Blood collection vials and clinically used intravenous fluids contain significant amounts of nitrite

• Published in: Free radical biology & medicine 2017-07, Vol.108, p.533-541
• Main Authors: Almeida, Luis E.F., Kamimura, Sayuri, Nettleton, Margaret Y., de Souza Batista, Celia M., Walek, Elizabeth, Khaibullina, Alfia, Wang, Li, Quezado, Zenaide M.N.
• Format: Article
• Language: English
• Subjects: Administration, Intravenous; Blood; Blood Specimen Collection - methods; Blood Transfusion; Citrates - chemistry; Colloid; Crystalloid; Edetic Acid - chemistry; Heparin - chemistry; Human; Humans; Isotonic Solutions - chemistry; Isotonic Solutions - therapeutic use; Method; Nitric oxide; Nitric Oxide - chemistry; Nitric Oxide - metabolism; Nitrite; Nitrites - chemistry; Plasma; Product Packaging; Red blood cells; Reproducibility of Results; Sensitivity and Specificity; Sodium Chloride - chemistry; Urine
• ISSN: 0891-5849; 1873-4596
• DOI: 10.1016/j.freeradbiomed.2017.04.014

The biology of the inorganic anion nitrite is linked to nitric oxide (NO) as nitrite can be reduced to NO and mediate its biological activities. Thus, studies of nitrite biology require sensitive and selective chemical assays. The acetic and ascorbic acids method is selective for nitrite and measures it in biological matrices. However, one of the pitfalls of nitrite measurements is its ubiquitous presence in sample collection tubes. Here, we showed high levels of nitrite in collection tubes containing EDTA, sodium citrate or sodium heparin and smaller amounts in tubes containing lithium heparin or serum clot activator. We also showed the presence of nitrite in colloid and crystalloid solutions frequently administered to patients and found variable levels of nitrite in 5% albumin, 0.9% sodium chloride, lactated ringer's, and dextrose-plus-sodium chloride solutions. These levels of nitrite varied across lots and manufacturers of the same type of fluid. Because these fluids are administered intravenously to patients (including those in shock), sometimes in large volumes (liters), it is possible that infusions of these nitrite-containing fluids may have clinical implications. A protocol for blood collection free of nitrite contamination was developed and used to examine nitrite levels in whole blood, red blood cells, plasma and urine from normal volunteers. Nitrite measurements were reproducible, had minimal variability, and did not indicate sex-differences. These findings validated a method and protocol for selective nitrite assay in biological fluids free of nitrite contamination which can be applied for study of diseases where dysfunctional NO signaling has been implicated. [Display omitted] •Nitrite is one of the most important NO-derived chemical species.•Nitrite contamination during sample collection is an issue for nitrite assays.•Variable levels of nitrite were found in blood collection tubes.•Variable levels of nitrite were found in intravenous fluids used clinically.•A protocol to collect biological samples without nitrite contamination is described.