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Direct Compression (direct + compression)
Selected AbstractsEchocardiographic Diagnosis of Right Ventricular Inflow Compression Associated with Pectus Excavatum During Spinal Fusion in Prone PositionCONGENITAL HEART DISEASE, Issue 3 2009James M. Galas MD ABSTRACT Introduction., Pectus excavatum is commonly viewed as a benign condition. Associated alterations in hemodynamics are rare. We present an unusual case of right ventricular inflow obstruction and hemodynamic compromise as a consequence of pectus excavatum encountered during surgical intervention. Case., a 15-year-old male with pectus excavatum and thoracolumbar scoliosis developed severe hypotension after induction of general anesthesia and placement in the prone position for elective spinal fusion. A transesophageal echocardiogram revealed anterior compression of the right heart by the sternum with peak and mean right ventricular inflow gradients of 7 and 4 mm Hg, respectively. The gradient resolved with supine positioning and was reproduced with direct compression of the sternum. Conclusions., Although pectus excavatum is generally a benign condition, the cardiologist should be aware of the potential for serious hemodynamic compromise related to positioning in these patients. [source] Cerebral arteriovenous malformation presenting as visual deterioration in a childDEVELOPMENTAL MEDICINE & CHILD NEUROLOGY, Issue 10 2000Lesley C Kaye MRC Ophth Associate Specialist in Ophthalmology A rare case of visual loss as the presenting feature of a central arteriovenous malformation involving the vein of Galen is reported. A 5-year-old girl with a history of deteriorating vision for the past 6 months was examined. Ocular examination showed a left hemianopia, left optic atrophy, and dilated vessels of the right optic disc. MRI revealed a massive deep-seated central arteriovenous malformation involving the vein of Galen. The mechanism of visual loss is likely to be a combination of ischaemic optic atrophy associated with a steal phenomenon and direct compression of the right optic radiation. [source] Lesion of the anterior branch of axillary nerve in a patient with hereditary neuropathy with liability to pressure palsiesEUROPEAN JOURNAL OF NEUROLOGY, Issue 5 2000S. Simonetti We report the case of a 30-year-old woman affected by hereditary neuropathy with liability to pressure palsies (HNPP), who developed a painless left axillary neuropathy after sleeping on her left side, on a firm orthopaedic mattress, in her eighth month of pregnancy. Electromyography (EMG) showing neurogenic signs in the left anterior and middle deltoid, and normal findings in the left teres minor, posterior deltoid and other proximal upper limb muscles, demonstrated that the lesion was at the level of the axillary anterior branch. A direct compression of this branch against the surgical neck of the humerus seems the most likely pathogenic mechanism. This is the first documented description of an axillary neuropathy in HNPP. Knowledge of its possible occurrence may be important for prevention purposes. [source] Improving Mechanical Properties of Crystalline Solids by Cocrystal Formation: New Compressible Forms of ParacetamolADVANCED MATERIALS, Issue 38-39 2009Shyam Karki Poor mechanical properties of paracetamol are improved through the strategy of cocrystal formation. Mechanochemical screening by liquid-assisted grinding generated four cocrystals of paracetamol that readily form tablets by direct compression. Computational studies reveal the mechanical properties can be related to structural features, before all the formation of hydrogen-bonded layers. [source] Wear in molded tibial inserts: Knee simulator study of H1900 and GUR1050 polyethylenesJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 2 2008Riichiro Tsukamoto Abstract Hi-fax 1900Ô tibial inserts were used in the IB-1 total knee replacement (TKR) beginning 1978, soon followed by the AGC design. Such direct compression molded (DCM) inserts was relatively immune to oxidation. Unfortunately the Hi-fax 1900Ô resin (H1900) was taken off the market in year 2004. As an alternate, GUR1050 was introduced in the VanguardÔ TKR. However there appeared to be little or no wear comparisons of molded inserts. Therefore the study aim was to compare wear performance of GUR1050 to the historical H1900. The hypothesis was that Hi-fax and GUR1050 would show comparable wear performance. The VanguardÔ was a posterior-cruciate sacrificing design (Biomet Inc.). All tibial inserts were sterilized by gamma-radiation (3.2 Mrad) under argon. A 6-channel, displacement,controlled knee simulator was used with serum lubricant (protein concentration 20 mg/mL). Wear assessments were by gravimetric methods and linear regression techniques. The gross weight-loss trends over 2.5 Mc duration demonstrated excellent linear behavior with good agreement between TKR sets (<±10%). Fluid sorption artifacts in control represented less than 5% of gross wear magnitudes. Thus suitable corrections could be made in determining net wear. The H1900 and GUR1050inserts demonstrated net wear-rates of 3.6 and 3.4 mm3/Mc, respectively. This difference was not found to be statistically significant. This wear study demonstrated that GUR1050 inserts were indistinguishable from the Hi-fax 1900 in terms of laboratory wear performance, proving our hypothesis. Given the excellent clinical history of DCM Hi-fax 1900, the GUR1050 should be an ideal candidate for TKR. