Absence of Relevant Clinical Effects of SARS-COV-2 on the Affinity of Hemoglobin for O2 in Patients with COVID-19

Haematological Manifestations of SARS-CoV-2: Insights into Erythropoiesis, Hepcidin Regulation, and Cytokine Storm

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes COVID-19, a respiratory disease that can range in presentation from mild symptoms to severe conditions such as pneumonia and acute respiratory distress syndrome. SARS-CoV-2, a single-stranded RNA virus, spreads through aerosols and respiratory droplets. It enters human cells by binding to the angiotensin-converting enzyme 2 receptor, leading to various complications, including significant alterations in red blood cells and potential disruptions in haemoglobin function and oxygen transport. During infection, the interaction between hypoxia, inflammation, and haematopoiesis affects erythropoiesis at multiple levels. Hypoxia and inflammation, resulting from lung complications and a reduced red blood cell count, influence the regulation of hepcidin, a key regulator of iron levels in the blood. Elevated hepcidin levels are associated with hypoxia and the suppression of erythroferrone, a hormone that normally inhibits hepcidin production. Despite high levels of inflammation, patients in intensive care units often exhibit elevated ferritin levels, which, rather than indicating low hepcidin, suggest disrupted iron metabolism and the development of severe anaemia. Iron is kept in stores, likely due to paradoxically high hepcidin levels, which explains the elevated ferritin measurements. An increase in immature blood cells and a decrease in CD71+ erythroid cells are observed. The elevated levels of CD71+ erythroid cells highlight their dual role in modulating hyper-inflammation and immune response during disease progression. This review examines the pathway by which SARS-CoV-2 affects red blood cell production and the haematopoietic system and how it triggers cytokine storms through interleukins, immature blood cells, and CD71+ erythroid cells. Understanding these processes provides novel pathways for managing haematological manifestations and immune responses in patients with COVID-19.

The oxygen dissociation curve of blood in COVID-19-An update

An impressive effect of the infection with SARS-Co-19 is the impairment of oxygen uptake due to lung injury. The reduced oxygen diffusion may potentially be counteracted by an increase in oxygen affinity of hemoglobin. However, hypoxia and anemia associated with COVID-19 usually decrease oxygen affinity due to a rise in [2,3-bisphosphoglycerate]. As such, COVID-19 related changes in the oxygen dissociation curve may be critical for oxygen uptake and supply, but are hard to predict. A Pubmed search lists 14 publications on oxygen affinity in COVID-19. While some investigations show no changes, three large studies found an increased affinity that was related to a good prognosis. Exact causes remain unknown. The cause of the associated anemia in COVID-19 is under discussion. Erythrocytes with structural alterations of membrane and cytoskeleton have been observed, and virus binding to Band 3 and also to ACE2 receptors in erythroblasts has been proposed. COVID-19 presentation is moderate in many subjects suffering from sickle cell disease. A possible explanation is that COVID-19 counteracts the unfavorable large right shift of the oxygen dissociation curve in these patients. Under discussion for therapy are mainly affinity-increasing drugs.

Clinical features and high-resolution chest computerized tomography findings of children infected by the B.1.617.2 variant of coronavirus disease 2019

PURPOSE

To analyse the clinical symptoms, laboratory examinations and chest CT findings of children infected by the B.1.617.2 variant of COVID-19 and to compare the differences between clinical subtypes.

METHODS

Fifty-three children (28 males, 25 females; age ranging from 4 months to 17 years) were included with B.1.617.2 variant infection in Nanjing, China, from July 21 to August 12 2021. Clinical data from patients were collected and analysed in groups of mild and common types. Imaging data were divided into three stages for evaluation: early, intermediate and late stages.

RESULTS

In our study, fever (53%), cough (34%) and pharyngeal discomfort (28%) were the main symptoms. There were no differences in clinical symptoms between the mild and common type. The most common laboratory test items outside the normal range were decreased mean corpuscular volume (68%), lymphocyte percentage (64% elevated and 2% decreased) and decreased serum alkaline phosphatase concentration (66%). The differences in haemoglobin and monocyte percentages between the mild and common types were statistically significant (p = .037 and .033, respectively). No influencing factor was statistically significant in the regression analysis of both symptoms and clinical subtypes. The main CT findings were ground-glass opacity and consolidation located in the periphery and bilateral multilobed involvement. The mean CT score was 1.6. CT score correlated with packet cell volume, haemoglobin, mean erythrocyte volume, mean platelet volume and platelet distribution width.

CONCLUSION

The pathogenetic condition of children with B.1.617.2 variant infection is mild. Although there were intergroup differences in some blood cell analyses, T-lymphocyte counts, and comprehensive biochemical indicators, no factors had a significant effect on clinical typing and the presence or absence of symptoms. CT findings and CT scores reflect disease stage and pathological changes and correlate moderately with laboratory tests, making them of good value for disease diagnosis and monitoring.Key MessagesPaediatric patients infected with B.1.617.2 variant have a milder clinical and imaging presentation than adults and are similar to the prototype infection.CT findings and scores which reflect disease stages and pathological changes.There is a correlation between chest CT and laboratory tests, which can be useful for the diagnosis and follow-up of the disease.

Temporal Changes in the Oxyhemoglobin Dissociation Curve of Critically Ill COVID-19 Patients

Critical COVID-19 is a life-threatening disease characterized by severe hypoxemia with complex pathophysiological mechanisms that are not yet completely understood. A pathological shift in the oxyhemoglobin curve (ODC) was previously described through the analysis of p50, intended as the oxygen tension at which hemoglobin is saturated by oxygen at 50%. The aim of this study was to analyze Hb-O₂ affinity features over time in a cohort of critically ill COVID-19 patients, through the analysis of ODC p50 behavior. A retrospective analysis was performed; through multiple arterial blood gas (ABG) analyses, each p50 was calculated and normalized according to PaCO₂, pH and temperature; patients' p50 evolution over time was reported, comparing the first 3 days (early p50s) with the last 3 days (late p50s) of ICU stay. A total of 3514 ABG analyses of 32 consecutive patients were analyzed. The majority of patients presented a left shift over time (p = 0.03). A difference between early p50s and late p50s was found (20.63 ± 2.1 vs. 18.68 ± 3.3 mmHg, p = 0.03); median p50 of deceased patients showed more right shifts than those of alive patients (24.1 vs. 18.45 mmHg, p = 0.01). One-way ANOVA revealed a p50 variance greater in the early p50s (σ² = 8.6) than in the late p50s (σ² = 3.84), associated with a reduction over time (p < 0.001). Comparing the Hb-O₂ affinity in critically ill COVID-19 patients between ICU admission and ICU discharge, a temporal shift in the ODC was observed.