Simultaneous measurements of arterial diameter and blood pressure to determine the arterial compliance, wall mechanics and stresses in vivo.
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BACKGROUND: to develop a periarterial dimensional clip-probe which, associated with endovascular pressure measurement, real-time digital signal processing/data treatment systems, enables characterisation of the basic wall mechanics in given arterial sites. DESIGN: experimental study. MATERIAL: a facing pair of ultrasonic crystals was incorporated in periarterial highlight probes, made of sterilisable silicone and manufactured from computer-designed stainless steel casts. The A/D converted diameter and pressure (from an endovascular micro-tip probe) signals, triggered by the ECG, were on-line processed to provide their respective profiles during an averaged cardiac cycle, and subsequently the arterial wall physics. The technique was tested in the iliac and renal arteries in eight pigs. RESULTS: the technique was found to indicate adequately that arterial responses to distending blood pressure, as given by Petersons modulus and relative pulsatility, were identical in renals and iliacs. In contrast, the compliance, circumferential incremental elastic modulus and midwall circumferential stress were higher in iliacs than in renals, whereas arterial stiffness of the renals surpassed that of the iliacs. DISCUSSION: the technique with sterilisable probes produces in vivo pressure-diameter relationships, arterial compliance, and wall mechanics and stresses, whatever the arterial size. The porcine iliacs and renals are elastic and viscorigid arteries, respectively. (+info)
A comparison of tracheal tube tip designs on the passage of an endotracheal tube during oral fiberoptic intubation.
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BACKGROUND: The design of an endotracheal tube has been shown to influence the passage of the tube through the glottis during fiberoptic intubation. Difficulty in passing the endotracheal tube can occur if the aryepiglottic folds obstruct the passage of the bevel. The relevant aspects of endotracheal tube design include the shape of the bevel, the material used by the manufacturer, and the ability of the tube to conform to the shape of the fiberscope. The aim of the current study was to compare the ease of passage through the glottis of two different tubes. One tube was a wire reinforced polyvinyl chloride tube with a standard bevel and the other was a newly designed tube with a bevel of different shape and made of silicone rubber. The new design is for use with the a commerical intubating laryngeal mask. METHODS: The authors studied a population of 30 patients who received a standard anesthetic. In all cases, oral fiberoptic intubation was attempted. Anesthetic was administered to each patient using both tubes, and before the study the order of the tubes was randomized. The difficulty in passing the tube was assessed by a blinded observer and graded using a three-point scale (grade 1: no difficulty passing the tube; grade 2: obstruction to passing the tube relieved by withdrawal and a 90 degrees anticlockwise rotation; grade 3: obstruction necessitating more than one manipulation or external laryngeal manipulation). RESULTS: In 27 patients, no difficulty was shown by use of the silicone-tipped tube. In only three patients was there difficulty that necessitated a 90 degrees anticlockwise twist. With the wire-reinforced tube, no difficulty was experienced on 14 occasions. Grade 1 difficulty was experienced eight times and difficulty necessitating more than one maneuver, head movement, or external laryngeal manipulation was seen on eight occasions. Statistical significance was achieved at P = 0.0002 (Wilcoxon signed rank test). CONCLUSIONS: The authors conclude that the use of the silicone-tipped tube with the new bevel design may provide an advantage in the clinical situation of fiberoptic intubation. (+info)
Durability of anti-infective effect of long-term silicone sheath catheters impregnated with antimicrobial agents.
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This study was performed to test the long-term antimicrobial efficacy of impregnated silicone catheters comprising an antimicrobial layer sandwiched between an external surface sheath and a luminal surface silicone sheath. The design of the catheter permits the introduction of various antimicrobials in addition to anticoagulants or antifibrins in the antimicrobial layer and allows their gradual release over a period of months after insertion. The in vitro data presented show that the catheter can provide antimicrobial activity for 90 days, after being replated for 15 7-day cycles of replating. When the catheters were immersed in human serum and incubated at 37 degrees C, they demonstrated significant antimicrobial activity after more than 325 days of incubation. The significant long-term in vitro antimicrobial activity observed may imply effective in vivo activity for almost 1 year after insertion and could serve as a cost-effective alternative to surgically implantable silicone catheters. (+info)
Anesthetic considerations for orthognathic surgery with evaluation of difficult intubation and technique for hypotensive anesthesia.