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2008 [source] Tissue reaction and biodegradation of implanted cross-linked high amylose starch in ratsJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 6 2002Cyril Désévaux Abstract The biocompatibility and degradation characteristics of cross-linked high amylose starch (Contramid®) were investigated in rats over 4 months. Contramid® pellets (3-mm diameter and thickness) obtained by direct compression, were implanted subcutaneously and intramuscularly. On sequential time points, macroscopic observations of implantation sites were performed and tissue samples were removed, fixed, and histologically evaluated. No macroscopic inflammatory reaction was observed with Contramid®. Upon histologic examination, inflammatory reaction produced by Contramid® was moderate and restricted to implantation sites. The sequence of inflammatory events with Contramid® was similar regardless of implantation site. Degradation of Contramid® pellets was characterized by fragmentation with formation of fibrovascular septa and phagocytosis by macrophages. Finally Contramid® was mostly absorbed by the end of the 4-month period and substituted by adipocytes. It has been demonstrated that Contramid® is a biocompatible and absorbable material. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res (Appl Biomater) 63: 772,779, 2002 [source] Novel biopolymers as implant matrix for the delivery of ciprofloxacin: Biocompatibility, degradation, and in vitro antibiotic releaseJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 1 2007Suniket V. Fulzele Abstract The purpose of this study was to investigate the in vitro,in vivo degradation and tissue compatibility of three novel biopolymers viz. polymerized rosin (PR), glycerol ester of polymerized rosin (GPR) and pentaerythritol ester of polymerized rosin (PPR) and study their potential as implant matrix for the delivery of ciprofloxacin hydrochloride. Free films of polymers were used for in vitro degradation in PBS (pH 7.4) and in vivo in rat subcutaneous model. Sample weight loss, molecular weight decline, and morphological changes were analyzed after periodic intervals (30, 60, and 90 days) to monitor the degradation profile. Biocompatibility was evaluated by examination of the inflammatory tissue response to the implanted films on postoperative days 7, 14, 21, and 28. Furthermore, direct compression of dry blends of various polymer matrices with 20%, 30%, and 40% w/w drug loading was performed to investigate their potential for implant systems. The implants were characterized in terms of porosity and ciprofloxacin release. Biopolymer films showed slow rate of degradation, in vivo rate being faster on comparative basis. Heterogeneous bulk degradation was evident with the esterified products showing faster rates than PR. Morphologically all the films were stiff and intact with no significant difference in their appearance. The percent weight remaining in vivo was 90.70,±,6.2, 85.59,±,5.8, and 75.56,±,4.8 for PR, GPR, and PPR films respectively. Initial rapid drop in Mw was demonstrated with nearly 20.0% and 30.0% decline within 30 days followed by a steady decline to nearly 40.0% and 50.0% within 90 days following in vitro and in vivo degradation respectively. Biocompatibility demonstrated by acute and subacute tissue reactions showed minimal inflammatory reactions with prominent fibrous encapsulation and absence of necrosis demonstrating good tissue compatibility to the extent evaluated. All implants showed erosion and increase in porosity that affected the drug release. Increase in drug loading significantly altered the ciprofloxacin release in extended dissolution studies. PPR produced drug release >90% over a period of 90 days promising its utility in implant systems. The results demonstrated the utility of novel film forming biopolymers as implant matrix for controlled/sustained drug delivery with excellent biocompatibility characteristics. © 2006 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 96:132,144, 2007 [source] Controlled and complete release of a model poorly water-soluble drug, prednisolone, from hydroxypropyl methylcellulose matrix tablets using (SBE)7m -,-cyclodextrin as a solubilizing agentJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 7 2001Venkatramana M. Rao Abstract Sustained-release formulations such as hydroxypropyl methylcellulose (HPMC)-based hydrophilic matrix tablets of poorly water-soluble drugs often result in incomplete release because of the poor solubility and dissolution rate of the drug in the hydrophilic matrix. Sulfobutylether-,-cyclodextrins ((SBE)7M -,-CDs) have been known to improve the solubility of such drugs by forming inclusion complexes. The present paper deals with the modification of drug release from an HPMC-based matrix tablet of a sparingly water-soluble drug, prednisolone (PDL), using (SBE)7M -,-CD as a solubilizing agent. Tablets were prepared by direct compression of a physically mixed PDL, (SBE)7M -,-CD, and polymer. On exposure to water, an in situ PDL:(SBE)7M -,-CD complex was formed in the gel layer, and enhanced drug release relative to a control formulation was observed (lactose used as the excipient instead of (SBE)7M -,-CD ). Other possible changes due to the incorporation of (SBE)7M -,-CD in the formulation were also probed. Incorporation of (SBE)7M -,-CD lead to a higher water uptake relative