In vitro elution characteristics of gentamicin- and teicoplanin-loaded CMW1 and Palacos R bone cement

Purpose

To compare the in vitro elution characteristics of CMW1 and Palacos R bone cement loaded with gentamicin, teicoplanin, or in combination.

Methods

Four bone cement discs were prepared for each cement type. Disc 1 contained no antibiotics; disc 2 contained 0.5 g gentamicin; disc 3 contained 2 g teicoplanin; disc 4 contained 0.5 g gentamicin and 2 g teicoplanin. Elution studies were conducted using a fluorescence polarisation immunoassay technique and performed at intervals of 6 weeks.

Results

For CMW1, gentamicin and teicoplanin elution levels in combination discs were higher than those in the single antibiotic discs (p < 0.001 & p < 0.06). For Palacos R, gentamicin elution levels in combination discs were higher than those in the single antibiotic discs (p < 0.001), but teicoplanin elution levels in combination discs were lesser than that from the single antibiotic discs (p < 0.02). In single and combination discs, gentamicin elution levels in Palacos R were higher than those in CMW1 (p < 0.001 & p < 0.001). Palacos R eluted more teicoplanin than CMW1, except in combined disc with gentamicin, when less teicoplanin was eluted.

Conclusion

Antibiotic elution is higher in Palacos R than CMW1. Antibiotic combination in both cement types has the synergistic effect of increasing antibiotic elution, except for teicoplanin from Palacos R. When high elution of gentamicin is required, Palacos R is preferable. When high elution of teicoplanin is required, Palacos R with only teicoplanin is superior to CMW1.

Pseudomonas aeruginosa infection in augmented care: the molecular ecology and transmission dynamics in four large UK hospitals

BACKGROUND

Pseudomonas aeruginosa is a common opportunistic pathogen and molecular typing in outbreaks has linked patient acquisition to contaminated hospital water systems.

AIM

To elucidate the role of P. aeruginosa transmission rates in non-outbreak augmented care settings in the UK.

METHODS

Over a 16-week period, all water outlets in augmented care units of four hospitals were sampled for P. aeruginosa and clinical isolates were collected. Outlet and clinical P. aeruginosa isolates underwent whole-genome sequencing (WGS), which with epidemiological data identified acquisition from water as definite (level 1), probable (level 2), possible (level 3), and no evidence (level 4).

FINDINGS

Outlets were positive in each hospital on all three occasions: W (16%), X (2.5%), Y (0.9%) and Z (2%); and there were 51 persistently positive outlets in total. WGS identified likely transmission (at levels 1, 2 and 3) from outlets to patients in three hospitals for P. aeruginosa positive patients: W (63%), X (54.5%) and Z (26%). According to the criteria (intimate epidemiological link and no phylogenetic distance), approximately 5% of patients in the study 'definitely' acquired their P. aeruginosa from their water outlets in the intensive care unit. This study found extensive evidence of transmission from the outlet to the patients particularly in the newest hospital (W), which had the highest rate of positive outlets.

CONCLUSIONS

The overall findings suggest that water outlets are the most likely source of P. aeruginosa nosocomial infections in some settings, and that widespread introduction of control measures would have a substantial impact on infections.

Prophylactic oral nystatin for preterm babies under 33 weeks' gestation decreases fungal colonisation and invasive fungaemia

BACKGROUND

Invasive fungal infection is an important cause of mortality and morbidity in extremely preterm babies. Colonisation with Candida is a risk factor for systemic infection. A policy of oral nystatin prophylaxis was introduced in November 2000 with the aim of reducing the incidence of invasive fungaemia.

AIM

To determine whether this policy had reduced the rates of fungal colonisation and invasive fungal infection.

METHODS

All neonates of <33 weeks' gestation born between 1998 and 2003 were studied. Neonates born between January 1998 and October 2000 who did not receive nystatin prophylaxis (group A) were compared with those born between November 2000 and December 2003 who received nystatin prophylaxis (group B). Infant details, blood culture results and the results of weekly surface swabs were recorded.

RESULTS

1459 neonates (group A = 724 , group B = 735) of <33 weeks' gestation were admitted in the study period. There were no differences in birth weight, gestation, gender or proportion of babies transferred in from other units between the groups. There was a reduction in colonisation from 257 (35.5%) in group A to 132 (18%) in group B. The incidence of invasive fungaemia decreased from 30 (4.1%) to 13 (1.8%) between the two groups. There was also a reduction in mortality between the two groups from 17.8% to 11.8%.

CONCLUSIONS

The introduction of a prophylactic nystatin administration policy for babies born before 33 weeks was associated with a significant reduction in fungal colonisation and invasive fungal infection.

