Antimineralization treatments in stentless porcine bioprostheses: an experimental study

BACKGROUND AND AIM OF THE STUDY

Photo-oxidation treatment of porcine stentless bioprostheses (Photofix) was compared with glutaraldehyde fixation, with either AOA (Freestyle valve) or Tween-80 (Edwards Prima Plus valve).

METHODS

Six valves of each type were implanted in juvenile sheep, in the pulmonary position. Valves were explanted after three or six months and examined macroscopically, by X-radiography, and by light and transmission electron microscopy. Calcium content was determined by atomic absorption spectrometry.

RESULTS

The cusps of all valves were free of calcification, and had normal histology and function. Calcium contents (median +/- IQR) were 0.63+/-0.45, 0.73+/-1.46 and 0.46+/-1.42 microg/mg for the Photofix, Freestyle and Prima Plus valves, respectively (p = NS). Calcium contents of the aortic wall portions were 0.71+/-1.27 (Photofix), 10.78+/-77.22 (Freestyle) and 28.70+/-66.53 (Prima Plus) (p <0.05 for Photofix versus Freestyle or Prima Plus).

CONCLUSION

Photo-oxidation of a porcine stentless valve prevents calcification not only in the cusps, but also in the aortic wall portion.

Tissue damage and calcification may be independent mechanisms of bioprosthetic heart valve failure

BACKGROUND AND AIM OF THE STUDY

Porcine bioprosthetic valves have excellent hemodynamics and do not require anticoagulation, but have limited durability. Cusp tearing is a major cause of bioprosthetic valve failure. It has been suggested that the mechanism of bioprosthetic valve failure is stiffening by calcification, which leads to elevated stresses and secondary collagen fiber damage and leaflet tearing. This thesis was tested in explanted porcine bioprostheses.

METHODS

A total of 60 explanted porcine bioprosthetic valves was tested mechanically, and 15 explanted valves were examined grossly and histologically. Circumferentially and radially oriented samples of cusp tissue were tested uniaxially in a materials testing machine and compared with five controls.

RESULTS

Mean (+/-SD) duration of implantation was 10.9+/-5.6 years. Circumferential specimens from explants were less extensible than controls (11.0+/-5.5% versus 24.5+/-2.8% strain, p <0.001), and failed at lower tensions (973+/-733 versus 3075+/-911 N/m, p = 0.001) and at lower strains (21.2+/-8.1% versus 47.3+/-7.1% strain, p <0.001). Radial specimens from explants were less extensible (28.7+/-6.8% versus 39.2+/-5.9% strain, p = 0.002) and failed at lower strains (60.3+/-17.3% versus 112.2+/-24.9% strain, p <0.001) than the controls. The stiffness of the explants was unchanged from controls in both circumferential and radial samples. There were no differences between explants and controls in radial and circumferential stiffness, and in radial failure strength. Calcification was mild and diffuse in most of the tested samples. Tears were found in areas without calcific deposits, along with breaks in collagen fiber bundles.

CONCLUSION

These results do not support the thesis that calcification stiffens glutaraldehyde-fixed porcine bioprostheses, except when the entire cusp is transformed into a solid mass of mineral. Rather, leaflet tears may develop as a result of accumulated mechanical damage that is independent of calcification.

Diagnosis by intraoperative transesophageal echocardiography of acute thrombosis of mechanical aortic valve prosthesis associated with the use of biological glue

Mechanical aortic valve thrombosis is an uncommon complication of valve replacement. Inadequate anticoagulation is observed in 45% of patients presenting with this complication and it occurs as close as 15 days postoperation (1). Failure to wean from cardiopulmonary bypass (CPB) after aortic valve replacement may be because of a multitude of pathologies. We present a case where easy access to transesophageal echocardiography (TEE) allowed a rapid diagnosis of acute mechanical aortic valve occlusion with subsequent successful surgical management.

