine concentration between jawbone and mucosa within either the E+ or the E0 groups at all time points, although the E0 group had significantly lower jawbone and mucosa concentrations than the E+ group at all time points when comparing the 2 groups to each other. Addition of epinephrine to the local anesthetic inhibited systemic absorption of local anesthetic into the blood such that a high concentration could be maintained in the tissue. Epinephrine-induced vasoconstrictive effect was observed not only in the oral mucosa but also in the jawbone.

Changes of lidocaine concentration and physiological indices in dogs during anaesthesia with lidocaine and isoflurane combined with ketamine or fentanyl

Fentanyl and ketamine are often used as adjuvants in intravenous anaesthesia to prolong analgesia. The aim of this study was to compare changes of the basic physiological variables of intravenous lidocaine administration in combination with ketamine or fentanyl, and to evaluate the impact of addition of fentanyl or ketamine to lidocaine on serum lidocaine concentrations in dogs after intravenous administration. During general anaesthesia, dogs of group L received 2% lidocaine intravenously, dogs of group LF received 2% lidocaine and fentanyl, and dogs of the group LK received 2% lidocaine and ketamine. The heart rate, systolic arterial pressure, diastolic arterial pressure, mean arterial pressure and rectal temperature decreased in all groups, and group LF showed the biggest effect on the basic physiological variables, with the lowest heart rate during the test, significantly decreased rectal temperature, and the most decreased values of arterial pressure. Blood for determination of serum lidocaine concentration was taken before anaesthesia and 5, 30, 60, 90, 120, 150 and 180 min after initial intravenous injection of drugs. Fentanyl and ketamine did not cause significant changes of serum lidocaine concentration in dogs and may be used as adjuvant in intravenous anaesthesia without a significant increase in lidocaine absorption.