Toward acellular xenogeneic heart valve prostheses: Histological and biomechanical characterization of decellularized and enzymatically deglycosylated porcine pulmonary heart valve matrices.

The use of decellularized xenogeneic heart valves might offer a solution to overcome the issue of human valve shortage. The aim of this study was to revise decellularization protocols in combination with enzymatic deglycosylation, in order to reduce the immunogenicity of porcine pulmonary heart valves, in means of cells, carbohydrates, and, primarily, Galα1-3Gal (α-Gal) epitope removal. In particular, the valves were decellularized with sodium dodecylsulfate/sodium deoxycholate (SDS/SD), Triton X-100 + SDS (Tx + SDS), or Trypsin + Triton X-100 (Tryp + Tx) followed by enzymatic digestion with PNGaseF, Endoglycosidase H, or O-glycosidase combined with Neuraminidase. Results showed that decellularization alone reduced carbohydrate structures only to a limited extent, and it did not result in an α-Gal free scaffold. Nevertheless, decellularization with Tryp + Tx represented the most effective decellularization protocol in means of carbohydrates reduction. Overall, carbohydrates and α-Gal removal could strongly be improved by applying PNGaseF, in particular in combination with Tryp + Tx treatment, contrary to Endoglycosidase H and O-glycosidase treatments. Furthermore, decellularization with PNGaseF did not affect biomechanical stability, in comparison with decellularization alone, as shown by burst pressure and uniaxial tensile tests. In conclusion, valves decellularized with Tryp + Tx and PNGaseF resulted in prostheses with potentially reduced immunogenicity and maintained mechanical stability.

Albumin-glutaraldehyde glue for repair of superficial lung defect: an in vitro experiment.

BACKGROUND: Albumin-glutaraldehyde glue gained a widespread acceptance in repair of superficial lung defects associated with alveolar air leaks (AAL). As its sealing efficacy has not yet been thoroughly corroborated by clinical studies, we sought to assess the properties of commercially available albumin-glutaraldehyde glue (BioGlue™) in an in vitro lung model. METHODS: The lower lobe of freshly excised swine lung (n = 10) was intubated and ventilated. A focal superficial parenchymal defect (40 × 25 mm) was created on the inflated lung. AAL was assessed with increasing inspired tidal volume (TVi). After glue application, AAL was assessed until burst failure occurred. To evaluate glue elasticity, the length of defect was recorded in the inflated lung. RESULTS: Superficial parenchymal defects resulted in AAL increasing with ascending TVi. Multiple linear regression analysis revealed strong correlation between AAL and maximal inspiratory pressure. There was one application error. At TVi = 400, 500, 600, 700, 800 and 900 ml, BioGlue™ achieved complete sealing in nine, six, five, four two and one specimens, respectively. Mean burst pressure was 38.0 ± 4.2 cmH2O. All sealant failures were cohesive. BioGlue™ allowed an expansion of covered lung defects of 1.5 ± 1.7 mm. CONCLUSIONS: Our in vitro tests demonstrated a high sealing efficacy of BioGlue™ for repair of superficial lung defects. Due to the rigid nature, caution should be taken to use this kind of sealant in trapped lungs.

In Vitro Lung Model Assessing the Efficacy of Surgical Sealants in Treating Alveolar Air Leaks.

PURPOSE: The lack of reliable testing methods limits the evidence-based practice of surgical sealants in treating alveolar air leak (AAL). We developed an in vitro lung model to evaluate sealants' efficacy and tested the widely used human thrombin-fibrinogen sponge, TachoSil as an example. MATERIALS AND METHODS: The caudal lobe of freshly excised swine lung (n = 10) was intubated and ventilated. A focal superficial parenchymal defect (40 × 25 mm) was created in the inflated lung. AAL was assessed with increasing inspired tidal volume (TVi). After sealant application, AAL was assessed in the same way until burst failure, defined as an AAL exceeding 20 mL. To evaluate the elasticity of the sealant, the length of defect was recorded in the inflated lung. RESULTS: Superficial parenchymal defects resulted in AAL increasing with ascending TVi. Multiple linear regression analysis revealed strong correlation between AAL and maximal inspiratory pressure, compliance and resistance. At TVi = 400, 500, and 600 mL, TachoSil achieved sealing in ten, eight, and seven tests, respectively. As TVi increased, superficial defects were still sealed in four, two, and two tests at TVi = 700, 800, and 900 mL, respectively. The burst pressure was 42 ± 5 cmH2O. Adhesive failures were found at the burst pressure in all tests. Concerning elasticity, TachoSil allowed an expansion of the covered lung defect of 7 ± 6 mm. CONCLUSIONS: TachoSil demonstrated a strong sealing efficiency and marked elasticity in treating AAL. These results are consistent to that of the previously published animal experiment, suggesting the reliability of the presented in vitro model.

Electroencephalographic Narcotrend index, spectral edge frequency and median power frequency as guide to anaesthetic depth for cardiac surgery in laboratory sheep.

In order to provide objective measures of anaesthetic depth for periods without clinical signs (e.g., cardiopulmonary bypass [CPB]), the correlation between the electroencephalographic Narcotrend index (NI), 95% spectral edge frequency (SEF95), median power frequency (MPF) and clinical stages of anaesthesia was investigated in 16 juvenile sheep. Data were recorded during recovery from anaesthesia for pulmonary or aortic valve replacement. A significant (P<0.05) negative correlation was found between clinical stages of anaesthesia and NI (r(s) = -0.534) and SEF95 (r(s) = -0.543). No significant correlation existed between anaesthetic stages and MPF (r(s) = -0.292, P>0.05). The sensitivity of NI, SEF95 and MPF to assure an adequate level of anaesthesia was 71.43%, 66.67% and 44.44%, respectively, while the specificity of the descriptors ranged between 97.44 and 92.31%. No significant age-related effect on EEG data and stages of anaesthesia was detected when data from sheep between 4 and 6 months of age were compared with data obtained from 8- to 12-month old sheep. In conclusion, NI seems to be the most appropriate EEG descriptor to assure adequate depth of anaesthesia in juvenile, isoflurane-anaesthetized sheep.

