Feasibility of aligning creatine kinase MB activity and mass data in multicentre trials using generalized additive modelling.

OBJECTIVES: Elevated serum creatine kinase isoenzyme MB (CK-MB) levels indicate myocardial ischaemia and periprocedural myocardial injury during treatment of heart diseases. We established a method to predict CK-MB mass from activity data based on a prospective pilot study in order to simplify multicentre trials. METHODS: 38 elective cardiac surgery patients without acute myocardial ischaemia and terminal renal failure were recruited. CK-MB mass and activity were determined in venous blood samples drawn preoperatively, postoperatively, 6 h post-op, and 12 h post-op. Linear regression and generalized additive models (GAMs) were applied to describe the relationship of mass and activity. Influences of demographic and perioperative factors on the fit of GAMs was evaluated. The agreement of predicted and measured CK-MB masses was assessed by Bland-Altman analyses. RESULTS: Linear regression provided an acceptable overall fit (r2 = 0.834) but showed deviances at low CK-MB levels. GAMs did not benefit from the inclusion of age, body mass index and surgical times. The minimal adequate model predicted CK-MB masses from activities, sex and sampling time with an r2 of 0.981. Bland-Altman analyses confirmed narrow limits of agreement (spread: 8.87 µg/l) and the absence of fixed (P = 0.41) and proportional (P = 0.21) biases. CONCLUSIONS: GAM-based modelling of CK-MB data in a representative patient cohort allowed to predict CK-MB masses from activities, sex and sampling time. This approach simplifies the integration of study centres with incompatible CK-MB data into multicentre trials in order to facilitate inclusion of CK-MB levels in statistical models.

Cell-type-specific consequences of mosaic structural variants in hematopoietic stem and progenitor cells.

The functional impact and cellular context of mosaic structural variants (mSVs) in normal tissues is understudied. Utilizing Strand-seq, we sequenced 1,133 single-cell genomes from 19 human donors of increasing age, and discovered the heterogeneous mSV landscapes of hematopoietic stem and progenitor cells. While mSVs are continuously acquired throughout life, expanded subclones in our cohort are confined to individuals >60. Cells already harboring mSVs are more likely to acquire additional somatic structural variants, including megabase-scale segmental aneuploidies. Capitalizing on comprehensive single-cell micrococcal nuclease digestion with sequencing reference data, we conducted high-resolution cell-typing for eight hematopoietic stem and progenitor cells. Clonally expanded mSVs disrupt normal cellular function by dysregulating diverse cellular pathways, and enriching for myeloid progenitors. Our findings underscore the contribution of mSVs to the cellular and molecular phenotypes associated with the aging hematopoietic system, and establish a foundation for deciphering the molecular links between mSVs, aging and disease susceptibility in normal tissues.

Target flow deviations on the cardiopulmonary bypass cause postoperative delirium in cardiothoracic surgery-a retrospective study evaluating temporal fluctuations of perfusion data.

OBJECTIVES: Postoperative delirium (POD) is common, costly and associated with long-term morbidity and increased mortality. We conducted a cohort study to assess the contribution of cardiopulmonary bypass (CPB) to the development of POD by means of algorithm-based data processing. METHODS: A database was compiled from 3 datasets of patients who underwent cardiac surgery between 2014 and 2019: intensive care unit discharge files, CPB protocols and medical quality management records. Following data extraction and structuring using novel algorithms, missing data were imputed. Ten independent imputations were analysed by multiple logistic regression with stepwise deletion of factors to arrive at a minimal adequate model. RESULTS: POD was diagnosed in 456/3163 patients (14.4%). In addition to known demographic risk factors and comorbidities like male sex, age, carotid disease, acute kidney failure and diabetes mellitus, cardiopulmonary parameters like total blood volume at the CPB [adjusted odds ratio (AOR) 1.001; confidence interval (CI) 1.1001-1.002] were independent predictors of POD. Higher values of the minimal blood flow were associated with a lower risk of POD (AOR 0.993; CI 0.988-0.997). Flow rates at least 30% above target did emerge in the minimal adequate model as a potential risk factor, but the confidence interval suggested a lack of statistical significance (AOR 1.819; 95% CI: 0.955-3.463). CONCLUSIONS: CPB data processing proved to be a useful tool for obtaining compact information to better identify the roles of individual operational states. Strict adherence to perfusion limits along with tighter control of blood flow and acid-base balance during CPB may help to further decrease the risk of POD.

