Predosing Chemical Stability of Admixtures of Propofol, Ketamine, Fentanyl, and Remifentanil.

Admixtures of propofol-ketamine, propofol-ketamine-fentanyl, and propofol-ketamine-remifentanil were subjected to various clinically relevant conditions to study their chemical stability. A novel high-performance liquid chromatography-mass spectrometry method revealed no degradation of any compound by incubation at 37°C, constant mixing, or table-top storage for 6- and 24-hour time periods, except variable recovery of both propofol and fentanyl in the admixtures of propofol-ketamine-fentanyl suggesting possible degradation.

Antibacterial activity of remifentanil and mixtures of remifentanil and propofol.

STUDY OBJECTIVE: To investigate the antibacterial activity of glycine, which is contained in remifentanil, when combined with propofol. DESIGN: Prospective study. SETTING: Departments of anesthesiology and microbiology of a university hospital. MEASUREMENTS: Growth of the microorganisms Staphylococcus epidermidis, Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, and Candida albicans in propofol 1%; saline dilutions of remifentanil at one-, 10-, and 100-microg/mL concentrations; and 1:1 mixtures of propofol with remifentanil solutions was determined. MAIN RESULTS: Remifentanil inhibits bacterial growth in a concentration-dependent manner. The antibacterial effects were more pronounced with Staphylococcus aureus and Pseudomonas aeruginosa at cultures obtained at the fifth hour. The inhibition of bacterial growth was less influenced with Escherichia coli and Candida albicans. CONCLUSIONS: Propofol and remifentanil mixtures decreased bacterial growth, and combinations may reduce the infectious complications from accidentally contaminated propofol.

An analysis of the need for anesthetic interventions with differing concentrations of labor epidural bupivacaine: an observational study.

BACKGROUND: Labor epidural analgesia techniques using lower concentrations of bupivacaine are designed to maintain pain control with fewer side effects such as hypotension and motor block. However, the increase in sensation may allow breakthrough pain resulting in the need for additional interventions. We examined the number of interventions, both for analgesia and for treatment of side effects, required when using three concentrations of bupivacaine. METHODS: Retrospective observational investigation examining 4493 women who received epidural analgesia during two periods. In the first period, higher concentrations of bupivacaine were used (0.125% and 0.0625%, both with fentanyl 2 microg/mL). In the second period, a very low concentration was used (0.04% plus fentanyl 1.7 microg/mL and epinephrine 1.7 microg/mL). Outcomes were compared using univariate tests, and multivariate Poisson regression was used to identify independent factors influencing interventions. RESULTS: The frequencies of interventions were similar for women receiving bupivacaine concentrations of 0.04% (1.4+/-2.0) and 0.125% (1.5+/-2.0), while women receiving the 0.0625% solution required more interventions (1.8+/-2.3; P<0.001). Women who received 0.04% or 0.0625% bupivacaine required more treatment of breakthrough pain (P<0.002), while those receiving 0.125% bupivacaine required more treatment for hypotension and motor block (P<0.05). Multivariate Poisson regression showed that duration of treatment, maternal age and body mass index were independent factors for the number of interventions. CONCLUSIONS: Neither the total interventions nor intervention rate per hour varied significantly with the concentrations of bupivacaine used in this study. Lower concentrations produced fewer side effects including hypotension, while the higher concentration resulted in less breakthrough pain.

Validation of data on the use of twin mix in minor oral surgery: comparative evaluation of efficacy of twin mix versus 2 % lignocaine with 1:200000 epinephrine based on power analysis and an UV spectrometry study for chemical stability of the mixture.

INTRODUCTION: There is convincing evidence supporting the addition of dexamethasone to lignocaine and its administration as an intra-space injection to achieve benefit of a single dose steroid after third molar surgery. This study was undertaken to validate the existing data on the use of twin mix in minor oral surgery based on power analysis, statistical sample size estimation and an ultraviolet (UV) spectrometry study for chemical stability of the mixture. MATERIAL AND METHODS: A prospective, randomized, double-blind trial was designed to validate the pilot study on the efficacy of twin mix and 2 % lignocaine with 1:200,000 epinephrine in the surgical removal of impacted mandibular third molars. Clinical parameters of anaesthetic latency, anaesthetic duration, efficacy of twin mix as an anaesthetic and post-operative patient discomfort were assessed. The stability of active ingredients in the solution was assessed using a double beam UV-visible spectrophotometery. RESULTS: The results of the study showed better post-operative outcome with administration of dexamethasone and lignocaine as an intra-space injection in decreasing the post-operative patient discomfort. The anaesthetic efficacy of the twin-mix admixture was found statistically similar to the control solution of 2 % lignocaine with 1:200,000 epinephrine. The λmax recorded for dexamethasone and local anaesthetic individually was obtained with the twin-mix solution, which indicated no change in the active pharmacological compounds. DISCUSSION: Clinical anaesthetic efficacy of twin mix is comparable to 2 % lignocaine with 1:200,000 epinephrine when administered in the pterygomandibular space with the additional advantage of a single prick co-administration of dexamethasone with local anaesthetic, lesser sting of the local anaesthetic injection, shorter anaesthetic latency, prolonged duration of the soft tissue anaesthesia and decrease in post-operative discomfort after the oral surgical procedure.

