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Blood osmolality in vitro: dependence on base addition, buffer value, and temperature.
Journal of Applied Physiology (Bethesda, Md. : 1985)
|June 1, 1987
Summary
Blood osmolality increases with CO2 levels due to gas absorption. Factors like temperature and hemoglobin affect this, with base infusions requiring careful consideration of osmotic effects.
Area of Science:
- Physiology
- Biochemistry
Background:
- Blood osmolality (Osm) is influenced by carbon dioxide (CO2) levels.
- Understanding these changes is crucial for physiological and therapeutic contexts.
Purpose of the Study:
- To investigate how NaOH addition, equilibration temperature, and hemoglobin concentration affect blood osmolality changes related to CO2.
- To evaluate the osmotic impact of therapeutic base infusions.
Main Methods:
- Utilized freezing-point determination in true plasma.
- Measured blood osmolality under varying conditions of PCO2, NaOH addition, temperature, and hemoglobin concentration.
Main Results:
- NaOH addition increased Osm by 2 mosmol/kg H2O per mmol base at constant PCO2, with further increases due to respiratory pH compensation.
- Elevating equilibration temperature decreased Osm by 0.5 mosmol/kg H2O per degree C at constant pH.
- The slope of Osm vs. pH during CO2 equilibration increased with hemoglobin, indicating a direct relationship with nonbicarbonate buffer value.
Conclusions:
- Respiratory compensation of pH changes significantly impacts blood osmolality.
- Equilibration temperature and hemoglobin concentration are key modulators of CO2-related osmolality shifts.
- The delta Osm/delta pH quotient may estimate whole-body nonbicarbonate buffer value; therapeutic base infusions warrant caution due to osmotic effects.