Combined administration of nitric oxide gas and iloprost during cardiopulmonary bypass reduces platelet dysfunction: a pilot clinical study

Evaluation of nitric acid donor, transdermal glycerol trinitrate patches for facilitating cervical ripening: a randomised controlled trial

PURPOSE

To evaluate the efficacy and safety of transdermal glycerol trinitrate skin patches as an additive and effective agent for facilitating cervical ripening for labour induction.

METHODS

This was a double-blinded prospective randomised clinical trial carried out in a major obstetric unit in India. Women who planned for labour induction were randomly allocated for induction either by combined application of glycerol trinitrate skin patches [GTN patch] and intracervical dinoprostone gel or by the gel only. Sample randomisation was done using a stratified block randomisation technique with a sealed envelope. The numbers designating the group allocation sequence were concealed from doctors, research staff, and investigators. Six hourly improvements were assessed in the modified Bishop's score, induction-delivery time interval, the need for oxytocin, maternal side effects and foetal outcomes. Data were analysed using SPSS software.

RESULTS AND DISCUSSION

Recruitment Bishop scores, parity and gestational age were matched in both cases and the control group. The modified Bishop's score was statistically improved in study groups, as evidenced compositely and irrespective of parity. The two groups appeared to have no significant differences regarding other outcomes. The additional application of the GTN patch seems helpful to accelerate the progress of labour but could not yield any favourable labour outcome. The GTN patch does not impose additional feto-maternal adverse effects apart from increased incidences of headaches.

Inhaled nitric oxide and postoperative outcomes in cardiac surgery with cardiopulmonary bypass: A systematic review and meta-analysis

Cardiac surgeries under cardiopulmonary bypass (CPB) are complex procedures with high incidence of complications, morbidity and mortality. The inhaled nitric oxide (iNO) has been frequently used as an important composite of perioperative management during cardiac surgery under CPB. We conducted a meta-analysis of published randomized clinical trials (RCTs) to assess the effects of iNO on reducing postoperative complications, including the duration of postoperative mechanical ventilation, length of intensive care unit (ICU) stay, length of hospital stay, mortality, hemodynamic improvement (the composite right ventricular failure, low cardiac output syndrome, pulmonary arterial pressure, and vasoactive inotropic score) and myocardial injury biomarker (postoperative troponin I levels). Subgroup analyses were performed to assess the effect of modification and interaction. These included iNO dosage, the timing and duration of iNO therapy, different populations (children and adults), and comparators (other vasodilators and placebo or standard care). A comprehensive search for iNO and cardiac surgery was performed on online databases. Twenty-seven studies were included after removing the duplicates and irrelevant articles. The results suggested that iNO could reduce the duration of mechanical ventilation, but had no significance in the ICU stay, hospital stay, and mortality. This may be attributed to the small sample size of the most included studies and heterogeneity in timing, dosage and duration of iNO administration. Well-designed, large-scale, multicenter clinical trials are needed to further explore the effect of iNO in improving postoperative prognosis in cardiovascular surgical patients.

The beneficial use of nitric oxide during cardiopulmonary bypass on postoperative outcomes in children and adult patients: a systematic review and meta-analysis of 2897 patients

PURPOSE

Investigate inhaled nitric oxide's influence on mortality rates, mechanical ventilation and cardiopulmonary bypass duration, and length of stay in the intensive care unit and hospital when administered during cardiopulmonary bypass.

METHODS

Following the PRISMA guidelines, we searched four electronic databases (PubMed, EMBASE, Cochrane Library, and Web of Science) up to 4th March 2023. The protocol was registered in the PROSPERO database with ID: CRD42023423007. Using Review Manager software, we reported outcomes as risk ratios (RRs) or mean difference (MD) and confidence intervals (CIs).

RESULTS

The meta-analysis included a total of 17 studies with 2897 patients. Overall, there were no significant differences in using nitric oxide over control concerning mortality (RR = 1.03, 95% CI 0.73 to 1.45; P = 0.88) or cardiopulmonary bypass duration (MD = -0.14, 95% CI - 0.96 to 0.69; P = 0.74). The intensive care unit days were significantly lower in the nitric oxide group than control (MD = -0.80, 95% CI - 1.31 to -0.29; P = 0.002). Difference results were obtained in terms of the length of stay in the hospital according to sensitivity analysis (without sensitivity [MD = -0.41, 95% CI - 0.79 to -0.02; P = 0.04] vs. with sensitivity [MD = -0.31, 95% CI - 0.69 to 0.07; P = 0.11]. Subgroup analysis shows that, in children, nitric oxide was favored over control in significantly reducing the duration of mechanical ventilation (MD = -4.58, 95% CI - 5.63 to -3.53; P < 0.001).

