Andre Dejam

Plasma nitrite reflects constitutive nitric oxide synthase activity in mammals

Changes in plasma nitrite concentration in the human forearm circulation have recently been shown to reflect acute changes in endothelial nitric oxide synthase (eNOS)-activity. Whether basal plasma nitrite is a general marker of constitutive NOS-activity in vivo is yet unclear. Due to the rapid metabolism of nitrite in blood and the difficulties in its analytical determination literature data on levels of nitrite in mammals are largely inconsistent. We hypothesized that constitutive NOS-activity in the circulatory system is relatively uniform throughout the mammalian kingdom. If true, this should result in comparable systemic plasma nitrite levels in different species. Using three different analytical approaches we determined plasma nitrite concentration to be in a nanomolar range in a variety of species: humans (305 +/- 23 nmol/l), monkeys (367 +/- 62 nmol/l), minipigs (319 +/- 24 nmol/l), dogs (305 +/- 50 nmol/l), rabbits (502 +/- 21 nmol/l), guinea pigs (412 +/- 44 nmol/l), rats (191 +/- 43 nmol/l), and mice (457 +/- 51 nmol/l). Application of different NOS-inhibitors in humans, minipigs, and dogs decreased NOS-activity and thereby increased vascular resistance. This was accompanied by a significant, up to 80%, decrease in plasma nitrite concentration. A comparison of plasma nitrite concentrations between eNOS(-/-) and NOS-inhibited wild-type mice revealed that 70 +/- 5% of plasma nitrite is derived from eNOS. These results provide evidence for a uniform constitutive vascular NOS-activity across mammalian species.

Nitrite Infusion in Humans and Nonhuman Primates Endocrine Effects, Pharmacokinetics, and Tolerance Formation

Background— The recent discovery that nitrite is an intrinsic vasodilator and signaling molecule at near-physiological concentrations has raised the possibility that nitrite contributes to hypoxic vasodilation and to the bioactivity of nitroglycerin and mediates the cardiovascular protective effects of nitrate in the Mediterranean diet. However, important questions of potency, kinetics, mechanism of action, and possible induction of tolerance remain unanswered. Methods and Results— In the present study, we performed biochemical, physiological, and pharmacological studies using nitrite infusion protocols in 20 normal human volunteers and in nonhuman primates to answer these questions, and we specifically tested 3 proposed mechanisms of bioactivation: reduction to nitric oxide by xanthine oxidoreductase, nonenzymatic disproportionation, and reduction by deoxyhemoglobin. We found that (1) nitrite is a relatively potent and fast vasodilator at near-physiological concentrations; (2) nitrite functions as an endocrine reservoir of nitric oxide, producing remote vasodilation during first-pass perfusion of the opposite limb; (3) nitrite is reduced to nitric oxide by intravascular reactions with hemoglobin and with intravascular reductants (ie, ascorbate); (4) inhibition of xanthine oxidoreductase with oxypurinol does not inhibit nitrite-dependent vasodilation but potentiates it; and (5) nitrite does not induce tolerance as observed with the organic nitrates. Conclusions— We propose that nitrite functions as a physiological regulator of vascular function and endocrine nitric oxide homeostasis and suggest that it is an active metabolite of the organic nitrates that can be used therapeutically to bypass enzymatic tolerance.

Plasma Nitrosothiols Contribute to the Systemic Vasodilator Effects of Intravenously Applied NO Experimental and Clinical Study on the Fate of NO in Human Blood

Abstract— Higher doses of inhaled NO exert effects beyond the pulmonary circulation. How such extrapulmonary effects can be reconciled with the presumed short half-life of NO in the blood is unclear. Whereas erythrocytes have been suggested to participate in NO transport, the exact role of plasma in NO delivery in humans is not clear. Therefore, we investigated potential routes of NO decomposition and transport in human plasma. NO consumption in plasma was accompanied by a concentration-dependent increase in nitrite and S-nitrosothiols (RSNOs), with no apparent saturation limit up to 200 &mgr;mol/L. The presence of red blood cells reduced the formation of plasma RSNOs. Intravenous infusion of 30 &mgr;mol/min NO in healthy volunteers increased plasma levels of RSNOs and induced systemic hemodynamic effects at the level of both conduit and resistance vessels, as reflected by dilator responses in the brachial artery and forearm microvasculature. Intravenous application of S-nitrosoglutathione, a potential carrier of bioactive NO, mimicked the vascular effects of NO, whereas nitrite and nitrate were inactive. Changes in plasma nitrosothiols were correlated with vasodilator effects after intravenous application of S-nitrosoglutathione and NO. These findings demonstrate that in humans the pharmacological delivery of NO solutions results in the transport and delivery of NO as RSNOs along the vascular tree.

