A. Trouwborst

Cardiovascular Responses, Hemodynamics and Oxygen Transport to Tissue during Moderate Isovolemic Hemodilution in Pigs

In conclusion, in contrast to many reports obtained from dogs, in pigs the rise in CO during moderate isovolemic hemodilution is, besides the increased venous return, more induced by increased work performance of the heart and less by a decreased SVR. The rise in CO did not compensate for the decrease in oxygen transport capacity. Our results confirm most of the reported findings in humans at the same stage of hemodilution. Besides changes in hemodynamics, in our study a gradual decreased oxygen affinity of hemoglobin could be observed. That the pig animal model for studying hemodilution and oxygen transport to the tissue is more appropriate than the dog model is open to discussion.

Tissue Oxygenation by Fluorocarbons

Fluorocarbons have a very high solubility for oxygen and this was very dramatically shown by Clark and Gollan (1966), when they were able to demonstrate survival of mice completely immersed in these liquids for extended periods of time. The animals were able to obtain sufficient oxygen by respiring the liquid and after removal showed no apparent ill effects from the experience.

Hemodilution and Oxygen Transport

Several risks are associated with transfusion of homologous blood and blood products. The risk of alloimmunisation is well known. Transmission of viral infections from homologous blood transfusion (e.g. hepatitis, and especially AIDS) draw increasing the attention (Adler, 1984; Alter et al., 1972; Curran et al., 1984). In addition, it is suggested that transfusion of homologous blood promotes markedly increased tumor growth and growth of established metastases, and induces more postoperative infections, because blood transfusions exert a long-term (months) immunosuppressive action, increasing during the first week after transfusion (Schriemer et al., 1988; Waymack et al., 1989).

Regional Cardiac Hemodynamics and Oxygenation during Isovolemic Hemodilution in Anesthetized Pigs

Hemodilution causes a drop in hematocrit, thereby lowering the oxygen carrying capacity of blood, necessitating an increase in flow or an augmented oxygen extraction by the tissues to meet their oxygen demands. Under normal conditions the myocardial oxygen extraction is already high and the capacity to increase is limited. In the heart the decrease in arterial oxygen content during hemodilution therefore is mainly compensated by an increase in coronary flow. This increase in flow can be achieved by both reduction of the blood viscosity and coronary vasodilatation. The hemodynamic changes during hemodilution may increase myocardial oxygen consumption and, therefore, an even greater increase in coronary flow might be needed.

Comparative Study of the Accuracy of Two Fiberoptic Mixed Venous Saturation Catheters (Spectracath® vs Opticath®) during Acute Changes in Hematocrit and Cardiac Output in Humans

The mixed venous oxygen saturation of hemoglobin (SvO2) reflects, under many circumstances, the state of tissue oxygenation. Changes in cardiac output (CO), arterial oxygen content, and oxygen uptake by the tissue influence this parameter (Miller, 1982; Trouwborst et al., 1990a). Therefore continuous fiber optic monitoring of SvO2 has been developed. Due to scattering of the erythrocyte wall itself, however, sudden changes in hematocrit (Hct) might influence the reliability of SvO2 values, measured by such fiber optic systems (Martin et al., 1973). Two manufacturers claim that their system overcome this problem, one because of using three wavelengths (Opticath®) and the other using two wavelengths via one fiber but receiving backscattered light by two other fibers (Spectracath®). The manufacturers claim that with their systems the reliability of SvO2 measurements are not affected by sudden changes in Hct and that any change in Hct will not entail the need to update or recalibrate the device. In this study, during acutely induced hypervolemic hemodilution (Trouwborst et al., 1990b) followed by surgical blood loss and with no recalibration of the systems during the study period, the in vivo SvO2 values measured with the fiber optic devices were compared with the in vitro SvO2 values obtained with a multiwave length spectrophotometer.

Alterations in Oxyhemoglobin Dissociation Curve During Normoxic Acute Normovolemic Hemodilution

Shifts in the oxygen dissociation curve (O.D.C.) have been taken into account when studying oxygen delivery to tissue as a dependent factor of oxygen availability. It can be assumed that changes in the oxyhemoglobin dissociation characteristics of the blood will have a certain effect on the amount of oxygen available (1,2).

Role of Arachidonic Acid Metabolites in Pulmonary Oxygen Toxicity

Arachidonic acid metabolites have biologic properties that can mimic the pulmonary changes produced by hyperoxic exposure. They have potent vasoactive, bronchoactive, and chemoattractant properties, and can increase vascular permeability; all of these are features of hyperoxic lung injury.

Is Oxygen Consumption Measurement during Anesthesia for Liver Transplantation Valuable for a Rapid Assessment of Adequate Function of the Graft

Several metabolic tests have been used to estimate the initial function of the transplanted liver. Most of them are clearance tests of exogenous or endogenous substances. Hyperkalemia and hypoglycemia during the immediate postoperative period are signs for poor liver function, while decreases in lactate and amino-acids levels, indicate good transplant function (Shapiro et al., 1986). Unfortunately, measurements of these latter parameters are only available postoperatively. Therefore intraoperatively, other available parameters must be relied on. A persistent reperfusion hyperglycemia peroperatively seems to be an early prognostic sign for impaired graft function (Mallett et al., 1989).

Endotoxin Protection against Pulmonary Oxygen Toxicity and Plasma Prostaglandin Levels in the Rat

Exposure of rats to high concentrations of oxygen (greater than 95%) at 1 ATA pressure (101 kPa) is lethal within three days. Rats treated with a small dose of endotoxin are protected against these lethal effects of hyperoxia. Recently, we found that the lysine salt of acetylsalicylic acid antagonises this protective action of endotoxin. This suggests that prostaglandin metabolism plays an important role in the protective action of endotoxin against pulmonary oxygen toxicity. Therefore, we measured the plasma levels of 6KPGF1 alpha, a stable degradation product of prostacyclin (PGI2), PGE2 and thromboxane B2, the stable degradation product of thromboxane A2, in rats exposed to air or greater than 95% oxygen for 48 hours. We compared these with the plasma levels of rats treated with endotoxin (Salmonella typhimurium lipopolysaccharide 1 mg/kg) and exposed to air or greater than 95% oxygen for 48 hours. We found that exposure of rats to greater than 95% oxygen for 48 hours leads to a significant rise in the 6KPGF1 alpha levels. Rats exposed to greater than 95% oxygen for 48 hours and treated with endotoxin had significantly higher PGE2 and significantly lower 6KPGF1 alpha plasma levels than saline-treated rats exposed to greater than 95% oxygen for 48 hours.

The Ability of Perfluorochemicals to Provide Microcirculatory Oxygenation

Perfluorochemicals have recently become available in the form of oxygen-carrying plasma substitutes containing 20% or 35% (weight by volume) of perfluorocarbons respectively. These preparations are known as Fluosol-DA 20% and Fluosol-DA 35%. The composition of these products is shown in Table 1. They have a number of interesting properties in relation to their oxygen-carrying ability and their ability to penetrate the microcirculation. This paper will discuss some of these properties.