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
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.
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This study determined the relationships of metabolic acidosis, cortical oxygen pressure, and striatal extracellular dopamine in the brain of newborn piglets. After a baseline period of 120 minutes, a 0.6 N HCl solution was infused intravenously to decrease the blood pH to about 7.0-7.05. The metabolic acidosis was then corrected by injecting sodium bicarbonate and measurements were continued for one hour. ⋯ The extracellular dopamine increased to 1270% of the control on the end of HCl injection. Infusion of bicarbonate to correct the acidosis resulted in an increase of cortical oxygen and progressive decline of dopamine in the extracellular medium. It is suggested that the level of extracellular dopamine in the striatum of newborn piglets was not directly affected by decrease in pH but was dependent on changes in tissue oxygen pressure during metabolic acidosis.
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Detecting uptake or production of "metabolic acid" by a given tissue is often of interest. [Base excess] ([BE]) is the change in [strong acid] or [strong base] needed to restore pH to normal at normal PCO2. However, [BE] seems to have the potential for minor inaccuracy during hypercarbia, and venous blood is hypercarbic relative to arterial. Another approach is [strong ion difference] ([SID]), where a strong ion is one that is always dissociated in solution, and where [SID] = [strong cation] - [strong anion]. ⋯ An alternative approach to acid-base analysis is strong ion difference (SID) where a strong ion is one that is always dissociated in physiologic solution. [SID] can usually be approximated as: [Na+] + [K+] - [Cl-] - [La-]. Although [BE] does not equal [SID], a change in [BE] must always accompany a change in [SID], and vice-versa. While the [SID] approach is tedious, and often unnecessarily so, [SID] ca
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A new near infrared reflectance spectroscopy based technology (MULTISCAN OS 10/30) for non-invasive measurements of tissue oxygenation allows detection of absolute tissue hemoglobin concentration and saturation values in real time. ⋯ MULTISCAN OS 10/30 is a new and useful tool for in vivo characterization of oxygen and cytochrome in healthy and tumor tissues. In many clinically relevant situations oxygen measurements can be helpful and support the clinical routine diagnostics.