Charge-ordering breakdown dynamics and ferromagnetic resonance studies ofB-site Cu diluted Pr1‒xSrxMnO3.

Here, we report the influence of Jahn-Teller active Cu substitution on the charge-ordering (CO) characteristics of one of the well-known manganite Pr0.45Sr0.55MnO3(S55) with a distorted tetragonal structure. Magnetization studies unveil a complex magnetic phase diagram for S55, showing distinct temperature ranges corresponding to various magnetic phases: a ferromagnetic phase dominated by the Double Exchange interaction withTC∼ 220.5 K, an antiferromagnetic phase belowTN∼ 207.6 K induced by CO with a transition temperature ofTCO∼ 210 K consistent with the specific heatCP(T) data, and a mixed phase in the rangeTNTN(T

Spin-liquid state with precursor ferromagnetic clusters interacting antiferromagnetically in frustrated glassy tetragonal spinel Zn0.8Cu0.2FeMnO4.

Spinels (AB2O4) with magnetic ions occupying only the octahedralBsites have inherent magnetic frustration which inhibits magnetic long-range order (LRO) but may lead to exotic states. Here we report on the magnetic properties of the tetragonal spinel Zn0.8Cu0.2FeMnO4, the tetragonality resulting from the Jahn-Teller active Mn3+ions. X-ray diffraction and x-ray photoelectron spectroscopy of the sample yielded the composition (Zn0.82+Cu0.22+)A[Fe0.42+Fe0.63+Mn3+]BO4‒δ. Analysis of the temperature dependence of magnetization (M), ac magnetic susceptibilities (χ'andχ''), dc susceptibility (χ), heat capacityCp, and neutron diffraction (ND) measurements show complex temperature-dependent short-range order (SRO) but without LRO. The data ofχ vs. Tfits the Curie-Weiss law:χ = C/(T ‒ θ) fromT= 250 K to 400 K withθ≃ 185 K signifying dominant ferromagnetic (FM) coupling with the FM exchange constantJ/kB= 17 K, andC= 3.29 emu K mol‒1Oe‒1yielding an effective magnetic momentµeff= 5.13µBresulting from the high-spin states of Cu2+(Asite) and Fe2+(Bsite), while theBsite trivalent ions Mn3+and Fe3+are in their low-spin states. The extrapolated saturation magnetization obtained from theM vs. Hdata atT= 2 K is explained using the spin arrangement (Cu2+↓)A[Fe2+↑, Fe3+↓, Mn3+↑]Bleading to FM clusters interact antiferromagnetically at low temperatures. Temperature dependence of d(χT)/dTshows the onset of ferrimagnetism below ∼100 K and peaks near 47 K and 24 K. The relaxation timeτobtained from temperature and frequency dependence ofχ″when fit to the power law and Vogel-Fulcher laws confirm the cluster spin-glass (SG) state. The magnetic field dependence of the SG temperatureTSGHfollows the equation:TSGH=TSG01-AH2/ϕwithTSG(0) = 46.6 K,A= 8.6 × 10‒3Oe‒0.593andϕ= 3.37. The temperature dependence of hysteresis loops yields coercivityHC∼ 3.8 kOe at 2 K without exchange-bias, butHCdecreases with increase inTbecoming zero above 24 K, theTSG(H) forH= 800 Oe. Variations ofCpvs. Tfrom 2 K to 200 K inH=0 andH=90 kOe do not show any peak characteristic of LRO. However, after correcting for the lattice contribution, a broad weak peak typically of SRO becomes evident centered around 40 K. ForT< 9 K,Cpvaries asT2; a typical signature of spin-liquids (SLs). Comparison of the ND measurements at 1.7 K and 79.4 K shows absence of LRO. Time dependence of thermo-remanent magnetizationMTRM(t) studies below 9 K reveal weakening of the inter-cluster interaction with increase in temperature. A summary of these results is that in Zn0.8Cu0.2FeMnO4, ferromagnetic clusters interact antiferromagnetically without LRO but producing a cluster SG state atTSG(0) = 46.6 K, followed by SL behavior below 9 K.

Investigating the magnetic and magnetocaloric behaviors of LiSm(PO3)4.