Chemotherapy for tumors: an analysis of the dynamics and a study of quadratic and linear optimal controls

We investigate a mathematical model of tumor-immune interactions with chemotherapy, and strategies for optimally administering treatment. In this paper we analyze the dynamics of this model, characterize the optimal controls related to drug therapy, and discuss numerical results of the optimal strategies. The form of the model allows us to test and compare various optimal control strategies, including a quadratic control, a linear control, and a state-constraint. We establish the existence of the optimal control, and solve for the control in both the quadratic and linear case. In the linear control case, we show that we cannot rule out the possibility of a singular control. An interesting aspect of this paper is that we provide a graphical representation of regions on which the singular control is optimal.

Fusobacterium necrophorum-induced sepsis: an unusual case of Lemierre's syndrome

Classical Lemierre's syndrome is characterized by severe sepsis with metastatic abscess formation in young, previously fit people from a primary head or neck focus. The causative organisms are the anaerobic fusobacteria, most commonly Fusobacterium necrophorum. We describe the evaluation, therapeutic interventions and management of a patient with Lemierre's syndrome who presented in septic shock with multiple organ dysfunction. The patient required immediate interventions including endotracheal intubation and mechanical ventilation, fluid resuscitation, inotropic support, bilateral thoracostomy tube drainage of empyemata and antimicrobial therapy. The unexpected isolation of Fusobacterium necrophorum from blood cultures and empyema fluid necessitated a change of antibiotic regime to provide anaerobic cover. The patient required 4 weeks of intensive support including prolonged antimicrobial therapy, and after a further 2 weeks was discharged home from hospital. This case highlights the need to raise the awareness of 'the forgotten disease': Lemierre's syndrome. Its diagnosis may, as in this case, be confounded by a lack of symptoms of pharyngitis at the time of presentation, and end-organ dysfunction associated with severe sepsis, possibly suggesting an alternative source of infection. As appropriate antibiotics reduce mortality dramatically, clinicians need to be alert to Lemierre's syndrome and include it in the differential diagnosis in young but otherwise healthy patients presenting with severe sepsis.

Fungal infection but not type of bacterial infection is associated with a high mortality in primary and secondary infected pancreatic necrosis

INTRODUCTION

Knowledge of microbiology in the prognosis of patients with necrotizing pancreatitis is incomplete.

AIM

This study compared outcomes based on primary and secondary infection after surgery for pancreatic necrosis.

METHOD

From a limited prospective database of pancreatic necrosectomy, a retrospective case note review was performed (October 1996 to April 2003).

RESULTS

55 of 73 patients had infected pancreatic necrosis at the first necrosectomy. 25 of 47 patients had resistant bacteria to prophylactic antibiotics (n = 21) or did not receive prophylactic antibiotics (n = 4), but this was not associated with a higher mortality (9 of 25) compared to those with sensitive organisms (4 of 22). Patients with fungal infection (n = 6) had a higher initial median (95% CI) APACHE II score compared to those without (11 (9-13) verus 8.5 (7-10), p = 0.027). Five of six patients with fungal infection died compared to 13 of 47 who did not (p = 0.014). With the inclusion of secondary infections 21 (32%) of 66 patients had fungal infection with 10 (48%) deaths compared to 11 (24%) of 45 patients without fungal infection (p = 0.047).

CONCLUSION

Whether associated with primary or secondary infected pancreatic necrosis, fungal but not bacterial infection was associated with a high mortality.

Degradation of dehydroascorbic acid in parenteral nutrition mixtures

The degradation of ascorbic acid (AA) stored in parenteral nutrition (PN) regimens is initially by oxidation, catalysed by trace elements, in particular copper. After prolonged storage the concentration of AA remains relatively constant, with little variation, due to the lack of available oxygen. The initial degradation product is dehydroascorbic acid (DHAA). This is generated in an anaerobic environment, and is hypothesised to degrade by hydrolysis. It is the purpose of this investigation to ascertain the effect of temperature and trace elements on the anaerobic degradation of DHAA, and to identify the kinetics of the reaction. A stability-indicating reversed-phase HPLC assay was used. The column contained C(18) reverse-phase packing (Luna), mean diameter 5 microm. The column dimensions were 15 cm long with an internal diameter of 0.4 cm. The mobile phase consisted of methanol: phosphate buffer (pH 7.8: 0.067 mol dm(-3)) at a ratio of 40: 60 (v/v) and also included Cetrimide (mixed alkyltrimethylammonium bromide) (0.05 mol dm(-3)) as an ion pair reagent. The flow rate was 0.7 ml min(-1) and detection was by ultra-violet light absorption at 278 nm. This assay was used to monitor the degradation rate of DHAA in PN mixtures with and without trace elements over a range of temperatures (5-35 degrees C). Results indicated a first order reaction that was temperature-dependent but trace elements independent.

