Growth of Escherichia coli in propofol, lidocaine, and mixtures of propofol and lidocaine

A review and new insights to antimicrobial action of local anesthetics

Local anesthetics (LAs) are medications which can provide analgesia in distinct body regions through the blockade of voltage-gated sodium channels. Besides pain management, the supplemental role of LAs as antimicrobial agents has been documented in several studies. Different databases including PubMed, Scopus, and Web of Science with the name of different local anesthetics and related names for antimicrobial keywords were searched without time limitation. This review summarized different in vitro and in vivo studies regarding antimicrobial effects of different LAs with focuses on antimicrobial applications of most studied LAs, interaction with different agents which combined with LAs, and mechanisms of action and structural dependence of LAs antibacterial effects. Among different LAs, lidocaine is the most studied preparation. Reduction of the incidence of endophthalmitis after intravitreal injection, prophylaxis for surgical wound infections, prevention of the incidence of catheter-associated infections, oral biofilm reduction on the buccal mucosa, and prevention against bacteria that produced nosocomial infection are some examples of lidocaine antimicrobial application. Studies showed that different factors including structure, concentration, duration of exposure, type of microorganism tested, and temperature affect the degree of LA antimicrobial activity. In addition, various agents such as antibiotics, preservatives, opioids, epinephrine, and propofol can combine with LAs and affect their antimicrobial properties through synergistic or antagonistic action. Due to antibacterial activities, LAs could be applied in a clinic for prophylaxis of surgical site infection. In the application of LAs prior to diagnostic procedures caution should be needed; otherwise, when culturing the specimen, they could lead to false negative results.

Is it safe to re-access sodium bicarbonate bottles for use in minor surgery?

BACKGROUND/PURPOSE

Sodium bicarbonate is added to lidocaine to reduce injection pain. In Canada, it is available in vials exceeding the injection volume 100-fold. These are single-use vials that should be disposed of after one access. Some surgeons re-use vials to reduce waste, potentially causing contamination. This study aims to review the safety of sodium bicarbonate and assess alternatives to current practice.

METHODS

Strains of Staphylococcus aureus, Staphylococcus epidermidis, Pseudomonas aeruginosa, and Burkholderia cepacia were used to assess bacterial growth in vials of sodium bicarbonate. Each pathogen was inoculated into a vial for 14 days at room temperature. At several time points, 1 mL of solution was removed and diluted. One hundred microliters were transferred to blood agar plates and incubated at 35 °C. Colony counts were calculated, averaged and plotted onto a logarithmic graph.

RESULTS

Colony counts of all strains fell below observational threshold after 7 days in sodium bicarbonate.

CONCLUSIONS

Although all strains were reduced, bacteria can survive in sodium bicarbonate for several days, during which transmission may occur. Sodium bicarbonate vials should be treated as single-dose, as indicated by the manufacturers. To reduce waste, hospital pharmacies can repackage sodium bicarbonate into smaller vials or pre-alkalize lidocaine with sodium bicarbonate.

The growth of bacteria in infusion drugs: propofol 2% supports growth when remifentanil and pantoprazole do not

BACKGROUND AND OBJECTIVES

Contamination risks of propofol 2%, remifentanil, and pantoprazole; and in vitro effects of these drugs on the growth of common infective agents in intensive care units were evaluated.

METHODS

For detection of contamination risk, drugs were prepared ready to use under intensive care unit conditions, were tested. Effects of these three drugs on bacterial growth were also investigated. Drugs were prepared at the concentrations used in the intensive care unit and inoculated with common pathogens after which they were incubated at 4°C, 22°C and 36°C. Subcultures were made at 0, 2, 4 and 8h and colony counts were evaluated. Minimum inhibitory concentration values were determined for all drugs at 4°C, 22°C and 36°C.

RESULTS

No growth was observed in the drugs prepared in the intensive care unit. Propofol tended to support while remifentanil inhibited bacterial growth. Effect of pantoprozole differed according to the bacteria tested. None of the drugs showed antibacterial activity at the maximum concentrations which may be achieved in blood of the patients.

CONCLUSION

Propofol strongly supports the growth of the microorganisms tested, although remifentanil and pantoprazole do not. Therefore, it is important to follow the strict aseptic techniques for the preparation of propofol.

