Neutrophil extracellular traps - a potential trigger for the development of thrombocytopenia during extracorporeal membrane oxygenation

Neutrophil extracellular traps (NETs) have recently emerged as a potential link between inflammation, immunity, and thrombosis, as well as other coagulation disorders which present a major challenge in the context of extracorporeal membrane oxygenation (ECMO). By examining blood from ECMO patients for NETs and their precursors and correlating them with clinical and laboratory biomarkers of coagulation and inflammation, this study aims to evaluate the association between the presence of NETs in the bloodstream of ECMO patients and the development of potentially severe coagulation disorders during ECMO therapy. Therefore, blood samples were collected from healthy volunteers (n=13) and patients receiving veno-venous (VV) ECMO therapy (n=10). To identify NETs and their precursors, DNA and myeloperoxidase as well as granulocyte marker CD66b were visualized simultaneously by immunofluorescence staining in serial blood smears. Differentiation of DNA-containing objects and identification of NETs and their precursors was performed semiautomatically by a specific algorithm using the shape and size of DNA staining and the intensity of MPO and CD66b signal. Neutrophil extracellular traps and their precursors could be detected in blood smears from patients requiring VV ECMO. Compared to volunteers, ECMO patients presented significantly higher rates of NETs and NET precursors as well as an increased proportion of neutrophil granulocytes in all detected nucleated cells. A high NET rate prior to the initiation of ECMO therapy was associated with both increased IL-6 and TNF-α levels as an expression of a high cytokine burden. These patients with increased NET release also presented an earlier and significantly more pronounced decrease in platelet counts and ATIII activity following initiation of therapy compared with patients with less elevated NETs. These findings provide further indications for the development of immune-mediated acquired thrombocytopenia in ECMO patients.

Clinical relevance of cell-free DNA during venovenous extracorporeal membrane oxygenation

BACKGROUND

Thrombosis remains a critical complication during venovenous extracorporeal membrane oxygenation (VV ECMO). The involvement of neutrophil extracellular traps (NETs) in thrombogenesis has to be discussed. The aim was to verify NETs in the form of cell-free DNA (cfDNA) in the plasma of patients during ECMO.

METHODS

A fluorescent DNA-binding dye (QuantifFluor®, Promega) was used to detect cell-free DNA in plasma samples. cfDNA concentrations from volunteers (n = 21) and patients (n = 9) were compared and correlated with clinical/technical data before/during support, ECMO end and time of a system exchange.

RESULTS

Before ECMO, patients with a median (IQR) age of 59 (51/63) years, SOFA score of 11 (10/15), and ECMO run time of 9.0 (7.0/19.5) days presented significantly higher levels of cfDNA compared to volunteers (6.4 (5.8/7.9) ng/μL vs. 5.9 (5.4/6.3) ng/μL; p = 0.044). Within 2 days after ECMO start, cfDNA, inflammatory, and hemolysis parameters remained unchanged, while platelets decreased (p = 0.005). After ECMO removal at the end of therapy, cfDNA, inflammation, and coagulation data (except antithrombin III) remained unchanged. The renewal of a system resulted in known alterations in fibrinogen, d-dimers, and platelets, while cfDNA remained unchanged.

CONCLUSION

Detection of cfDNA in plasma of ECMO patients was not an indicator of acute and circuit-induced thrombogenesis.

A solution for global hygienic challenges regarding the application of heater-cooler systems in cardiac surgery

71.759 surgical procedures were performed in 2019 with the aid of cardiopulmonary bypass in Germany. To adjust the patient's body temperature on extracorporeal circulation, the application of a heater-cooler unit (HCU) is mandatory. However, in case of insufficient sanitisation of HCU, life-threatening infections can be transmitted by the device to the patients, including Legionella bacteria, Mycobacterium chimaera, Pseudomonas aeruginosa. To avoid disease transmission, as a requirement for safe medical practice established by regulatory authorities, HCUs must be regularly disinfected by hazardous chemicals posing a danger for both handling humans and the environment. Therefore, to comply with regulations, HCU manufacturers have introduced both timely and financially extensive sanitisation procedures. Our paper describes a novel, effective and easy to handle disinfection method for the above problematics without utilising hazardous chemicals. The method's technical principle is electrolysis, resulting in drinking water quality regarding the analysed germs in the worldwide most commonly utilised heater-cooler device. The main aim of the study was to prove the efficacy and reliability of the device cleansing process. Furthermore, the economic impact of the novel method was evaluated. Therefore, we have undertaken 60 microbiological sampling series between December 2019 and November 2020 from a conventional HCU (3T LivaNova, Germany). During the total investigational period, no contamination with Pseudomonas aeruginosa or Legionellae could have been demonstrated in the HCU. The extreme slow-growing nontuberculous M. chimaera was detected only in one sample obtained from diamond electrode cleansed HCU water, and source of contamination was promptly eliminated by a simple technical modification of the device test-site. Additionally, the diamond electrode application is beneficial for eliminating potentially hazardous cleansing material from the process, which may affect otherwise both patients operated on cardiopulmonary bypass and the perfusionists.

Introduction of a New ex vivo Porcine Coronary Artery Model: Evaluation of the Direct Vascular Injury after Stent Implantation with and without Dogbone Effect

INTRODUCTION

Neointimal hyperplasia after percutaneous coronary intervention remains a major determinant of in-stent restenosis (ISR). The extent of mechanical vessel injury correlates with ISR. A new ex vivo porcine stent model was introduced and evaluated comparing different stent designs.

METHODS

Coronary arteries were prepared from pig hearts from the slaughterhouse and used for ex vivo implantations of coronary stents. One basic stent design in two configurations (dogbone, DB; nondogbone, NDB) was used. Vascular injury was determined according to a modified injury score (IS).

RESULTS

Standardized experimental conditions ensured comparable vessel dimensions and overstretch data. DB stents caused more severe IS compared to NDB stents. The mean IS and the IS at the distal end of all stents were significantly reduced for NDB stents (ISMean, DB, 1.16 ± 0.12; NDB, 1.02 ± 0.12; p = 0.018; ISDist, DB, 1.39 ± 0.28; NDB, 1.13 ± 0.24; p = 0.03).

DISCUSSION/CONCLUSION

The introduced ex vivo model allowed the evaluation of different stent designs, which exclude unfavorable stent designs.

Prevalence and outcomes of patients developing heparin-induced thrombocytopenia during extracorporeal membrane oxygenation

Objectives

Unfractionated heparin (UFH) is the commonly used anticoagulant to prevent clotting of the ECMO circuit and thrombosis of the cannulated vessels. A side effect of UFH is heparin-induced thrombocytopenia (HIT). Little is known about HIT during ECMO and the impact of changing anticoagulation in ECMO patients with newly diagnosed HIT. The aim of the study was to determine the prevalence, complications, impact of switching anticoagulation to argatroban and outcomes of patients developing heparin-induced thrombocytopenia (HIT) during either veno-venous (VV) or veno-arterial (VA) ECMO.