CONCLUSION

Using inhaled nitric oxide during cardiopulmonary bypass reduces the length of stay in the intensive care unit, and for children, it reduces the duration of mechanical ventilation.

Effect of stimulated platelets in COVID-19 thrombosis: Role of alpha7 nicotinic acetylcholine receptor

Since early 2020, SARS-CoV-2-induced infection resulted in global pandemics with high morbidity, especially in the adult population. COVID-19 is a highly prothrombotic condition associated with subsequent multiorgan failure and lethal outcomes. The exact mechanism of the prothrombotic state is not well understood and might be multifactorial. Nevertheless, platelets are attributed to play a crucial role in COVID-19-associated thrombosis. To date, platelets' role was defined primarily in thrombosis and homeostasis. Currently, more focus has been set on their part in inflammation and immunity. Moreover, their ability to release various soluble factors under activation as well as internalize and degrade specific pathogens has been highly addressed in viral research. This review article will discuss platelet role in COVID-19-associated thrombosis and their role in the cholinergic anti-inflammatory pathway. Multiple studies confirmed that platelets display a hyperactivated phenotype in COVID-19 patients. Critically ill patients demonstrate increased platelet activation markers such as P-selectin, PF4, or serotonin. In addition, platelets contain acetylcholine and express α7 nicotinic acetylcholine receptors (α7nAchR). Thus, acetylcholine can be released under activation, and α7nAchR can be stimulated in an autocrine manner and support platelet function. α7 receptor is one of the most important mediators of the anti-inflammatory properties as it is associated with humoral and intrinsic immunity and was demonstrated to contribute to better outcomes in COVID-19 patients when under stimulation. Hematopoietic α7nAchR deficiency increases platelet activation and, in experimental studies, α7nAchR stimulation can diminish the pro-inflammatory state and modulate platelet reactiveness via increased levels of NO. NO has been described to inhibit platelet adhesion, activation, and aggregation. In addition, acetylcholine has been demonstrated to decrease platelet aggregation possibly by blocking the e p-38 pathway. SARS-CoV-2 proteins have been found to be similar to neurotoxins which can bind to nAChR and prevent the action of acetylcholine. Concluding, the platelet role in COVID-19 thrombotic events could be explained by their active function in the cholinergic anti-inflammatory pathway.

Anticoagulation Strategies during Extracorporeal Membrane Oxygenation: A Narrative Review

The development of extracorporeal life support technology has added a new dimension to the care of critically ill patients who fail conventional treatment options. Extracorporeal membrane oxygenation (ECMO)—specialized temporary life support for patients with severe cardiac or pulmonary failure—plays a role in bridging the time for organ recovery, transplant, or permanent assistance. The overall patient outcome is dependent on the underlying disease, comorbidities, patient reaction to critical illness, and potential adverse events during ECMO. Moreover, the contact of the blood with the large artificial surface of an extracorporeal system circuit triggers complex inflammatory and coagulation responses. These processes may further lead to endothelial injury and disrupted microcirculation with consequent end-organ dysfunction and the development of adverse events like thromboembolism. Therefore, systemic anticoagulation is considered crucial to alleviate the risk of thrombosis and failure of ECMO circuit components. The gold standard and most used anticoagulant during extracorporeal life support is unfractionated heparin, with all its benefits and disadvantages. However, therapeutic anticoagulation of a critically ill patient carries the risk of clinically relevant bleeding with the potential for permanent injury or death. Similarly, thrombotic events may occur. Therefore, different anticoagulation strategies are employed, while the monitoring and the balance of procoagulant and anticoagulatory factors is of immense importance. This narrative review summarizes the most recent considerations on anticoagulation during ECMO support, with a special focus on anticoagulation monitoring and future directions.

Paroxysmal Finger Hematoma-A Probable Vascular Disorder in Post-COVID-19 Condition: Two Clinical Case Presentations

Background and Objectives: Achenbach's syndrome is usually a benign, self-limiting clinical condition presented with finger discoloration, pain, and edema. Etiology, pathogenesis, and incidence remain unknown due to the variety of clinical features and the diversity of disease states leading to digital ischemia. COVID-19 primarily affects microcirculation, causing endothelial damage and disseminated microthrombosis. Materials and Methods: We reviewed two cases of Caucasian women with Achenbach's syndrome after COVID-19 infection recovery between April and May 2021. Results: Here are presented two extremely rare cases of paroxysmal finger hematoma in two female patients after COVID-19 infection recovery. Conclusions: The exact etiology and pathophysiology of Achenbach's syndrome remain unclear. It is assumed that SARS-CoV-2 infection could be the triggering factor in the pathophysiological mechanism of paroxysmal finger hematoma. We highly recommend the implication of the synthetic prostacyclin receptor agonist (Iloprost) as a first-line conservative treatment in patients with Achenbach's syndrome and COVID-19 infection recovery.