Local anesthetics as antimicrobial agents: a review

BACKGROUND

Since the introduction of cocaine in 1884, local anesthetics have been used as a mainstay of pain management. However, numerous studies over the past several decades have elucidated the supplemental role of local anesthetics as antimicrobial agents. In addition to their anesthetic properties, medications such as bupivacaine and lidocaine have been shown to exhibit bacteriostatic, bactericidal, fungistatic, and fungicidal properties against a wide spectrum of microorganisms.

METHODS

A comprehensive literature search was conducted using MEDLINE 1950-present for in vitro and in vivo studies pertaining to the antimicrobial activity of various local anesthetics on a broad range of bacterial and fungal pathogens. Studies testing the effect on microbial growth inhibition of local anesthetics alone and in combination with other agents, such as preservatives and other medications, as well as the effect of conditions such as concentration and temperature, were included for review. Outcome measures included colony counts, area-under-the-curve and time-kill curve calculations, minimum inhibitory concentrations, and post-antibiotic effect.

RESULTS

Evidence suggests that local anesthetics as a class possess inherent antimicrobial properties against a wide spectrum of human pathogens. Multiple local anesthetics at concentrations typically used in the clinical setting (e.g., bupivacaine 0.125%-0.75%; lidocaine 1%-3%) inhibit the growth of numerous bacteria and fungi under various conditions. Different local anesthetics showed various degrees of antimicrobial capacity; bupivacaine and lidocaine, for example, inhibit growth to a significantly greater extent than does ropivacaine. Greater concentrations, longer exposure, and higher temperature each correlate with a proportional increase in microbial growth inhibition. Addition of other agents to the anesthetic solutions, such as preservatives, opioids, or intravenous anesthetics such as propofol, modify the antimicrobial activity via either synergistic or antagonistic action. Limited studies attribute the mechanism of action of antimicrobial activity of local anesthetics to a disruption of microbial cell membrane permeability, leading to leakage of cellular components and subsequent cell lysis.

CONCLUSIONS

Local anesthetics not only serve as agents for pain control, but possess antimicrobial activity as well. In such a capacity, local anesthetics can be considered as an adjunct to traditional antimicrobial use in the clinical or laboratory setting. Additionally, caution should be exercised when administering local anesthetics prior to diagnostic procedures in which culture specimens are to be obtained, as the antimicrobial activity of the local anesthetic could lead to false-negative results or suboptimal culture yields.

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.

Comparison of antimicrobial effects of dexmedetomidine and etomidate-lipuro with those of propofol and midazolam

BACKGROUND AND OBJECTIVES

The aim of our study was to investigate the antimicrobial effects of dexmedetomidine and etomidate-lipuro, and to compare these effects with those of midazolam and propofol on Staphylococcus aureus, Escherichia coli, Pseudomonas aeroginosa, Acinetobacter baumannii and extended-spectrum beta-lactamase Escherichia coli ( E. coli ESBL).

METHODS

All hypnotic dilutions were exposed to micro-organisms for 0, 30, 60, 120 and 240 min at room temperature in vitro. The inoculums taken from diluted suspensions were re-inoculated on blood agar and incubated for 18-24 h at 35 degrees C after which a count of the colonies was compared.

RESULTS

Midazolam reduced the viable cells of S. aureus at 30, 60, 120 and 240 min, and also completely inhibited the growth of E. coli, P. aeroginosa, A. baumannii and E. coli ESBL. Dexmedetomidine, etomidate-lipuro and propofol, however, did not inhibit any of the micro-organisms tested.

CONCLUSION

In vitro, midazolam had an antimicrobial effect on E. coli, P. aeroginosa, A. baumannii and E. coli ESBL. Like propofol and dexmedetomidine, etomidate-lipuro had no antimicrobial effect on any of the micro-organisms tested.

Recent advances in intravenous anaesthesia

Efforts to develop new hypnotic compounds continue, although several have recently failed in development. Propofol has been reformulated in various presentations with and without preservatives. Pharmacokinetic and pharmacodynamic differences exist between some of these preparations, and it is currently unclear whether any have substantial advantages over the original presentation. The use of target-controlled infusion (TCI) has been extended to include paediatric anaesthesia and sedation. Application of TCI to remifentanil is now licensed. Linking of electroencephalogram (EEG) monitoring to TCI for closed-loop anaesthesia remains a research tool, although commercial development may follow. The availability of stereoisomer ketamine and improved understanding of its pharmacology have increased non-anaesthetic use of ketamine as an adjunct analgesic. It may be useful in subhypnotic doses for postsurgical patients with pain refractory to morphine administration.

