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Biomedical subjects

R Gunning

Publications and source records attributed to R Gunning.

8 recordsLinked to original sources
PubMed2003

Gauze and tape and transparent polyurethane dressings for central venous catheters.

BACKGROUND: Central venous catheters facilitate venous access, allowing the intravenous administration of complex drug treatments, blood products and nutritional support, without the trauma associated with repeated venepuncture. However, central venous catheters are associated with a risk of infection. Some studies have indicated that the type of dressing used for central venous catheters may affect the risk of infection. Gauze and tape or transparent polyurethane film dressings such as Tegaderm, Opsite or Opsite IV3000 are the most common types of dressing used to secure central venous catheters. Currently, it is not clear which type of dressing is the most appropriate. OBJECTIVES: To compare gauze and tape and transparent polyurethane central venous catheter dressings in terms of catheter related infection, catheter security, tolerance to dressing material and dressing condition in hospitalised adults and children. SEARCH STRATEGY: The Cochrane Wounds Group Specialised Trials Register (October 2002), the Cochrane Controlled Trials Register (4th Quarter 2002) and the databases; MEDLINE (1966-December 2002, CINAHL (1982-October 2002) and EMBASE (1980-December 2002) were searched to identify any randomised controlled trials comparing the effects of gauze and tape and/or transparent polyurethane dressings for central venous catheter sites. Additional references were identified from bibliographies of published literature and were also sought from other sources. SELECTION CRITERIA: All randomised controlled trials evaluating the effects of dressing type (i.e. gauze and tape and/or transparent polyurethane dressings) on central venous catheter related infection, catheter security, tolerance to dressing material and dressing condition in hospitalised patients. DATA COLLECTION AND ANALYSIS: Twenty-three studies were reviewed. Data was extracted from each paper by two members of the review team independently and results then compared. Differences were resolved either by consensus or by referral to a third member of the review team. Authors were contacted for missing information. MAIN RESULTS: Of the 23 studies reviewed, 14 were excluded. Nine studies were included. Data was only available for meta-analysis from six of the nine included studies. Of the six included studies with available data, two compared gauze and tape with Opsite IV3000, two compared Opsite with Opsite IV3000, one compared gauze and tape with Tegaderm, and one compared Tegaderm with Opsite. There was no evidence of any difference in the incidence of infectious complications between any of the dressing types compared in this review. Each of these comparisons was based on no more than two studies and all of these studies reported data from a small patient sample. Therefore it is probable that the finding of no difference between dressing types is due to the lack of adequate data. REVIEWER'S CONCLUSIONS: There is a high level of uncertainty regarding the risk of infection with the central venous catheter dressings identified in this review. Therefore, at this stage it appears that the choice of dressing for central venous catheters can be based on patient preference. To identify the most appropriate central venous catheter dressings, further research is necessary. It is paramount that any future studies investigating this issue must be rigorously performed randomised controlled trials.

Bacterial Infections↗
PubMed2001

Population pharmacokinetics of amphotericin B in children with malignant diseases.

AIMS: To construct a population pharmacokinetic model for the antifungal agent, amphotericin B (AmB), in children with malignant diseases. METHODS: A two compartment population pharmacokinetic model for AmB was developed using concentration-time data from 57 children aged between 9 months and 16 years who had received 1 mg kg(-1) day(-1) doses in either dextrose (doseform=1) or lipid emulsion (doseform=2). P-Pharm (version 1.5) was used to estimate the basic population parameters, to identify covariates with significant relationships with the pharmacokinetic parameters and to construct a Covariate model. The predictive performance of the Covariate model was assessed in an independent group of 26 children (the validation group). RESULTS: The Covariate model had population mean estimates for clearance (CL), volume of distribution into the central compartment (V) and the distributional rate constants (k12 and k21) of 0.88 l h(-1), 9.97 l, 0.27 h(-1) and 0.16 h(-1), respectively, and the intersubject variability of these parameters was 19%, 49%, 55% and 48%, respectively. The following covariate relationships were identified: CL (l h(-1)) = 0.053 + 0.0456 weight (0.75) (kg) + 0.242 doseform and V (l) = 7.11 + 0.107 weight (kg). Our Covariate model provided unbiased and precise predictions of AmB concentrations in the validation group of children: the mean prediction error was 0.0089 mg l(-1) (95% confidence interval: -0.0075, 0.0252 mg l(-1)) and the root mean square prediction error was 0.1245 mg l(-1) (95% confidence interval: 0.1131, 0.1349 mg l(-1)). CONCLUSIONS: A valid population pharmacokinetic model for AmB has been developed and may now be used in conjunction with AmB toxicity and efficacy data to develop dosing guidelines for safe and effective AmB therapy in children with malignancy.

Adolescent↗
PubMed1999

Amphotericin B in children with malignant disease: a comparison of the toxicities and pharmacokinetics of amphotericin B administered in dextrose versus lipid emulsion.