Hemostasis in neonatal ECMO

Extracorporeal membrane oxygenation (ECMO) is a life-saving support for cardio-respiratory function. Over the last 50 years, the extracorporeal field has faced huge technological progress. However, despite the improvements in technique and materials, coagulation problems are still the main contributor to morbidity and mortality of ECMO patients. Indeed, the incidence and survival rates of the main hemorrhagic and thrombotic complications in neonatal respiratory ECMO are relevant. The main culprit is related to the intrinsic nature of ECMO: the contact phase activation. The exposure of the human blood to the non-endothelial surface triggers a systemic inflammatory response syndrome, which chronically activates the thrombin generation and ultimately leads to coagulative derangements. Pre-existing illness-related hemostatic dysfunction and the peculiarity of the neonatal clotting balance further complicate the picture. Systemic anticoagulation is the management's mainstay, aiming to prevent thrombosis within the circuit and bleeding complications in the patient. Although other agents (i.e., direct thrombin inhibitors) have been recently introduced, unfractionated heparin (UFH) is the standard of care worldwide. Currently, there are multiple tests exploring ECMO-induced coagulopathy. A combination of the parameters mentioned above and the evaluation of the patient's underlying clinical context should be used to provide a goal-directed antithrombotic strategy. However, the ideal algorithm for monitoring anticoagulation is currently unknown, resulting in a large inter-institutional diagnostic variability. In this review, we face the features of the available monitoring tests and approaches, mainly focusing on the role of point-of-care (POC) viscoelastic assays in neonatal ECMO. Current gaps in knowledge and areas that warrant further study will also be addressed.

Renal and Cerebral Hypoxia and Inflammation During Cardiopulmonary Bypass

Cardiac surgery-associated acute kidney injury and brain injury remain common despite ongoing efforts to improve both the equipment and procedures deployed during cardiopulmonary bypass (CPB). The pathophysiology of injury of the kidney and brain during CPB is not completely understood. Nevertheless, renal (particularly in the medulla) and cerebral hypoxia and inflammation likely play critical roles. Multiple practical factors, including depth and mode of anesthesia, hemodilution, pump flow, and arterial pressure can influence oxygenation of the brain and kidney during CPB. Critically, these factors may have differential effects on these two vital organs. Systemic inflammatory pathways are activated during CPB through activation of the complement system, coagulation pathways, leukocytes, and the release of inflammatory cytokines. Local inflammation in the brain and kidney may be aggravated by ischemia (and thus hypoxia) and reperfusion (and thus oxidative stress) and activation of resident and infiltrating inflammatory cells. Various strategies, including manipulating perfusion conditions and administration of pharmacotherapies, could potentially be deployed to avoid or attenuate hypoxia and inflammation during CPB. Regarding manipulating perfusion conditions, based on experimental and clinical data, increasing standard pump flow and arterial pressure during CPB appears to offer the best hope to avoid hypoxia and injury, at least in the kidney. Pharmacological approaches, including use of anti-inflammatory agents such as dexmedetomidine and erythropoietin, have shown promise in preclinical models but have not been adequately tested in human trials. However, evidence for beneficial effects of corticosteroids on renal and neurological outcomes is lacking. © 2021 American Physiological Society. Compr Physiol 11:1-36, 2021.

Effects of inorganic nitrate on ischaemia-reperfusion injury after coronary artery bypass surgery

Background

Nitric oxide (NO) is an important signalling molecule in the cardiovascular system with protective properties in ischaemia–reperfusion injury. Inorganic nitrate, an oxidation product of endogenous NO production and a constituent in our diet, can be recycled back to bioactive NO. We investigated if preoperative administration of inorganic nitrate could reduce troponin T release and other plasma markers of injury to the heart, liver, kidney, and brain in patients undergoing cardiac surgery.

Methods

This single-centre, randomised, double-blind, placebo-controlled trial included 82 patients undergoing coronary artery bypass surgery with cardiopulmonary bypass. Oral sodium nitrate (700 mg×2) or placebo (NaCl) were administered before surgery. Biomarkers of ischaemia–reperfusion injury and plasma nitrate and nitrite were collected before and up to 72 h after surgery. Troponin T release was our predefined primary endpoint and biomarkers of renal, liver, and brain injury were secondary endpoints.