We report a detailed study on the magnetic behaviors and magnetocaloric (MC) effect of a single crystal of lithium samarium tetraphosphate, LiSm(PO3)4. The analyses of temperature-dependent magnetization data have revealed magnetic ordering established with decreasing temperature below T p, where T p is the minimum of a dM/dT vs. T curve and varies as a linear function of the applied field H. The Curie temperature has been extrapolated from T p(H) data, as H → 0, to be about 0.51 K. The establishment of magnetic-ordering causes a substantial change in the heat capacity C p. Above T p, the crystal exhibits paramagnetic behavior. Using the Curie-Weiss (CW) law and Arrott plots, we have found the crystal to have a CW temperature θ CW ≈ -36 K, and short-range magnetic order associated with a coexistence of antiferromagnetic and ferromagnetic interactions ascribed to the couplings of magnetic dipoles and octupoles at the Γ7 and Γ8 states. An assessment of the MC effect has shown increases in value of the absolute magnetic-entropy change (|ΔS m|) and adiabatic-temperature change (ΔT ad) when lowering the temperature to 2 K, and increasing the magnetic-field H magnitude. Around 2 K, the maximum value of |ΔS m| is about 3.6 J kg-1 K-1 for the field H = 50 kOe, and ΔT ad is about 5.8 K for H = 20 kOe, with the relative cooling power (RCP) of ∼82.5 J kg-1. In spite of a low MC effect in comparison to Li(Gd,Tb,Ho)(PO3)4, the absence of magnetic hysteresis reflects that LiSm(PO3)4 is also a candidate for low-temperature MC applications below 25 K.

Effect of Ce substitution on the local magnetic ordering and phonon instabilities in antiferromagnetic DyCrO3perovskites.

A detailed crystal structure analysis, temperature and field dependence of magnetic characteristics and phonon instabilities for different compositions (0.1 ⩽x⩽ 0.5) of Dy1-xCexCrO3solid-solutions have been reported. All the investigated compounds exhibit distorted orthorhombic crystal structure with a distortion factor ofdOct/dCell∼ 6 × 10-3/3.5 ppm (forx∼ 0.2) forPbnmspace group that follows Vegard's law. The bonds between apical oxygen atoms (OA1) and Cr atoms stand more rigidly in comparison with the basal oxygen atoms (OB1/OB2) resulting the octahedral distortion and thereby causing the changes in phonon modes. The CrO6octahedral tilt angleθrotates with respect to the Miller pseudocubic axis [101] which varies from 10.36° (x= 0.1) to 12.25° (x= 0.5) and significantly influences the Ag(5) phonon stability by 3% for a change in A-site mean radius from 1.095 Å to 1.141 Å forx= 0.1 and 0.5, respectively. From the magnetization measurements we find that these series of compositions exhibit canted antiferromagnetic (AFM) ordering with Néel temperature,TN1that increases from 151.8 K (x= 0.1) to 162 K (x= 0.5) which also manifests as a significant reduction in the magneto-crystalline anisotropy (HK∼ 2.58 kOe → 2.07 kOe,K1∼ 36.47 J m-3→ 18.97 J m-3) while maintaining the stable Γ4(Gx,Ay,Fz) AFM configuration. Both Dzyaloshinskii-Moriya interaction method and modified Curie-Weiss law are employed to analyse the inverse paramagnetic susceptibility,χ-1(T>TN1). Further, we have evaluated the symmetric (JS) and antisymmetric exchange (DAS) constants, which show progressively increasing trend (JS→ 10.08 K to 11.18 K andDAS→ 1.24 K to 1.73 K) with the incorporation of Ce inside the perovskite lattice. Furthermore, the role of Ce substitution on the low-temperature spin reorientation transition (TSR∼ 3.5 K → 16.8 K pertaining to the Γ25phase configuration) and emergence ofΓ2(Fx,Cy,Gz;FxR,CyR)weak-FM phase between 31 K and 45.5 K are discussed in consonance with the phonon spectra.

Magnetization reversal, field-induced transitions andH-Tphase diagram of Y1-xCexCrO3.