Methods

Retrospective observational single centre study of prospectively collected data of consecutive patients receiving VV ECMO therapy for severe respiratory failure and VA ECMO for circulatory failure from January 2006 to December 2016 of the Medical intensive care unit (ICU) of the University Hospital of Regensburg. Treatment of HIT on ECMO was done with argatroban.

Results

507 patients requiring ECMO were included. Further HIT-diagnostic was conducted if HIT-4T-score was ≥4. The HIT-confirmed group had positive HIT-enzyme-linked-immunosorbent-assay (ELISA) and positive heparin-induced-platelet-activation (HIPA) test, the HIT-suspicion group a positive HIT-ELISA and missing HIPA but remained on alternative anticoagulation until discharge and the HIT-excluded group a negative or positive HIT-ELISA, however negative HIPA. These were compared to group ECMO-control without any HIT suspicion. The prevalence of HIT-confirmed was 3.2%, of HIT-suspicion 2.0% and HIT-excluded 10.8%. Confirmed HIT was trendwise more frequent in VV than in VA (3.9 vs. 1.7% p = 0.173). Compared to the ECMO control group, patients with confirmed HIT were longer on ECMO (median 13 vs. 8 days, p = 0.002). Different types of complications were higher in the HIT-confirmed than in the ECMO-control group, but in-hospital mortality was not different (31% vs. 41%, p = 0.804).

Conclusion

HIT is rare on ECMO, should be suspected, if platelets are decreasing, but seems not to increase mortality if treated promptly.

Coagulation abnormalities in patients with COVID-19 on venovenous ECLS increased risk for technical complications and support times but had no impact on survival

BACKGROUND

Patients with severe coronavirus disease-19 (COVID-19)-associated acute respiratory distress on venovenous extracorporeal lung support (V-V ECLS) showed high incidence of vascular as well as ECLS-related thrombotic complications. The latter may influence the outcome of the patients.

METHODS

This is a retrospective monocentric study on prospectively collected data of technical complications including 69 adult COVID-19 patients on V-V ECLS (ECLS Registry, March 2020 until April 2021) without and with system exchanges. Alterations in ECLS-specific data, hemolysis, coagulation and hemostasis parameters were analyzed.

RESULTS

Every second COVID-19 patient on V-V ECLS developed technical complications. Optimized ECLS management at our ECLS center reduced cases of acute clot formation (pump head thrombosis, acute oxygenator thrombosis) (17%), and allowed early identification of progressive clotting processes (worsened gas transfer, coagulation disorder) (14%, 54%) with a significant overhang of hyperfibrinolysis (37%). Although COVID-19 disease and technical complications caused prolonged length of stay at the intensive care unit and ECLS support times, the proportion of successful weaning and survival rates were comparable with patients without system exchange.

CONCLUSION

The survival of ECLS patients with COVID-19 was independent of the requirement for system exchange due to technical-induced coagulation disorders. Close monitoring for circuit clotting is mandatory in COVID-19 patients and is one prerequisite for successful organ support in these difficult patients.

Different mechanisms of oxygenator failure and high plasma von Willebrand factor antigen influence success and survival of venovenous extracorporeal membrane oxygenation

OBJECTIVE

Failure of membrane oxygenator (MO) function of venovenous extracorporeal membrane oxygenators (VV ECMO) remains problematic. The development of device-induced coagulation disorder (COD) or worsened gas transfer (WGT) necessitates a system exchange. The aim was to correlate von Willebrand factor antigen (vWF:Ag) with the predisposition to MO failure and mortality.

METHODS

Laboratory parameters (inflammation, coagulation) and ECMO-related data from 31 VV ECMO patients were analyzed before and after the first MO exchange. Study groups were identified according to the exchange reasons (COD, WGT) and the extent of vWF:Ag (low, ≤425%; high, >425%).

RESULTS

vWF:Ag remained unchanged after system exchange. High vWF:Ag was associated with systemic endothelial activation of older and obese patients with elevated SOFA score, increased norepinephrine and higher requirement of continuous renal replacement therapy without an effect on MO runtime and mortality. Including the mechanism of MO failure (COD, WGT), various patient group emerged. COD/low vWF:Ag summarized younger and less critically ill patients that benefit mainly from ECMO by a significant improvement of their inflammatory and coagulation status (CRP, D-dimers, fibrinogen) and highest survival rate (91%). Instead, WGT/high vWF:Ag presented older and more obese patients with a two-digit SOFA score, highest norepinephrine, and aggravated gas transfer. They benefited temporarily from system exchange but with worst survival (33%).

CONCLUSIONS

vWF:Ag levels alone cannot predict early MO failure and outcome in VV ECMO patients. Probably, the mechanism of clotting disorder in combination with the vWF:Ag level seems to be essential for clot formation within the MO. In addition, vWF:Ag levels allows the identification different patient populations In particular, WGT/high vWF:Ag represented a critically ill population with higher ECMO-associated mortality.

Analysis of Thrombotic Deposits in Extracorporeal Membrane Oxygenators by High-resolution Microcomputed Tomography: A Feasibility Study

Coagulative disorders, especially clotting during extracorporeal membrane oxygenation, are frequent complications. Direct visualization and analysis of deposits in membrane oxygenators using computed tomography (CT) may provide an insight into the underlying mechanisms causing thrombotic events. However, the already established multidetector CT (MDCT) method shows major limitations. Here, we demonstrate the feasibility of applying industrial micro-CT (µCT) to circumvent these restrictions. Three clinically used membrane oxygenators were investigated applying both MDCT and µCT. The scans were analyzed in terms of clot volume and local clot distribution. As validation, the clot volume was also determined from the fluid volume, which could be filled into the respective used oxygenator compared to a new device. In addition, cross-sectional CT images were compared with crosscut oxygenators. Based on the µCT findings, a morphological measure (sphericity) for assessing clot structures in membrane oxygenators is introduced. Furthermore, by comparing MDCT and µCT results, an augmentation of the MDCT method is proposed, which allows for improved clot volume determination in a clinical setting.

Anti-oxidative effect of the tyrosine kinase inhibitor nintedanib: a potential therapy for chronic lung allograft dysfunction?