Results

Plasma concentrations of nitrate and nitrite were elevated in nitrate-treated patients compared with placebo. The 72-h release of troponin T did not differ between groups. Other plasma biomarkers of organ injury were also similar between groups. Blood loss was not a predefined outcome parameter, but perioperative bleeding was 18% less in nitrate-treated patients compared with controls.

Conclusion

Preoperative administration of inorganic nitrate did not influence troponin T release or other plasma biomarkers of organ injury in cardiac surgery.

Clinical trial registration

NCT01348971.

Nitric oxide added to the sweep gas of the oxygenator during cardiopulmonary bypass in infants: A pilot randomized controlled trial

Our objective was to assess the effect of nitric oxide added to the sweep gas of the oxygenator during cardiopulmonary bypass (CPB) in infants on platelet count, platelet function, clinical outcomes, and safety. A randomized, double-blinded, placebo-controlled clinical trial in infants less than a year of age undergoing cardiac surgery requiring CPB was undertaken. Nitric oxide at a dose of 20 ppm was added to the sweep gas in the treatment group. Blood was collected at baseline and prior to separation from CPB to measure platelet count and function as determined by responsiveness to specific agonists. Clinical outcomes were observed through hospital discharge. Methemoglobin levels were measured preoperatively, at the conclusion of CPB, and upon admission to the ICU. Forty patients consented and were randomized in the trial. Eighteen patients were randomized to the treatment group and 22 were included in the placebo group. The groups were similar in terms of age, weight, gender, and surgical complexity. No significant differences were found in measures of platelet count, platelet response to agonist, or clinical outcomes. Patients in the treatment group had higher methemoglobin levels after receiving nitric oxide, but no levels approached toxicity (maximum 2.4%). Nitric oxide added to the sweep gas of the oxygenator during CPB in infants did not have an appreciable effect on the preservation of platelet count, platelet responsiveness to agonist, or clinical outcomes. Methemoglobin levels were increased after receiving nitric oxide but were far below a toxic level of 15%.

Extracellular vesicles: biomarkers and regulators of vascular function during extracorporeal circulation

Extracellular vesicles (EVs) are generated at increased rates from parenchymal and circulating blood cells during exposure of the circulation to abnormal flow conditions and foreign materials associated with extracorporeal circuits (ExCors). This review describes types of EVs produced in different ExCors and extracorporeal life support (ECLS) systems including cardiopulmonary bypass circuits, extracorporeal membrane oxygenation (ECMO), extracorporeal carbon dioxide removal (ECCO₂R), apheresis, dialysis and ventricular assist devices. Roles of EVs not only as biomarkers of adverse events during ExCor/ECLS use, but also as mediators of vascular dysfunction are explored. Manipulation of the number or subtypes of circulating EVs may prove a means of improving vascular function for individuals requiring ExCor/ECLS support. Strategies for therapeutic manipulation of EVs during ExCor/ECLS use are discussed such as accelerating their clearance, preventing their genesis or pharmacologic options to reduce or select which and how many EVs circulate. Strategies to reduce or select for specific types of EVs may prove beneficial in preventing or treating other EV-related diseases such as cancer.

Nitric Oxide in Cardiac Surgery: A Meta-Analysis of Randomized Controlled Trials

OBJECTIVES

To investigate the efficacy and safety of perioperative administration of nitric oxide in cardiac surgery.

DESIGN

Meta-analysis of randomized controlled trials (RCTs).

PARTICIPANTS

Cardiac surgery patients.

INTERVENTIONS

A search of Cochrane Central Register of Controlled Trials (CENTRAL), Embase, and MEDLINE for RCTs that compared nitric oxide with placebo or other comparators.

MEASUREMENTS AND MAIN RESULTS

The primary outcome was intensive care unit (ICU) stay, and secondary outcomes were mortality, duration of mechanical ventilation, and reduction of mean pulmonary artery pressure. The study included 18 RCTs comprising 958 patients. The authors calculated the pooled odds ratio (OR) and the mean difference (MD) with random-effects model. Quantitative synthesis of data demonstrated a clinically negligible reduction in the length of ICU stay (MD -0.38 days, confidence interval CI [-0.65 to -0.11]; p = 0.005) and mechanical ventilation duration (MD -4.81 hours, CI [-7.79 to -1.83]; p = 0.002) compared with all control interventions with no benefit on mortality.