[Analgesia with oxygen-nitrous oxide mixture during percutaneous renal biopsy in children]. / Analgésie par le protoxyde d'azote pour la réalisation de la biopsie rénale percutanée chez l'enfant.

UNLABELLED: The efficacy of an inhaled equimolar mixture of nitrous oxide and oxygen (Entonox/MEOPA) to prevent procedural pain during renal percutaneous biopsies in children was assessed. PATIENTS AND METHODS: One hundred and seven children who underwent 113 renal biopsies during a 17-month period were included in a prospective uncontrolled pediatric study. Efficacy was evaluated using patients' answers to a questionnaire and nurses' observations. RESULTS: Pain was absent in 86.5% of the cases. Mild adverse events were noted in one-third of the procedures, and were always reversible within a few minutes when the inhalation stopped. Acceptability was good. The use of this gas is easy and safe provided a few precautions are observed. CONCLUSION: Inhaled equimolar mixture of nitrous oxide and oxygen prevents procedural pain during renal percutaneous biopsies.

Adverse effects of topical anesthetics for dermatologic procedures.

INTRODUCTION: Topical anesthetics are frequently used to decrease the pain associated with a variety of procedures including cutaneous surgery, cosmetic treatments and laser surgery. They are also routinely used in children prior to invasive procedures, such as venipuncture. The ideal topical anesthetic should safely increase patient comfort associated with these procedures with minimal potential for adverse effects. AREAS COVERED: Topical anesthetic formulations have evolved over the past several decades to include formulations with improved efficacy and side effect profiles. However, significant adverse events are still possible. EXPERT OPINION: Medical practitioners can mitigate the risk of side effects and toxicity with careful selection of anesthetic type, concentration, body location and dermatologic procedure. Compounded formulations should be used with caution in medical settings only on limited body surface areas without occlusion. This review presents a detailed analysis of products available, reported complications and an outline for appropriate use of topical anesthetics in combination with dermatologic procedures.

The anesthetic efficacy of eugenol and the essential oils of Lippia alba and Aloysia triphylla in post-larvae and sub-adults of Litopenaeus vannamei (Crustacea, Penaeidae).

The aim of this study was to evaluate the anesthesia induction and recovery times of sub-adult and post-larvae white shrimp (Litopenaeus vannamei) that were treated with eugenol and the essential oils (EOs) from Lippia alba and Aloysia triphylla. Oxidative stress parameters in the hemolymph of this species were also analyzed. The concentrations of eugenol, A. triphylla EO and L. alba EO recommended for anesthesia were 200, 300 and 750 µL L(-1) for sub-adults and 175, 300 and 500 µL L(-1) for post-larvae, respectively. The concentrations studied during the transport of sub-adults were between 20 and 50 µL L(-1) eugenol, 20-30 µL L(-1)A. triphylla EO and 50 µL L(-1)L. alba EO. For post-larvae, the optimal concentrations for transport were 20 µL L(-1) eugenol and between 20 and 50 µL L(-1)A. triphylla EO. The white shrimp sub-adults that were exposed to A. triphylla EO (20 µL L(-1)) showed increases in their total antioxidant capacities (150%), catalase (70%) and glutathione-S-transferase (615%) activity after 6 h. L. alba EO (50 µL L(-1)) and eugenol (20 µL L(-1)) also increased GST activity (1292 and 1315%) after 6 h, and eugenol (20 µL L(-1)) decreased the total antioxidant capacity (100%). Moreover, concentrations above 30 µL L(-1) for the EOs of A. triphylla and L. alba and 20 µL L(-1) eugenol were effective at inducing anesthesia and improving the antioxidant system against reactive oxygen species (ROS) after 6 h.

A fundamental investigation into the effects of eutectic formation on transmembrane transport.

Eutectic systems enhance the permeation of therapeutic agents across biological barriers, but the mechanism by which this occurs has not previously been elucidated. Using human skin it has proven difficult to isolate the fundamental effects of eutectic formation on molecule diffusion and partition from those that arise as a consequence of the simultaneous application of two agents. The aim of this work was to employ a model hydrophobic membrane to understand the fundamental permeation characteristics of two agents when applied as a eutectic mixture. Lidocaine and prilocaine were selected as model agents and infinite-dose permeation studies were carried out using pre-calibrated Franz diffusion cells with two thicknesses of silicone membrane. Membrane solubility was determined by HCl solution extraction and the membrane diffusion coefficients were calculated from the permeation lag-times. The maximum permeation enhancement was achieved using a eutectic mixture at a 0.7:0.3 prilocaine/lidocaine ratio. A higher solubility of both agents in silicone membrane, enhanced diffusivity of prilocaine and superior release of both drugs, all contributed to produce enhanced permeation from the eutectic mixtures. Deconvolution of the transmembrane transport process suggests that the eutectic enhancement phenomena is a consequence of more favorable permeation characteristics of the two molecules in the absence of a formulation vehicle which competes in the transport process.

