Anesthesia and Critical Care Reviews and Commentary (ACCRAC) Podcast Episode 20: pH Stat and Alpha Stat
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Nov 20, 2016 Dive into the intriguing world of anesthesia techniques with a focus on pH Stat and Alpha Stat methods. These techniques are vital for managing blood gases in hypothermic patients during cardiac surgery. Learn how they impact CO2 levels and pH, especially with fluctuating temperatures. The discussion highlights crucial implications for cerebral blood flow in both adult and pediatric patients, making it a must-listen for those interested in critical care and surgical anesthesia.
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Physiology of CO2 and pH in Hypothermia
- Cooling causes more CO2 to dissolve in blood while the blood's PCO2 actually drops.
- Blood pH increases (alkaline shift) because of decreased weak acid dissociation as temperature drops.
Blood Gas Analyzer Always Heats to 37°C
- Blood gas analyzers heat blood samples to 37°C regardless of the patient's actual temperature.
- This warming normalizes PCO2 readings, obscuring the true lower PCO2 in hypothermic patients.
pH Stat Increases Cerebral Blood Flow
- pH stat management back-calculates pH and PCO2 to the patient’s actual temperature.
- Adding CO2 to reach normal pH at low temperature increases cerebral blood flow by raising PCO2.