CONCLUSIONS

Perioperative delivery of inhaled nitric oxide resulted to be of no or minimal benefit in patients with pulmonary hypertension undergoing cardiac surgery. Large, randomized trials are needed to further assess its effect on major clinical outcomes and its cost-effectiveness.

Low-Dose Sevoflurane May Reduce Blood Loss and Need for Blood Products After Cardiac Surgery: A Prospective, Randomized Pilot Study

Patients undergoing cardiac surgery often experience abnormal bleeding, due primarily to cardiopulmonary bypass (CPB)-induced activation of platelets. Sevoflurane may inhibit platelet activation, raising the possibility that administering it during CPB may reduce blood loss.Patients between 18 and 65 years old who were scheduled for cardiac surgery under CPB at our hospital were prospectively enrolled and randomized to receive intravenous anesthetics alone (control group, n = 77) or together with sevoflurane (0.5-1.0 vol/%) from an oxygenator (sevoflurane group, n = 76). The primary outcome was postoperative blood loss, the secondary outcome was postoperative need for blood products.Volume of blood loss was 48% lower in the sevoflurane group than the control group at 4 hours after surgery, and 33% lower at 12 hours after surgery. Significantly fewer patients in the sevoflurane group lost >700 mL blood within 24 hours (9 of 76 vs 28 of 77, P < 0.001). As a result, the sevoflurane group received significantly smaller volumes of packed red blood cells (1.25 ± 2.36 vs 2.23 ± 3.75 units, P = 0.011) and fresh frozen plasma (97 ± 237 vs 236 ± 344 mL, P = 0.004). Thus the sevoflurane group was at significantly lower risk of requiring complex blood products after surgery (adjusted odds ratio [OR] 0.34, 95% confidence interval [CI] 0.17-0.68, P = 0.002).Sevoflurane inhalation from an oxygenator during CPB may reduce blood loss and need for blood products after cardiac surgery.

Anticoagulation strategies and difficulties in neonatal and paediatric extracorporeal membrane oxygenation (ECMO)

Objective:

The aim of this review is to highlight an emerging problem with anticoagulation-related complications in neonatal and paediatric ECMO, to explore for flaws in the currently recommended anticoagulation management responsible for these problems and to discuss possible strategies mitigating further escalation of the issue.

Data Sources:

Pertinent neonatal and paediatric literature on the topic of interest and international Extracorporeal Life Support Organisation (ELSO) registry data request.

Conclusions:

The international ELSO registry data reveals increasing rates of anticoagulation-related complications during neonatal and paediatric ECMO worldwide. The causes are multifactorial and the proposed solution to the problem is to match anticoagulation management to the pathophysiological complexity of haemostasis on ECMO.

Blood biocompatibility of surface-bound multi-walled carbon nanotubes

Blood clots when it contacts foreign surfaces following platelet activation. This can be catastrophic in clinical settings involving extracorporeal circulation such as during heart-lung bypass where blood is circulated in polyvinyl chloride tubing. Studies have shown, however, that surface-bound carbon nanotubes may prevent platelet activation, the initiator of thrombosis. We studied the blood biocompatibility of polyvinyl chloride, surface-modified with multi-walled carbon nanotubes in vitro and in vivo. Our results show that surface-bound multi-walled carbon nanotubes cause platelet activation in vitro and devastating thrombosis in an in vivo animal model of extracorporeal circulation. The mechanism of the pro-thrombotic effect likely involves direct multi-walled carbon nanotube-platelet interaction with Ca(2+)-dependant platelet activation. These experiments provide evidence, for the first time, that modification of surfaces with nanomaterials modulates blood biocompatibility in extracorporeal circulation.