A novel pulsatile blood pump design for cardiothoracic surgery: Proof-of-concept in a mock circulation.

BACKGROUND: Pulsatile perfusion during extracorporeal circulation is a promising concept to improve perfusion of critical organs. Clinical benefits are limited by the amount of pulsatile energy provided by standard pumps. The present study investigated the properties of a novel positive displacement blood pump in a mock circulation. METHODS: The pump was attached to an aortic model with a human-like geometry and compliance as a pseudo patient. Hemodynamic data were recorded while the pump settings were adjusted systematically. RESULTS: Using a regular oxygenator, maximum flow was 2.6 L/min at a pressure of 27 mm Hg and a frequency (F) of 90 bpm. Pulse pressure (PP; 28.9 mm Hg) and surplus hemodynamic energy (SHE; 26.1% of mean arterial pressure) were highest at F = 40 bpm. Flow and pressure profiles appeared sinusoid. Using a low-resistance membrane ventilator to assess the impact of back pressure, maximum flow was 4.0 L/min at a pressure of 58.6 mm Hg and F = 40 bpm. At F = 40 bpm, PP was 58.7 mm Hg with an SHE of 33.4%. SHE decreased with increasing flow, heart rate, and systolic percentage but surpassed 10% with reasonable settings. CONCLUSIONS: The present prototype achieved sufficient flow and pressure ranges only in the presence of a low-resistance membrane ventilator. It delivered supraphysiologic levels of pulse pressure and SHE. Further modifications are planned to establish this concept for adult pulsatile perfusion.

Improving adult pulsatile minimal invasive extracorporeal circulation in a mock circulation.

BACKGROUND: Pulsatile extracorporeal circulation (ECC) may improve perfusion of critical organs during cardiac surgery. This study analyzed the influence of the components of a minimal invasive ECC (MiECC) on the transfer of pulsatile energy into the pseudo-patient of a mock circulation. METHODS: An aortic model with human-like geometry and compliance was perfused by a diagonal pump. Surplus hemodynamic energy (SHE) was determined from flow and pressure data. Five adult-size oxygenator models and three sizes of cannulas were compared. Pulsatile pump settings were optimized, and parallel dual-pump configurations were evaluated. RESULTS: Oxygenator models showed up to twofold differences in pressure gradients and influenced SHE at flow rates up to 2.0 L min-1 . Adjustments of frequency, systole duration, and rotational speed gain significantly improved SHE compared with empirical settings, with SHE above 21% of mean arterial pressure at flow rates of 1.0 L min-1 to 1.5 L min-1 and SHE above 5% at 3.5 L min-1 . Small diameter cannula (15 Fr) limited SHE compared with larger cannula (21 Fr and 23 Fr). Two diagonal pumps did not provide higher SHE than a single pump, but permitted additional control over pulse pressure and SHE by varying the total fraction of pulsatile flow and the fraction of flow bypassing the oxygenator. CONCLUSIONS: Proper selection of components and optimizations of pump settings significantly improved pulse pressure and SHE of pulsatile MiECC. Surplus hemodynamic energy depended on flow rate with a maximum at 1.0 L min-1 -1.5 L min-1 . Pulsatile MiECC may specifically assist organ perfusion during phases of low flow.

Effects of colloid-based (hydroxyethylstarch 6% 130/0.42, gelafundin 4%) and crystalloid-based volume regimes in cardiac surgery: a retrospective analysis.