Background: The long-term survival after lung transplantation (LTx) is often limited by the development of chronic lung allograft dysfunction (CLAD). Increased oxidative stress has been found to occur in chronic lung allograft dysfunction because of several risk factors, e.g. immunological factors or drug related factors. The aim of this study was to investigate the anti-oxidative effect of the receptor tyrosine kinase (RTK) inhibitor nintedanib on immunologically induced oxidative stress and on drug induced oxidative stress.Methods: In-vivo studies were used for investigation of immunologically induced oxidative stress: Immunohistochemistry of transglutaminase-2 (TGM-2) was used to figure out a potential anti-oxidative effect of receptor tyrosine kinase inhibitor nintedanib in a rat model of allogeneic left LTx. In-vitro studies were used for investigation of drug induced oxidative stress: Cell viability assay, 2'7'-dichlorodihydrofluorescein diacetate (DCFDA) and immunofluorescence of transglutaminase-2 were disposed to examine the potential impact of nintedanib on cyclosporin A (CsA) treated lung fibroblasts of the rat.Results: In-vivo studies: Allogeneic transplanted animals without drug interaction showed severe chronic rejection and an excessive expression of TGM-2, whereas the application of nintedanib significantly decreased the number of TGM-2 positive cells. In-vitro studies: Concentrations of CsA ranging from 250 ng/ml to 500 ng/ml demonstrated oxidative stress caused by an increased production of reactive oxygen species (ROS) and an overexpression of TGM-2 without inducing apoptosis in cells. Concentrations of more than 1000 ng/ml led to a considerable decrease of cellularity. 30 min-pre-incubation with nintedanib at a concentration between 25 and 100 nM reduced generation of intracellular ROS and expression of TGM-2.Conclusion: These results demonstrate a downregulation of ROS and TGM-2 by pretreatment with the receptor tyrosine kinase inhibitor nintedanib and present its potential anti-oxidative and immunomodulatory effect in the treatment of chronic lung allograft dysfunction.

Factors associated with hemolysis during extracorporeal membrane oxygenation (ECMO)-Comparison of VA- versus VV ECMO

Venovenous (VV) and venoarterial (VA) extracorporeal membrane oxygenation (ECMO) are effective support modalities to treat critically ill patients. ECMO-associated hemolysis remains a serious complication. The aim was to disclose similarities and differences in VA- and VV ECMO-associated hemolysis. This is a retrospective single-center analysis (January 2012 to September 2018) including 1,063 adult consecutive patients (VA, n = 606; VV, n = 457). Severe hemolysis (free plasma hemoglobin, fHb > 500 mg/l) during therapy occurred in 4% (VA) and 2% (VV) (p≤0.001). VV ECMO showed significantly more hemolysis by pump head thrombosis (PHT) compared to VA ECMO (9% vs. 2%; p≤0.001). Pretreatments (ECPR, cardiac surgery) of patients who required VA ECMO caused high fHb pre levels which aggravates the proof of ECMO-induced hemolysis (median (interquartile range), VA: fHb pre: 225.0 (89.3–458.0); VV: fHb pre: 72.0 (42.0–138.0); p≤0.001). The survival rate to discharge from hospital differed depending on ECMO type (40% (VA) vs. 63% (VV); p≤0.001). Hemolysis was dominant in VA ECMO patients, mainly caused by different indications and not by the ECMO support itself. PHT was the most severe form of ECMO-induced hemolysis that occurs in both therapies with low frequency, but more commonly in VV ECMO due to prolonged support time.

Accumulations of von Willebrand factor within ECMO oxygenators: Potential indicator of coagulation abnormalities in critically ill patients?

Clot formation within membrane oxygenators (MOs) remains a critical problem during extracorporeal membrane oxygenation (ECMO). The composition of the clots-in particular, the presence of von Willebrand factor (vWF)-may be an indicator for prevalent nonphysiological flow conditions, foreign body reactions, or coagulation abnormalities in critically ill patients. Mats of interwoven gas exchange fibers from randomly collected MOs (PLS, Maquet, Rastatt, Germany) of 21 patients were stained with antibodies (anti-vWF and anti-P-selectin) and counterstained with 4',6-diamidino-2-phenylindole. The extent of vWF-loading was correlated with patient and technical data. While 12 MOs showed low vWF-loadings, 9 MOs showed high vWF-loading with highest accumulations close to crossing points of adjacent gas fibers. The presence and the extent of vWF-fibers/"cobwebs," leukocytes, platelet-leukocyte aggregates (PLAs), and P-selectin-positive platelet aggregates were independent of the extent of vWF-loading. However, the highly loaded MOs were obtained from patients with a significantly elevated SOFA score, severe thrombocytopenia, and persistent liver dysfunction. The coagulation abnormalities of these critically ill patients may cause an accumulation of the highly thrombogenic and elongated high-molecular-weight vWF multimers in the plasma which will be trapped in the MOs during the ECMO therapy.

Quantitative assessment of peripheral limb perfusion using a modified distal arterial cannula in venoarterial ECMO settings

In cases of severe cardiopulmonary deterioration, quick establishment of venoarterial extracorporeal membrane oxygenation (ECMO) represents a support modality. After successful arterial peripheral cannulation, a certain grade of peripheral limb malperfusion is a fairly common phenomenon. Detection of peripheral malperfusion is vital, since it can result in compartment syndrome or even loss of the affected limb. To prevent or resolve emerging lower limb ischaemia, a newly designed perfusion catheter is placed into the superficial femoral artery, distal to the arterial cannula via ECMO. The aim of our study was to evaluate flow and haemodynamic characteristics of this novel distal limb perfusion cannula for ECMO therapy and present these important findings for the first time. The distal perfusion cannula blood flow increases in linear correlation with ECMO blood flow The variability of distal perfusion cannula blood flow with a 15 Fr cannula ranges between 160 ± 0.40 mL min−1 at 1.5 L min−1 ECMO flow rate and 480 ± 80 mL min−1 at 5.0 L min−1 ECMO blood flow, respectively. Comparatively, the 17-Fr-sized cannula performs on a scale of 140 ± 20 to 390 ± 60 mL distal perfusion cannula blood flow at 1.5-5.0 L min−1 ECMO blood flow, respectively. The quantitative assessment of the distal perfusion cannula blood flow has revealed that distal perfusion cannula blood flow can measure up to 10% of the ECMO blood flow. Furthermore, it has been also well demonstrated that the novel distal perfusion cannula is sufficient to compensate peripheral limb ischaemia.

Synergism of imatinib, vatalanib and everolimus in the prevention of chronic lung allograft rejection after lung transplantation (LTx) in rats

Chronic lung allograft dysfunction (CLAD) still remains a major drawback in the outcome following lung transplantation (LTx). New therapeutic strategies are warranted. Growth factors and their receptors like platelet-derived growth factor-receptor (PDGFR) and vascular endothelial growth factor-receptor (VEGFR), may play a crucial role in the development of CLAD, especially bronchiolitis obliterans (BO) and vasculopathy. In this study, we used an orthotopic left lung transplantation model from Fischer (F344) to Wystar Kyoto (WKY) rats to investigate the effect of the receptor tyrosine kinase inhibitor (RTKI) vatalanib alone, the dual combination of vatalanib and imatinib and a triple therapy consisting of vatalanib, imatinib and the mammalian target of rapamycin inhibitor (mTORI) everolimus on the development of CLAD after LTx in rats. With this trial we demonstrated that monotherapy with vatalanib attenuated mild and severe chronic vascular rejection, whereas dual therapy (vatalanib and imatinib) after LTx also showed a significant reduction of chronic bronchiolar rejection and interstitial fibrosis. By adding everolimus, the effect of vatalanib and imatinib could additionally be increased. In conclusion, the combination of mTORI and RTKIs might be a possible strategy in the prevention of CLAD and BO.