Mechanism of 3-methylaspartase probed using deuterium and solvent isotope effects and active-site directed reagents: identification of an essential cysteine residue

The mechanism of the L-threo-3-methylaspartate ammonia-lyase (EC 4.3.1.2) reaction has been probed using deuterium and solvent isotope effects with three different substrates, (2S,3S)-3-methylaspartic acid, (2S)-aspartic acid and (2S,3R)-3-methylaspartic acid. Each substrate appears to form a covalent adduct with the enzyme through the amination of a dehydroalanine (DehydAla-173) residue. The true substrates are N-protonated and at low pH, the alkylammonium groups are deprotonated internally in a closed solvent-excluded pocket after K+ ion, an essential cofactor, has become bound to the enzyme. At high pH, the amino groups of the substrates are able to react with the dehydroalanine residue prior to K+ ion binding. This property of the system gives rise to complex kinetics at pH 9.0 or greater and causes the formation of dead-end complexes which lack Mg2+ ion, another essential cofactor. The enzyme-substrate adduct is subsequently deaminated in two elimination processes. Hydrazines act as alternative substrates in the reverse reaction direction in the presence of fumaric acid derivatives, but cause irreversible inhibition in their absence. Borohydride and cyanide are not inhibitors. N-Ethylmaleimide also irreversibly inactivates the enzyme and labels residue Cys-361. The inactivation process is enhanced in the presence of cofactor Mg2+ ions and Cys-361 appears to serve as a base for the removal of the C-3 proton from the natural substrate, (2S,3S)-3-methylaspartic acid. The dehydroalanine residue appears to be protected in the resting form of the enzyme by generation of an internal thioether cross-link. The binding of the substrate and K+ ion appear to cause a conformational change which requires hydroxide ion. This is linked to reversal of the thioether protection step and generation of the base for substrate deprotonation at C-3. The deamination reaction displays high reverse reaction commitments and independent evidence from primary deuterium isotope effect data indicates that a thiolate acts as the base for deprotonation at C-3.

The influence of amino acid source on the stability of ascorbic acid in TPN mixtures

This study was undertaken to investigate the stability of ascorbic acid and its primary degradation product, dehydroascorbic acid, in total parenteral nutrition (TPN) mixtures. The influence of the type of bag and the commercial source of amino acid on ascorbate degradation was examined, using a stability-indicating high-pressure liquid chromatography (HPLC) method. Ascorbic acid was most stable in multilayered bags, compared with ethylvinyl acetate (EVA) bags. Results indicated that, in multilayered bags, the initial rapid ascorbic acid degradation was greatest in TPN mixtures containing amino acid infusions without reducing activity. In contrast, degradation in TPN mixtures containing amino acids with reducing compounds (Vamin 14 and Freamine III 8.5%) was less than 10% of the added amount. Dehydroascorbic acid degraded approximately in parallel with ascorbic acid, and it contributed to the total available ascorbate activity. The addition of air to TPN mixtures in multilayered bags caused accelerated degradation of both ascorbic acid and dehydroascorbic acid. It is concluded that TPN mixtures compounded in multilayered bags can be safely assigned extended shelf lives, especially if compounded using an amino acid with reducing activity. This is principally due to the protective effect of the bag wall in preventing oxygen transmission, the cause of ascorbic acid oxidation, because oxygen transmission through the bag wall is minimized during storage. TPN mixtures stored in EVA bags should be administered within 2-4 d of compounding, depending on the amino acid infusion used.

Justifying an information system

A four-step model for the hospital pharmacist to use in justifying a computerized information system is described. In the first step, costs are identified and analyzed. Both the costs and the advantages of the existing system are evaluated. A request for information and a request for proposal are prepared and sent to vendors, who return estimates of hardware, software, and support costs. Costs can then be merged and analyzed as one-time costs, recurring annual costs, and total costs annualized over five years. In step 2, benefits are identified and analyzed. Tangible economic benefits are those that directly reduce or avoid costs or directly enhance revenues and can be measured in dollars. Intangible economic benefits are realized through a reduction in overhead and reallocation of labor and are less easily measured in dollars. Noneconomic benefits, some involving quality-of-care issues, can also be used in the justification. Step 3 consists of a formal risk assessment in which the project is broken into categories for which specific questions are answered by assigning a risk factor. In step 4, both costs and benefits are subjected to a financial analysis, the object of which is to maximize the return on investment to the institution from the capital being requested. Calculations include return on investment based on the net present value of money, internal rate of return, payback period, and profitability index. A well-designed justification for an information system not only identifies the costs, risks, and benefits but also presents a plan of action for realizing the benefits.