Background: The restriction of hydroxyethylstarch (HES) necessitated changes in volume management in cardiac surgery, increasing the use of gelatin (GELA) and crystalloid (CRYS) mono strategies. Methods: This retrospective study evaluated the effects of changed volume replacement management to a GELA or CRYS mono therapy on mortality, acute kidney injury (AKI), blood loss, and transfusion in cardiac surgery patients with at least one coronary artery bypass grafting (CABG) at a university hospital. Three groups (HES n=938, GELA n=397, CRYS n=205) were derived from 1,540 patients with complete data sets. Data were analyzed by multiple regression models. Results: Patients had similar risk profiles, comorbidities, and preoperative routine diagnostics prior to surgery. No difference was observed in mortality and AKI. HES treated patients showed highest blood loss, followed by GELA while CRYS patients had the lowest (P<0.0001). Patients in the HES group had highest transfusion of packed red blood cells (PRBCs) and platelet concentrates (PCs), followed by GELA, whereas CRYS had the lowest (P<0.0001). Fresh frozen plasma (FFP) transfusion, administration of fibrinogen, and prothrombin complex concentrates (PCCs) were highest in HES group. CRYS showed the shortest time of mechanical ventilation (P<0.0001) and left the intensive care unit (ICU) significantly earlier (P<0.0001). Multivariable regression analysis found that colloid volume significantly predicted hospital mortality and renal replacement therapy (RRT), but not AKI. Conclusions: Administration of crystalloids without any colloid showed no differences in mortality or AKI, but less blood loss and transfusion. Colloids should be considered critically and further studies should investigate effects of GELA in cardiac surgery.

Preservation of Adrenoceptor and Endothelin Receptor Mediated Vasoconstriction and of Endothelium-Dependent Relaxation after Cold Storage of Explanted Blood Vessels for ex vivo Analyses.

INTRODUCTION: Adrenoceptor and endothelin (ET) receptor-mediated vasoconstriction as well as endothelium-dependent vasodilation of human saphenous veins were compared before and after 20 h of cold storage. METHODS: Contractile responses to potassium chloride (KCl), norepinephrine (NE), and ET-1 as well as vasodilator responses to acetylcholine (ACh) were evaluated. RESULTS: Storage in HEPES-supplemented Dulbecco's modified Eagle's medium (HDMEM) diminished KCl induced contractile forces to 71% (p = 0.002) and NE induced contractions to 80% (p = 0.037), in contrast to HEPES-supplemented Krebs-Henseleit solution (HKH) and TiProtec solution. KCl-normalized NE contractions were not affected by storage. NE EC50 values were slightly lower (7.1E-8 vs. 7.5E-8, p = 0.019) after storage in HKH, with no changes after storage in the other solutions. Endothelium-dependent responses to ACh were not affected by storage. ET-1 induced contractions were attenuated after storage in HDMEM (77%, p = 0.002), HKH (75%, p = 0.020), and TiProtec (73%, p = 0.010) with no changes in normalized constrictions. ET-1 EC50 values were not affected by storage. CONCLUSION: Loss of contractility after storage in HDMEM may reflect the lower content of dextrose. There was no specific attenuation of adrenoceptor, ET-receptor, or ACh receptor mediated signal transduction after storage in any of the media. HKH or TiProtec are equally suitable cold storage solutions for ex vivo measurements.

Aging of human hematopoietic stem cells is linked to changes in Cdc42 activity.