We report a systematic study of the magnetic phase diagram in theH-Tplane, negative magnetization (NM), exchange interactions and field-induced spin-flop transitions in the distorted perovskite Y1-xCexCrO3. Locked AFM and weak-FM configurations in Γ4(Gz,Fy,Ax) phase of YCrO3(S= 3/2 ground state) unlocks into the Γ2(Fz,Gy,Cx;FzR,CxR) phase of the canted AFM and FM structures with the dilute substitution of Ce (x⩾ 0.05). The asymmetric and symmetric exchange interaction (JAS∼ 0.11 meV andJS∼ 0.85 meV) between the trivalent Ce and Cr enable the positive quartic-anisotropy field (HK4∼ 2.85 × 102Oe) along with the second order anisotropy field (HK2∼ 5.93 × 102Oe). Unlike the pristine YCrO3compound, the Ce incorporated system exhibits a giant fourth-order anisotropy constant (K4= 1.35 × 105erg/c.c.) due to the asymmetric exchange interaction between the trivalent Ce-Cr which further lifts the free energy of the system and causes lag in the onset of AFM ordering showing the significant thermal hysteresis (ΔT∼ 10 K) in the field-cooled (FC)-warming measurement protocol as compared to the FC-cooling mode. The H-T phase diagram, mapped from the isothermal magnetization data and differential magnetic susceptibility data with different measurement protocols clearly distinguishes three prominent regions below theTN(∼150 K), viz (i) long-range canted AFM + weak FM phase (Γ4(Gz,Fy,Ax)), (ii) Γ24mixed phase and (iii) robust Γ2(Fz,Gy,Cx;FzR,CxR) AFM + FM phases. Tunable spin-flopped transition (∼ 30 kOe), significant negative exchange-bias field (HEB∼ 2.5 kOe), huge coercive field (HC∼ 22 kOe) and large NM (ΔM∼ 280 emu/mole) are the unique characteristic features of the current investigated system.

Role of disorder when upscaling magnetocaloric Ni-Co-Mn-Al Heusler alloys from thin films to ribbons.

Research in functional magnetic materials often employs thin films as model systems for finding new chemical compositions with promising properties. However, the scale-up of thin films towards bulk-like structures is challenging, since the material synthesis conditions are entirely different for thin films and e.g. rapid quenching methods. As one of the consequences, the type and degree of order in thin films and melt-spun ribbons are usually different, leading to different magnetic properties. In this work, using the example of magnetocaloric Ni-Co-Mn-Al melt-spun ribbons and thin films, we show that the excellent functional properties of the films can be reproduced also in ribbons, if an appropriate heat treatment is applied, that installs the right degree of order in the ribbons. We show that some chemical disorder is needed to get a pronounced and sharp martensitic transition. Increasing the order with annealing improves the magnetic properties only up to a point where selected types of disorder survive, which in turn compromise the magnetic properties. These findings allow us to understand the impact of the type and degree of disorder on the functional properties, paving the way for a faster transfer of combinatorial thin film research towards bulk-like materials for magnetic Heusler alloys.

Record-high thermal barrier of the relaxation of magnetization in the nitride clusterfullerene Dy2ScN@C80-Ih.

The Dy-Sc nitride clusterfullerene Dy2ScN@C80-Ih exhibits slow relaxation of magnetization up to 76 K. Above 60 K, thermally-activated relaxation proceeds via the fifth-excited Kramers doublet with the energy of 1735 ± 21 K, which is the highest barrier ever reported for dinuclear lanthanide single molecule magnets.

Anti-infective-treated central venous catheters for total parenteral nutrition or chemotherapy: a systematic review.

This systematic review assesses the effect of anti-infective-treated central venous catheters (CVCs) on catheter-related bloodstream infection (CRBSI) in patients who received a CVC for total parenteral nutrition (TPN) or chemotherapy. Randomised controlled trials were retrieved from Medline and the Cochrane Library up to 14 October 2007. Two reviewers independently assessed trial quality and extracted data. Data for CRBSI were combined where appropriate, using a random effects model, and subgroup meta-analysis was carried out where applicable. The impact of the risk for CRBSI in the control group on the effect of anti-infective CVCs was studied by using meta-regression based on the bivariate meta-analysis model. Nine trials were included in the review. One trial showed that antibiotic-treated CVCs reduced the risk for CRBSI in outpatients with chemotherapy and a CVC in-situ during a period of about nine weeks. Eight trials did not find an overall significant benefit in favour of antiseptic-treated CVCs in patients who had a CVC during a mean of about two weeks. No relationship could be established between the effect of anti-infective-treated CVCs and the underlying risk for CRBSI, although nearly all trials had serious methodological shortcomings. Thus, available scientific evidence to prevent CRBSI by the use of anti-infective-treated CVCs in patients receiving chemotherapy or TPN is not sufficient as a basis to recommend their use. The recommendation of the Centers for Disease Control and Prevention to use antibiotic- or antiseptic-impregnated CVCs, when the risk for CRBSI remains high despite good hygienic practice, should therefore be limited to patients in the intensive care/perioperative setting.