Ecotoxicology of glutaraldehyde: review of environmental fate and effects studies

Glutaraldehyde is a biocide used in many industrial applications with potential releases to the environment. This review discusses the environmental fate and effects data on this important biocide. Information drawn from this review indicates that glutaraldehyde is acutely toxic to aquatic organisms. Glutaraldehyde is equally toxic to warm water and cold water fish, but is slightly more toxic to freshwater fish than salt water fish. The acute toxicity of glutaraldehyde for avian species is comparable to that for mammalian species. The toxicity of glutaraldehyde is not appreciably increased with repeated long-term exposures. Results from environmental partitioning studies indicate that glutaraldehyde tends to remain in the aquatic compartment and has little tendency to bioaccumulate. Aqueous solutions of glutaraldehyde are stable at room temperature under acidic to neutral conditions, and to sunlight, but unstable at elevated temperatures, and under alkaline conditions. Glutaraldehyde is readily biodegradable in the freshwater environment and has the potential to biodegrade in the marine environment. Aquatic metabolism studies suggest that glutaraldehyde, under aerobic conditions, is metabolized to CO(2) via glutaric acid as an intermediate. Under anaerobic conditions, glutaraldehyde is metabolized to 1,5-pentanediol. Pretreatment with sodium bisulfite is the best method for inactivating glutaraldehyde prior to disposal to treatment systems.

Glutaraldehyde-induced colitis

OBJECTIVE

To describe the etiology and clinical course of acute colitis occurring after flexible endoscopy.

DESIGN

Chart review.

SETTING

A university teaching hospital.

PATIENTS

Eight patients who sought assessment of potential colonic disease.

INTERVENTION

Colonoscopy in 5 patients and flexible sigmoidoscopy in 3 patients. The indication for endoscopy was screening in 5 patients, cancer surveillance in 2 patients and preoperative evaluation of colon carcinoma in 1 patient.

OUTCOME MEASURES

The relation of presenting symptoms to glutaraldehyde exposure, the response to therapy and the need for further therapy.

RESULTS

All patients had abdominal pain, mucus diarrhea and rectal bleeding within 48 hours after endoscopy. Most patients reported that the symptoms started within 12 hours of the procedure. All patients were confirmed by sigmoidoscopy to have colitis within 72 hours of the first endoscopic procedure. One patient required hospitalization. In the first 7 patients several stool cultures were negative for Clostridium difficile using the cytotoxin assay by the cell culture method. Four patients had negative cultures for Yersinia, Salmonella and Shigella spp. Three patients were treated with metronidazole initially. Two patients underwent endoscopic biopsy and examination of the biopsy specimen showed fibrinoleukocytic exudate and ischemic type injury. One patient underwent the scheduled sigmoid resection within 48 hours of endoscopy for a Dukes' stage B adenocarcinoma. Concomitant acute ischemic colitis limited to the mucosa and submucosa was noted in the resected specimen. Symptoms resolved in all patients and follow-up endoscopy revealed normal mucosa.

CONCLUSION

The entity of glutaraldehyde-induced colitis should be recognized and special attention should be given during instrument cleansing to minimize the risk of its development.

Symptoms in health personnel exposed to disinfectants

BACKGROUND

While the biocidal efficacy of disinfectants available for use in health facilities has been widely investigated, little attention has been paid to their potential side effects to users.

OBJECTIVE

To describe the occurrence of symptoms attributable to occupational exposure to disinfectants with emphasis on gluteraldehyde.

DESIGN

Exploratory cross-sectional study.

SETTING

Kenyan health facilities.

SUBJECTS

One hundred and fifteen members of various health cadres.

RESULTS

All the respondents reported using disinfectants. Glutaraldehyde-based preparations, either alone or alongside other agents (excluding hypochlorite), were used by 52.2% of the respondents. Hypochlorite-based preparations, either alone or alongside other agents, were used by 18.3%, while cetrimide preparations and ethanol alongside other agents were used by 13% of the respondents. More than sixty two per cent of the respondents had suffered one or more symptoms during the use of these disinfectants. Among the users of glutaraldehyde preparations, the most common symptoms reported were sneezing (38.3%), headache (31.7%), watering of eyes (25%), skin rash (10%) and chronic cough (8.3%). Among users of hypochlorite and cetrimide preparations, the most commonly reported symptoms were sneezing, headaches and watering of eyes.

CONCLUSIONS

Our findings suggest possible occupation-related adverse reactions that may be attributed to the use of disinfectants. Awareness of these potential hazards needs to be increased among users and efforts made to introduce techniques to minimise exposure to liquid and vapourised disinfectants. Further studies involving larger sample sizes, are necessary to unequivocally apportion the various symptoms to specific disinfecting agents.