In this study, we characterize age-related phenotypes of human hematopoietic stem cells (HSC). We report increased frequencies of HSC, hematopoietic progenitor cells and lineage negative cells in the elderly but a decreased frequency of multi-lymphoid progenitors. Aged human HSC further exhibited a delay in initiating division ex vivo though without changes in their division kinetics. The activity of the small RhoGTPase Cdc42 was elevated in aged human hematopoietic cells and we identified a positive correlation between Cdc42 activity and the frequency of HSC upon aging. The frequency of human HSC polar for polarity proteins was, similar to the mouse, decreased upon aging, while inhibition of Cdc42 activity via the specific pharmacological inhibitor of Cdc42 activity, CASIN, resulted in re-polarization of aged human HSC with respect to Cdc42. Elevated activity of Cdc42 in aged HSC thus contributed to age-related changes in HSC. Xenotransplant, using NBSGW mice as recipients, showed elevated chimerism in recipients of aged compared to young HSC. Aged HSC treated with CASIN ex vivo displayed an engraftment profile similar to recipients of young HSC. Taken together, our work reveals strong evidence for a role of elevated Cdc42 activity in driving aging of human HSC, and similar to mice, this presents a likely possibility for attenuation of aging in human HSC.

Influence of Obesity on the Organization of the Extracellular Matrix and Satellite Cell Functions After Combined Muscle and Thorax Trauma in C57BL/6J Mice.

Obesity has been described as a major factor of health risk in modern society. Next to intricately linked comorbidities like coronary artery disease or diabetes, an influence of obesity on regeneration after muscle injury has been described previously. However, the influence of obesity on tissue regeneration in a combined trauma, merging the more systemic influence of a blunt lung trauma and the local blunt muscle trauma, has not been investigated yet. Therefore, the aim of this study was to investigate the influence of obesity on regeneration in a mouse model that combined both muscle and thorax trauma. Using gene expression analysis, a focus was put on the structure as well as the organization of the extracellular matrix and on functional satellite cell physiology. An increased amount of debris in the lung of obese mice compared to normal weight mice up to 192 h after combined trauma based on visual assessment can be reported which is accompanied by a decreased response of Mmp2 in obese mice. Additionally, a delayed and elongated response of inhibitor genes like Timp1 has been revealed in obese mice. This elongated response to the trauma in obese mice can also be seen in plasma based on increased levels of pro-inflammatory chemo- and cytokines (IL-6, MCP-1, and IL 23) 192 h post trauma. In addition to changes in the lung, morphological analysis of the injured extensor iliotibialis anticus of the left hind leg in lean and diet-induced obese mice revealed deposition of fat in the regenerating muscle in obese animals hindering the structure of a compact muscle. Additionally, decreased activation of satellite cells and changes in organization and build-up of the ECM could be detected, finally leading to a decreased stability of the regenerated muscle in obese mice. Both factors contribute to an attenuated response to the trauma by obese mice which is reflected by a statistically significant decrease in muscle force of obese mice compared to lean mice 192 h post trauma induction.

Pericardial fluids or Cardiopulmonary Bypass-Is There a Major Culprit for Changes in Coagulation and Inflammation?

BACKGROUND: From the results of a previous study, it remained to be investigated if a perioperative rise of few tested coagulation and inflammation markers is caused by conventional cardiopulmonary bypass (CPB) itself or rather by direct recirculation of pericardial fluids. METHODS: Forty-eight patients operated on with conventional CPB for myocardial revascularization were randomized either for direct recirculation of pericardial suction fluids or for cell saving (CS). RESULTS: Thrombin-antithrombin complexes showed lower values intraoperatively in the CS group (p < 0.0001), and D-dimers tended to remain lower at intensive care unit arrival (p = 0.095). Tests of inflammation markers were less meaningful. CONCLUSION: Direct recirculation of pericardial fluids rather than conventional CPB itself causes major intraoperative changes of some coagulation markers. Pericardial blood loss with direct recirculation should be kept to a minimum to avoid unnecessary activation of coagulation. Inflammation markers need further investigations.

Effects of pulsatile minimal invasive extracorporeal circulation on fibrinolysis and organ protection in adult cardiac surgery-a prospective randomized trial.