TissuePatch™ as a novel synthetic sealant for repair of superficial lung defect: in vitro tests results.

BACKGROUND: Controversies surrounding the efficacy of surgical sealants against alveolar air leaks (AAL) in lung surgery abound in the literature. We sought to test the sealing efficacy of a novel synthetic sealant, TissuePatch™ in an in vitro lung model. METHODS: The lower lobe of freshly excised swine lung (n = 10) was intubated and ventilated. A superficial parenchymal defect (40 × 25 mm) was created, followed by AAL assessment. After sealant application, AAL was assessed again until burst failure occurred. The length of defect was recorded to evaluate the elasticity of the sealant. RESULTS: Superficial parenchymal defects resulted in AAL increasing disproportionally with ascending maximal inspiratory pressure (Pmax). Multiple linear regression analysis revealed strong correlation between AAL and Pmax, compliance, resistance. After sealant application, AAL was sealed in all ten tests at an inspired tidal volume (TVi) of 400 ml, in nine tests at TVi = 500 ml, in seven at TVi = 600 ml and in five at TVi = 700 ml. The mean burst pressure was 42 ± 9 mBar. Adhesive and cohesive sealant failures were found in six and three tests respectively. The length of defect before sealant failure was 8.9 ± 4.9% larger than that at TVi = 400 ml, demonstrating an adequate elasticity of this sealant film. CONCLUSIONS: TissuePatch™ may be a reliable sealant for alternative or adjunctive treatment for repair of superficial parenchymal defects in lung surgery. The clinical benefits of this sealant should be confirmed by prospective, randomised controlled clinical trials. ABSTRAKT: HINTERGRUND: Die Wirksamkeit von chirurgischen Klebstoffen zur Prävention von alveolo-pleuralem Luftleck (APL) ist trotz zunehmenden klinischen Anwendungen in Lungenchirurgie immer noch kontrovers diskutiert. Wir evaluierten die Abdichtungswirksamkeit von einem neuartigen synthetischen Kleber, TissuePatch™ mittels eines in vitro Lungenmodels. METHODE: Der Unterlappen von frisch entnommenen Schweinlungen (n = 10) wurde intubiert und beatmet. Eine pleurale Läsion (40 × 25 mm) wurde erstellt und APL mit steigendem inspiratorischem Tidalvolumen (TVi) untersucht. Nach Applikation von TissuePatch™ wurde APL auf die gleiche Weise gemessen bis zur Auftritt von Kleberbruch. Zur Untersuchung der Elastizität des Klebers wurde die Länge der pleuralen Läsion gemessen. ERGEBNIS: Pleurale Läsion führte bei aufsteigendem maximalem inspiratorischem Druck (Pmax) zu überproportionalem Anstieg von APL. Multiple lineare Regressionsanalyse ergab eine starke Korrelation zwischen APL und Pmax, Lungencompliance sowie Widerstand. Nach der Applikation von Klebstoff wurde APL bei TVi = 400 ml in allen zehn Testen versiegelt, bei TVi = 500 ml in neun Testen, bei TVi = 600 ml in sieben und bei TVi = 700 ml in fünf Testen. Der mittlere Pmax, der zu Kleberbruch führte, betrug 42 ± 9 mBar. Bei den Versuchen wurden adhäsiver und kohäsiver Kleberbruch in jeweils sechs und drei Testen gefunden. Die Länge der pleuralen Läsion vor dem Kleberbruch war 8,9 ± 4,9% größer als die bei TVi = 400 ml. SCHLUSSFOLGERUNG: Unsere Versuche zeigten eine zuverlässige Versiegelung von TissuePatch™ unter mechanischer Ventilation. Die klinische Nützlichkeit vom Kleber als unterstützende Maßnahme zur Prävention von alveolo-pleuralem Luftleck in Lungenchirurgie sollte durch prospektive, randomisierte kontrollierte klinische Studien bestätigt werden.

Relation between isoflurane concentration, body temperature and EEG variables during hypothermic cardiopulmonary bypass in juvenile sheep.

Isolation of lungs from the circulation during cardiopulmonary bypass (CPB) results in the loss of end-tidal anaesthetic measurement as a monitor of anaesthetic depth. The objective of our study was to test whether the isoflurane concentration measured at the oxygenator exhaust (ISO(PO-OX)) could be used as an alternative. Five juvenile ewes were anaesthetised for experimental aortic valve replacement during hypothermic CPB. One sheep recovered from anaesthesia with signs of CNS excitement and was excluded from electroencephalogram (EEG) data analysis. ISO(PO-OX) was similar to the end-tidal anaesthetic concentration measured before start of CPB (ISO(ET(PRE-CPB))) and was positively correlated (P<0.001; R=0.431) to the bypass temperature (T(CPB)). EEG burst suppression ratio was negatively correlated with the oesophageal temperature (T(ESO)) (P=0.002; R=0.433) whilst data analysis revealed only a weak association between EEG variables and ISO(PO-OX). Therefore, EEG monitoring may be the only valuable quantitative measure of adequate anaesthetic depth during hypothermic CPB.