Interaction Effect Between Hemoglobin and Hypoxemia on COVID-19 Mortality: an observational study from Bogotá, Colombia

Abstract

Purpose We aimed to assess the effect of hemoglobin (Hb) concentration and oxygenation index on COVID-19 patients’ mortality risk. Patients and Methods We retrospectively reviewed sociodemographic and clinical characteristics, laboratory findings, and clinical outcomes from patients admitted to a tertiary care hospital in Bogotá, Colombia, from March to July 2020. We assessed exploratory associations between oxygenation index and Hb concentration at admission and clinical outcomes. We used a generalized additive model (GAM) to evaluate the observed nonlinear relations and the classification and regression trees (CART) algorithm to assess the interaction effects. Results We included 550 patients, of which 52% were male. The median age was 57 years old, and the most frequent comorbidity was hypertension (29%). The median value of SpO 2 /FiO 2 was 424, and the median Hb concentration was 15 g/dL. The mortality was 15.1% (83 patients). Age, sex, and SpO 2 /FiO 2 , were independently associated with mortality. We described a nonlinear relationship between Hb concentration and neutrophil-to-lymphocyte ratio with mortality and an interaction effect between SpO 2 /FiO 2 and Hb concentration. Patients with a similar oxygenation index had different mortality likelihoods based upon their Hb at admission. CART showed that patients with SpO 2 /FiO 2 < 324, who were less than 81 years with an NLR >9.9, and Hb > 15 g/dl had the highest mortality risk (91%). Additionally, patients with SpO 2 /FiO 2 > 324 but Hb of < 12 g/dl and a history of hypertension had a higher mortality likelihood (59%). In contrast, patients with SpO 2 /FiO 2 > 324 and Hb of > 12 g/dl had the lowest mortality risk (9%). Conclusion We found that a decreased SpO 2 /FiO 2 increased mortality risk. Extreme values of Hb, either low or high, showed an increase in the likelihood of mortality. However, Hb concentration modified the SpO 2 /FiO 2 effect on mortality; the probability of death in patients with low SpO 2 /FiO 2 increased as Hb increased.

Association Between Hemoglobin-Albumin-Lymphocyte-Platelet Index and Mortality in Hospitalized COVID-19 Omicron BA.2 Infected Patients

“… 39 , 40 Moreover, low hemoglobin can affect the oxygen supply which exacerbates hypoxia due to lung injury in COVID-19 patients. 41 Consistent with previous studies, we found that hypoalbuminemia and low hemoglobin were related to poor OS in COVID-19 Omicron BA.2 infected patients.…”

COVID-19: The Development and Validation of a New Mortality Risk Score

“…A systematic review of 63 studies showed that severe SARS-CoV-2 infection is associated with lower Hb levels [35], and a study by Fan et al showed that 1.6% of SARS-CoV-2 patients admitted to the intensive care unit received blood transfusions for anemia correction [36]. Most studies, including ours, have shown that anemia is an independent predictor of mortality and that each unit of increase in Hb in COVID-19 patients enhanced the survival rate by 4% [30,37,38]. A meta-analysis based on risk factor-adjusted effect estimates indicated that anemia was independently associated with a significantly elevated risk for mortality among COVID-19 patients [39], while another study documented that in COVID-19 patients, anemia is both associated with a more pronounced baseline pro-inflammatory profile and a higher incidence of in-hospital mortality and severe disease [40].…”

“…Physiologically, anemic hypoxia induces general vasodilation, but also pulmonary vasoconstriction, with an increase in fibrin formation in lung microvasculature [29]. Indeed, patients with similar SpO 2 % were more likely to die when their Hb decreased below 12.1 g/dL [30]. SARS-CoV-2-related infection can also impair iron metabolism and reduce iron availability [31].…”

O2 Saturation Predicted the ICU Stay of COVID-19 Patients in a Hospital at Altitude: A Low-Cost Tool for Post-Pandemic

“…PO 2 S values of 92-93% were found in high-altitude COVID-19 survivors [2], equal to 94.2% (±7.9) in COVID-19 patients [10]. PO 2 S values ≥ 85% were also reported in a large number of high-altitude COVID-19 hospitalisations [3], a median of 90% (86-93) [14], an average of 88.2% (±3.3) [15], and a median of 90.5% (86.9-93.6) in patients in ICU for COVID-19 at high altitude, the latter being lower in those who died than in survivors [16]. With all this evidence, PO 2 S of between 89% and 93% was established as normative values at altitude, increasing patients' chances of COVID-19 survival [4].…”