Blood Volume Assessment in COVID-19 and Bacterial Sepsis

Acute respiratory failure related to infection by the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), is the main reason for ICU admission in in the majority of patients admitted to the ICU in this viral syndrome, and it presents a significant clinical challenge. Severe hypoxemia in these patients is thought to be related in part to generation of alveolar edema. This would be related to the specific infection related injury of the alveoli-capillary membrane, however other factors could be related to edema formation. Although patients meet criteria for the Acute Respiratory Distress Syndrome (ARDS), there is significant controversy about whether the lungs of the COVID-19 patients have the characteristics of ARDS and thus whether the treatment should mimic treatment of ARDS due to other causes. A general principle in ARDS patients is to avoid positive fluid balances as this may contribute to alveolar edema. Also, the guidelines on the management of COVID-19 patients by the Society of Critical Care Medicine advocate a conservative fluid strategy. However, uncorrected hypovolemia may result in additional organ dysfunction (especially kidney injury). The clinical fluid status is usually estimated by the presence of peripheral edema and daily fluid balances and thus prone to errors as these are poorly related to the circulating blood volume. Management of patients with sepsis based on blood volume measurements and red blood cell volume, to disclose true anemia, has been shown to improve outcome. Finally, the transudation of albumin in the extravascular space has been shown to be associated with outcome of critically ill patients. It is highly plausible that these parameters could help guide the care of COVID-19 patients given the available data in the literature, thus promoting better treatment of these patients.

This is a prospective multicenter study where the treatment team is blinded to the results of the study. The primary objective of the study is to describe the blood volume, the volume of blood components, the capillary leak and parameters of cardiac performance, lung edema and sublingual microcirculatory perfusion and their trajectory during the early phase of hospitalization of patients with SARS-CoV-2 or bacterial infection.

Inclusion criteria

• Confirmed SARS-CoV-2 or bacterial infection
• Patient admitted to the ICU
• Patient age is between 18 and 95 years
• Patent peripheral or central venous line from which blood draws can be made and through which the 131I bolus can be administered
• Arterial catheter considered indicated by primary team caring for the patient

Exclusion criteria

• Refused informed consent to participate in the study
• Pregnant or possible pregnant women
• Patient unlikely to survive more than 72h
• Patient with life sustaining treatment limitations (use of renal replacement therapy)
• Patient already on or likely to be placed on extra-corporeal membrane oxygenation support within 48h after admission
• Known allergy to iodine or iodinated 131I albumin
• Patients with chronic renal failure requiring renal replacement therapy