Using the rabbit ear chamber (REC) method, the author compared the effect of hypocapnia and that of normocapnia on cutaneous microcirculation of rabbits. Eight rabbits, weighting 3-4kg, were used for this study, which were anesthetized with pentobarbital and pancuronium. To maintain PaO₂ at 100-150mmHg and PaCO₂ at 20-25mmHg (HYPOCAPNIC GROUP), they were mechanically ventilated with air-O₂ and regulated. After observing the circulation of arteriole during hypocapnia for 15-20 minutes, to induce normocapnia, 100% CO₂ was added to the inspired gas stepwise until PaCO₂ reached 35-45mmHg (NORMOCAPNIC GROUP). And the circulationof arteriole was observed during normocapnia for 15-20 minutes.
No significant changes were observed in the blood pressure, heart rate and pulse pressure. However, significant change was observed in pH. During hypocapnia, the diameter, blood-flow velocity and blood-flow rate of the arterioles were markedly reduced (p<0.05).
This study using REC has shown that hypocapnia causes cutaneous microcirculatory changes and increase systemic vascular resistance.

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The effects of contrast media (CM) on the filterability and morphology of human red blood cells (RBCs) were investigated by testing the impact of CM partition coefficient, as well as CM osmolality and viscosity, using a recently developed nickel mesh filtration method and a differential interference contrast microscope. The low-osmolality CM, iomeprol and iohexol, and the recently synthesized isotonic CM, iotrolan were studied. Among them, the partition coefficient (l-butanol/water) of iotrolan was the smallest; i. e., iomeprol (0.105)>iohexol (0.082)>>iotrolan (0.005). RBCs suspended in iomeprol or iohexol revealed a marked decrease in filterability and several stages of echinocytic shape changes with an increase in incubation time, CM concentration and experimental temperature; the impact of iomeprol was stronger than that of iohexol. However, at the same CM concentration, iotrolan caused very small decrease in filterability and little shape changes even with incubation for 60 minutes at 36°C. The results strongly suggest that the difference of the impact of CM on RBC rheology may arise from the difference of CM partition coefficient. Thus, it can be concluded that CM partition coefficient, as well as CM osmolality and viscosity, is a predominant factor that exerts direct influences on RBC rheology.

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