Benefit of Transferring ST-Segment–Elevation Myocardial Infarction Patients for Percutaneous Coronary Intervention Compared With Administration of Onsite Fibrinolytic Declines as Delays Increase

Background— Although randomized trials suggest that transfer for primary percutaneous coronary intervention (X-PCI) in ST-segment–elevation myocardial infarction is superior to onsite fibrinolytic therapy (O-FT), the generalizability of these findings to routine clinical practice is unclear because door-to-balloon (XDB) times are rapid in randomized trials but are frequently prolonged in practice. We hypothesized that delays resulting from transfer would reduce the survival advantage of X-PCI compared with O-FT. Methods and Results— ST-segment–elevation myocardial infarction patients enrolled in the National Registry of Myocardial Infarction (NRMI) within 12 hours of pain onset were identified. Propensity matching of patients treated with X-PCI and O-FT was performed, and the effect of PCI-related delay on in-hospital mortality was assessed. PCI-related delay was calculated by subtracting the XDB from the door-to-needle time in each matched pair. Conditional logistic regression adjusted for patient and hospital variables identified the XDB door-to-needle time at which no mortality advantage for X-PCI over O-FT was present. Eighty-one percent of X-PCI patients were matched (n=9506) to O-FT patients (n=9506). In the matched cohort, X-PCI was performed with delays >90 minutes in 68%. Multivariable analysis found no mortality advantage for X-PCI over O-FT when XDB door-to-needle time exceeded ≈120 minutes. Conclusion— PCI-related delays are extensive among patients transferred for X-PCI and are associated with poorer outcomes. No differential excess in mortality was seen with X-PCI compared with O-FT even with long PCI-related delays, but as XDB door-to-needle time times increase, the mortality advantage for X-PCI over O-FT declines.

Endothelial progenitor cell mobilization and increased intravascular nitric oxide in patients undergoing cardiac rehabilitation.

PURPOSE: We investigated whether cardiac rehabilitation participation increases circulating endothelial progenitor cells (EPCs) and benefits vasculature in patients already on stable therapy previously shown to augment EPCs and improve endothelial function. METHODS: Forty-six of 50 patients with coronary artery disease completed a 36-session cardiac rehabilitation program: 45 were treated with HMG-CoA reductase inhibitor (statin) therapy ≥1 month (average baseline low-density lipoprotein cholesterol = 81 mg/dL). Mononuclear cells isolated from blood were quantified for EPCs by flow cytometry (CD133+/VEGFR-2+ cells) and assayed in culture for EPC colony-forming units (CFUs). In 23 patients, EPCs were stained for annexin-V as a marker of apoptosis, and nitrite was measured in blood as an indicator of intravascular nitric oxide. RESULTS: Endothelial progenitor cells increased from 35 ± 5 to 63 ± 10 cells/mL, and EPC-CFUs increased from 0.9 ± 0.2 to 3.1 ± 0.6 per well (both P < .01), but 11 patients had no increase in either measure. Those patients whose EPCs increased from baseline showed significant increases in nitrite and reduction in annexin-V staining (both P < .01) versus no change in patients without increase in EPCs. Over the course of the program, EPCs increased prior to increase in nitrite in the blood. CONCLUSIONS: Cardiac rehabilitation in patients receiving stable statin therapy and with low-density lipoprotein cholesterol at goal increases EPC number, EPC survival, and endothelial differentiation potential, associated with increased nitric oxide in the blood. Although this response was observed in most patients, a significant minority showed neither EPC mobilization nor increased nitric oxide in the blood.

Role of Endothelial Progenitor Cells and Inflammatory Cytokines in Healing of Diabetic Foot Ulcers

Background To evaluate changes in endothelial progenitor cells (EPCs) and cytokines in patients with diabetic foot ulceration (DFU) in association with wound healing. Methods We studied healthy subjects, diabetic patients not at risk of DFU, at risk of DFU and with active DFU. We prospectively followed the DFU patients over a 12-week period. We also investigated similar changes in diabetic rabbit and mouse models of wound healing. Results All EPC phenotypes except the kinase insert domain receptor (KDR)+CD133+ were reduced in the at risk and the DFU groups compared to the controls. There were no major EPC differences between the control and not at risk group, and between the at risk and DFU groups. Serum stromal-cell derived factor-1 (SDF-1) and stem cell factor (SCF) were increased in DFU patients. DFU patients who healed their ulcers had lower CD34+KDR+ count at visits 3 and 4, serum c-reactive protein (CRP) and granulocyte-macrophage colony-stimulating factor (GM-CSF) at visit 1, interleukin-1 (IL-1) at visits 1 and 4. EPCs tended to be higher in both diabetic animal models when compared to their non-diabetic counterparts both before and ten days after wounding. Conclusions Uncomplicated diabetes does not affect EPCs. EPCs are reduced in patients at risk or with DFU while complete wound healing is associated with CD34+KDR+ reduction, suggesting possible increased homing. Low baseline CRP, IL-1α and GM-CSF serum levels were associated with complete wound healing and may potentially serve as prognostic markers of DFU healing. No animal model alone is representative of the human condition, indicating the need for multiple experimental models.

