Transesophageal echocardiography-guided technique for extracorporeal membrane oxygenation dual-lumen catheter placement.

In acute respiratory distress syndrome (ARDS) with severe hypoxemia or respiratory acidosis, veno-venous extracorporeal membrane oxygenation (VV-ECMO) ensures oxygenation and decarboxylation. Commonly, simultaneous cannulation of jugular and femoral veins is used for VV-ECMO. A recently introduced dual-lumen cannula for VV-ECMO promises single vessel access through the right internal jugular vein and patient ambulation. However, correct direction of the reinfusion jet toward the tricuspid valve during ECMO treatment requires more demanding cannula placement control. We present a new ultrasound-guided technique for the placement of a dual-lumen VV-ECMO cannula in a patient with ARDS and extreme obesity.

The tyrosine phosphatase, SHP-1, is a negative regulator of endothelial superoxide formation.

OBJECTIVES: We investigated the role of SH2-domain containing phosphatase-1 (SHP-1) in endothelial reduced nicotinamide adenine dinucleotide (phosphate) (NAD[P]H)-oxidase-dependent oxidant production. BACKGROUND: Superoxide (O2*-) generation by endothelial NAD(P)H-oxidase promotes endothelial dysfunction and atherosclerosis. Signaling pathways that regulate NAD(P)H-oxidase activity are, however, poorly understood. METHODS: SH2-domain containing phosphatase-1 was inhibited using site-directed magnetofection of antisense oligodesoxynucleotides (AS-ODN) or short interfering ribonucleic acid (siRNA) in vitro in human umbilical vein endothelial cells (HUVEC) and in isolated hamster arteries; O2*- was measured by cytochrome c reduction in vitro. Activities of NAD(P)H-oxidase activity, phosphatidyl-inositol-3-kinase (PI3K), and SHP-1 were assessed by specific assays; Rac1 activation was assessed by a pull-down assay. RESULTS: Basal endothelial O2*- release was enhanced after inhibition of endothelial SHP-1 (p < 0.01), which could be prevented by specific inhibition of NAD(P)H-oxidase (p < 0.01); SHP-1 activity was high under basal conditions, further increased by vascular endothelial growth factor (10 ng/ml, p < 0.05), and abolished by SHP-1 AS-ODN treatment (p < 0.01), which also increased NAD(P)H-oxidase activity 3.3-fold (p < 0.01). Vascular endothelial growth factor also induced O2*- release (p < 0.01), which was even more enhanced when SHP-1 was knocked down (p < 0.05). The effect of SHP-1 was mediated by inhibition of PI3K/Rac1-dependent NAD(P)H-oxidase activation (p < 0.01); SHP-1 AS-ODN augmented tyrosine phosphorylation of the p85 regulatory subunit of PI3K (p < 0.05) and Rac1 activation. The latter was prevented by wortmannin, a blocker of PI3K. CONCLUSIONS: In HUVEC, SHP-1 counteracts basal and stimulated NAD(P)H-oxidase activity by negative regulation of PI3K-dependent Rac1 activation; SHP-1 thus seems to be an important part of endothelial antioxidative defense controlling the activity of the O2(*-)-producing NAD(P)H-oxidase.

Selective inhibition of cyclooxygenase-2 enhances platelet adhesion in hamster arterioles in vivo.

BACKGROUND: Selective inhibitors of cyclooxygenase-2 (Cox-2) are reported to cause cardiovascular side effects in patients at risk. However, direct proof of prothrombotic effects of these drugs is lacking. We investigated in the microcirculation in vivo whether selective inhibition of Cox-2 induces platelet activation. METHODS AND RESULTS: The behavior of fluorescence-labeled human platelets was studied in hamster arterioles (dorsal skinfold chamber) by intravital microscopy. Transient platelet-vessel wall interactions (PVWIs), firm platelet adhesion to the vessel wall, and vessel occlusion after FeCl3-induced wall injury were analyzed as platelet activation parameters. In vitro experiments in human umbilical vein endothelial cells (HUVECs) were performed to assess specific effects of Cox-2 inhibition on platelet adhesion under shear stress (16 dyn/cm2) and on endothelial release of 6-ketoprostaglandin (PG) F(1alpha). Selective inhibition of Cox-2 (NS-398, 0.5 mg/kg) increased platelet adhesion to the vessel wall in vivo (11.9+/-3.9 platelets/mm2; controls, 1.4+/-1.4 platelets/mm2, P<0.05) and platelet adhesion after ADP stimulation in vitro. PVWIs were significantly enhanced in NS-398-treated animals, which were reduced by platelet pretreatment with aspirin (5 mg/kg) or iloprost (1 nmol/L). Inhibition of Cox-2 reduced levels of 6-keto-PGF1alpha in vivo and in HUVEC supernatants. Time to occlusion after vessel wall injury was significantly shortened by NS-398 (125.4+/-13.6 seconds in NS-398-treated animals versus 270.8+/-46 seconds in controls; P<0.01). CONCLUSIONS: Selective inhibition of Cox-2 reduces 6-keto-PGF(1alpha) endothelial release, increases PVWIs, and increases firm platelet adhesion in hamster arterioles. Moreover, it leads to faster occlusion of damaged microvessels. Thus, selective inhibition of Cox-2 may trigger thrombotic events by diminishing the antiplatelet properties of the endothelium.

Membrane-potential-dependent inhibition of platelet adhesion to endothelial cells by epoxyeicosatrienoic acids.

OBJECTIVE: Epoxyeicosatrienoic acids (EETs) are potent vasodilators produced by endothelial cells. In many vessels, they are an endothelium-derived hyperpolarizing factor (EDHF). However, it is unknown whether they act as an EDHF on platelets and whether this has functional consequences. METHODS AND RESULTS: Flow cytometric measurement of platelet membrane potential using the fluorescent dye DiBac4 showed a resting potential of -58+/-9 mV. Different EET regioisomers hyperpolarized platelets down to -69+/-2 mV, which was prevented by the non-specific potassium channel inhibitor charybdotoxin and by use of a blocker of calcium-activated potassium channels of large conductance (BK(Ca) channels), iberiotoxin. EETs inhibited platelet adhesion to endothelial cells under static and flow conditions. Exposure to EETs inhibited platelet P-selectin expression in response to ADP. Stable overexpression of cytochrome P450 2C9 in EA.hy926 cells (EA.hy2C9 cells) resulted in release of EETs and a factor that hyperpolarized platelets and inhibited their adhesion to endothelial cells. These effects were again inhibited by charybdotoxin and iberiotoxin. CONCLUSIONS: EETs hyperpolarize platelets and inactivate them by inhibiting adhesion molecule expression and platelet adhesion to cultured endothelial cells in a membrane potential-dependent manner. They act as an EDHF on platelets and might be important mediators of the anti-adhesive properties of vascular endothelium.