Evaluating and selecting an information system, Part 2

Final steps in the evaluation and selection of a computerized information system for the pharmacy department are described. Once the computerization committees have been established, the needs assessment has been conducted, and vendors have responded to the request for proposal, the vendors and their products are subjected to quantitative and qualitative evaluations. The quantitative evaluation involves factors that can be counted, weighted, or tabulated and involves little professional judgment. Vendors can be quantitatively evaluated on the basis of the utility and features of the proposal, the fields to which the product applies, financial strength, product maturity, number of installations, regional presence, user group, software releases and upgrades, personnel, technology, and system costs. The qualitative evaluation requires judgment and intuition and is best performed by pharmacists. Vendors can be qualitatively evaluated on the basis of references, site visits, personnel, demonstrations and presentations, history and plans, user group, product literature, implementation plans, technology, and personalities. The steering committee makes the final selection of a system, and a contract is written that safeguards the hospital's interests. The contract should include performance criteria, promises made orally by salespersons, protection against software and other defects, a phased-in payment schedule, and language covering hardware, support and maintenance, default, and liability. Resources should be budgeted for implementation and stress testing after the contract is signed. Costly errors in selecting a pharmacy information system can be avoided by thoroughly evaluating vendors and writing a contract that protects the hospital.

Evaluating and selecting an information system, Part 1

Initial steps in the process of evaluating and selecting a computerized information system for the pharmacy department are described. The first step in the selection process is to establish a steering committee and a project committee. The steering committee oversees the project, providing policy guidance, making major decisions, and allocating budgeted expenditures. The project committee conducts the departmental needs assessment, identifies system requirements, performs day-to-day functions, evaluates vendor proposals, trains personnel, and implements the system chosen. The second step is the assessment of needs in terms of personnel, workload, physical layout, and operating requirements. The needs assessment should be based on the department's mission statement and strategic plan. The third step is the development of a request for information (RFI) and a request for proposal (RFP). The RFI is a document designed for gathering preliminary information from a wide range of vendors; this general information is used in deciding whether to send the RFP to a given vendor. The RFP requests more detailed information and gives the purchaser's exact specifications for a system; the RFP also includes contractual information. To help ensure project success, many institutions turn to computer consultants for guidance. The initial steps in selecting a computerized pharmacy information system are establishing computerization committees, conducting a needs assessment, and writing an RFI and an RFP. A crucial early decision is whether to seek a consultant's expertise.

Developing the request for proposal

The development of a request for proposal (RFP) to computer hardware and software vendors is described. The RFP functions as a planning document, facilitating communication with a selection of vendors, contract negotiations, and development of acceptance criteria. Development of the pharmacy specifications for the RFP involves evaluating and collecting statistics on the existing manual system, planning future services to be provided by the pharmacy and the hospital, evaluating any computer systems already within the hospital, and assessing the impact of pharmacy's interaction with other departments. This information is translated into descriptions of exactly what is to be provided by computerization. The resulting RFP should include a description of the current manual or electronic data processing system. The priority of each function requested, requests for vendor-specific data, contract information, and instructions for the vendor to use in submitting a proposal. Because the RFP's purpose is to communicate unique system needs, the less specific it is written, the greater the opportunity for misinterpretation.

Pharmacy analyzes costs, savings of computer information system

Cost justification of proposed computerization of the pharmacy department's information processing system involved identification of tangible and "intangible" savings and of a reasonable payback period.

Minimum standards aid performance

The pharmacy department at Virginia Mason Hospital developed a minimum standards document that has proved to be a valuable management tool.

A simple method for incorporating single pass dialysate delivery and controlled ultrafiltration with the RP-6 high flux dialyzer

A simple hemodialysis protocol has been developed to permit significant "middle molecule" clearance, yet retain normal low molecular weight clearance. The high flux RP-6 dialyzer has been combined with a single pass dialysate delivery system to provide accurate control of ultrafiltration without resorting to specialized or expensive equipment. By operating the RP-6 in the co-current mode, a simple valve on the dialysate output can be used to regulate ultrafiltration. At QB = 200 ml/min and QD = 500 ml/min, CU = 127 ml/min and CB12 = 56 ml/min at zero ultrafiltration rate; these values increase considerably with ultrafiltration. This protocol offers dialysis centers with standard equipment the opportunity to use high flux membranes in a routine manner.