[Preliminary assessment of occupational exposure to Glutaraldehyde in selected endoscopic workplaces]

The effect of occupational exposure to glutaric aldehyde in 17 endoscopic laboratories of the Wrocław region was assessed. The level of glutaraldehyde concentration was measured, and the survey was carried out in a group of 34 laboratory employees. In 11 laboratories MAC and STEL values were exceeded. Undesirable effects following the contact with glutaric aldehyde were noted in 28 subjects (82%). The skin, mucous membrane and respiratory system irritations predominated among the symptoms observed. The data show that glutaric aldehyde may induce irritation or exert an allergic effects in medical personnel.

Survey of symptoms, respiratory function, and immunology and their relation to glutaraldehyde and other occupational exposures among endoscopy nursing staff

OBJECTIVES

To find the nature and incidence of symptoms experienced by a large sample of hospital endoscopy nurses. To find whether nurses in endoscopy units develop asthma under current working conditions in endoscopy units. To obtain analytically reliable data on exposure concentrations of glutaraldehyde (GA) vapour in endoscopy units, and to relate them to individual hygiene and work practices. To characterise any exposure-response relations between airborne GA and the occurrence of work related symptoms (WRSs). Due to the growing concern about the perceived increase in WRSs among workers regularly exposed to biocides, all of whom work within a complex multiexposure environment, a cross sectional study was designed.

METHODS

Current endoscopy nurses (n=348) from 59 endoscopy units within the United Kingdom and ex-employees (who had left their job for health reasons (n=18) were surveyed. Symptom questionnaires, end of session spirometry, peak flow diaries, skin prick tests (SPTs) to latex and common aeroallergens, and measurements of total immunoglobulin E (IgE) and IgE specific to GA and latex were performed. Exposure measurements included personal airborne biocide sampling for peak (during biocide changeover) and background (endoscopy room, excluding biocide changeover) concentrations.

RESULTS

All 18 ex-employees and 91.4% of the current nurses were primarily exposed to GA, the rest were exposed to a succinaldehyde-formaldehyde (SF) composite. Work related contact dermatitis was reported by 44% of current workers exposed to GA, 56.7% of those exposed to SF composite, and 44.4% of ex-employees. The prevalence of WRSs of the eyes, nose, and lower respiratory tract in current workers exposed to GA was 13.5%, 19.8%, and 8.5% respectively and 50%, 61.1%, and 66.6% in the ex-employees. The mean percentage predicted forced expired volume in 1 second (ppFEV(1)) for ex-employees (93.82, 95% confidence interval (95% CI) 88.53 to 99.11) was significantly lower (p<0.01) than that of current workers exposed to GA (104.08, 95% CI 102.35 to 105.73). Occupational peak flow diaries completed by current workers with WRSs of the lower respiratory tract showed no evidence of bronchial asthma (<15% variation). Six per cent of the population had positive latex SPTs. Positive indications of one GA specific IgE and 4.1% latex specific IgE occurred. There was no conformity between the latex specific IgE and positive SPTs. Positive SPTs to latex were associated with WRSs of dermatitis and ocular WRSs, but no other WRSs. Exposures were above the current maximum exposure limit (MEL) of 0.2 mg/m(3) (0.05 ppm) in eight of the units investigated. A significant relation existed between peak GA concentrations and work related chronic bronchitis and nasal symptoms (after adjustment for types of local ventilation) but not to other WRSs. Peak GA concentrations were significantly higher in units that used both negative pressure room and decontaminating unit ventilation.

CONCLUSION

This study documents a significant level of symptoms reported in the absence of objective evidence of the physiological changes associated with asthma. Ex-employees and current workers with WRSs warrant further study to elucidate the cause and mechanisms for their symptoms. Ventilation systems used for the extraction of aldehydes from the work area may be less effective than expected and due to poor design may even contribute to high peak exposures.

