Growth of microorganisms in propofol, thiopental, and a 1:1 mixture of propofol and thiopental

Investigating antimicrobial features and drug interactions of sedoanalgesics in intensive care unit: an experimental study

Study Objective

Aim of this study was to evaluate antimicrobial effects and interaction between analgesic combinations of fentanyl citrate, dexmedetomidine hydrochloride and tramadol hydrochloride on Staphylococcus aureus, Klebsiella pneumoniae, Escherichia coli, Pseudomonas aeruginosa and Candida albicans which are some of the most common nosocomial infection related microorganisms.

Design

In vitro prospective study.

Setting

University Clinical Microbiology Laboratory.

Measurements

In order to evaluate in vitro antimicrobial effects and interaction between analgesic combinations, tramadol hydrochloride, fentanyl citrate and dexmedetomidin were used against S. aureus ATCC 29213, K. pneumoniae, E. coli ATCC 25922, P. aeruginosa ATCC 27853 and C. albicans ATCC 10231 standard strains by microdilution method.

Main Results

According to microdilution assays tramadol has shown the most efficient antimicrobial activity also it has been observed that 10 μg/ml concentrated dexmedetomidine has antimicrobial effects on S. aureus, K. pneumoniae and P. aeruginosa. Fentanyl has displayed evident inhibitory potency on the pathogens except for Klebsiella pneumoniae, nevertheless our predefined minimum concentration inhibited growth by 9.5 %. Fentanyl and dexmedetomidine together exhibited more antimicrobial effect on P. aeruginosa and E. coli growth. Additionally, when the three drugs examined together, microbial inhibition occurred more than expected on E. coli again and also on C. albicans growth.

Conclusions

Our results revealed the antimicrobial properties and synergy with the different combinations of fentanyl, dexmedetomidine and tramadol against the most common nosocomial infection agents in the ICU. This is the first study in the literature looking into the microbial “interactions” of opioids and sedative drugs but more research is needed in order to define clinico-laboratory correlation.

The Role of GABA Receptor Agonists in Anesthesia and Sedation

GABA (γ-aminobutyric acid) receptors, of which there are two types, are involved in inhibitory synapses within the central nervous system. The GABA_A receptor (GABAAR) has a central role in modern anesthesia and sedation practice, which is evident from the high proportion of agents that target the GABAAR. Many GABAAR agonists are used in anesthesia practice and sedation, including propofol, etomidate, methohexital, thiopental, isoflurane, sevoflurane, and desflurane. There are advantages and disadvantages to each GABAAR agonist currently in clinical use. With increasing knowledge regarding the pharmacology of GABAAR agonists, however, newer sedative agents have been developed which employ 'soft pharmacology', a term used to describe the pharmacology of agents whereby their chemical configuration allows rapid metabolism into inactive metabolites after the desired therapeutic effect(s) has occurred. These newer 'soft' GABAAR agonists may well approach ideal sedative agents, as they can offer well-controlled, titratable activity and ultrashort action. This review provides an overview of the role that GABAAR agonists currently play in sedation and anesthesia, in addition to discussing the future role of novel GABAAR agonists in anesthesia and sedation.

Comparison of propofol (1%) with admixture (1:1) of thiopentone (1.25%) and propofol (0.5%) for laryngeal mask airway insertion in children undergoing elective eye surgery: Double-masked randomized clinical trial

Intravenous propofol 1% has been the preferred agent for Laryngeal Mask Airway (LMA) insertion. Admixture of thiopentone 1.25% and propofol 0.5% (1:1) has been used by various authors for induction as well as insertion of LMA in adults. There is no previous report where this admixture has been used for insertion of LMA in children. This study has been designed to investigate whether this admixture can be a suitable alternative to propofol, in relation to ease of insertion of the LMA, haemodynamic stability, cost containment, pain on injection and recovery in children. In this randomized, double-masked study, 50 ASA grade 1 and 2 patients of age 3 - 15 years and weighing more than 10 kg were included. The patients were divided into two groups; the P group received propofol 1%, while the Ad group received an admixture of thiopentone 1.25% and propofol 0.5% (1:1). All the children were evaluated for incidence of apnoea, pain on injection, jaw relaxation, ease of LMA insertion, coughing, gagging, laryngospasm, involuntary limb movements, incidence of hypotension and recovery. The demographic data, incidence of apnoea, pain on injection, jaw relaxation, ease of LMA insertion, coughing, gagging and involuntary movements were comparable in both groups. In the P group recovery was faster as compared to the Ad group. The admixture was cost effective as compared to Propofol alone [Indian National Rupees (INR) 24.64 +/- 7.62 vs. INR 48.75 +/- 23.25] (P = 0.001)). Admixture of propofol and thiopentone was a cheap, safe and effective alternative to propofol alone, for LMA insertion in children.

Propofol lipidic infusion promotes resistance to antifungals by reducing drug input into the fungal cell

Background

The administration of non-antifungal drugs during patient hospitalization might be responsible for discrepancies between in vitro and in vivo susceptibility to antifungals. Propofol is often administered to intensive care units as a sedative.

The purpose of this study was to evaluate the effect of propofol lipidic infusion upon the growth and susceptibility profile of pathogenic fungi.

Candida and Aspergillus were studied regarding the ability to grow and its susceptibility profile to antifungals in the presence of propofol infusion (Fresenius^®) (1.25, 2.5 and 5 mg.ml^-1) and its lipidic vehicle. The intensity of fluorescence after staining with FUN1, in the presence and absence of propofol infusion, was determined by flow cytometry. Radioactivity assays were also performed in order to quantify the input of [³H]- itraconazole into the fungal cell in the presence of propofol. Assays were repeated after addition of sodium azide, in order to block efflux pumps.

Results

Propofol infusion promoted budding of Candida and the germination of Aspergillus, latter forming a lipid layer around the hypha. An increase of minimal fungicidal concentrations regarding both Candida and Aspergillus strains was found for all antifungals when incubated simultaneously with propofol infusion. A decrease of the intensity of fluorescence of Candida cells was systematically observed, as well as a significant reduced intracellular uptake of [³H] itraconazole in cells treated with propofol infusion, even after the blockade of efflux pumps. The results obtained when testing with the lipid vehicle were similar.

Conclusion

Propofol infusion, due to its lipidic vehicle, increased the fungal germination and promoted resistance to antifungals. This effect seems to be related to the reduced access and/or permeabilization to fungal cells by antifungals.

A novel, lipid-free nanodispersion formulation of propofol and its characterization

PURPOSE

Propofol is a widely used anesthetic agent with highly desirable fast "on" and "off" effects. It is currently formulated as lipid emulsions, which are known to support microbial growth. In this study, a novel, lipid-free nanodispersion formulation of propofol was characterized.

METHODS

The formulation was evaluated for its physical and chemical stability, in vitro compatibility with red blood cells, and its antimicrobial effectiveness. In vivo pharmacokinetic and pharmacodynamic properties of the formulation were evaluated in rats.

RESULTS

Our data suggest that this lipid-free formulation is physically and chemically stable. Compared to the commercial emulsion formulation Diprivan, it causes less hemolysis with red blood cells and has improved antimicrobial activity. In addition, the lipid-free formulation demonstrates similar pharmacological effects to Diprivan in rats.

CONCLUSIONS

This novel, lipid-free formulation exhibits improved in vitro properties without compromising in vivo effects, therefore representing a promising new alternative for propofol.

[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.