Particle Spallation Induced by Blood Pumps in Hemodialysis Tubing Sets

The repeated flexion and compression of pump segments by the rollers of peristaltic pumps results in cracking and abrasion of the inner surfaces of the pump segment, leading to shedding of particles into the extracorporeal circuit. A series of studies to assess the rate of particle release from silicone rubber, polyvinyl chloride (PVC), and Pivipol, a coextruded polyurethane-coated PVC tubing, when these materials were used with blood pumps of the type found in hemodialysis units, was undertaken. The studies show that with all tubing/pump combinations there is an overall increase in the total number of particles released, but an analysis of the particle size distribution indicates that the majority of the particles are less than 16 micron in diameter. The rate of increase may be reduced, however, by decreasing the occlusion pressure.     

Long-term follow-up of a free groin flap in hemifacial atrophy

Summary A review of the different techniques for correction of hemifacial atrophy described in the literature is given. The advantages and disadvantages of free groin flaps, omentum and silicone injections are discussed. A free groin flap with preservation of a skin island that can be divided later into small dermal flaps in a secondary correction is described; the result five and a half years later is presented.     

Removal of silicone breast implants and review of literature

Silicone breast implants have a finite life span and may need changing over the lifetime of the patient. The experience with removing first- and second-generation implants is frustrating, because thick capsules often form, in association with rupture and spread of the silicone gel into the surrounding tissue. Different techniques have been employed to try and avoid an unnecessarily large incision, yet still control the dissection so that entire capsule and contained silicone can be removed en bloc. The authors describe a technique that facilitates atraumatic removal using an effective and time-saving vacuum principle.     

唇裂术后鼻畸形修复中硅胶假体的应用

目的 探讨硅胶假体在唇裂术后鼻畸形修复中的应用。方法 用常规方法矫正鼻畸形，使移位的鼻翼软骨、鼻中隔软骨复位，恢复正常的解剖关系，并于术中植入硅胶假体以达到更好的塑型。结果 行硅胶假体修复唇裂鼻畸形21例，无并发症发生，随访1～3年，外观满意。结论 在唇裂术后鼻畸形修复中应用硅胶假体可以获得更好的塑型。     

Refractive Change Caused Silicone Oil Adhesion to the Intraocular Lens Following Nd:YAG Posterior Capsulotomy

A 32-year-old female who had undergone the silicone oil removal procedure presented with visual disturbance in her left eye. Several months previous, she had cataract surgery in a private clinic, and a month later she had a Nd:YAG laser procedure for posterior capsulotomy. The slit-lamp examination revealed silicone oil droplets that had adhered to the intraocular lens where the posterior capsulotomy was performed. She had experienced high myopia as a manifestation of the resulting refractive changes. We replaced the previous intraocular lens with a new acrylic intraocular lens with resulting improvement to her vision. Here we report the case of a female patient with a history of silicone oil removal surgery where the resulting silicone bubbles had not been removed thoroughly and remained in the vitreous cavity. These bubbles subsequently adhered to the intraocular lens following YAG laser posterior capsulotomy, resulting in refractive changes. We recommend that implanting a silicone intraocular lens in anyone with a history of the silicone oil removal procedure or who has a possible history of silicone oil use should be avoided.     

Late results of silicone rubber perianal suture for rectal prolapse

Twenty-one patients were reviewed five to 12 years after silicone rubber perianal suture for rectal prolapse. Sixteen patients (76 percent) were continent with control of prolapse and two patients (9 percent) suffered only from occasional prolapse or incontinence. Rebanding for silicone cutout or fracture was required in four patients and a second rebanding operation was needed in two. Silicone rubber perianal suture for rectal proplapse stands the test of time and might be recommended for more widespread use in younger patients.     

Oranwash在间接法铸造桩核中的应用及护理

目的 探讨在间接法铸造桩核过程中应用硅胶印模材料Oranwash的护理要点。方法183例患者接受桩冠修复，使用Oranwash取根管印模及制备铸造桩核，根据各项操作步骤进行器械、材料准备及护理配合，并加以分析和讨论。结果 除2例出现桩脱住外，其余患者修复效果均满意。结论 在取模、制备铸造桩核过程中，护理配合的关键在于熟悉新材料特性和操作步骤。     

