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.

Intravenous patient controlled analgesia(IV-PCA) has been widely used to control postoperative pain. The increase in stress hormone level and hyperventilation caused by the postoperative pain may contribute to the development of hypokalemia during postoperative period. Hypokalemia is a risk factor for postoperative arrhythmia. 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, and the incidence of hypokalemia may be reduced. The researchers tried to investigate the effect of IV-PCA on potassium regulation during the postoperative period.

The researchers divided the patients undergoing laparoscopic cholecystectomy into two groups of IV-PCA group and control group. The researchers compared the plasma potassium concentration from the preoperative to postoperative period.

Inclusion Criteria:

• Patients undergoing laparoscopic cholecystectomy
• ASA class I or II

Exclusion Criteria:

• Any patients with plasma aldosterone, or glucocorticoid disorder including primary hyperaldosteronism, renovascular hypertension, rennin-secreting tumor, salt-wasting renal disease, Cushing syndrome
• Patients with recent exogenous steroid administration or previous diuretics therapy