[Comparative studies of two different systems for bonding composites with tissue of the tooth]

The objective of studies was the clinical evaluation concerning the influence of the bonding systems Syntac and Gluma exerted on the quality of compositive fillings in various types of defects in humans, in comparison to fillings, in which Compa Bond resin was used. The question was studied to answer whether there were any significant differences in respect of the assessed parameters between fillings by Syntac system and the fillings by Gluma system with preservation and marginal adaptation being taken into consideration. The studies were performed on 98 patients of both sexes, therein 56 women and 42 men. The assessment included 248 classified fillings, namely: 82 of Tetric material, 78 of Pekalux material and 88 of C-Fill MH and C-Molar materials. The fillings were estimated directly after placement, as well as after 6, 12, and 24 months, under artificial light by making use of dental mirror, a probe and an optic device (magnifying glass of fivefold magnification), on the basis of own card of investigations for compositive fillings. The dental pulp reaction to thermic simuli and faradic current was also taken into account. Fillings classified by grades 0 degree and 1 degree were defined as clinically acceptable, while 2 degrees and 3 degrees as clinically unacceptable. The statistical analysis was carried out by means of Chi 2 test. The number of Tetric and Pekalux materials fillings lost after 24 months of studies was substantially lower than the number of lost fillings made of C-Fill MH and C-Molar materials. The loss only concerned defects of non-carious origin, namely wedge shaped defects and pathological attrition of teeth (Tab. 1 and Tab. 2). The fillings by Syntac system are characterized by better marginal adaptation as compared with fillings, wherein the Gluma system was applied, however, no statistically significant differences between these groups were disclosed (Tab. 3). Significant differences were found to appear between the groups, of fillings, in which use was made of bonding systems Syntac and Gluma on the one hand, and the fillings set up by Compa Bond resin on the other. Assessing the colour, smoothness of surface and the anatomical shape of the fillings after 24 months no essential differences between the studied material groups were revealed. Secondary caries and post-procedural sensitivity involved only the cases, in which Compa Bond resin and C-Fill MH material were employed. After 24 months of studies the percentage of clinically acceptable fillings claimed to be as follows: Tetric 93.51%, Pekalux 91.55%, C-Fill MH and C-Molar 75.36%. Thus, it was disclosed that there were significantly more clinically acceptable fillings made of Tetric and Pekalux materials than of C-Fill MH and C-Molar materials. The Syntac and Gluma systems exerted significant influence on better preservation and marginal adaptation of fillings mainly in defects of non carious origin, in comparison to the fillings in which the conventional Compa Bond resin was being used. In cases, wherein Syntac and Gluma systems were applied, no post-procedural hypersensitivity was recorded. This ailment was evidenced in 4.5% of cases after implementing Compa Bond resin.

Allergic contact dermatitis from glutaraldehyde in health-care workers

Glutaraldehyde is considered the disinfectant of choice for sterilizing medical and dental equipment. Unfortunately, glutaraldehyde has many toxic side-effects, including the ability to induce allergic contact dermatitis. In a 5-year study at the University of Kansas, 468 patients were patch tested to glutaraldehyde. A comparison of results was made between those employed in a healthcare related field and those who were not. Health-care workers (HCWs) were more than 8x more likely to be allergic to glutaraldehyde than their non-health-care working peers (NHCWs). Statistically significant differences between HCWs and NHCWs were seen in their reactivity to glutaraldehyde, thimerosal, benzalkonium chloride and methyl methacrylate. A higher than expected co-reactivity between glutaraldehyde and formaldehyde was also noted among HCWs and NHCWs, which cannot fully be explained by concomitant exposure. Allergic contact dermatitis from glutaraldehyde often causes persistent dermatitis, which frequently forces patients to leave their jobs. Although the National Institute of Occupational Safety and Health has published guidelines for safe handling of glutaraldehyde, allergy appears to continue to rise, especially among those employed in health-care professions. Until a less sensitizing disinfectant is developed, it is in the best interest of those in health-care professions, and other professions exposed to glutaraldehyde, to heighten occupational safety standards and to improve methods of barrier protection.

Biaxial mechanical properties of the native and glutaraldehyde-treated aortic valve cusp: Part II--A structural constitutive model

We have formulated the first constitutive model to describe the complete measured planar biaxial stress-strain relationship of the native and glutaraldehyde-treated aortic valve cusp using a structurally guided approach. When applied to native, zero-pressure fixed, and low-pressure fixed cusps, only three parameters were needed to simulate fully the highly anisotropic, and nonlinear in-plane biaxial mechanical behavior. Differences in the behavior of the native and zero- and low-pressure fixed cusps were found to be primarily due to changes in the effective fiber stress-strain behavior. Further, the model was able to account for the effects of small (< 10 deg) misalignments in the cuspal specimens with respect to the biaxial test axes that increased the accuracy of the model material parameters. Although based upon a simplified cuspal structure, the model underscored the role of the angular orientation of the fibers that completely accounted for extreme mechanical anisotropy and pronounced axial coupling. Knowledge of the mechanics of the aortic cusp derived from this model may aid in the understanding of fatigue damage in bioprosthetic heart valves and, potentially, lay the groundwork for the design of tissue-engineered scaffolds for replacement heart valves.

