Exploiting light-based 3D-printing for the fabrication of mechanically enhanced, patient-specific aortic grafts

Despite polyester vascular grafts being routinely used in life-saving aortic aneurysm surgeries, they are less compliant than the healthy, native human aorta. This mismatch in mechanical behaviour has been associated with disruption of haemodynamics contributing to several long-term cardiovascular complications. Moreover, current fabrication approaches mean that opportunities to personalise grafts to the individual anatomical features are limited. Various modifications to graft design have been investigated to overcome such limitations; yet optimal graft functionality remains to be achieved. This study reports on the development and characterisation of an alternative vascular graft material. An alginate:PEGDA (AL:PE) interpenetrating polymer network (IPN) hydrogel has been produced with uniaxial tensile tests revealing similar strength and stiffness (0.39 ± 0.05 MPa and 1.61 ± 0.19 MPa, respectively) to the human aorta. Moreover, AL:PE tubular conduits of similar geometrical dimensions to segments of the aorta were produced, either via conventional moulding methods or stereolithography (SLA) 3D-printing. While both fabrication methods successfully demonstrated AL:PE hydrogel production, SLA 3D-printing was more easily adaptable to the fabrication of complex structures without the need of specific moulds or further post-processing. Additionally, most 3D-printed AL:PE hydrogel tubular conduits sustained, without failure, compression up to 50% their outer diameter and returned to their original shape upon load removal, thereby exhibiting promising behaviour that could withstand pulsatile pressure in vivo. Overall, these results suggest that this AL:PE IPN hydrogel formulation in combination with 3D-printing, has great potential for accelerating progress towards personalised and mechanically-matched aortic grafts.

Obesity-related health status is a better predictor of pregnancy with fertility treatment than body mass index: a prospective study

This study assessed whether an obesity-related health status instrument (Edmonton obesity scoring system - EOSS) or body mass index (BMI) better predicted pregnancy rates in overweight women undergoing fertility treatments. A prospective cohort study was conducted on patients with a BMI ≥ 25 kg m(-2) undergoing a fertility treatment cycle (ovulation induction, superovulation, or in vitro fertilization). Obesity-related health status including blood pressure, blood work, health history, and functional assessment were assessed. A total of 101 patients were included in the study with an average age of 36.3 ± 4.2 years and a mean BMI of 31.8 ± 5.2 kg m(-2) . EOSS was found to be statistically predictive of pregnancy rate/cycle (OR 0.51, 95% CI 0.27-0.94; P = 0.03), whereas BMI was not (OR 0.95, 95% CI 0.86-1.05). A similar trend was seen for clinical pregnancy rate/cycle started. However, the association between clinical pregnancy rates and EOSS or BMI did not reach statistical significance (OR 0.53, P = 0.06 and OR 0.98, P = 0.62 respectively). Our results demonstrated that EOSS better predicted pregnancy rates after fertility treatments than BMI. In fact, for every EOSS stage increased by one unit, the odds of pregnancy were approximately halved. A multi-centre study powered for live birth is warranted to establish effective pre-fertility management of overweight women.

Predictors of pulmonary exacerbations in patients with cystic fibrosis infected with multi-resistant bacteria

BACKGROUND

This study examined characteristics of adult and adolescent patients with cystic fibrosis (CF) to determine factors associated with an increased risk of pulmonary exacerbations.

METHODS

249 patients with CF infected with multidrug resistant bacteria were recruited and prospectively followed for up to 4.5 years until they experienced a pulmonary exacerbation severe enough to require intravenous antibiotics. Multivariable regression analyses were used to compare the characteristics of patients who experienced an exacerbation with those who did not.

RESULTS

124 of the 249 patients (50%) developed a pulmonary exacerbation during the first year and 154 (62%) experienced an exacerbation during the 4.5 year study period. Factors predictive of exacerbations in a multivariable survival model were younger age (OR 0.98, 95% CI 0.96 to 0.99), female sex (OR 1.45, 95% CI 1.07 to 1.95), lower forced expiratory volume in 1 second (FEV(1)) (OR 0.98, 95% CI 0.97 to 0.99), and a previous history of multiple pulmonary exacerbations (OR 3.16, 95% CI 1.93 to 5.17). Chronic use of inhaled corticosteroids was associated with an increased risk of exacerbation (OR 1.92, 95% CI 1.00 to 3.71) during the first study year.

CONCLUSIONS

Patients who experience pulmonary exacerbations are more likely to be younger, female, using inhaled steroids, have a lower FEV(1), and a history of multiple previous exacerbations. It is hoped that knowledge of these risk factors will allow better identification and closer monitoring of patients who are at high risk of exacerbations.

Lithium monitoring before and after the distribution of clinical practice guidelines

OBJECTIVE

To determine whether distribution of clinical practice guidelines improves lithium monitoring and whether standards of monitoring differed between patients in psychiatric contact and those seen only in primary care.

METHOD

Standards of monitoring were assessed for patients on lithium in northeast Scotland throughout 1995 and/or throughout 1996. Guidelines were circulated in January 1996 to all local general practitioners and psychiatrists. Monitoring was compared between 1995 and 1996 and for patients with and without psychiatric contact.

