Background: One of the pathological effects of carbon monoxide (CO) on blood is the formation of carboxyhemoglobin. Carboxyhemoglobin completely blocks oxygen transfer; therefore, there is a net decrease in oxygen transport by red blood cells potentially resulting in tissue hypoxia. The effects of CO on blood can also damage cell membranes. Atomic force microscopy (AFM) has been recognized as effective for investigation into the mechanisms of structural damage in erythrocyte membranes. Aim: By means of AFM, to identify characteristics of changes in morphology and aggregation of erythrocytes exposed to CO in vitro.Materials and methods: All experiments were performed in vitro. We studied the morphology of erythrocytes and their aggregates with AFM. Blood sampling (150 μl) in microvettes with EDTA (Sarstedt AG & Co., Germany) was carried out during a prophylactic work-up of 5 volunteers. To obtain CO in a test tube, formic acid was mixed with sulfuric acid 1:1. Blood levels of carboxyhemoglobin were measured by spectrophotometry. A nonlinear fitting method of the experimental spectra was used to calculate the concentrations of hemoglobin derivatives in blood. Statistical analysis was done with the Origin software (OriginLab Corporation, Northampton, MA, USA).Results: After CO exposure, a shift in peaks was observed. At exposure time t₂=320 s, the percentage of carboxyhemoglobin (CHbCO) was 88±2%. As a result of blood exposure to CO, at t₁=160 s 10% of the cells differed in their shape from discocytes, whereas at t₂=320 s their proportion was 38%. With increasing duration of exposure to CO, erythrocyte aggregation occurred with formation of their large conglomerates up to 30 μm in size. In the control smear, the proportion of discocytes was 96±2%, and the remaining 4±1% of the cells had the form of echinocytes. The cell diameter (Dcont) was in the range 7.5±0.8 μm. After blood exposure to CO at t₁=160 s in the monolayer, 28±5% of cells had a diameter less than<5.7 μm. After CO exposure at t₂=320 s, the proportion of cells with a diameter of less than<5.7 μm increased to 72±11%.Conclusion: The experiments have shown that blood exposure to CO changed the morphology of erythrocytes. The formation of interconnected structures made of red blood cells was observed. With increased time of exposure, erythrocytes demonstrated aggregation with conglomerate formation.

Red blood cells are the most required blood transfusion products worldwide. Safety and efficacy of blood transfusion are still relevant issues. Clarification of the causes and mechanisms of post-transfusion complications requires additional research.Aim of the review is to summarize the data of clinical and research studies on transfusion of red blood cell suspension with various storage times.Material. We selected 76 sources from Web of Science, Scopus, and RSCI databases containing pertinent clinical and scientific research data, as well as blood transfusion guidelines.Results. We reviewed the main stages of preparation and storage of filtered red blood cells, described biochemical and structural alterations occurring during blood storage, summarized clinical data on post-transfusion complications, and analyzed clinical consequences and molecular structure abnormalities of red blood cells in relation to their storage time.Conclusion. During long-term storage, red blood cells undergo significant structural and metabolic changes. The clinical use of relatively «old» red blood cells increases the risk of post-transfusion complications. However, the pathophysiological differences between «young» and «old» erythrocytes remain unclear. Large clinical and molecular research studies may add to our understanding of the complex issues related to blood transfusion.