Time course of chemotaxis and chemokinesis of neutrophils following stimulation with IL-8 or FMLP

Polymorphonuclear cells (PMNs) attend to inflammatory sites by chemotactic movement, caused by chemoattractants (CAs) like n-formyl-l-methionyl-l-leucyl-l-phenylalanine (FMLP) and interleukin-8 (IL-8). However, distinct but applicable assays for investigations of PMNs’ migration limit in vitro examination. We integrated CD15-bead-based isolation of PMNs with analysing their chemotaxis in a novel 3D-µ-Slide migration chamber. The PMNs were exposed to different concentrations of FMLP and IL-8 (1, 10 and 100 nM) and observed for 180 min in cell-physiological environment conditions. Moving PMNs’ percentage (median and interquartile range) decreased from 62% (27%) to 36% (31%) without CA, from 88% (30%) to 22% (26%) for 1 nM IL-8, from 70% (22%) to 28% (13%) for 100 nM IL-8, from 30% (23%) to 18% (46%) for 1 nM FMLP and from 76% (20%) to 28% (13%) for 100 nM FMLP. Centres of cell movement turned towards the CAs (negative values) within a single 30-min observation period: 5.37 µm (16.82 µm) without CA, −181.37 µm (132.18 µm) with 10 nM and −239.34 µm (152.19 µm) with 100 nM IL-8; −116.2 µm (69.07 µm) with 10 nM and −71.59 µm (98.58 µm) with 100 nM FMLP. FMLP and IL-8 ensure chemotaxis without increase of chemokinesis. 3D-µ-Slide chemotaxis chambers facilitate time course analyses of PMNs’ migration in stable conditions over a long time with concise distinction of chemotaxis and chemokinesis.

Intravenous hydrogen sulfide does not induce neuroprotection after aortic balloon occlusion-induced spinal cord ischemia/reperfusion injury in a human-like porcine model of ubiquitous arteriosclerosis

Objective

In rodents, intravenous sulfide protected against spinal cord ischemia/reperfusion (I/R) injury during aortic balloon occlusion. We investigated the effect of intravenous sulfide on aortic occlusion-induced porcine spinal cord I/R injury.

Methods

Anesthetized and mechanically ventilated “familial hypercholesterolemia Bretoncelles Meishan” (FBM) pigs with high-fat-diet-induced hypercholesterolemia and atherosclerosis were randomized to receive either intravenous sodium sulfide 2 h (initial bolus, 0.2 mg kg body weight (bw)⁻¹; infusion, 2 mg kg bw⁻¹ h⁻¹; n = 4) or vehicle (sodium chloride, n = 4) prior to 45 min of thoracic aortic balloon occlusion and for 8 h during reperfusion (infusion, 1 mg kg bw⁻¹ h⁻¹). During reperfusion, noradrenaline was titrated to maintain blood pressure at above 80% of the baseline level. Spinal cord function was assessed by motor evoked potentials (MEPs) and lower limb reflexes using a modified Tarlov score. Spinal cord tissue damage was evaluated in tissue collected at the end of experiment using hematoxylin and eosin and Nissl staining.

Results

A balloon occlusion time of 45 min resulted in marked ischemic neuron damage (mean of 16% damaged motoneurons in the anterior horn of all thoracic motor neurons) in the spinal cord. In the vehicle group, only one animal recovered partial neuronal function with regain of MEPs and link motions at each time point after deflating. All other animals completely lost neuronal functions. The intravenous application of sodium sulfide did not prevent neuronal cell injury and did not confer to functional recovery.

Conclusion

In a porcine model of I/R injury of the spinal cord, treatment with intravenous sodium sulfide had no protective effect in animals with a pre-existing arteriosclerosis.

Superior vasodilation of human pulmonary vessels by vardenafil compared with tadalafil and sildenafil: additive effects of bosentan

OBJECTIVES

Pulmonary arterial hypertension is characterized by pulmonary vascular proliferation and remodelling, leading to a progressive increase in pulmonary arterial resistance. Vasodilator properties of 3 different phosphodiesterase (PDE)-5 inhibitors alone and in combination with an endothelin (ET) receptor antagonist were compared in an ex vivo model.

METHODS

Segments of human pulmonary arteries (PAs) and pulmonary veins (PVs) were harvested from lobectomy specimens. Contractile forces were determined in an organ bath. Vessels were constricted with norepinephrine (NE) to determine the effects of sildenafil, tadalafil and vardenafil and with ET-1 to assess the effects of bosentan.

RESULTS

All 3 PDE-5 inhibitors had no relevant effect on the basal tone of the vessels. Both sildenafil and vardenafil significantly (P < 0.0001) reduced the responses of the vessels to NE, whereas tadalafil was effective only in PA (P = 0.0009) but not in PV (P = 0.097). Sildenafil relaxed NE-preconstricted PV (P < 0.0001) but not PA (P = 0.143). Both tadalafil and vardenafil relaxed PA and PV significantly. Vardenafil appears to be the most potent of the PDE-5 inhibitors tested. Furthermore, we analysed the combination of bosentan and vardenafil in PA. Bosentan and vardenafil reduced ET-1 and NE induced vasoconstriction stronger than vardenafil alone (P ≤ 0.049).

CONCLUSIONS

Vardenafil caused the most consistent antihypertensive response in this ex vivo model. However, ET receptor antagonism appears to be an even more potent mechanism. A combination therapy using vardenafil and bosentan turned out to be an effective combination to lower vessel tension in PA.

The activity of nintedanib in an animal model of allogenic left lung transplantation resembling aspects of allograft rejection

AIM OF THE STUDY

The prevention and treatment of chronic lung allograft dysfunction (CLAD) after lung transplantation (LTx) remain unsatisfactory. Growth factors may play an important role in the development of CLAD. This study evaluated the effects of nintedanib, a receptor tyrosine kinase inhibitor, in the treatment of CLAD after experimental LTx.

MATERIALS AND METHODS

A rat model of left lung allo-transplantation (Fisher 344 to Wistar Kyoto) was used to evaluate the effect of nintedanib (50 mg/kg per day) on the development of CLAD. Therapy with nintedanib began 2 days before LTx and ended on postoperative day (POD) 20 (n = 6) or 60 (n = 6). Nontreated animals who underwent LTx (n = 12) were used as controls, whereas naïve lungs (n = 24) served as reference for physiological healthy organs without transplantation damage or medical effects. Acute and chronic rejection were evaluated on POD 20 and 60, respectively.