RESULTS

Both primary care and psychiatric records were scrutinized for 422 and 403 patients prescribed lithium throughout 1995 and 1996, respectively. While monitoring was poor on several parameters during both years, frequency of measurement of both thyroid and renal function improved in 1996. Standards of monitoring were better for patients in psychiatric care.

CONCLUSION

Standards of lithium monitoring require further improvement. Locally agreed practice guidelines are helpful but patients on lithium should be in continuing contact with an experienced psychiatrist.

The effect of allowing clinical discretion in ordering biochemical tests. Evaluation by complementary methods

We describe the effects on costs, working patterns, and clinical behavior of installing a DAX "discretionary" biochemistry analyzer. Use of the new analyzer encouraged doctors to be more specific in requesting biochemical tests, which substantially reduced the number of tests requested and slightly reduced overall costs. Doctors preferred being able to order tests in this more specific way.

Effect of sepsis and surgery on trace minerals

The purpose of this study was to evaluate effect of infection and surgery on serum iron, zinc, and the copper simultaneously. Twenty patients who had emergency abdominal surgery for acute inflammatory conditions, and 15 controls who had elective abdominal surgery were studied. Preoperatively, serum iron levels were significantly decreased in the septic group compared to controls (p less than 0.001). Following surgery and removal of the septic focus, serum iron, ferritin, and zinc levels increased, while serum transferrin levels decreased significantly. Serum copper levels did not show any significant difference. It is concluded that serum iron, transferrin, ferritin, and zinc levels are affected profoundly by septic and the surgical stress.

Pulmonary permeability edema in a large animal model of nonpulmonary sepsis. A morphologic study

Morphologic studies were undertaken in a sheep model of pulmonary permeability edema (PPE) induced by cecal ligation and perforation. Biopsies taken every 24 hours through 96 hours following induction of sepsis showed, at 24 hours, interstitial edema accompanied by widespread aggregation of polymorphonuclear leukocytes. This was confirmed by electron microscopy, which also demonstrated endothelial cell swelling, platelet aggregation, and fibrin deposition. By 48 hours, a "thromboangiitis" had developed that persisted through 96 hours. In vitro pulmonary angiograms done at 60 and 96 hours showed multiple filling defects; it was possible to demonstrate that these defects corresponded to the "thromboangiitis." These thrombotic lesions, which were not the result of embolization from indwelling lines, closely resembled vascular changes described in the adult respiratory distress syndrome. It is believed that this is the first time that such lesions have been described in a model of PPE resulting from nonpulmonary sepsis.

Evaluation of a time-resolved immunofluorometric assay for serum thyroid stimulating hormone

The LKB 'Delfia, immunofluorometric assay for serum TSH has been evaluated. The assay is simple and rapid to perform and is capable of processing in excess of 100 specimens within a working day. The sensitivity of the assay is 0.05 microU/L, with a working range extending beyond 324 microU/L. The change in signal at each point over the standard curve approaches 1000-fold, significantly greater than that of a typical immunoradiometric assay. Mean figures for intra-assay and inter-assay precision were 4.7% and 8.6% CV, respectively. Mean recovery of added TSH was 98.3%, and samples containing high levels of endogenous TSH diluted parallel to the standard curve. The method showed good correlation with an immunoradiometric assay for TSH. The reference ranges for clinically defined groups of subjects were euthyroid 0.47-3.84 microU/L (n = 83); primary hypothyroidism 15--greater than 324 microU/L (n = 28); thyrotoxicosis less than 0.05 microU/L (n = 46). It is concluded that the 'Delfia' assay offers the clinical biochemistry laboratory an attractive and reliable alternative to a sensitive immunoradiometric assay for serum TSH.

The analysis of tricyclic antidepressant drugs at therapeutic blood levels by reversed-phase high-performance liquid chromatography using pairing and organic counter-ions

A serum assay method incorporating two internal standards suitable for routine clinical analysis of tricyclic antidepressant drugs at the therapeutic level is described. The method involves extraction and chromatography using a reversed-phase high-performance liquid chromatography system incorporating pairing and organic counter-ions. The quantitative characteristics of the method are reported and results are compared with consensus values for four commonly encountered drugs, amitriptyline, nortriptyline, imipramine and desipramine. The method is shown to be applicable to more recently developed antidepressants such as nomifensine and maprotiline and the flexibility of the chromatography is discussed. Sample chromatograms obtained from patient samples in the presence and absence of potentially interfering drugs and metabolites are discussed.

Incorporation of a SMAC analyzer into the data-processing procedures of a computer-assisted laboratory

This paper describes the incorporation of a SMAC (Technicon) analyzer into data-processing techniques that have been developed on existing computer hardware during several years. The SMAC system is interfaced directly to a small computer, and suitable peripherals produce a manageable form of result tabulation for subsequent reporting, as well as provide quality-control information to the SMAC operators in real time. The design is such as to facilitate the performance analysis of the SMAC system during its initiation period and during normal service operation.

Incorporation of a SMAC analyzer into the data-processing procedures of a computer-assisted laboratory

This paper describes the incorporation of a SMAC (Technicon) analyzer into data-processing techniques that have been developed on existing computer hardware during several years. The SMAC system is interfaced directly to a small computer, and suitable peripherals produce a manageable form of result tabulation for subsequent reporting, as well as provide quality-control information to the SMAC operators in real time. The design is such as to facilitate the performance analysis of the SMAC system during its initiation period and during normal service operation.