Oxygen delivery and consumption in the microcirculation after extreme hemodilution with perfluorocarbons

Abstract

Intaglietta. Oxygen delivery and consumption in the microcirculation after extreme hemodilution with perfluorocarbons. Am J Physiol Heart Circ Physiol 287: H320 -H330, 2004; 10.1152/ajpheart.01166.2003.-The oxygen transport capacity of fluorocarbons was investigated in the hamster chamber window model microcirculation to determine the rate at which oxygen is delivered to the tissue in conditions of extreme hemodilution [hematocrit (Hct) 11%]. Hydroxyethlyl starch (HES 200; 200 kDa molecular mass) was used as a plasma expander for two isovolemic hemodilutions performed with 10% HES 200 until a Hct of 65%. A third step reduced the Hct to 75% of baseline and was performed with either HES 200 or a 60% perfluorocarbon (PFC) emulsion. Comparisons of HES 200-only-hemodiluted animals versus 4.2 g/kg PFC emulsion-hemodiluted animals were made at 21% and 100% normobaric oxygen ventilation. It was found that systemic and microvascular oxygen delivery was 25% and 400% higher in the PFC animals compared with HES 200 animals, respectively, showing that PFCs deliver oxygen to the tissue when combined with hyperoxic ventilation in the present experiments, with no evidence of vasoconstriction or impaired microvascular function. Oxygen ventilation (100%) led to a positive base excess for the PFC group (5.5 Ϯ 2.5 mmol/l) versus a negative balance (Ϫ0.8 Ϯ 1.4 mmol/l) for the HES 200 group, suggesting that microvascular findings corresponded to systemic events. hyperoxia; functional capillary density; oxygen-carrying capacity; blood substitutes; tissue oxygen delivery THE CORRECTION OF BLOOD LOSSES usually begins with the normalization of blood volume. The continued decrease of red blood cell (RBC) concentration is followed by the restoration of oxygen-carrying capacity. To date, this latter phase remains firmly within the purvey of blood transfusion medicine; however, alternative oxygen-carrying volume fluids such as modified hemoglobins (Hbs) and fluorocarbons have emerged in the past decade. Few of these materials have been objectively analyzed in terms of their transport properties at the level of the microscopic blood vessels, where the actual exchange of oxygen takes place, to determine if their properties lead to adequate transport processes at the cellular/tissue level (8).Fluorocarbons have been investigated by different approaches that extended to phase 3 clinical trials (9). These materials carry oxygen, are synthetic, and, in principle, are available in very large quantities at modest costs. This has tantalized investigators, medical practitioners, and business enterprises, because it could, in principle, lead to a convenient, largely available, and pathogen-free oxygen carrier. However, fluorocarbons only become miscible with water when emulsified with phospholipids (derived from egg yolk) and therefore are not completely synthetic. Furthermore, whereas Hb carries oxygen via a reversible chemical reaction, fluorocarbons carry oxygen as a function of their solubility; therefore, at the PO 2 s prevailing in the microcirc...

Effects of extreme hemodilution with hemoglobin-based O2 carriers on microvascular pressure

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Modulation of Perfusion and Oxygenation by Red Blood Cell Oxygen Affinity during Acute Anemia

“…This protocol was described in detail in our previous reports (14)(15)(16). Briefly, the volume of each exchange-transfusion step was calculated as a percentage of the blood volume (BV), estimated as 7% of body weight (BW).…”

Effects of erythrocyte flexibility on microvascular perfusion and oxygenation during acute anemia

“…This protocol was described in detail in our previous reports (6,8,42). Briefly, the volume of each exchange-transfusion step was calculated as a percentage of the blood volume (BV), estimated as 7% of body weight (BW).…”