RESULTS

Immunohistologic analysis showed a decrease in growth factors/receptors on POD 60 (nintedanib-treated vs. nontreated controls: platelet-derived growth factor (PDGF) A: [P ≤ 0.001]; PDGF receptor-α: [P ≤ 0.001]; vascular endothelial growth factor (VEGF) A: [P ≤ 0.001]; VEGF receptor-2: [P ≤ 0.001]). However, no reductions in fibrotic changes were observed in nintedanib-treated allografts compared with nontreated allografts. Although nintedanib treatment started before LTx none of the animals showed impaired wound healing. No dehiscence of the sutures of the bronchus, vessels or skin, or stenosis of the bronchus was found.

CONCLUSION

In conclusion, while nintedanib reduced the expression of growth factors/receptors in a rat LTx model, a reduction in fibrotic alterations was not observed at POD 60.

Effect of Immobilized Antithrombin III on the Thromboresistance of Polycarbonate Urethane

The surface of foils and vascular grafts made from a thermoplastic polycarbonate urethanes (PCU) (Chronoflex AR) were chemically modified using gas plasma treatment, binding of hydrogels—(1) polyethylene glycol bisdiamine and carboxymethyl dextran (PEG-DEX) and (2) polyethyleneimine (PEI)—and immobilization of human antithrombin III (AT). Their biological impact was tested in vitro under static and dynamic conditions. Static test methods showed a significantly reduced adhesion of endothelial cells, platelets, and bacteria, compared to untreated PCU. Modified PCU grafts were circulated in a Chandler-Loop model for 90 min at 37 °C with human blood. Before and after circulation, parameters of the hemostatic system (coagulation, platelets, complement, and leukocyte activation) were analyzed. PEI-AT significantly inhibited the activation of both coagulation and platelets and prevented the activation of leukocytes and complement. In conclusion, both modifications significantly reduce coagulation activation, but only PEI-AT creates anti-bacterial and anti-thrombogenic functionality.

Plasma functionalization of polycarbonaturethane to improve endothelialization—Effect of shear stress as a critical factor for biocompatibility control

Medical devices made of polycarbonaturethane (PCU) combine excellent mechanical properties and little biological degradation, but restricted hemocompatibility. Modifications of PCU might reduce platelet adhesion and promote stable endothelialization. PCU was modified using gas plasma treatment, binding of hydrogels, and coupling of cell-active molecules (modified heparin, anti-thrombin III (ATIII), argatroban, fibronectin, laminin-nonapeptide, peptides with integrin-binding arginine-glycine-aspartic acid (RGD) motif). Biocompatibility was verified with static and dynamic cell culture techniques. Blinded analysis focused on improvement in endothelial cell (EC) adhesion/proliferation, anti-thrombogenicity, reproducible manufacturing process, and shear stress tolerance of ECs. EC adhesion and antithrombogenicity were achieved with 9/35 modifications. Additionally, 6/9 stimulated EC proliferation and 3/6 modification processes were highly reproducible for endothelialization. The latter modifications comprised immobilization of ATIII (A), polyethyleneglycole-diamine-hydrogel (E) and polyethylenimine-hydrogel connected with modified heparin (IH). Under sheer stress, only the IH modification improved EC adhesion within the graft. However, ECs did not arrange in flow direction and cell anchorage was restricted. Despite large variation in surface modification chemistry and improved EC adhesion under static culture conditions, additional introduction of shear stress foiled promising preliminary data. Therefore, biocompatibility testing required not only static tests but also usage of physiological conditions such as shear stress in the case of vascular grafts.

Protective function of pirfenidone and everolimus on the development of chronic allograft rejection after experimental lung transplantation

Long-term survival of lung allografts is limited by chronic rejection (CR). Oxidative stress (OxS) plays a central role in the development of CR. We investigated the influence of pirfenidone (alone or in combination with everolimus) on OxS and CR. A rat model of left lung allo-transplantation (F344-to-WKY) was used to evaluate the effects of pirfenidone alone [0,85% in chow from postoperative day (POD) -3 to 20/60] and in combination with everolimus [2,5 mg/kg bw daily from POD 7 to 20/60]. Allografts of non-treated animals, everolimus treated animals and right, non-transplanted lungs were used as references. Immunohistology of myeloperoxidase (MPO), haemoxygenase-1 (HO-1), iron and platelet-derived-growth-factor-receptor-alpha (PDGFR-a) were performed. On POD 20, all groups showed severe acute rejection (ISHLT A3-4/B1R-B2R). Groups treated with pirfenidone showed a lower interstitial inflammatory infiltration and a lower participation of highly fibrotic degenerated vessels (ISHLT-D2R). In the long term follow up (POD 60), pirfenidone alone significantly reduced chronic airway rejection (ISHLT-C; p≤0.05), interstitial fibrosis (IF; p≤0.05), content of collagen (p≤0.05), expression of PDGFR-a (p≤0.05) and the deposition of iron (p≤0.05). All groups treated with pirfenidone showed a high expression of the cytoprotective enzyme HO-1 (p≤0.05). The additional application of everolimus resulted in a significant decrease of chronic airway rejection (ISHLT-C; p≤0.05), vasculopathy (ISHLT; p≤0.05) and IF (p≤0.05). In conclusion, early application of pirfenidone inhibited the progression of CR by its anti-fibrotic and anti-oxidative properties. The additional application of an m-TOR-inhibitor increased the anti-fibrotic effects of pirfenidone which resulted in a reduction of CR after experimental LTx.

Technical-Induced Hemolysis in Patients with Respiratory Failure Supported with Veno-Venous ECMO - Prevalence and Risk Factors

The aim of the study was to explore the prevalence and risk factors for technical-induced hemolysis in adults supported with veno-venous extracorporeal membrane oxygenation (vvECMO) and to analyze the effect of hemolytic episodes on outcome. This was a retrospective, single-center study that included 318 adult patients (Regensburg ECMO Registry, 2009–2014) with acute respiratory failure treated with different modern miniaturized ECMO systems. Free plasma hemoglobin (fHb) was used as indicator for hemolysis. Throughout a cumulative support duration of 4,142 days on ECMO only 1.7% of the fHb levels were above a critical value of 500 mg/l. A grave rise in fHb indicated pumphead thrombosis (n = 8), while acute oxygenator thrombosis (n = 15) did not affect fHb. Replacement of the pumphead normalized fHb within two days. Neither pump or cannula type nor duration on the first system was associated with hemolysis. Multiple trauma, need for kidney replacement therapy, increased daily red blood cell transfusion requirements, and high blood flow (3.0–4.5 L/min) through small-sized cannulas significantly resulted in augmented blood cell trauma. Survivors were characterized by lower peak levels of fHb [90 (60, 142) mg/l] in comparison to non-survivors [148 (91, 256) mg/l, p≤0.001]. In conclusion, marked hemolysis is not common in vvECMO with modern devices. Clinically obvious hemolysis often is caused by pumphead thrombosis. High flow velocity through small cannulas may also cause technical-induced hemolysis. In patients who developed lung failure due to trauma, fHb was elevated independantly of ECMO. In our cohort, the occurance of hemolysis was associated with increased mortality.