[Total intravenous anesthesia. On the way to standard practice in pediatrics]

Since venous cannulation in children has become easier and extensive experience has been gained with total intravenous anaesthesia (TIVA) in adults, the interest in TIVA for children has recently increased. An intensified sensitivity of the operating room atmosphere to contamination with volatile anaesthetic agents is another important reason to choose intravenous techniques for paediatric anaesthesia. One of the most interesting agents for TIVA in paediatric anaesthesia is propofol. The pharmacokinetic and pharmacodynamic data for modern intravenous drugs is poor. Because the interpatient variability is relatively large, pharmacokinetic data can only provide guidelines for the dosage of propofol. Propofol has a rapid and smooth onset of action and is as easy to titrate in children as in adults. Propofol can be excellently controlled. Severe haemodynamic side-effects are missing in healthy children and plasma is cleared rapidly of propofol by redistribution and metabolism. There is no evidence of significant accumulation, not even after prolonged infusion times. Because propofol has no analgetic properties it must be combined with analgetics or a regional block for all painful procedures. The combination with the ultra-short acting remifentanil is a major advantage, but requires effective analgetic concepts for painful procedures. In comparison the combination of propofol with long acting opioids abolishes some of the favourable properties of propofol. Further studies of the kinetics and dynamics of propofol and other intravenous agents are needed in paediatrics which should focus on age, maturity and severity of illness. The whole importance of the propofol-infusion syndrome has to be cleared up urgently. TIVA has an important significance in paediatric anaesthesia for diagnostic and therapeutic procedures, especially where these have to be repeated. In day-case anaesthesia TIVA has advantages for all short procedures and for ENT and ophthalmic surgery: even after prolonged infusion children have an short recovery time. There is no evidence of agitation or other behavioural disorders after TIVA with propofol in paediatric anaesthesia. Propofol has anti-emetic properties. TIVA with propofol can be combined with regional anaesthesia advantageously to provide long-lasting analgesia after surgery. TIVA with propofol has been used successfully for sedation of spontaneously breathing children for MRI and CT and other procedures with open airways like bronchoscopy or endoscopy. Propofol facilitates endotracheal intubation without the use of muscle relaxants. Of course, in malignant hyperthermia TIVA will continue to be the technique of choice. Nothing is known about awareness under TIVA in paediatric patients. TIVA must be considered by comparison with the volatile agents. The use of ultra-short acting agents may cause problems such as awareness, vagal response, involuntary movements and in some cases slow recovery after prolonged infusion of propofol. But it is not known exactly how often this happens during paediatric anaesthesia. With TIVA an effective postoperative analgesia must be provided. Newer administration techniques such as the target-controlled infusions or closed-loop control systems are under development and will help to minimise the potential risk of overdosage with TIVA in paediatrics. At the present TIVA is an interesting and practicable alternative to volatile anaesthesia for pre-school and school children. TIVA with propofol in infants younger than 1 year old requires extensive experience with TIVA in older children and with the handling of this special age group and should be undertaken with maximum precautionary measures.

Growth of microorganisms in propofol and methohexital mixtures

PURPOSE

The purpose of this study was to evaluate the growth of 4 different microorganisms in propofol, methohexital, and 1:1 and 1:3 mixtures of propofol and methohexital.

MATERIALS AND METHODS

The microbial growth of Staphylococcus aureus, Pseudomonas aeruginosa, Candida albicans, and Escherichia coli in 1:1 and 3:1 mixtures of methohexital and 2 types of propofol was measured for 48 hours after mixing the solutions. Two of the 4 test solutions were composed of 1% methohexital combined with Diprivan (AstraZeneca Pharmaceuticals, Wilmington, DE), which uses EDTA as a microbial growth inhibitor. The growth of the same 4 microorganisms was also evaluated in 1:1 and 3:1 mixtures of 1% methohexital and a recently introduced generic propofol marketed by Baxter Pharmaceuticals (Deerfield, IL) that uses sodium metabisulfite as a preservative.

RESULTS

Combining either Diprivan or generic propofol with methohexital in a 1:1 or 1:3 mixture ratio resulted in a solution that, like methohexital alone, significantly resisted the growth of C albicans, E coli, S aureus, and P aeruginosa for 48 hours.