BACKGROUND: Minimal invasive extracorporeal circulation (MiECC) reduces the impact of cardiopulmonary bypass during cardiac surgery on inflammation and hemostasis. Pulsatile perfusion may enhance organ perfusion and help to prevent renal and neuronal damage. The present study investigated the impact of pulsatile MiECC in low-risk coronary artery bypass grafting (CABG) patients. METHODS: CABG patients were prospectively randomized for non-pulsatile (np: n=19) and pulsatile (p: n=21) MiECC. Blood and urine samples were collected at several time points until 72 h post-operative and analyzed for biochemical markers of fibrinolytic capacity, renal damage, and neuronal damage. RESULTS: Although intraoperative tissue plasminogen activator (tPA) levels tended to be higher in the p group, none of the fibrinolysis markers including plasminogen activator inhibitor (PAI-1) and the PAI-1/tPA ratio were significantly affected by pulsation. Hemolysis and markers of renal and neuronal damage were comparable between groups. Intraoperative urinary excretion [np: 400 mL (355 to 680) vs. p: 530 mL (360 to 900)] and cumulative 24 h volume intake [np: 7,090 mL (5,492 to 7,544) vs. p: 7,155 mL (6,682 to 8,710)] were increased by pulsation whereas blood losses up to 12 h post-operative [np: 365 mL (270 to 515) vs. p: 310 mL (225 to 470)] and up to 24 h post-operative [np: 760 mL (555 to 870) vs. p: 520 mL (460 to 670)] were attenuated. CONCLUSIONS: The present study did not find evidence for a beneficial effect of pulsation on markers of fibrinolysis, renal damage, and neuronal damage. However, pulsatile perfusion increased intraoperative urinary secretion and reduced post-operative blood losses.

Combination Therapy of Pulmonary Arterial Hypertension with Vardenafil and Macitentan Assessed in a Human Ex Vivo Model.

PURPOSE: Treatment of pulmonary arterial hypertension (PAH) by vasodilator drug monotherapy is often limited in its effectiveness. Combination therapy may help to improve treatment and to reduce drug toxicity. This study assessed the combination of the endothelin receptor antagonist macitentan and the phosphodiesterase-5 inhibitor vardenafil in a human ex vivo model. METHODS: Study patients did not suffer from PAH. Human pulmonary arteries (PA) and veins (PV) were harvested from resected pulmonary lobes. Contractile forces of blood vessel segments in the presence and absence of the vasodilator drugs macitentan, its main metabolite ACT-132577, and vardenafil were determined isometrically in an organ bath. RESULTS: Macitentan 1E-7 M was sufficient to significantly abate endothelin-1-induced vasoconstriction in PA. A concentration of 1E-6 M was required for significant effects of macitentan on PV and of ACT-132577 on both vessel types. Combination of 1E-7 M macitentan and 1E-6 M vardenafil inhibited sequential constriction with endothelin-1 and norepinephrine of PA significantly more than either compound alone. Effects of 3E-7 M and 1E-6 M macitentan and effects of all doses of ACT-132577 were not further enhanced by 1E-6 M vardenafil. CONCLUSIONS: These data suggest that vasodilator effects of macitentan and vardenafil combined may surpass monotherapy in vivo if drug doses are adjusted properly. Vasodilation by the longer-acting metabolite ACT-132577 was not further enhanced by vardenafil.

Hemodynamic energy during pulsatile extracorporeal circulation using flexible and rigid arterial tubing: a reassessment.

INTRODUCTION: Pulsatile extracorporeal circulation may improve organ perfusion during cardiac surgery. Some minimally invasive extracorporeal circulation (MiECC) systems allow pulsatile perfusion. The present study investigated the influence of arterial tubing compliance on hemodynamic energy transfer into the patient. METHODS: Aortic models with adult human geometry were perfused in a mock circulation. A MiECC system was connected using either high-compliance silicone tubing or standard kit tubing. Energy equivalent pressure (EEP) and surplus hemodynamic energy (SHE) were computed from flow and pressure data. Aortic models with physiological and sub-physiological compliance were tested to assess the influence of the pseudo-patient. RESULTS: Non-pulsatile flow did not generate SHE. SHE during pulsatile flow in the compliant aortic model was significantly higher with kit tubing compared to silicone tubing. Maximum SHE was achieved at 1.6 L/min with kit tubing (7.7% of mean arterial pressure) and with silicone tubing (4.9%). Using the low-compliance aortic model, SHE with kit tubing reached a higher maximum of 14.2% at 1.8 L/min compared to silicone tubing (11.8% at 1.5 L/min). CONCLUSIONS: Flexible arterial tubing did not preserve more hemodynamic energy from a pulsatile pump compared to standard kit tubing in a model of adult extracorporeal circulation. The pseudo-patient's compliance significantly affected the properties of the mock circulation.