Accumulation of Multipotent Progenitor Cells on Polymethylpentene Membranes During Extracorporeal Membrane Oxygenation

Multipotent progenitor cells were mobilized during pediatric extracorporeal membrane oxygenation (ECMO). We hypothesize that these cells also adhered onto polymethylpentene (PMP) fibers within the membrane oxygenator (MO) during adult ECMO support. Mononuclear cells were removed from the surface of explanted PMP-MOs (n = 16). Endothelial-like outgrowth and mesenchymal-like cells were characterized by flow cytometric analysis using different surface markers. Spindle-shaped attaching cells were identified early, but without proliferative activity. After long-term cultivation palisading type or cobblestone-type outgrowth cells with high proliferative activity appeared and were characterized as (i) leukocytoid CD45+/CD31+ (CD133+/VEGFR-II+/CD90+/CD14+/CD146dim/CD105dim); (ii) endothelial-like CD45-/CD31+ (VEGF-RII+/CD146+/CD105+/CD133-/CD14-/CD90-); and (iii) mesenchymal-like cells CD45-/CD31- (CD105+/CD90+/CD133dim/VEGFR-II-/CD146-/CD14-). The distribution of the cell populations depended on the MO and cultivation time. Endothelial-like cells formed capillary-like structures and did uptake Dil-acetylated low-density lipoprotein. Endothelial- and mesenchymal-like cells adhered on the surface of PMP-MOs. Further research is needed to identify the clinical relevance of these cells.

D-dimers Are a Predictor of Clot Volume Inside Membrane Oxygenators During Extracorporeal Membrane Oxygenation

Thrombosis inside the membrane oxygenator (MO) is a critical complication during venovenous extracorporeal membrane oxygenation (ECMO). The aim of this study was to prove if thrombotic clots manifest within the MO when D-dimer levels are elevated over a long-term period. Heparin-coated polymethylpentene MOs (n = 13) were exchanged due to high plasma D-dimer levels. Clot volume was calculated using multidetector computed tomography (MDCT). Coagulation parameters and MO function were analyzed before and after MO exchange. Before MO exchange, D-dimer levels increased significantly in each patient (11.5 [6.5-15.5] mg/L to 35.0 [34-35] mg/L, P ≤ 0.001). High levels of D-dimers were tolerated for 1 to 6 days. Additionally, fibrinogen concentration (n = 8) and platelet count decreased (n = 8). Within 48 h after exchange, D-dimer levels decreased significantly (n = 11, 12 [8-16] mg/L, P = 0.004). Fibrinogen concentration and platelet counts increased. Clots were found in all MOs in the inlet part of the device. Clot volume (16-106 cm(3) ) did not correlate with MO support time but increased significantly when high D-dimer levels were accepted for >2 days. An increase or high levels of D-dimers in absence of other explaining pathology during ECMO therapy reflected coagulation activity within the MO. Evidence of clots within the MO at high D-dimer levels and decrease after exchange underline the relevance of D-dimer testing during ECMO treatment. Besides, surveillance of MOs during ongoing ECMO therapy will help to predict clot formation, and to avoid system-induced coagulation disorders as well as critical situations.

Technical complications during veno-venous extracorporeal membrane oxygenation and their relevance predicting a system-exchange--retrospective analysis of 265 cases

OBJECTIVES

Technical complications are a known hazard in veno-venous extracorporeal membrane oxygenation (vvECMO). Identifying these complications and predictive factors indicating a developing system-exchange was the goal of the study.

METHODS

Retrospective study on prospectively collected data of technical complications including 265 adult patients (Regensburg ECMO Registry, 2009-2013) with acute respiratory failure treated with vvECMO. Alterations in blood flow resistance, gas transfer capability, hemolysis, coagulation and hemostasis parameters were evaluated in conjunction with a system-exchange in all patients with at least one exchange (n = 83).

RESULTS

Values presented as median (interquartile range). Patient age was 50(36-60) years, the SOFA score 11(8-14.3) and the Murray lung injury Score 3.33(3.3-3.7). Cumulative ECMO support time 3411 days, 9(6-15) days per patient. Mechanical failure of the blood pump (n = 5), MO (n = 2) or cannula (n = 1) accounted for 10% of the exchanges. Acute clot formation within the pump head (visible clots, increase in plasma free hemoglobin (frHb), serum lactate dehydrogenase (LDH), n = 13) and MO (increase in pressure drop across the MO, n = 16) required an urgent system-exchange, of which nearly 50% could be foreseen by measuring the parameters mentioned below. Reasons for an elective system-exchange were worsening of gas transfer capability (n = 10) and device-related coagulation disorders (n = 32), either local fibrinolysis in the MO due to clot formation (increased D-dimers [DD]), decreased platelet count; n = 24), or device-induced hyperfibrinolysis (increased DD, decreased fibrinogen [FG], decreased platelet count, diffuse bleeding tendency; n = 8), which could be reversed after system-exchange. Four MOs were exchanged due to suspicion of infection.

CONCLUSIONS

The majority of ECMO system-exchanges could be predicted by regular inspection of the complete ECMO circuit, evaluation of gas exchange, pressure drop across the MO and laboratory parameters (DD, FG, platelets, LDH, frHb). These parameters should be monitored in the daily routine to reduce the risk of unexpected ECMO failure.

Efficiency of gas transfer in venovenous extracorporeal membrane oxygenation: analysis of 317 cases with four different ECMO systems

PURPOSE

Polymethylpentene membrane oxygenators used in venovenous extracorporeal membrane oxygenation (vvECMO) differ in their physical characteristics. The aim of the study was to analyze the gas transfer capability of different ECMO systems in clinical practice, as the choice of the appropriate system may be influenced by the needs of the patient.

METHODS

Retrospective study on prospectively collected data of adults with severe respiratory failure requiring vvECMO support (Regensburg ECMO Registry, 2009-2013). Oxygen (O2) transfer and carbon dioxide (CO2) elimination of four different ECMO systems (PLS system, n = 163; Cardiohelp system (CH), n = 59, Maquet Cardiopulmonary, Rastatt, Germany; Hilite 7000 LT system, n = 56, Medos Medizintechnik, Stolberg, Germany; ECC.05 system, n = 39, Sorin Group, Mirandola (MO), Italy) were analyzed.

