Background: Acute respiratory distress syndrome (ARDS) is a severe respiratory manifestation
of COVID-19 disease associated with high mortality. The impact on outcomes of anemia (low
hemoglobin concentration), altered oxygen delivery, and use of transfusion in patients intubated
because of COVID-19 ARDS remain unclear. The objectives of this study were to explore the
association between low hemoglobin concentration, global oxygen delivery, use of transfusion,
and clinical outcomes in patients intubated because of COVID-19- ARDS.
Methodology: Retrospective monocentric study using clinical data recorded during the ICU stay
of intubated COVID-19 ARDS patients hospitalized during the first wave of the COVID-19
pandemic (2020) in the Adult ICU of the Lausanne University hospital (CHUV), Switzerland.
Results: Fifty-five patients (41 men -74.5%- and 14 women -25.5%-) were included in the present
study. They were 65.0 [57,5, 72.0] years old and had a median body mass index of 26.9 [24.1,
30.4] kg/m2
. At day of intubation the majority of the COVID-19 ARDS patients did not have low
hemoglobin [Hb] levels. The median [Hb] at that time was 126.0 [114.2, 137.5] g/L. The patients
experienced a progressive decrease of hemoglobin concentration during mechanical ventilation.
In parallel, a decrease in oxygen delivery (DO2) was observed. Low hemoglobin levels were not
associated with ICU mortality but with prolonged duration of mechanical ventilation. Oppositely,
DO2 was not correlated with outcome. Around 25.5% of patients received at least one transfusion
during the ICU stay, which did not significantly impact ICU mortality, even if a trend toward an
increase in mortality (57.1% vs 29.3%, p-value = 0.0612) was observed. Transfused patients
stayed longer in the ICU compared to non-transfused patients (29.5 [24.8, 36.8] days vs 12.8 [6.2,
18.3] days, p < 0.05) and had prolonged durations of mechanical ventilation (23.5 [20.0, 33.7]
days vs 10.3 [4.8, 14.1] days, p < 0.05). Baseline characteristics of the transfused and non-
transfused patients were similar. However, during the ICU stay, the transfused patients received
noradrenaline during more days and were also more often tracheostomized during the ICU stay.
The use of veno-venous extracorporeal membrane oxygenation (VV-ECMO) was also more
frequent in the transfused patients. The median [Hb] at the time of transfusion was 88 [81, 100]
g/L.
Conclusion: In our retrospective study, COVID-19 ARDS patients were not anemic at admission
but showed a progressive decrease in hemoglobin concentration over time. Low hemoglobin level
was not associated with ICU mortality but with increased duration of mechanical ventilation. DO2
was oppositely not correlated with outcome. Transfusion was used frequently and for higher [Hb]
thresholds than usually recommended. Transfused patients stayed longer under mechanical
ventilation and in the ICU. Despite similar admission characteristics, they however probably were
more severely ill. Our study suggests that factors other than hemoglobin levels (i.e. comorbidities
or illness severity) probably play an important role in patient outcomes. Further investigations are
necessary to understand the complex relationship between anemia, transfusion, and outcomes
in COVID-19 ARDS patients.