Adv Exp Med Biol
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Comparative Study
[Base excess] vs [strong ion difference]. Which is more helpful?
Blood [base excess] ([BE]) is defined as the change in [strong acid] or [strong base] needed to restore pH to normal at normal PCO2. Some believe that [BE] is unhelpful because [BE] may be elevated with a "normal" [strong ion difference] ([SID]), where a strong ion is one that is always dissociated in physiological solution, and where [SID] = [strong cations]-[strong anions]. Using a computer simulation, the hypothesis was tested that [SID] = [SID Excess] ([SIDEx]), where [SIDEx] is the change in [SID] needed to restore pH to normal at normal PCO2. ⋯ The idea was that hypoproteinemia caused the alkalosis, due to a deficiency of plasma weak acid buffer, necessitating increased [HCO3-]p to maintain electrical neutrality. How could [SID] be "normal," but [BE] increased? The purpose of the current exercise was to address this question. An [SID excess] ([SIDEx]) formula was developed, conceptually identical to Siggaard-Andersen's [BE], and [SID] was compared to [SIDEx] over the physiological range of plasma [albumin] ([alb]p), plasma [phosphate] ([Pi]p), and plasma pH (pHp).
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Comparative Study
Determination of the PCO2-dependent component of the H+ concentration in venous and arterial blood plasma.
In normal venous blood plasma, the regression line of [H+] plotted against the PCO2 was linear against the square root of PCO2. Sequential measurements in venous and arterial blood of PCO2 and [H+] showed that the venous-arterial (V-A) difference in [H+] was linearly related to the V-A difference in the square root of PCO2, the regression line having the same slope as that of the venous [H+] plotted against the square root of PCO2. ⋯ The PCO2-independent component, delta [H+], can then be given by subtracting [H+]* from the measured [H+]. The delta [H+] in venous blood agreed well with that in arterial blood with a correlation coefficient of 0.99, supporting the validity of the value of [H+]*.
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Comparative Study
Simultaneous assessment of cerebral oxygenation and hemodynamics during a motor task. A combined near infrared and transcranial Doppler sonography study.
During performance of a sequential finger opposition task we measured changes in regional cerebral blood oxygenation (rCBO) over the motor cortex and blood flow velocity changes (CBFV) in the middle cerebral artery in a combined near-infrared spectroscopy (NIRS) and transcranial Doppler Sonography (TCD) study. Stimulus duration was 60 followed by a 90 s rest period. ⋯ The time course of changes in [oxy-Hb] and CBFV were strikingly similar, showing a pronounced initial over-shoot. This study proves the feasibility of a simultaneous assessment of microcirculatory hemodynamics and cerebral oxygenation at high temporal resolution.