Alpha stat usage statement

• A. It is performed at 37°C and favored when core temperature varies with environment
• B. It is performed at 25°C
• C. It is performed at 0°C
• D. It is performed at 37°C but not used for poikilotherms

Answer: (A)

Alpha-stat interprets arterial blood gas values using a fixed reference temperature of 37°C, so pH and pCO2 are not corrected for the patient’s actual temperature during bypass. This keeps the acid–base interpretation consistent with normal physiology and helps preserve cerebral autoregulation when core temperature is changing during cooling or rewarming. Because you’re not adjusting the ABG for how cold or warm the patient is, the approach remains stable even as temperature fluctuates, which is why it’s favored when core temperature varies with environment.

That’s why the statement describing it as being performed at 37°C and favored when core temperature varies best captures the concept. Interpreting ABG at cooler temperatures (or at 0°C) reflects a different strategy (pH-stat), and the claim that alpha-stat isn’t used for poikilotherms isn’t accurate.