RESULTS

Gas transfer depended on type of ECMO system, blood flow, and gas flow (p ≤ 0.05, each). CO2 removal is dependent on sweep gas flow and blood flow, with higher blood flow and/or gas flow eliminating more CO2 (p ≤ 0.001). CO2 elimination capacity was highest with the PLS system (p ≤ 0.001). O2 transfer at blood flow rates below 3 l/min depended on blood flow, at higher blood flow rates on blood flow and gas flow. The system with the smallest gas exchange surface (ECC.05 system) was least effective in O2 transfer, but in terms of the gas exchange surface was the most effective.

CONCLUSION

Our analysis suggests that patients with severe hypoxemia and need for high flow ECMO benefit more from the PLS/CH or Hilite 7000 LT system. The ECC.05 system is advisable for patients with moderate hypoxemia and/or hypercapnia.

Assessment of cisplatin concentration and depth of penetration in human lung tissue after hyperthermic exposure

OBJECTIVES

The effects of cisplatin on the lung parenchyma during hyperthermic intrathoracic chemotherapy perfusion have not been analysed in detail. The objective of this study was to evaluate both the concentration and depth of the penetration of cisplatin in human lung tissue after hyperthermic exposure under ex vivo conditions.

METHODS

This experimental study was approved by the local ethics committee. Twelve patients underwent pulmonary wedge resections after elective thoracic lobectomies were performed (resected lobe), and the lung tissue (approximately 1-2 cm(3)) was incubated (in vitro) with cisplatin (0.05 mg/ml; 60 min, 42°C). Subsequent tissue beds (depth, 0.5 mm; median weight, 70-92 mg) were prepared from the outside to the middle, and the amount of cisplatin per tissue weight was analysed using atomic absorption spectrometry. Afterwards, the penetration of cisplatin depth was calculated and related to the different concentrations per tissue.

RESULTS

Cisplatin penetrated into the human lung tissue after ex vivo hyperthermic exposure. The median amount of platinum [nmol cisplatin/g lung tissue] decreased significantly (P ≤ 0.05) depending on the penetration depth: 32 nmol/g (1 mm), 20 nmol/g (2 mm) and 6.8 nmol/g (4 mm). The calculated median concentrations of cisplatin (µg/ml) were 2.4 µg/ml (1 mm), 1.4 µg/ml (2 mm) and 0.5 µg/ml (4 mm), respectively.

CONCLUSIONS

Under ex vivo hyperthermic conditions, cisplatin diffused into human lung tissue. The median penetration depth of the cisplatin was approximately 3-4 mm. The penetration of cisplatin into lung tissue may affect the local therapy of residual tumour cells on the lung surface using hyperthermic intrathoracic chemotherapy perfusion in patients with malignant pleural tumours.

Everolimus's influence on persistent acute rejection after experimental lung transplantation

BACKGROUND

In lung transplantation, acute rejection episodes increase the risk of chronic rejection. Therefore treatment of acute rejection needs to be optimized for better long-term outcome of lung-transplantation and patient survival.

OBJECTIVES

The aim was to verify whether an inhibitor of the mammalian target of rapamycin (Everolimus) contained the extent of persistent acute rejection after left lung allo-transplantation in rats.

MATERIAL AND METHODS

Rats (F344-to-WKY) with a high grade of acute rejection were treated with methylprednisolone (10mg/kg, postoperative days 14-16) alone or in combination with everolimus (2.5 mg/kg, postoperative days 14-30). The rats were killed on postoperative day 20 and 30. Infiltration of inflammatory cells (ED1, CD11a, CD18) and activation of endothelial cells (ICAM-1) were measured by immunohistochemistry

RESULTS

Everolimus treatment significantly reduced the number of ICAM-1 positive small vessels (66%; p<0.05) and suppressed the infiltration of leucocytes (CD11a (64%), CD18 (42%); p<0.05) and macrophages (ED1; 22%) in the allografts on POD 30. Despite this clear anti-inflammatory effects, lung allografts still showed severe acute vascular rejection in combination with high grade small airway inflammation.

CONCLUSIONS

The shown anti-inflammatory effects of Everolimus could not delay the progression of acute rejection in rat lung allografts.

Pharmacokinetics of a self-microemulsifying drug delivery system of tacrolimus

This study evaluated the pharmacokinetics of tacrolimus (Tac) in a novel self-microemulsifying drug delivery system (SMEDDS) for improved oral administration. SMEDDS Tac consisted of ethyl oleate as the oily phase, Solutol HS 15 as the surfactant and glycofurol as the co-surfactant and contained 0.5mg/mL tacrolimus. Blood and tissue concentrations of tacrolimus from two study groups (oral application of SMEDDS Tac and Prograf®) were determined using ELISA technique following tacrolimus administration in rats. There was no difference between area under the whole blood concentration-time curve in the SEDDM Tac group and the Prograf® group. Maximum concentrations of the drug were three times higher (P<0.05) in the SEDDM Tac group accompanied by a 3-fold earlier peak time. Elimination half-life was significantly lower in the SEDDM Tac group. Application of SMEDDS Tac increased tissue accumulation. Already after 15 min, Tac levels of small intestine, liver, kidney, spleen, heart and bone marrow were significantly higher in the SMEDDS Tac group than in the Prograf® group (P<0.05). However, the Tac concentration in the kidney was significantly lower in the SMEDDS Tac group. Formulation of SMEDDS did not affect blood-brain barrier function. The SMEDDS is a potentially useful method for a local delivery of Tac to target organs. The selection of the optimum SMEDDS Tac composition might have advantage as an alternative oral dosage form for Tac.

Synergism of imatinib mesylate and everolimus in attenuation of bronchiolitis obliterans after rat LTX

Bronchiolitis obliterans (BO) is a progressive and fatal disease after lung transplantation (LTX). Dysregulated growth factor-induced proliferation of myofibroblasts seems to be responsible for the development of BO. The aim was to confirm the efficacy of both inhibitors of receptor tyrosine kinases (RTKI) and of mammalian target of rapamycin (mTORI) after rat LTX. We used a rat model of left lung allo-transplantation (F344-to-WKY) to evaluate the effect of imatinib (RTKI; 20 mg/kg/day; postoperative day (POD) 0-100) alone or in combination with everolimus (mTORI; 2.5 mg/kg/day; POD 14-100). Non-treated animals were the reference. In non-treated rats, acute rejection (AR) peaked between POD 20 and 30 (19/19) and ended in chronic rejection (CR) on POD 60/100 (12/12). Imatinib alone did not prevent AR (6/6), but attenuated the degree of degenerated bronchioles on POD 30 (non-treated, 57%; imatinib, 4%), and increased the allografts free of CR on POD 60/100 (3/12). A combination of imatinib and everolimus significantly reduced AR, attenuated fibrotic degenerated bronchioles (5%) and vessels (non-treated, 24%; combination therapy, 11%) on POD 30, and reduced fibrotic degenerated vessels (non-treated, 97%; combination therapy, 43%) and bronchioles (non-treated, 88%; combination therapy, 34%) on POD 60/100. Fifty percent of the animals were completely free of BO and vasculopathy. In conclusion, co-application of RTKI and mTORI attenuated the development of BO and vasculopathy. Thus, imatinib might be an interesting therapeutic approach after LTX.