Anti-infective-treated central venous catheters: a systematic review of randomized controlled trials.

OBJECTIVE: This systematic review assesses the effect of anti-infective-treated central venous catheters (CVCs) on catheter-related bloodstream infection (CRBSI) in the acute care setting. METHODS: Randomized controlled trials were retrieved from Medline and the Cochrane Library up to 15 January 2007. Two reviewers independently assessed trial quality and extracted data. Data for CRBSI were combined where appropriate, using a random effects model. The impact of the risk for CRBSI in the control group (baseline risk) on the benefit of anti-infective CVCs was studied by using meta-regression based on the binomial normal bivariate meta-analysis model. RESULTS: Twenty-one trials were included in the review. Mainly intensive care (IC) patients were studied. Eighteen trials showed that anti-infective CVCs reduced the risk of CRBSI. The number needed to treat (NNT) varied from 182 to 12, with baseline risks ranging from 1% to 10%. Nearly all trials had serious methodological shortcomings. Three trials comparing minocycline-rifampicin-treated catheters with antiseptic-treated catheters showed inconsistent results. One trial suggested that there is not any difference in CRBSI between heparin- and antiseptic-treated CVCs. CONCLUSION: Because the NNT is large when the baseline risk is low, the use of anti-infective-treated CVCs in the acute care setting should only be considered in situations in which background rates of CRBSI are high. The magnitude of benefit as calculated in this review should be interpreted with caution because of strong arguments in favor of a systematic overestimation of the effect. Which type of anti-infective catheter is most effective could not be established from the available data.

Policies for endotracheal suctioning of patients receiving mechanical ventilation: a systematic review of randomized controlled trials.

OBJECTIVE: The Dutch Working Party on Infection Prevention (Werkgroep Infectiepreventie [WIP]) aimed to determine whether certain policies on endotracheal suctioning are better than others in terms of prevention of ventilator-associated pneumonia (VAP) in patients receiving mechanical ventilation in the intensive care unit. METHODS: Publications were retrieved by a systematic search of Medline and the Cochrane Library for literature published before February 2006. Additionally, the reference lists of all identified trials were examined. All randomized trials, quasi-randomized trials, and systematic reviews or meta-analyses of randomized or quasi-randomized trials that compared different policies on endotracheal suctioning for patients receiving mechanical ventilation in the intensive care unit were selected. Two reviewers independently assessed trial quality and extracted data. Disagreements were resolved by discussion with a third reviewer. Data from the original publications were used to calculate the relative risk of VAP. Data for VAP were combined in the analysis where appropriate, by use of a random-effects model. RESULTS: Ten trials were included in the review. The quality of the trials and the way they were reported were generally unsatisfactory. Eight low-quality trials indicate that use of closed instead of open suction systems has no effect on the incidence of VAP. Two moderate-quality trials indicate that changing in-line suction catheters less frequently than every 24 hours does not increase the incidence of VAP. CONCLUSION: The WIP recommends that there be no preferential use of either open or closed endotracheal suction systems to reduce the rate of VAP, but it elucidates that the quality of the evidence is low. Considerations other than prevention of VAP should determine the choice of the suction system. When closed systems are used, the WIP recommends changing the in-line suction catheters every 48 hours. In case of mechanical failure or soiling of the suction system, they may be changed more frequently.

Humidification policies for mechanically ventilated intensive care patients and prevention of ventilator-associated pneumonia: a systematic review of randomized controlled trials.