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Orthognathic surgery is carried out to improve facial appearance and/or to improve malocclusion. Usually, patients are young and healthy. However, they may have airway problems. Reinforced silicone low-pressure, high-volume endotracheal tubes and p-xylometazoline (Otrivin) for nasal vasoconstriction reduces problems due to the endotracheal tubes. A head-up position with ventilator and monitoring equipment at the foot end helps the surgeons as well as the surgery. Surgeons may be the cause of endotracheal tube problems. Bleeding is a major problem that may be encountered and is reduced by induced hypotension. During osteotomies, severe bradycardia may occur and may even lead to cardiac arrest. In the early postoperative period, bleeding may be a problem. Later ulceration at the tip of the nose and on the buttocks may be seen if preventive measures are not carried out. (+info)
Calcification comparison of polymers for vascular graft.
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Polytetrafluoroethylene (PTFE), polyurethane (PU) and silicone are widely known biocompatible polymers which are commonly used for vascular grafts. However, in vitro and in vivo calcifications of these polymers have been found to seriously compromise their quality as biomaterials. In consideration of this problem, the present study compared the calcification rate and extent of PTFE, PU and silicone. Using the in vitro flow-type method, PTFE, PU and silicone films were tested for 1, 4, 7, 10, 14 and 21 days. After 21 days of in vitro calcification test, the calcium levels on PTFE, PU and silicone were 35.89 +/- 5.01 microg/cm2, 23.73 +/- 0.68 microg/cm2 and 19.86 +/- 5.28 microg/cm2, respectively. The higher observed calcium level for PTFE may be due to the effect of the rough surface of PTFE in accumulating calcium ions on the polymer surface. From the 7th day of test, the [Ca]/[P] molar ratio started to decrease over time, and PTFE showed a faster calcification process. This decreasing [Ca]/[P] molar ratio demonstrated the typical calcification mechanism consisting of phosphorus ion accumulation following calcium ion accumulation. This study concluded that PU and silicone are less calcified than PTFE film, a finding in good agreement with previously published studies. (+info)
Improved resolution of natural diacylglycerols by gas-liquid chromatography on polar siloxanes.
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A new cyanoalkylphenylsiloxane (SILAR 5CP) liquid phase is shown to possess sufficient polarity to permit improved GC separations of natural diacylglycerols based on unsaturation and positional placement of fatty acids as well as on molecular weight, which was previously possible only on ethylene glycol succinate polyesters. Unlike the polyesters, the polar siloxane polymer has moderate thermal stability and provides GC columns which can be used for several months without replacing the packing. The GC analyses were made with conventional columns containing 3% SILAR 5CP on Gas Chrom Q at 270 degrees C isothermally. The diacylglycerols were chromatographed as the TMS ethers. Excellent seperations were obtained for the 1,2(2,3)- and 1,3-diacyglycerols derived from corn, linseed, peanut and cod liver oils and for the 1,2-diacyl-sn-glycerols from hepatic glycerophospholipids. (+info)
Biofilm formation by the fungal pathogen Candida albicans: development, architecture, and drug resistance.
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Biofilms are a protected niche for microorganisms, where they are safe from antibiotic treatment and can create a source of persistent infection. Using two clinically relevant Candida albicans biofilm models formed on bioprosthetic materials, we demonstrated that biofilm formation proceeds through three distinct developmental phases. These growth phases transform adherent blastospores to well-defined cellular communities encased in a polysaccharide matrix. Fluorescence and confocal scanning laser microscopy revealed that C. albicans biofilms have a highly heterogeneous architecture composed of cellular and noncellular elements. In both models, antifungal resistance of biofilm-grown cells increased in conjunction with biofilm formation. The expression of agglutinin-like (ALS) genes, which encode a family of proteins implicated in adhesion to host surfaces, was differentially regulated between planktonic and biofilm-grown cells. The ability of C. albicans to form biofilms contrasts sharply with that of Saccharomyces cerevisiae, which adhered to bioprosthetic surfaces but failed to form a mature biofilm. The studies described here form the basis for investigations into the molecular mechanisms of Candida biofilm biology and antifungal resistance and provide the means to design novel therapies for biofilm-based infections. (+info)
Thrombolytic therapy for adhesion of percutaneous central venous catheters to vein intima associated with Malassezia furfur Infection.
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OBJECTIVE: To report our experience with thrombolytic agents in the management of two infants with silicone central venous catheters that had adhered to the vein wall as a result of infection with Malassezia furfur. STUDY DESIGN: Case review of two very low birth weight infants with adherent central venous catheters. RESULTS: Treatment with urokinase and tissue plasminogen activator facilitated the removal of these catheters without breakage or surgical intervention. CONCLUSIONS: Thrombolytic agents should be considered as a treatment of adhered catheters, as well as of occluded catheters. (+info)