In a prospective, randomized clinical trial, the toxicity of 1 mg of amphotericin B (AmB) per kg of body weight per day infused in 5% dextrose was compared with that of AmB infused in lipid emulsion in children with malignant disease. In an analysis of 82 children who received a full course of 6 days or more of AmB (117 courses), it was shown that there were significant increases in plasma urea and creatinine concentrations and in potassium requirement after 6 days of therapy with both AmB infused in dextrose and AmB infused in lipid emulsion, with there being no difference between the two methods of AmB administration. An intent-to-treat comparison of the numbers of courses affected by acute toxicity (fever, rigors) and chronic toxicity (nephrotoxicity) also indicated that there was no significant difference between AmB infused in dextrose (78 courses) and AmB infused in lipid emulsion (84 courses). The pharmacokinetics of AmB were investigated in 20 children who received AmB in dextrose and 15 children who received AmB in lipid emulsion. Blood samples were collected up to 24 h after administration of the first dose, and the concentration of AmB in plasma was analyzed by a high-performance liquid chromatography assay. The clearance (CL) of AmB in dextrose (0.039 +/- 0.016 liter. h-1. kg-1) was significantly lower (P < 0.005) than the CL of AmB in lipid emulsion (0.062 +/- 0. 024 liter. h-1. kg-1). The steady-state volume of distribution for AmB in dextrose (0.83 +/- 0.33 liter. kg-1) was also significantly lower (P < 0.005) than that for AmB in lipid emulsion (1.47 +/- 0.77 liter. kg-1). Although AmB in lipid emulsion is apparently cleared faster and distributes more widely than AmB in dextrose, this study did not reveal any significant advantage with respect to safety and tolerance in the administration of AmB in lipid emulsion compared to its administration in dextrose in children with malignant disease.

Adolescent↗
PubMed1987

Increased numbers of ion channels promoted by an intracellular second messenger.

The anomalous rectifier potassium current in Aplysia neurons was examined to determine the immediate cause of an increase in conductance induced by serotonin and mediated by adenosine 3',5'-monophosphate. Voltage-dependent cesium ion block and steady-state current power spectral density were measured under voltage clamp before and after application of serotonin. The amplitude of the anomalous rectifier conductance was increased by adding serotonin, but the shapes of the conductance-voltage curve and the power spectrum were not altered. Calculation of the number of functional channels and of the single-channel conductance from the power spectra indicates that the serotonin-induced increase in conductance resulted from an increase in the number of functional channels, while the single-channel conductance and the open-channel probability were unchanged.

Aplysia↗
PubMed1984

Steady state current noise from the intrinsic gating of inward rectifier channels.

Steady-state current noise from the intrinsic gating of inward rectifier channels in the eggs of the marine polychaete Neanthes arenaceodentata was recorded under voltage clamp conditions. Lorentzian-shaped power spectra with corner frequencies near 1 Hz and zero-frequency asymptotes of 1 - 5 X 10(-23) A2/Hz were obtained for test potentials 15-45 mV positive to EK in solutions containing 10-40 mM Ko. The spectra are compatible with the predictions of a three-state kinetic model for inward rectification in which the single channel rectification is independent of voltage. The single channel conductance derived from this interpretation is 8 pS with 40 mM Ko.

Animals↗
PubMed1983

Kinetics of inward rectifier gating in the eggs of the marine polychaete, Neanthes arenaceodentata.

Potassium current through the inward rectifier of Neanthes arenaceodentata eggs was studied using a voltage-clamp technique. The instantaneous conductance, steady-state conductance and the time constant of current relaxation were analysed as functions of the membrane potential and the external potassium concentration ([K]o). Both the instantaneous and the steady-state conductances increased sigmoidally with hyperpolarization, reaching saturation values at potentials 40 mV more negative than the potassium equilibrium potential (EK). The time-dependent change in conductance followed first-order kinetics throughout an 80 mV potential range centred at EK. The conductances increased with time during hyperpolarizations and decreased with time during depolarizations. The time constant decreased sigmoidally about EK as the membrane potential (Vm) was made more positive. The results are interpreted in terms of two models. The first model assumes single-channel rectification. Forcing the data to conform with this assumption necessitates that the single-channel conductance, the open-channel probability, and the time constant of current relaxation all be nearly identical functions of Vm--EK. This coincidence is considered implausible. The second model ascribes the apparent instantaneous rectification to a fast kinetic process. This model correctly predicts the steady-state conductance, the time-constant of current relaxation, and the unexpected proportionality between the ratio of the steady-state and 'instantaneous' conductances and the time constant of current relaxation. This agreement between data and model is obtained even though neither of the rate constants of the slow gating process has the flexibility of voltage or potassium dependence. The results are considered to imply the existence of a fast gating mechanism in the kinetics of inward rectification.

Animals↗