Description of a flow optimized oxygenator with integrated pulsatile pump

Extracorporeal membrane oxygenation (ECMO) is a well-established therapy for several lung and heart diseases in the field of neonatal and pediatric medicine (e.g., acute respiratory distress syndrome, congenital heart failure, cardiomyopathy). Current ECMO systems are typically composed of an oxygenator and a separate nonpulsatile blood pump. An oxygenator with an integrated pulsatile blood pump for small infant ECMO was developed, and this novel concept was tested regarding functionality and gas exchange rate. Pulsating silicone tubes (STs) were driven by air pressure and placed inside the cylindrical fiber bundle of an oxygenator to be used as a pump module. The findings of this study confirm that pumping blood with STs is a viable option for the future. The maximum gas exchange rate for oxygen is 48mL/min/L(blood) at a medium blood flow rate of about 300mL/min. Future design steps were identified to optimize the flow field through the fiber bundle to achieve a higher gas exchange rate. First, the packing density of the hollow-fiber bundle was lower than commercial oxygenators due to the manual manufacturing. By increasing this packing density, the gas exchange rate would increase accordingly. Second, distribution plates for a more uniform blood flow can be placed at the inlet and outlet of the oxygenator. Third, the hollow-fiber membranes can be individually placed to ensure equal distances between the surrounding hollow fibers.     

Alcohol enhanced permeation in model membranes. Part II. Thermodynamic analysis of membrane partitioning

The role of solvents in drug transport has not been properly addressed in the literature, despite its well known influence on drug permeation. Previously we have conducted thermodynamic and kinetic analyses to probe the molecular mechanisms of alcohol enhanced permeation. In the present study, the influence of temperature on the partitioning of methyl paraben into silicone membranes is investigated. In line with previous membrane transport studies of methyl paraben in silicone membranes, butanol and heptanol are used as representative alcohols. The results show higher amounts of methyl paraben extracted from the silicone membrane following equilibration with butanol, at all experimental temperatures. This was in line with alcohol uptake data. In fact, a linear correlation (r² ∼0.97) was found between the amount of methyl paraben in the silicone membrane and the corresponding alcohol uptake. Calculated “specific” vehicle-membrane partition coefficients for both alcohols were approximately one, suggesting that the effective concentrations of methyl paraben inside and outside the membrane were the same. Thermodynamic analysis of the alcohol-membrane partition coefficients as a function of temperature showed no apparent trend for butanol, with an associated enthalpy change of approximately zero. Conversely, there was a positive trend in the van’t Hoff plot for methyl paraben in heptanol, indicative of an exothermic process. Moreover, the partitioning trends of methyl paraben in silicone membranes obtained from membrane transport and equilibrium experiments were not the same. This reflects the fundamental differences between the calculated vehicle-membrane partition coefficients in the two studies. Finally, the findings from membrane transport and equilibrium experiments support a model of alcohol enhanced permeation where high solvent sorption promotes high solute concentrations in the overall volume of the membrane (i.e. K), thus leading to modified solute transport (i.e. increased flux). The same model also accounts for changes in membrane diffusivity (i.e. D) related to the properties of the imbibed alcohol.     

The influence of volatile solvents on transport across model membranes and human skin

Simple topical formulations which include volatile components, such as gels or sprays, are appealing from a cosmetic perspective. However, complex formulation effects may result from the use of volatile excipients in topical formulations, particularly when applied at clinically relevant doses (typically less than a few mg cm⁻²). The present investigation aims to study the role of the volatile solvent ethanol (EtOH), in combination with Transcutol P^® (TC), dimethyl isosorbide (DMI) and isopropyl myristate (IPM), on the efficacy of dermal delivery of a model compound (i.e. methyl paraben). The methodology consisted of in vitro diffusion experiments conducted using silicone membranes and human epidermis. Finite dose studies were performed with two types of formulations: saturated solutions of methyl paraben in each vehicle alone and incorporating the volatile solvent in a 50:50 (v/v) proportion. The kinetics of EtOH evaporation from the formulations were also investigated by monitoring the weight loss of the formulation over time. The results showed that the presence of EtOH had little effect on the skin flux of methyl paraben compared with the corresponding saturated solutions. Formulations incorporating the volatile solvent were clearly more efficient, in line with the data obtained with silicone membranes. Furthermore, the permeation of methyl paraben from the saturated EtOH solution in both silicone and skin showed an initial period of relatively fast permeation, after which there was a marked decrease in the permeation rate. This reflected significant ethanol depletion from the formulation (chiefly by evaporation), causing most of the dose of methyl paraben applied to crystallise as a deposited film at the skin surface (observed experimentally and confirmed by mass balance studies), thus decreasing its availability to permeate. Studies of the kinetics of ethanol evaporation from the formulations confirm these findings, demonstrating a very short residence time of the volatile solvent at the surface of the membrane (approx. 6 min). In conclusion, the findings suggest that rapid evaporation of EtOH takes place from the formulations applied at the surface of the skin, leaving a saturated residue of the drug in the vehicle. The presence of EtOH clearly influenced the efficiency of the formulation, underlining the application of volatile components to optimise dermal delivery.