Influence of 6% Hydroxyethyl Starch 130/0.4 Versus Crystalloid Solution on Structural Renal Damage Markers After Coronary Artery Bypass Grafting: A Post Hoc Subgroup Analysis of a Prospective Trial.

OBJECTIVE: The restriction of hydroxyethyl starch (HES) has mandated changes in volume management based on data of critically ill patients. Reliable data of structural renal damage after HES treatment in cardiac surgical patients are lacking. The influence of 6% HES 130/0.4 was investigated in this study. DESIGN: An exploratory post hoc subgroup analysis of a prospective trial was performed. SETTING: The study was carried out at a university hospital. PARTICIPANTS: Forty-four low-risk cardiac surgical patients were examined. INTERVENTIONS: Twenty-two patients received only crystalloid solutions, and 22 were treated with balanced 6% HES 130/0.4. MEASUREMENTS AND MAIN RESULTS: Functional renal parameters and the structural biomarkers α-glutathione S-transferase, kidney injury molecule-1, liver fatty acid-binding protein, and neutrophil gelatinase-associated lipocalin were investigated. Volume balances, vasopressor dosages, blood losses, and coagulation parameters were compared. Most functional and structural renal parameters did not differ between the groups (serum creatinine p = 0.8380). Liver fatty acid-binding protein was transiently higher in the HES group only at 24 hours postoperatively (p = 0.0002). No differences in mortality, acute kidney injury, and need for renal replacement therapy were observed. Blood coagulation was significantly more compromised in the HES group at intensive care unit arrival (factor II, p = 0.0012; factor X, p = 0.0031; thrombocytes, p = 0.0010). Blood losses, and vasopressor dosages tended to be higher in HES-treated patients without significance. CONCLUSION: Overall, the values and time courses of the biomarkers used did not indicate evidence of a mechanism for tubular injury caused by HES.

Extraction of Total RNA from Calcified Human Heart Valves for Gene Expression Analysis.

BACKGROUND: The isolation of high-quality RNA is an important first step in gene expression studies. However, difficult tissue disruption, low cell content and low RNA content makes consistent RNA extraction from human aortic valve tissue a challenging task. METHODS: A protocol has been developed for the successful isolation of high-quality RNA from human aortic valve samples by optimizing RNA extraction protocols based on a comparison of commercial kits. RESULTS: Guanidinium thiocyanate-phenolchloroform extraction was found to be a prerequisite for successful purification. Two protocols based on this extraction were further optimized. RNA quality and quantity were assessed spectrophotometrically, using a Bioanalyzer and by PCR analysis of several housekeeping genes. Optimized parameters included storage in RNAlater™, DNase digestion, the amount of tissue, homogenization time, and freezing of tissue after homogenization. CONCLUSIONS: The modified protocol for fatty and fibrous tissue achieved satisfactory results for gene expression analysis of human aortic valve samples.

Influence of Cannulation Site on Carotid Perfusion During Extracorporeal Membrane Oxygenation in a Compliant Human Aortic Model.