Coagulation management in patients undergoing mechanical circulatory support

The incidence of bleeding and thrombo-embolic complications in patients undergoing mechanical circulatory support therapy remains high and is associated with bad outcomes and increased costs. The need for anticoagulation and anti-platelet therapy varies widely between different pulsatile and non-pulsatile ventricular-assist devices (VADs) and extracorporeal membrane oxygenation (ECMO) systems. Therefore, a unique anticoagulation protocol cannot be recommended. Notably, most thrombo-embolic complications occur despite values of conventional coagulation tests being within the targeted range. This is due to the fact that conventional coagulation tests such as international normalised ratio (INR), activated partial thromboplastin time (aPTT) and platelet count cannot detect hyper- or hypofibrinolysis, hypercoagulability due to tissue factor expression on circulating cells or increased clot firmness, and platelet aggregation as well as response to anti-platelet drugs. By contrast, point-of-care (POC) whole blood viscoelastic tests (thromboelastometry/-graphy) and platelet function tests (impedance or turbidimetric aggregometry) reflect in detail the haemostatic status of patients undergoing mechanical circulatory support therapy and the efficacy of their anticoagulation and antiaggregation therapy. Therefore, monitoring of haemostasis using POC thromboelastometry/-graphy and platelet function analysis is recommended during mechanical circulatory support therapy to reduce the risk of bleeding and thrombo-embolic complications. Notably, these haemostatic tests should be performed repeatedly during mechanical circulatory support therapy since thrombin generation, clot firmness and platelet response may change significantly over time with a high inter- and intra-individual variability. Furthermore, coagulation management can be hampered in non-pulsatile VADs by acquired von Willebrand syndrome, and in general by acquired factor XIII deficiency as well as by heparin-induced thrombocytopenia. In addition, POC testing can be used in bleeding patients to guide calculated goal-directed therapy with allogeneic blood products, haemostatic drugs and coagulation factor concentrates to optimise the haemostasis and to minimise transfusion requirements, transfusion-associated adverse events and to avoid thrombo-embolic complications, as well. However, coagulation management in patients undergoing mechanical circulatory support therapy is somehow like navigating between Scylla and Charybdis, and development of protocols based on POC testing seems to be beneficial.

Optimal Versus Suboptimal Perfusion During Cardiopulmonary Bypass and the Inflammatory Response

Despite major improvements in perfusion techniques over the past 50 years, it is still not possible to formulate a clear definition of what is meant by optimal perfusion. In part this is due to the lack of sufficient evidence-based data and in part because of the complex pathophysiology that takes place during cardiac surgery with cardiopulmonary bypass. To find an answer we need to understand the exact mechanism of the inflammatory reaction triggered by the cardiopulmonary bypass. However, it is clear that further improvement of the cardiopulmonary bypass components alone will be sufficient. Only a combined strategy can further improve cardiopulmonary bypass—related morbidity and mortality. Such a combined strategy will embrace perfusion techniques as well as a pharmacological approach. It will also require a continuous monitoring of the microcirculation. The latter will not only allow to rapidly sense changes in the quality of perfusion but, even more important, also make it possible to intervene at the moment of deterioration. Recent research shows that such an approach has positive an impact on cardiopulmonary bypass—related morbidity postoperatively.

Platelet Activation during Haemodialysis: Comparison of Cuprammonium Rayon and Polysulfone Membranes

BACKGROUND/AIM

Haemodialysis-treated patients are at a high risk of developing cardiovascular disease. Part of this risk may be attributable to the type of the dialysis membrane used. We evaluated whether different dialysis membranes differ with respect to platelet activation.

METHODS

In a randomized crossover trial, the platelet activation was measured in 14 patients treated with two different dialyzers (cuprammonium rayon membrane and polysulfone membrane). We compared the platelet activation over the dialyzer and between dialyzers after several weeks of dialysis.

RESULTS

There were no differences between the two dialyzers in platelet activation over the dialyzer. After 2 weeks, however, the expression of CD62P, CD63, and PAC-1 was statistically significantly lower after cuprammonium membrane treatment than after polysulfone membrane treatment (mean fluorescence intensity in arbitrary units 8.0 vs. 11.1, 2.64 vs. 4.01, and 5.61 vs. 9.74, respectively).

CONCLUSION

Dialysis with a polysulfone membrane seems to lead to more platelet activation than dialysis with a cuprammonium membrane.

Procoagulant Microparticles

Apoptosis and vascular cell activation are main contributors to the release of procoagulant microparticles (MPs), deleterious partners in atherothrombosis. Elevated levels of circulating platelet, monocyte, or endothelial-derived MPs are associated with most of the cardiovascular risk factors and appear indicative of poor clinical outcome. In addition to being a valuable hallmark of vascular cell damage, MPs are at the crossroad of atherothrombosis processes by exerting direct effects on vascular or blood cells. Under pathological circumstances, circulating MPs would support cellular cross-talk leading to vascular inflammation and tissue remodeling, endothelial dysfunction, leukocyte adhesion, and stimulation. Exposed membrane phosphatidylserine and functional tissue factor (TF) are 2 procoagulant entities conveyed by circulating MPs. At sites of vascular injury, P-selectin exposure by activated endothelial cells or platelets leads to the rapid recruitment of MPs bearing the P-selectin glycoprotein ligand-1 and blood-borne TF, thereby triggering coagulation. Within the atherosclerotic plaque, sequestered MPs constitute the main reservoir of TF activity, promoting coagulation after plaque erosion or rupture. Lesion-bound MPs, eventually harboring proteolytic and angiogenic effectors are additional actors in plaque vulnerability. Pharmacological strategies aimed at modulating the release of procoagulant MPs appear a promising therapeutic approach of both thrombotic processes and bleeding disorders.