The Dutch Working Party on Infection Prevention (WIP) aimed to determine whether certain humidification policies are better than others in terms of prevention of ventilator-associated pneumonia (VAP) in mechanically ventilated intensive care unit (ICU) patients. Publications were retrieved by a systematic search of Medline and the Cochrane Library up to February 2006. All (quasi-) randomized trials and systematic reviews/meta-analyses comparing humidification methods in ventilated ICU patients were selected. Two reviewers independently assessed trial quality and extracted data. If the data was incomplete, clarification was sought from original authors and used to calculate the relative risk of VAP. Data for VAP were combined in the analysis, where appropriate, using a random-effects model. Ten trials were included in the review. In general, the quality of the trials and the way they were reported were unsatisfactory. The results did not show any benefit from specific humidification techniques in terms of reducing VAP. WIP do not recommend either passive or active humidifiers to prevent VAP, nor the type of passive humidifiers to be used. Regarding active humidification, WIP recommends using heated wire circuits. This is due to the theoretical consideration that less condensate reduces colonization and subsequent risk of spread throughout an ICU when condensate is removed.

Is there evidence for recommending needleless closed catheter access systems in guidelines? A systematic review of randomized controlled trials.

A systematic review was conducted to determine whether certain vascular access policies are better than others in terms of prevention of catheter-related infections. Publications were retrieved by a search of Medline, the Cochrane Library and Embase up to May 2005. All randomized trials and systematic reviews/meta-analyses of randomized trials evaluating the effect of vascular access policies (i.e. needleless closed systems, conventional closed systems or conventional open systems) on catheter-related infection in hospitalized patients with intravascular catheters in situ were selected. Two reviewers independently assessed trial quality and extracted data. Data from the original publications were used to calculate the relative risk or the incidence-density relative rate of catheter-related infection. Data for similar outcomes were combined in the analysis where appropriate using a random-effects model. Of the six studies reviewed, one was excluded. Five randomized controlled trials were included in the review. The quality of the trials and the way they were reported were generally unsatisfactory. Four trials compared needleless closed systems with conventional open systems. There was a trend for an advantage of the needleless closed devices in terms of less catheter-associated bloodstream infection, less catheter tip colonization and less hub inlet colonization. There were no possibilities for combining data because of clinical heterogeneity. One trial compared needleless closed systems with conventional closed systems and the evidence was inconclusive. From the point of view of infection prevention, there are no objections to use these new systems. However, there is insufficient evidence at this stage to recommend the needleless closed vascular devices.

Urinary catheter policies for short-term bladder drainage in adults.

BACKGROUND: Indwelling urinary catheters are often used for bladder drainage during hospital care. Urinary tract infection is a common complication. Other issues that should be considered when choosing an approach to catheterisation are patients' comfort, other complications/adverse effects, and costs. OBJECTIVES: To determine the advantages and disadvantages of alternative approaches to catheterisation for short-term bladder drainage in adults. SEARCH STRATEGY: We searched the Cochrane Incontinence Group Specialised Register (searched 20 December 2004). Additionally, we examined all reference lists of identified trials. SELECTION CRITERIA: All randomised and quasi-randomised trials comparing catheter route of insertion for adults catheterised for up to 14 days. DATA COLLECTION AND ANALYSIS: Data were extracted by both reviewers independently and compared. Disagreements were resolved by discussion. Data were processed as described in the Cochrane Handbook. If the data in trials had not been fully reported, clarification was sought directly from the authors. MAIN RESULTS: Seventeen parallel-group randomised controlled trials met the inclusion criteria. Fourteen trials compared indwelling urethral catheterisation with suprapubic catheterisation. Groups managed with an indwelling catheter had more cases of bacteriuria (RR 2.60; 95%CI 2.12 to 3.18), more frequent recatheterisation (RR 4.12; 95%CI 2.94 to 7.56), and more people with discomfort (RR 2.98; 95%CI 2.31 to 3.85). There were no reports of complications during insertion, although not all trials stated this explicitly. Three trials compared indwelling urethral catheterisation with intermittent catheterisation. In the two trials with data, there were fewer cases of bacteriuria in the intermittent catheterisation group (RR 2.90; 95%CI 1.44 to 5.84). Costs analyses reported in two trials favoured the indwelling group. AUTHORS' CONCLUSIONS: There was evidence that suprapubic catheters have advantages over indwelling catheters in respect of bacteriuria, recatheterisation and discomfort. The clinical significance of bacteriuria was uncertain, however, and there was no information about possible complications or adverse effects during catheter insertion. There was more limited evidence that the use of intermittent catheterisation was also associated with a lower risk of bacteriuria than indwelling urethral catheterisation, but might be more costly. Using intermittent catheterisation postoperatively limits catheterisation to those people who definitely need it.