[Respiratory distress in three newborns after mask disinfection with Endosporine. Probable role of glutaraldehyde]

BACKGROUND

Disinfectants for medical devices are uncommonly a cause of iatrogenic adverse effects. Nevertheless, when misused, they can induce severe complications. Three cases of acute respiratory distress in newborns probably induced by glutaraldehyde are reported.

CASE REPORTS

Three children born by Caesarean section between 8 and 19 May 1999 in the same hospital presented acute respiratory distress requiring hospitalization in the neonatal intensive care unit; one child was premature. The clinical appearance, which was initially normal, deteriorated with a respiratory distress in 30 to 60 minutes. Recovery was uneventful in all cases. The diagnosis considered was a hyaline membrane disease. The enquiry conducted after this cluster onset identified, as a main contributing factor, the disinfection procedure recently introduced in the surgical theater.

CONCLUSION

Review of toxicologic data on glutaraldehyde shows this is a highly irritating chemical for the respiratory tract, even at low concentrations. Clinical and radiologic features in these three neonates are compatible with a pulmonary sub-edema on an immature alveolar setting. The hypothesis proposed is that glutaraldehyde, the active ingredient of the biocidal formula used to disinfect the respiratory masks, was massively desorbed from the rubber and foam of which masks are made.

Safe use of glutaraldehyde

Glutaraldehyde is an effective chemical for killing micro-organisms that is used in a variety of healthcare settings to rapidly clean instruments. It is highly toxic in even small concentrations and needs to stored and handled carefully. Diane Romano-Woodward explains how nurses can ensure that adequate precautions are taken to prevent harm to staff and patients.

Induction of cataracts of varying degrees of hardness in human eyes obtained postmortem for cataract surgeon training

PURPOSE

To report a method of inducing nuclear cataracts of varying degree of hardness using intralenticular injection of the Karnovsky solution.

METHODS

Twelve postmortem human eyes were prepared according to the Miyake-Apple posterior video technique. After performing capsulorhexis and hydrodissection/delineation, 0.2 ml of the Karnovsky solution was injected into the lens nucleus of the eyes. Manual extracapular cataract extraction techniques and various two-handed phacoemulsification maneuvers were then practiced at various time intervals after the injection.

RESULTS

Uniform nuclear cataracts with varying degrees of hardness were successfully induced in all globes. The optimum dose of the Karnovsky solution and time for induction of nuclear hardness of grade 3 (ideal for practicing two-handed phacoemulsification maneuvers) were 0.2 ml and 15 minutes, respectively.

CONCLUSION

The Karnovsky solution can be successfully used for the induction of hard, uniform nuclear cataracts for learning/practicing extracapular cataract extraction and phacoemulsification.

Chemical hazards in radiology

A variety of chemicals are used in medical imaging as developer and fixer ingredients, germicides, and cleaning agents. Glutaraldehyde, a potent sensitizer, may cause occupational skin and respiratory diseases in exposed individuals. Poor ventilation, unsafe practices, and lack of hazard recognition may contribute to occupational asthma and other respiratory disease in susceptible medical imaging personnel. Failure to respond effectively to initial health complaints and reduce exposure levels can have serious consequences for affected employees. It is therefore important for occupational safety and health professionals to alert health facility managers to potential dangers and to recommend effective intervention strategies. When problems are identified, a multidisciplinary team approach is the best method for evaluating and controlling hazards. This team should include industrial hygienists, safety staff, occupational medicine physicians, mechanical and ventilation engineers, personnel specialists, and medical imaging staff. A thorough hazard assessment, medical diagnosis, and administrative personnel actions are critical to effective problem identification and correction. In the case of chemical sensitization, removal of the affected employee may be necessary. By working with designers and equipment installers to monitor compliance with appropriate codes and manufacturers' specifications, hazards can be prevented. We present additional operations, ventilation, and design improvements to reduce chemical exposures to radiology employees.