According to Gravlee, how should pH management during DHCA be conducted during cooling and warming phases?

The correct choice indicates that during deep hypothermic circulatory arrest (DHCA), pH management should utilize a pH-stat approach during the cooling phase and an alpha-stat approach during the warming phase.

In the cooling phase of DHCA, using a pH-stat strategy allows for the maintenance of physiological pH levels within the body. This approach is beneficial because it helps to preserve cerebral function during the critical time when the body's metabolic processes are slowed due to hypothermia. By maintaining a normal pH and thus allowing more CO2 to be retained, the blood's acid-base balance is managed in a way that enhances cerebral perfusion.

As the body is warmed during the rewarming phase, shifting to an alpha-stat strategy is optimal. This method takes into account temperature changes and aims to maintain a constant pH at physiological temperatures, correcting for the effects of hypothermia on blood gas values. This transition is key to ensuring that the metabolism of tissues, especially in the brain, normalizes as they are warmed back to body temperature. By not allowing the pH to change in response to the temperature increase, the perfusionist can better manage and anticipate the metabolic requirements of the brain as it resumes normal activity.

The combination of these