Blood oxygenized by veno-arterial extracorporeal membrane oxygenation (ECMO) can be returned to the aorta (central cannulation) or to peripheral arteries (axillar, femoral). Hemodynamic effects of these cannulation types were analyzed in a mock loop with an aortic model representative of normal anatomy and compliance under physiological pressures and flow rates. Pressures, flow rates, and contribution of ECMO flow to total flow as a measure of oxygen supply were monitored in the carotids. Steady or pulsatile ECMO flow, residual or no cardiac output, and intraaortic balloon pump counterpulsation were tested as independent factors. With residual heart function, central cannulation provided the best oxygenated flow and pressure to the carotid arteries (CA). Axillar cannulation preferentially perfused the right CA at the expense of the left CA. Femoral cannulation provided only lower amounts of oxygenated blood to both CA. Pulsation increased the surplus hemodynamic energy. Counterpulsation reduced flow with femoral cannulation but improved flow and pressure with axillar cannulation. Femoral cannulation failed to provide oxygenated blood to coronary and supraaortic arteries with residual heart function. Central cannulation provided the best hemodynamics and oxygen supply to the brain. With a resting heart but not with an ejecting heart, pulsatile ECMO flow enhanced CA hemodynamics.

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.

Selective venous vasodilator properties of the analgesic metamizole (dipyrone) in a human ex vivo model-implications for postoperative pain management.

Metamizole (dipyrone) is a first-line, non-opioid analgesic used for postoperative pain management. Clinical data and animal experiments indicate a possible vasodilator action of this drug. We investigated the effects of metamizole on human artery and vein tone in an ex vivo model to assess potential contributions to venous pooling. Excess segments of bypass grafts were harvested during coronary artery bypass grafting procedures. Tensions were measured in an organ bath for 120 min after adding metamizole to the preconstricted vessels. Contribution of endothelium was assessed in endothelium-denuded vessels, and indometacin was used to identify cyclooxygenase-mediated effects. Internal mammary arteries (n = 6) constricted after addition of 1, 3, and 10 µM metamizole and remained constricted at the lower doses. Transient constrictions also occurred in saphenous veins (n = 20), but veins relaxed below solvent controls after 20 min at all concentrations. Endothelium removal (n = 12) and cyclooxygenase inhibition (n = 12) suppressed the vasoconstrictor effect but not the vasodilator effect. Metamizole and its metabolites display counteracting effects on blood vessel tone ex vivo. The vasoconstrictor effect is mediated by cyclooxygenase-derived products. The net effect is site-specific, resulting in a selective venous vasodilator action. This may exacerbate unwanted venous pooling during postoperative pain therapy.

Contact-free monitoring of vessel graft stiffness - proof of concept as a tool for vascular tissue engineering.

Tissue-engineered vessel grafts have to mimic the biomechanical properties of native blood vessels. Manufacturing processes often condition grafts to adapt them to the target flow conditions. Graft stiffness is influenced by material properties and dimensions and determines graft compliance. This proof-of-concept study evaluated a contact-free method to monitor biomechanical properties without compromising sterility. Forced vibration response analysis was performed on human umbilical vein (HUV) segments mounted in a buffer-filled tubing system. A linear motor and a dynamic signal analyser were used to excite the fluid by white noise (0-200 Hz). Vein responses were read out by laser triangulation and analysed by fast Fourier transformation. Modal analysis was performed by monitoring multiple positions of the vessel surface. As an inverse model of graft stiffening during conditioning, HUV were digested proteolytically, and the course of natural frequencies (NFs) was monitored over 120 min. Human umbilical vein showed up to five modes with NFs in the range of 5-100 Hz. The first natural frequencies of HUV did not alter over time while incubated in buffer (p = 0.555), whereas both collagenase (-35%, p = 0.0061) and elastase (-45%, p < 0.001) treatments caused significant decreases of NF within 120 min. Decellularized HUV showed similar results, indicating that changes of the extracellular matrix were responsible for the observed shift in NF. Performing vibration response analysis on vessel grafts is feasible without compromising sterility or integrity of the samples. This technique allows direct measurement of stiffness as an important biomechanical property, obviating the need to monitor surrogate parameters. Copyright © 2016 John Wiley & Sons, Ltd.