Therapeutic hypothermia results in a shift of the oxygen dissociation curve to the:

• A. Left
• B. Right
• C. No Shift
• D. Undetermined

Answer: (A)

Cooling lowers hemoglobin’s affinity for oxygen, so the oxygen dissociation curve shifts to the left. This leftward shift means a lower P50 and higher HbO2 saturation at a given partial pressure of oxygen, so oxygen loading in the lungs is favored. However, unloading to tissues becomes less efficient until warmth returns. Factors that cause a rightward shift (temperature rise, acidosis, high CO2, increased 2,3-BPG) favor tissue oxygen delivery, whereas unchanged conditions would not explain the effect of cooling.