Relevance of maintenance triple-drug immunosuppression to bridle the amplification of rat cytomegalovirus infection after experimental lung transplantation

Immunosuppressive therapy required to treat rejection after lung transplantation (LTx) contributes significantly to the pathogenesis of cytomegalovirus (CMV) infection and disease. In a weak allogeneic left LTx model in the rat (Fisher 344 [F344] to Wistar Kyoto [WKY] rats) we analyzed the influence of acute CMV infection on postoperative day (POD) 3, with application of standard triple-drug immunosuppression (TD-IS) (cyclosporin A, azathioprine, prednisolone) on late outcome after LTx. Native right lungs and syngeneic grafts (WKY to WKY) served as controls. Rats were sacrificed on POD 15, 30, 60, and 100. TD-IS completely prevented acute and chronic rejection in non-infected rats. Allografts of CMV-infected rats treated with TD-IS showed only mild perivascular infiltrations in 6/10 rats (POD 15 and 30), which persisted up to POD 100 in 4/10 rats. In the long-term course, mild isolated interstitial and alveolar changes were found in 40% of these animals. In conclusion, rat CMV infection partially neutralized the immunosuppressive effect of TD-IS. However, an amplification of CMV infection under TD-IS can be controlled and does not result in fatal outcome.

Suppression of bronchiolitis obliterans in allogeneic rat lung transplantation--effectiveness of everolimus

BACKGROUND

Chronic rejection (CR) after lung transplantation (LTX) manifests pathologically by fibrotic airway remodelling and bronchiolitis obliterans (BO). The role of the mammalian target of rapamycin inhibitor everolimus in preventing this process is poorly understood.

METHODS

A rat model of left lung allo-transplantation (Fisher 344 to Wistar Kyoto) was used to analyze the effect of everolimus (2.5 mg/kg/day) on the development of CR. Drug therapy began on postoperative day (POD) 0, 7 and 14 characterizing different grade of acute rejection (AR) of the allograft before drug treatment.

RESULTS

Non-treated recipients developed severe acute rejection (AR) and first signs of CR on POD 20 and a pronounced CR on POD 60. On POD 20, only application of everolimus from POD 0 to 60 significantly reduced acute inflammatory infiltration (p<0.001). Independent of treatment scheme, everolimus suppressed the development of early signs of chronic alterations (POD 20). However, neither early (POD 7-60) nor late (POD 14-60) application of everolimus affected the progression of CR (POD 60). Only its initial treatment (POD 0-60) inhibited the development of BO and vasculopathy (p<0.001). An additional finding was a decrease in body weight after drug application.

CONCLUSION

The effectiveness of everolimus after rat LTX depended on the grade of inflammation of the allograft before initiation of drug treatment. Only allografts with no or low grade AR benefit from long-term treatment with everolilmus in the prevention of BO after LTX. It could be speculated that conversion to an everolimus-based immunosuppression after LTX might only be successful in patients free of BO.

Influence of Surface Processing on the Biocompatibility of Titanium

Surface conditioning of titanium middle ear implants results in an improved biocompatibility, which can be characterized by the properties of fibroblasts cultured on conditioned surfaces. Titanium has been established as a favorable biomaterial in ossicular chain reconstruction. The epithelization of the surface of the implants is important for their integration and stable positioning in the middle ear. Mouse fibroblast cells were cultured on platelets made from pure Grade 2 titanium. Platelets that had been etched along their production process were compared to unetched platelets. The DNA in the cell nuclei was stained with DAPI and the actin filaments of the cytoskeleton were stained with FITC-conjugated phalloidin in order to analyze the cells grown on etched and unetched platelets by fluorescence microscopy. SEM (scanning electron microscopic) images were used to compare the surface structure of etched and unetched titanium platelets. There was a statistically significant increase of the area covered by the cytoplasm and increased actin expression by fibroblasts grown on the etched titanium platelets. In addition, the area of the platelets covered by nuclei on the etched platelets exceeded on average the one on unetched platelets, although this difference was not significant. The SEM pictures comparing unetched and etched titanium platelets showed a clear difference in surface structure. Surface conditioning of titanium implants improved the epithelization by fibroblasts and consequently etched titanium should be the preferred biomaterial for reconstructive middle ear surgery.

Risk of circuit infection in septic patients on extracorporeal membrane oxygenation: a preliminary study

Extracorporeal membrane oxygenation (ECMO) is the ultimate treatment option to improve gas exchange and decrease the aggressiveness of mechanical ventilation in septic patients with uncontrolled severe lung failure. However, potential microbiological colonization of the artificial surfaces of membrane oxygenator (MO) remains a critical issue in patients with bacteremia. The current study investigates the risk of MO infection in 10 consecutive septic patients on long-term treatment with ECMO. The flushing fluids of all investigated MOs were sterile. After incubation with nutrient solution for 14 days in one MO Enterococci spp. were isolated. In the patient concerned, a diffuse, unaccountable bleeding diathesis had developed, which stopped after exchange of the MO. Analysis of clinical parameters showed that D dimers had increased and fibrinogen levels had decreased before exchange of this MO, but standard markers of infection had remained unremarkable. In conclusion, circuit infection may be a potential cause for unexplained clinical deterioration of patients on ECMO, which therefore should be considered as an indication for exchange of the device.

Minimized extracorporeal circulation in coronary artery bypass surgery is equivalent to standard extracorporeal circulation in patients with reduced left ventricular function

BACKGROUND

Minimized extracorporeal circulation (MECC) is a promising alternative to standard extracorporeal circulation (ECC) and its use is increasing in routine coronary bypass surgery. We analyzed the clinical outcome of patients with reduced left ventricular function who underwent coronary artery bypass surgery with MECC or with standard ECC.

METHODS

From January 2003 to September 2008, 238 patients with a left ventricular function < 30 % underwent bypass surgery with ECC or MECC. The primary end point of our retrospective observational study was 30-day mortality. Secondary endpoints were the transfusion requirements, as well as intensive care and the in-hospital course.

RESULTS

Demographic data, comorbidities and left ventricular function were similar in the study groups. MECC patients had a tendency towards a lower 30-day mortality rate, a better postoperative renal function and reduced ventilation times. Extracorporeal circulation time and postoperative high-dose inotropic support were significantly lower in the MECC group, while the stays in the intensive care unit and in hospital were comparable between the two groups. In our study, age in the ECC group, and previous infarction and New York Heart Association grade IV in the MECC group were preoperative risk factors associated with a higher mortality.

CONCLUSION

Coronary bypass surgery using MECC is feasible and safe for patients with severely impaired left ventricular function. It is a promising alternative to ECC with a low mortality rate and a more favorable postoperative course.