Lopinavir-Ritonavir: Effects on Endothelial Cell Function in Healthy Subjects

To differentiate between the effects that antiretroviral drugs have on the endothelium and the secondary effects that they have on immune function, viral load, and dyslipidemia, 6 non-human immunodeficiency virus-infected human subjects were treated with lopinavir-ritonavir for 1 month and, on the basis of forearm blood flow, the treatments effects on endothelial cell function were measured. Surprisingly, after exposure to lopinavir-ritonavir, absolute forearm blood-flow responses to the endothelium-dependent vasodilator, acetylcholine, increased significantly (P=.03), and forearm blood flow decreased to a greater extent during specific inhibition of NO synthase by N(G)-monomethyl-L-arginine. Thus, in this small cohort of subjects, short-term treatment with lopinavir-ritonavir does not appear to directly promote endothelial cell dysfunction.

APACHE II scoring to predict outcome in post-cardiac arrest

INTRODUCTION Despite advancements in management of cardiac arrest, mortality remains high and few severity of illness scoring systems have been calibrated in this population. The goal of the current investigation was to assess the Acute Physiology and Chronic Health Evaluation II score in post-cardiac arrest. MEASUREMENTS This is a prospective observational study of adult post-cardiac arrest patients at a tertiary-care center. The primary outcome variable was in-hospital mortality and secondary outcome variable was neurologic outcome. APACHE II scores were used to predict outcomes using logistic modeling. MAIN RESULTS A total of 228 subjects were included in the analysis. The median age of the cohort was 70 (IQR: 64-71) and 32% (72/228) of the patients were female. The median downtime was 15 min (IQR: 7-27) and initial lactate 5.9 mmol/L (IQR: 3.5-8.4). 71 (57%) of deaths occurred prior to the 72-h follow-up and overall in-hospital mortality was 55% (125/228). Discrimination of APACHE II score in all cardiac arrest patients increased in stepwise fashion from 0-h to 72-h follow-up (AUC: 0-h: 0.62; 24-h: 0.75; 48-h: 0.82; 72-h: 0.86). CONCLUSIONS APACHE II score is a poor predictor of outcome at time zero for out-of-hospital cardiac arrest (OHCA) post-arrest patients consistent with the original development of the score in the critically ill. For in-hospital cardiac arrest (IHCA) at time zero and for both IHCA and OHCA at 24h and beyond, the APACHE II score was a modest indicator of illness severity and predictor of mortality/neurologic morbidity.

The effect of age and clinical circumstances on the outcome of red blood cell transfusion in critically ill patients

IntroductionWhether red blood cell (RBC) transfusion is beneficial remains controversial. In both retrospective and prospective evaluations, transfusion has been associated with adverse, neutral, or protective effects. These varying results likely stem from a complex interplay between transfusion, patient characteristics, and clinical context. The objective was to test whether age, comorbidities, and clinical context modulate the effect of transfusion on survival.MethodsBy using the multiparameter intelligent monitoring in intensive care II database (v. 2.6), a retrospective analysis of 9,809 critically ill patients, we evaluated the effect of RBC transfusion on 30-day and 1-year mortality. Propensity score modeling and logistic regression adjusted for known confounding and assessed the independent effect of transfusion on 30-day and 1-year mortality. Sensitivity analysis was performed by using 3,164 transfused and non-transfused pairs, matched according the previously validated propensity model for RBC transfusion.ResultsRBC transfusion did not affect 30-day or 1-year mortality in the overall cohort. Patients younger than 55 years had increased odds of mortality (OR, 1.71; P < 0.01) with transfusion. Patients older than 75 years had lower odds of 30-day and 1-year mortality (OR, 0.70; P < 0.01) with transfusion. Transfusion was associated with worse outcome among patients undergoing cardiac surgery (OR, 2.1; P < 0.01). The propensity-matched population corroborated findings identified by regression adjustment.ConclusionA complex relation exists between RBC transfusion and clinical outcome. Our results show that transfusion is associated with improved outcomes in some cohorts and worse outcome in others, depending on comorbidities and patient characteristics. As such, future investigations and clinical decisions evaluating the value of transfusion should account for variations in baseline characteristics and clinical context.