Changes of P50 during Hypothermia for Cardiopulmonary Bypass Surgery / 대한마취과학회지

ABSTRACT

Hemodilution and hypothermia during extracorporeal circulation for open heart surgery affect the oxygen-carrying capacity to the tissue and hemog)obin affinity for oxygen. P50, as an indicator of alteration of hemoglobin affinity, is dependent on the temperature, pH, PCO2 concentration of 2, 3-DPG and type of hemoglobin, and thus it changes with the shift of the oxyhemoglobin dissociation curve to the right or left. We took the blood samples during 3-different stages of cardiopulmonary bypass in 23 patients who underwent open heart surgery; stage I(before chest incision), stage II(during hypothermia), stage III(after chest closure) and measured the level of arterial blood gas and the value of P50 The results were as follows 1) At the uncorrected temperature, the value of the P50 in stage II(24.80+/-2.06 mmHg) showed a significant decrease compared to the stage I(28.23+/-2.56 mmHg) (P<0.05), but this value was almostly in the normal range. 2) At the corrected temperature, the value of the P50 in stage II(18.59+/-1.88mmHg) showed also a significant decrease compared to the stage I(26.71+/-2.92mmHg) (P<0.01), and increased to the normal range after rewarming. 3) At the uncorrected temperature, arterial PO2 in stage II(380.18+/-48.86mmHg) showed a significant increase compared to stage I(237.62+/-29.20mmHg), which suggested that the increase of the PO was resulted from the effect of the increased FiO2 despite lowered body temperature, while PCO was decreased due to lowered body temperature.