Study Status: Completed
Recruit Status: Completed
Study Type: Interventional
Official Title: Hypokalemia and Intravenous Patient Controlled Analgesia
Brief Summary: The increase in stress hormone level and hyperventilation caused by the postoperative pain may contribute to the development of hypokalemia during postoperative period. Therefore, if the postoperative pain is well controlled by the IV-PCA,the plasma potassium level during the postoperative period may be not affected by stress response. The researchers tried to investigate the effect of IV-PCA on potassium regulation during the postoperative period.