CONCLUSION

The results of our study suggest that 1:1 and 1:3 mixtures of propofol (either Diprivan or generic propofol) and methohexital behave similarly to methohexital alone by resisting growth of the microorganisms studied over the 48-hour time period. If, as has been reported elsewhere, the mixture of these 2 agents results in a solution with desirable anesthetic properties, its ability to resist microbial growth becomes clinically significant by extending the shelf-life of propofol in these mixtures.

An admixture of 3 mg x kg(-1) of propofol and 3 mg x kg(-1) of thiopentone reduces pain on injection in pediatric anesthesia

PURPOSE

To evaluate the incidence of pain on injection in children during anesthetic induction with a 3:1.2 volume admixture of 1% propofol and 2.5% thiopentone (P/T) compared to a 10:1 volume admixture of 1% propofol and 2% lidocaine (P/L).

METHODS

After Ethics Committee approval and informed written parental consent, 127 children, aged one to ten years were studied and randomized into two groups; Group P/L received an induction with 5 mg x kg(-1) of 1% propofol and 1 mg x kg(-1) of lidocaine, Group P/T with 3 mg x kg(-1) of 1% propofol and 3 mg x kg(-1) of 2.5% thiopentone in a standardized fashion. A single, blinded observer scored pain behaviour defined as a motor response of the arm, a verbal complaint of pain, cry and/or one of three standardized facial expressions of pain.

RESULTS

The incidence of pain was 14% in the P/T group, compared to 35% in the P/L group (chi(2)(1) = 7.5, P = 0.006). Motor response was the most frequent pain response in the P/L group (68%).

CONCLUSION

The P/T admixture is a practical and efficacious alternative to P/L for reducing pain on induction in children. Further work to evaluate the optimum proportions and possible adverse effects of this admixture should be done.

Clinically significant concentrations of local anesthetics inhibit Staphylococcus aureus in vitro

This study explores which concentrations of local anesthetics might be expected to inhibit the growth of Staphylococcus aureus. Serial dilutions were made of 0.5% and 0.75% bupivacaine, 2% and 5% lidocaine, 2% and 3% chloroprocaine, and 0.2% and 1% ropivacaine. To each concentration of local anesthetic solution, Mueller Hinton broth medium and Staphylococcus aureus were added. The resulting solutions were incubated and then observed for growth 24 and 48 h later. The minimum concentrations of the local anesthetics that could inhibit growth of Staphylococcus aureus were 0.25% bupivacaine, 1.25% lidocaine and 0.75% chloroprocaine. The inhibitory concentration of ropivacaine could not be determined because the more concentrated solutions precipitated in the Mueller Hinton broth. Local anesthetics may help protect against epidural abscess formation if they are used in sufficiently high concentrations. This effect may help explain the very low reported incidence of epidural abscess.

Routine handling of propofol prevents contamination as effectively as does strict adherence to the manufacturer's recommendations

PURPOSE

Propofol is a potential vector of infection, because it contains no preservative. Thus, the manufacturer's specific recommendations for preparing injections or infusions go beyond the guidelines commonly used in our operating rooms for preparing other iv drugs. The purpose of the present study was to determine whether in the daily routine of an operating theatre a modified propofol handling technique can prevent contamination as effectively as do the manufacturer's handling recommendations.

METHODS

A total of 160 consecutive neurosurgical patients were allocated to either Group I (manufacturer's handling recommendations: i.e., 1) disinfecting propofol vials and ampoules before filling syringes; 2) replacing empty syringes; 3) discarding all material at the end of surgery); or Group II (modified propofol handling protocol: i.e., 1) refilling empty syringes; 2) renewing only the infusion line to the patient).

RESULTS

Total contamination rates were comparable in both groups (Group I: 14/160 (8.75%), Group II: 13/160 (8.13%) (chi2= 0.074; P=0.96). Frequency of contamination was not different between groups; either in sample 1 taken at the beginning of the procedure, (Group I: 5/80 (6.25%) vs Group II: 6/80 (7.5%); chi2=0.098; P=0.76) or in sample 2, taken at the end, (Group I: 9/80 (11.25%) vs Group II: 7/80 (8.75%); chi2=0.278; P=0.598).

CONCLUSION

We conclude that in the daily routine of the operating theatre following a modified propofol handling protocol prevents contamination of propofol syringes as effectively as does adhering to the manufacturer's specific handling recommendations. However, neither of the tested guidelines completely prevented contamination.