to the control (lactose) formulation. For a fixed total tablet weight, polymer type, and loading, the drug release rate appeared to depend on the molar ratio of (SBE)7M -,-CD to PDL and not the absolute amount of (SBE)7M -,-CD present in the matrix tablet. This work shows that incorporation of (SBE)7M -,-CD into the matrix tablets could be considered in designing a sustained-release tablet of poorly water-soluble drugs. © 2001 Wiley-Liss, Inc. and the American Pharmaceutical Association J Pharm Sci 90:807,816, 2001 [source] Development of a robust once-a-day glipizide matrix systemJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 6 2007Shahla Jamzad The robustness of a new hydroxypropylmethylcellulose (HPMC) based modified release glipizide (10 mg) formulation was studied. The tablet formulations were prepared by dry blending the ingredients and direct compression, incorporating a range of release modifying agents up to ± 20% w/w relative to an optimized formulation. The dissolution was assessed in 900 mL pH 6.8 buffer at 75 rev min,1 paddle speed. Calculated difference and similarity factors (f1 and f2) and results of analysis of variance suggest that the overall release profiles were similar. Compositional changes up to ± 20% w/w and a reduction of drug dose to half did not change the general release pattern of this low dose/pH-dependent drug in a significant way. It is concluded that the drug release from the developed matrix systems is highly dependent on the kinetics of hydration and erosion, and that the proposed compositional changes within ± 20% w/w did not alter this relationship. The particulate systems used were characterized by determining the Carr index, Hausner ratio and the rheological properties using a texture analyser. Results indicate that the release is reproducible and the system has potential for successful scale-up operation, while complying with recommended Food and Drug Administration guidelines "Scale Up and Post Approval Changes". [source] Epinephrine for the treatment of anaphylaxis: do all 40 mg sublingual epinephrine tablet formulations with similar in vitro characteristics have the same bioavailability?BIOPHARMACEUTICS AND DRUG DISPOSITION, Issue 9 2006Mutasem M. Rawas-Qalaji Abstract Epinephrine autoinjectors are underutilized in the first aid emergency treatment of anaphylaxis in the community; so non-invasive sublingual epinephrine administration is being proposed. In order to determine the effect of changing excipients on the bioavailability of sublingual epinephrine, four distinct fast-disintegrating epinephrine 40 mg tablet formulations, A, B, C and D, were manufactured using direct compression. All formulations were evaluated for tablet hardness (H), disintegration time (DT) and wetting time (WT). In a prospective 5-way crossover study, four sublingual formulations and epinephrine 0.3 mg i.m. as a control were tested sequentially in a validated rabbit model. Blood samples were collected before dosing and at intervals afterwards. Epinephrine plasma concentrations were measured using HPLC-EC. All tablet formulations met USP standards for weight variation and content uniformity, and resulted in similar mean H, DT and WT (n=6). The area under the curve (AUC), maximum concentration (Cmax) and time at which Cmax was achieved (Tmax) did not differ significantly after the sublingual administration of formulation A and epinephrine 0.3 mg i.m. The AUC after B, C and D were significantly lower (p<0.05) than after epinephrine 0.3 mg i.m. These results suggest that the selection of excipients used in these tablet formulations can affect the bioavailability of sublingually administered epinephrine. Copyright © 2006 John Wiley & Sons, Ltd. [source] Heel skin hyperaemia: direct compression versus vascular occlusionCLINICAL PHYSIOLOGY AND FUNCTIONAL IMAGING, Issue 6 2003Harvey N. Mayrovitz Summary Vulnerability of the heel to ulceration in bed-bound persons is related to direct pressure-induced blood flow decreases. Periodic pressure reduction is a clinical strategy to help prevent ulcers by allowing flow-repayment hyperaemia that has a magnitude and duration thought to be related to the duration of the prior interval of ischaemia. However, there are reasons to question whether effects of flow stoppages caused by direct tissue loading are similar to those because of ischaemia without superimposed direct pressure. This question was investigated by comparing posterior heel skin blood flow responses via laser-Doppler perfusion monitoring of 27 supine-lying subjects in whom blood flow was reduced by 5-min of direct heel loading on a support surface and by 5-min of ankle-cuff compression. Results showed that blood flow reductions were the same for both methods but the hyperaemia was significantly greater when flow reduction was produced by direct heel loading. This was true for ratio of peak hyperaemic flow to baseline (8·20 ± 1·32 s versus 4·68 ± 0·80 s, P,0·001), hyperaemic to baseline 3-min flow-time area ratios (4·70 ± 0·65 s versus 1·95 ± 0·29 s, P,0·001) and for total hyperaemia durations (352 ± 39 s versus 181 ± 14 s, P<0·001). These findings raise new questions regarding the precise physiological effects of heel and tissue loading in general, the factors that contribute to the hyperaemic response and their clinical impact and interpretation. Possible sources of the observed greater post-loading hyperaemia responses are discussed. [source] | |||||||||||||