Ex-vivo changes in amino acid concentrations from blood stored at room temperature or on ice: implications for arginine and taurine measurements

Background: Determination of the plasma concentrations of arginine and other amino acids is important for understanding pathophysiology, immunopathology and nutritional supplementation in human disease. Delays in processing of blood samples cause a change in amino acid concentrations, but this has not been precisely quantified. We aimed to describe the concentration time profile of twenty-two amino acids in blood from healthy volunteers, stored at room temperature or on ice.Methods: Venous blood was taken from six healthy volunteers and stored at room temperature or in an ice slurry. Plasma was separated at six time points over 24 hours and amino acid levels were determined by high-performance liquid chromatography.Results: Median plasma arginine concentrations decreased rapidly at room temperature, with a 6% decrease at 30 minutes, 25% decrease at 2 hours and 43% decrease at 24 hours. Plasma ornithine increased exponentially over the same period. Plasma arginine was stable in blood stored on ice, with a < 10% change over 24 hours. Plasma taurine increased by 100% over 24 hours, and this change was not prevented by ice. Most other amino acids increased over time at room temperature but not on ice.Conclusion: Plasma arginine concentrations in stored blood fall rapidly at room temperature, but remain stable on ice for at least 24 hours. Blood samples taken for the determination of plasma amino acid concentrations either should be placed immediately on ice or processed within 30 minutes of collection

Relationship of cell-free hemoglobin to impaired endothelial nitric oxide bioavailability and perfusion in severe falciparum malaria.

BACKGROUND: Hemolysis causes anemia in falciparum malaria, but its contribution to microvascular pathology in severe malaria (SM) is not well characterized. In other hemolytic diseases, release of cell-free hemoglobin causes nitric oxide (NO) quenching, endothelial activation, and vascular complications. We examined the relationship of plasma hemoglobin and myoglobin to endothelial dysfunction and disease severity in malaria. METHODS: Cell-free hemoglobin (a potent NO quencher), reactive hyperemia peripheral arterial tonometry (RH-PAT) (a measure of endothelial NO bioavailability), and measures of perfusion and endothelial activation were quantified in adults with moderately severe (n = 78) or severe (n = 49) malaria and control subjects (n = 16) from Papua, Indonesia. RESULTS: Cell-free hemoglobin concentrations in patients with SM (median, 5.4 micromol/L; interquartile range [IQR], 3.2-7.4 micromol/L) were significantly higher than in those with moderately severe malaria (2.6 micromol/L; IQR, 1.3-4.5 micromol/L) or controls (1.2 micromol/L; IQR, 0.9-2.4 micromol/L; P < .001). Multivariable regression analysis revealed that cell-free hemoglobin remained inversely associated with RH-PAT, and in patients with SM, there was a significant longitudinal association between improvement in RH-PAT index and decreasing levels of cell-free hemoglobin (P = .047). Cell-free hemoglobin levels were also independently associated with lactate, endothelial activation, and proinflammatory cytokinemia. CONCLUSIONS: Hemolysis in falciparum malaria results in NO quenching by cell-free hemoglobin, and may exacerbate endothelial dysfunction, adhesion receptor expression and impaired tissue perfusion. Treatments that increase NO bioavailability may have potential as adjunctive therapies in SM

Potential life-years gained over a 5-year period by correcting DOPPS-identified modifiable practices in haemodialysis: results from the European MONITOR-CKD5 study

BACKGROUND:DOPPS reported that thousands of life-years could be gained in the US and Europe over 5 years by correcting six modifiable haemodialysis practices. We estimated potential life-years gained across 10 European countries using MONITOR-CKD5 study data.METHODS:The DOPPS-based target ranges were used, except for haemoglobin due to label changes, as well as DOPPS-derived relative mortality risks. Percentages of MONITOR-CKD5 patients outside targets were calculated. Consistent with the DOPPS-based analyses, we extrapolated life-years gained for the MONITOR-CKD5 population over 5 years if all patients were within targets.RESULTS:Bringing the 10 MONITOR-CKD5 countries' dialysis populations into compliance on the six practices results in a 5-year gain of 97,428 patient-years. In descending order, survival impact was the highest for albumin levels, followed by phosphate levels, vascular access, haemoglobin, dialysis adequacy, and interdialytic weight gain.CONCLUSIONS:Optimal management of the six modifiable haemodialysis practices may achieve 6.2% increase in 5-year survival.TRIAL REGISTRATION:NCT01121237 . Clinicaltrials.gov registration May 12, 2010 (retrospectively registered)