Antibiotic policies for short-term catheter bladder drainage in adults.

BACKGROUND: Urinary tract infections account for about 40% of hospital-acquired (nosocomial) infections, and about 80% of urinary tract infections acquired in hospital are associated with urinary catheters. OBJECTIVES: To determine if certain antibiotic policies are better than others in terms of prevention of urinary tract infections, complications, quality of life and cost-effectiveness in short-term catheterised adults. SEARCH STRATEGY: We searched the Cochrane Incontinence Group Specialised Register (searched 20 December 2004). Additionally, we examined all reference lists of identified trials. SELECTION CRITERIA: All randomised and quasi-randomised trials comparing antibiotic policies for short-term (up to and including 14 days) catheterization in adults. DATA COLLECTION AND ANALYSIS: Data were extracted by both reviewers independently and compared. Disagreements were resolved by discussion. Data were processed as described in the Cochrane Handbook. If data had not been fully reported, clarification was sought directly from the authors of the trial. MAIN RESULTS: Six parallel-group randomised controlled trials met the inclusion criteria. In one trial comparing antibiotic prophylaxis with giving antibiotics when clinically indicated amongst female surgical patients who had a urethral catheter for more than 24 hours, symptomatic urinary tract infection was less common in the prophylaxis group (RR 0.20, 95% CI 0.06 to 0.66). Five trials compared antibiotic prophylaxis with giving antibiotics when microbiologically indicated, bacteriuria, pyuria and gram-negative isolates in patients' urine were less common in the prophylaxis group amongst surgical patients with bladder drainage for at least 24 hours postoperatively. Bacteriuria rates were also about five-fold lower in the prophylaxis group in trials involving urological surgery patients and non-surgical patients. No trial compared giving antibiotics when microbiologically indicated with giving antibiotics when clinically indicated. AUTHORS' CONCLUSIONS: There was weak evidence that antibiotic prophylaxis compared to giving antibiotics when clinically indicated reduced the rate of symptomatic urinary tract infection in female patients with abdominal surgery and a urethral catheter for 24 hours. The limited evidence indicated that receiving antibiotics during the first three postoperative days or from postoperative day two until catheter removal reduced the rate of bacteriuria and other signs of infection such as pyuria and gram-negative isolates in patients urine in surgical patients with bladder drainage for at least 24 hours postoperatively. There was also limited evidence that prophylactic antibiotics reduced bacteriuria in non-surgical patients.

Urinary catheter policies for long-term bladder drainage.

BACKGROUND: People requiring long-term bladder draining commonly experience catheter-associated urinary tract infection and other problems. OBJECTIVES: To determine if certain catheter policies are better than others in terms of effectiveness, complications, quality of life and cost-effectiveness in long-term catheterised adults and children. SEARCH STRATEGY: We searched the Cochrane Incontinence Group specialised trials register (searched 9 June 2003). Additionally, we examined all reference lists of identified trials. SELECTION CRITERIA: All randomised and quasi-randomised trials comparing catheter policies (route of insertion and use of antibiotics) for long-term (more than 14 days) catheterisation in adults and children. DATA COLLECTION AND ANALYSIS: Data were extracted by both reviewers independently and compared. Disagreements were resolved by discussion. Data were processed as described in the Cochrane Handbook. If the data in trials have not been fully reported, clarification were sought from the authors. When necessary, the incidence-density rates (IDR) and/or the incidence-density differences (IDD) within a certain time period were calculated. MAIN RESULTS: Seven trials met the inclusion criteria involving 328 patients in four crossover and three parallel-group randomised controlled trials. Only two of the pre-stated six comparisons were addressed in these trials. Three trials compared antibiotic prophylaxis with antibiotics when clinically indicated. For patients using intermittent catheterisation, there were inconsistent findings about the effect of antibiotic prophylaxis on symptomatic urinary tract infection. For patients using indwelling urethral catheterisation, one small trial reported fewer episodes of symptomatic UTI in the prophylaxis group.Four trials compared antibiotic prophylaxis with giving antibiotics when microbiologically indicated. For patients using intermittent catheterisation, there was limited evidence that receiving antibiotics reduced the rate of bacteriuria (asymptomatic and symptomatic). There was weak evidence that prophylactic antibiotics were better in terms of fewer symptomatic bacteriuria. AUTHORS' CONCLUSIONS: No eligible trials were identified that compared alternative routes of catheter insertion. The data from seven trials comparing differing antibiotic policies were sparse, particularly when intermittent catheterisation was considered separately from in-dwelling catheterisation. Possible benefits of antibiotic prophylaxis must be balanced against possible adverse effects, such as development of antibiotic resistant bacteria; these cannot be reliably estimated from currently available trials.