Pharmacologic relaxation of vein grafts is beneficial compared with pressure distention caused by upregulation of endothelial nitric oxide synthase and nitric oxide production

OBJECTIVE

Pressure distention of veins during preparation for bypass surgery is believed to impair vascular integrity and reduce graft patency. We previously suggested a combination of pharmacologic vasodilatators as an alternative to distention. Vascular homeostasis is largely regulated by nitric oxide. We investigated the role of distention in comparison with pharmacologic vasorelaxation in the regulation of nitric oxide synthases, nitric oxide bioavailability, and vascular reactivity in vein grafts.

METHODS

In a porcine model the internal jugular vein from either side received pressure distention or the combination of vasodilators (alpha-adrenergic antagonist, phenoxybenzamine, 10 micromol/L; Rho-kinase inhibitor, HA-1077 [fasudil], 50 mumol/L; calcium blocker, nicardipine, 1 micromol/L) and then was grafted into the carotid artery. Regulation of nitric oxide synthase, as well as nitrate and nitrite levels, were examined in vein grafts after 2 weeks of implantation.

RESULTS

Distention of jugular veins resulted in reduction of vasoconstriction in response to depolarization and agonist stimulation. Arterial grafting doubled inducible nitric oxide synthase expression in both grafts but caused a pronounced upregulation of endothelial nitric oxide synthase protein (by 57.3% +/- 5%) only in drug-treated grafts, whereas in distended grafts the endothelial nitric oxide synthase level was decreased by 27.5% +/- 2.7%. The downregulated endothelial nitric oxide synthase level in the distended grafts was accompanied by a 45.2% +/- 3.1% reduction of phospho-endothelial nitric oxide synthase Ser1177 levels and by a significant reduction in nitric oxide synthase activity (12.1% +/- 1.2%) and nitrate production (48.9% +/- 5.6%) in comparison with that seen in drug-treated grafts.

CONCLUSIONS

Pharmacologic preparation of the vein grafts results in upregulation of endothelial nitric oxide synthase and increased nitric oxide production in the vein grafts after arterial implantation. This might provide greater clinical benefit than conventional pressure-distention methods.

Increased Alveolar and Plasma Gelatinases Activity during Postpump Syndrome: Inhibition by Inhaled Nitric Oxide

Postpump syndrome is associated with systemic inflammation. Matrix metalloproteinases (MMP)-2 and -9 contribute to proinflammatory and platelet-activator reactions. Nitric oxide (NO) is involved in the regulation of MMPs. The objectives of our study were to investigate the intensity of inflammation induced by 3 different surgical procedures, the effects of inflammation on the activity of MMPs, and the regulation of inflammation by inhaled NO (20 ppm). Inhaled NO was initiated immediately after tracheal intubation and maintained for the total duration of the experiments. Thirty pigs were equally randomized into 6 groups [sham; sham + NO; cardiopulmonary bypass; bypass + NO; bypass + lipopolysaccharide (1 microg/kg for 50 min); bypass + lipopolysaccharide + NO] and animals were subjected to anesthesia and mechanical ventilation up to 24 h. The levels of MMP-2 and MMP-9 in plasma and bronchoalveolar lavage were measured using zymography. Bypass resulted in a time-dependent rise in MMP activity, an effect potentiated by lipopolysaccharide. Inhaled NO attenuated the effects of bypass + lipopolysaccharide. These results confirm that MMP-2 and MMP-9 are associated with the inflammatory process causing the postpump syndrome. Preemptive and continuous administration of inhaled NO helps to prevent increased MMP-2 and MMP-9 activity.

Extrapulmonary effects of inhaled nitric oxide: role of reversible S-nitrosylation of erythrocytic hemoglobin

Early applications of inhaled nitric oxide (iNO), typically in the treatment of diseases marked by acute pulmonary hypertension, were met by great enthusiasm regarding the purported specificity of iNO: vasodilation by iNO was specific to the lung (without a change in systemic vascular resistance), and within the lung, NO activity was said to be confined spatially and temporally by Hb within the vascular lumen. Underlying these claims were classical views of NO as a short-lived paracrine hormone that acts largely through the heme groups of soluble guanylate cyclase, and whose potential activity is terminated on encountering the hemes of red blood cell (RBC) Hb. These classical views are yielding to a broader paradigm, in which NO-related signaling is achieved through redox-related NO adducts that endow NO synthase products with the ability to act at a distance in space and time from NO synthase itself. Evidence supporting the biological importance of such stable NO adducts is probably strongest for S-nitrosothiols (SNOs), in which NO binds to critical cysteine residues in proteins or peptides. The circulating RBC is a major SNO reservoir, and RBC Hb releases SNO-related bioactivity peripherally on O2 desaturation. These new paradigms describing NO transport also provide a plausible mechanistic understanding of the increasingly recognized peripheral effects of inhaled NO. An explanation for the peripheral actions of inhaled NO is discussed here, and the rationale and results of attempts to exploit the "NO delivery" function of the RBC are reviewed.