Effect of temperature and some common metals on the stability of volatile anaesthetic-Entonox mixtures.

Thermal stability of pressurised ready-to-use volatile liquid anaesthetic mixtures (halothane, isoflurane and enflurane) in Entonox (commercially available premixed 50% N2O, 50% O2 mixture) were investigated at temperatures of 20, 258, 400, 503 and 602 degrees C on glass, stainless steel, copper and aluminium by gas chromatography and GC-MS. It was found that most of the decomposition products formed were halogenated compounds and the observed thermal stabilities in glass, stainless steel and copper allowed a thermal treatment up to 250 degrees C without any decomposition problem. Aluminium was found to be the most effective metal at causing decomposition of the anaesthetic mixtures even at lower temperatures.

Densities of dextrose-free intrathecal local anesthetics, opioids, and combinations measured at 37 degrees C.

Dextrose-free anesthetic medications are commonly used to provide subarachnoid anesthesia and analgesia. Hypobaricity has been proposed as a mechanism to explain postural effects on the extent of sensory block produced by these drugs. Densities of dextrose-free solutions of local anesthetics and opioids, and commonly used anesthetic/opioid mixtures were determined at 37.00 degrees C for comparison with the density of human cerebrospinal fluid (CSF). Measurements accurate to 0.00001 g/mL were performed using a mechanical oscillation resonance frequency density meter. All undiluted solutions tested are hypobaric relative to human lumbar CSF with the exception of lidocaine 1.5% and 2.0% with epinephrine 1:200,000. All mixtures of local anesthetics and opioids tested are hypobaric. We observed good agreement between measured densities and calculated weighted average densities of anesthetic mixtures. While the influence of baricity on the clinical effects of dextrose-free intrathecal anesthetics remains controversial, attempts to attribute postural effects to the baricity of these drugs requires establishment of accurate density values. These density data may facilitate elucidation of the mechanisms underlying the behavior of dextrose-free intrathecal anesthetics.

Topical anesthesia for pediatric lacerations: a randomized trial of lidocaine-epinephrine-tetracaine solution versus gel.

STUDY OBJECTIVE: To compare the adequacy and efficacy of anesthesia experienced with lidocaine-epinephrine-tetracaine (LET) solution versus LET gel during suturing of uncomplicated lacerations on the face or scalp in children. METHODS: Two hundred children with lacerations of the face and scalp requiring suturing were enrolled in this blinded, randomized controlled trial, in the emergency department of a university-affiliated children's hospital. After the application of anesthetic solution or gel, adequacy of anesthesia was determined before suturing. Efficacy of anesthesia during laceration repair was determined by the length of time after removal of the topical anesthetic to the first sign of discomfort that required additional anesthesia or until suture completion. RESULTS: Adequacy of initial anesthesia was equivalent between LET solution and LET gel. There was a significant difference in efficacy of anesthesia between the LET formulations. There were more patients with complete anesthesia (85% versus 76%), fewer persons with partial anesthesia (5% versus 21%), and more persons with incomplete anesthesia (9% versus 3%) in the gel group. CONCLUSION: LET gel is at least as effective as LET solution and possesses theoretical advantages for topical anesthesia during suturing of uncomplicated lacerations on the face and scalp in children.

Topical anesthesia.

OBJECTIVE: To consider topical anesthetic options available to primary care physicians, indications for their use, and efficacy and safety of these agents as supported by the literature. QUALITY OF EVIDENCE: Five randomized controlled trials were retrieved that compared various topical anesthetics as well as topical anesthetics versus infiltrative anesthesia. MAIN FINDINGS: A combination of lidocaine, epinephrine, and tetracaine (LET) is currently the topical anesthetic of choice for repair of simple lacerations involving the faces and scalps of children. A promising new topical preparation is bupivacaine and epinephrine, but its efficacy must be studied in larger populations before widespread use can be advocated. Using EMLA (eutectic mixture of local anesthetics) for repair of extremity lacerations requires further study and cannot yet be recommended. Continued use of topical tetracaine, adrenaline, and cocaine (TAC) is not supported in the literature, because of its greater expense, its status as a restricted narcotic, its potential for toxicity, and better availability of an equally efficacious alternative, LET. CONCLUSIONS: Children's simple facial and scalp lacerations can be safely repaired using topical LET gel. Physicians must adhere to recommendations to avoid mucous membrane contact and ensure appropriate dosing with these agents. Bupivacaine-epinephrine topical preparation is a promising analgesic agent that warrants further study.