Blood gases. Alfa-stat and pH-stat strategies during CPB.
Maintain arterial oxygen level not higher than 250 mmHg and less than 85 mmHg. Some clinical perfusions for cardiac surgery are performed at normothermia (≈37°C) and others at various levels of hypothermia: mild (30°C-35°C), moderate (25°C-30°C), or deep ( less than 25).Therefore, it is necessary to consider the strategy for controlling PaCO2 and, indirectly, pH. The alpha-stat strategy is based on using the pH measured at 37°C and uncorrected for the temperature of the patient’s blood, and maintaining this level at pH 7.4. That is, the ventilation of the oxygenator is maintained at the level appropriate for a body temperature of 37°C, no matter how low the temperature. This hyperventilation during hypothermia results in a decrease in PaCO2 and an increase in pH when the values for these are corrected for the temperature of the patient’s blood. Swan and Reeves and Rahn and colleagues have all emphasized that at low temperatures, neutra...