Hair removal policies in clean surgery: systematic review of randomized, controlled trials.

OBJECTIVE: To determine whether certain hair removal policies are better than others to prevent surgical-site infections in patients undergoing clean surgery. METHODS: Publications were retrieved by a systematic search of Medline, the Cochrane Library, and EMBASE up to February 2005. Additionally, the reference lists of all identified trials were examined. All randomized trials, quasi-randomized trials, and systematic reviews or meta-analyses of randomized or quasi-randomized trials comparing hair removal policies in clean surgery were selected. Trials involving patients undergoing cranial neurosurgery were excluded. Two reviewers independently assessed trial quality and extracted data. Disagreements were resolved by discussion with a third reviewer. Data from the original publications were used to calculate the relative risk or risk difference of surgical-site infection. Data for similar outcomes were combined in the analysis, where appropriate, with the use of a random effects model. RESULTS: Four trials were included in the review. No eligible systematic review or meta-analysis of randomized or quasi-randomized trials was found. The quality of the trials and how they were reported were generally unsatisfactory. Evidence regarding whether preoperative hair removal has any effect was inconclusive. When hair removal was considered necessary, evidence about the best time for removal was inconclusive. There was some evidence that hair removal by clipper is superior to removal by razor. CONCLUSIONS: Because of insufficient evidence as a basis for recommendations, the practical consequences for ward management were essential when the Dutch Working Party on Infection Prevention formulated its recommendations for hair removal policies. Large randomized, controlled trials are needed to determine the optimal policy for preoperative hair removal.

Is there evidence for recommending silver-coated urinary catheters in guidelines?

We evaluated the available literature on effectiveness of silver-coated versus uncoated catheters for the prevention of urinary tract infections in catheterized patients stratified by sex, systemic antibiotic use, renal function and duration of catheterization. Controlled clinical trials, randomized clinical trials and systematic reviews/meta-analysis were identified by a search strategy in Medline (1966-August 2001) and in the Cochrane Controlled Trials Register. Keywords were urinary catheterization, silver and infection. Trials using silver-coated catheters in the treatment group and uncoated catheters in the control group, with bacteriuria as the outcome measure, were selected. The quality of the methods used of all selected publications was assessed by using a quality assessment scale for randomized clinical trials. In addition we looked critically at subject-specific aspects. Data from the original publications were used to calculate the overall relative risk of bacteriuria in patients with silver-coated versus uncoated catheters, as well as the effect in subgroups. Thirteen trials and one meta-analysis were identified. Seven reports satisfied the selection criteria with only one achieving a high-quality score. Confounding variables were not considered in any trial. Additional studies with a high standard of internal quality and careful specification of the clinical question with regard to subject-specific critical points are necessary to decide whether the use of silver-coated catheters can be recommended.

Quality assessment of protected specimen brush samples by microscopic cell count.

Protected specimen brushing (PSB), combined with quantitative culture, is now recognized as one of the reference methods for diagnosis of nosocomial pneumonia. However, no criteria exist with which to assess the quality of the PSB sample. We studied numbers of inflammatory cells and bronchial cells per microscopic field (magnification: x500, objective x50) in cytospin preparations of PSB samples. Results of cell count and quantitative culture in a first study period were compared with those in a second study period, following adaptation of the PSB technique and collection of samples from more peripheral sites. The cellular content of samples from patients and controls was investigated. We examined 86 samples from patients with suspected nosocomial pneumonia and 15 samples from uninfected controls. The number of samples with a high cellular content was considerably greater in the second study period. No positive cultures were obtained from samples containing < 10 cells per field. The numbers of cells in samples from uninfected controls were comparable to the numbers in samples from patients. Our results indicate that absence of cells probably represents inadequate sampling. Negative PSB cultures with cytospin preparations containing < 10 cells per microscopic field should therefore be considered with caution, and resampling considered.