Cyclooxygenase-2 induction and prostacyclin release by protease-activated receptors in endothelial cells require cooperation between mitogen-activated protein kinase and NF-kappaB pathways

The functional significance of protease-activated receptors (PARs) in endothelial cells is largely undefined, and the intracellular consequences of their activation are poorly understood. Here, we show that the serine protease thrombin, a PAR-1-selective peptide (TFLLRN), and SLIGKV (PAR-2-selective peptide) induce cyclooxygenase-2 (COX-2) protein and mRNA expression in human endothelial cells without modifying COX-1 expression. COX-2 induction was accompanied by sustained production of 6-keto-PGF1alpha, the stable hydrolysis product of prostacyclin, and this was inhibited by indomethacin and the COX-2-selective inhibitor NS398. PAR-1 and PAR-2 stimulation rapidly activated both ERK1/2 and p38MAPK, and pharmacological blockade of MEK with either PD98059 or U0126 or of p38MAPK by SB203580 or SB202190 strongly inhibited thrombin- and SLIGKV-induced COX-2 expression and 6-keto-PGF1alpha formation. Thrombin and peptide agonists of PAR-1 and PAR-2 increased luciferase activity in human umbilical vein endothelial cells infected with an NF-kappaB-dependent luciferase reporter adenovirus, and this, as well as PAR-induced 6-keto-PGF1alpha synthesis, was inhibited by co-infection with adenovirus encoding wild-type or mutated (Y42F) IkappaBalpha. Thrombin- and SLIGKV-induced COX-2 expression and 6-keto-PGF1alpha generation were markedly attenuated by the NF-kappaB inhibitor PG490 and partially inhibited by the proteasome pathway inhibitor MG-132. Activation of PAR-1 or PAR-2 promoted nuclear translocation and phosphorylation of p65-NF-kappaB, and thrombin-induced but not PAR-2-induced p65-NF-kappaB phosphorylation was reduced by inhibition of MEK or p38MAPK. Activation of PAR-4 by AYPGKF increased phosphorylation of ERK1/2 and p38MAPK without modifying NF-kappaB activation or COX-2 induction. Our data show that PAR-1 and PAR-2, but not PAR-4, are coupled with COX-2 expression and sustained endothelial production of vasculoprotective prostacyclin by mechanisms that depend on ERK1/2, p38MAPK, and IkappaBalpha-dependent NF-kappaB activation.

Treatment of pulmonary hypertension with selective pulmonary vasodilators

PURPOSE OF REVIEW

Pulmonary vasodilators are important in the management of pulmonary hypertension. Although systemic vasodilators may be effective in lowering pulmonary artery pressure, systemic vasodilation is the main limitation to dose titration. This review summarizes the latest research and developments in pulmonary vasodilators in the management of acute and chronic pulmonary hypertension.

RECENT FINDINGS

Nitric oxide, the prototype of selective pulmonary vasodilators, remains an effective option in the management of pulmonary hypertension; however, cost and complexity of administration have led to consideration of other pulmonary vasodilators. Animal research suggests that nitric oxide may have an important role in the prevention of pulmonary hypertension after cardiopulmonary bypass. Experience with phosphodiesterase inhibitors, as monotherapy or as part of combination therapy, suggests that these agents improve cardiopulmonary hemodynamics and can be considered as alternatives and/or adjuncts to nitric oxide. Prostacyclins are a versatile class of pulmonary vasodilator as they have been shown to improve pulmonary hemodynamics administered intravenously or via inhalation. Endothelin receptor antagonists have been shown to be effective for long-term management of pulmonary hypertension. Several gene therapy strategies are currently undergoing evaluation.

SUMMARY

Selective pulmonary vasodilation can be achieved through delivery of vasodilators directly to the lungs or targeting pulmonary specific processes. Several therapeutic options are available that demonstrate selectivity for the pulmonary vasculature. These agents can facilitate optimization of cardiopulmonary hemodynamics.