Clonidine premedication prevents preoperative hypokalemia

Study Objective: To test the hypothesis that clonidine premedication could prevent an increase of plasma epinephrine occurring as a result of anxiety, and a decrease of the serum potassium (K+) levels before the induction of anesthesia. Design: Randomized, double-blinded study.Setting: University Hospital of Seoul. Patients: 44 ASA physical status I and II patients, aged 20 to 50 years, scheduled for knee, ear, or nose surgery.Intervention: 44 patients were randomly allocated into one of two groups: 22 patients (clonidine group) received clonidine 300 μg orally at 120 minutes before the induction of anesthesia. The other 22 patients (control group) received a placebo. Measurements and Main Results: Anxiety level, serum K+, and plasma epinephrine were measured at an outpatient clinic, and immediately before the induction of anesthesia. There were no differences between groups in degree of anxiety experienced, serum K+, or plasma epinephrine levels as measured at the out-patient clinic. Immediately before the induction of anesthesia, the serum K+ levels of the clonidine group were higher than those of the control group (3.89 ± 0.26 mEq/L vs. 3.50 ± 0.36 mEq/L), and anxiety and plasma epinephrine levels of clonidine group were lower than those of the control group (p < 0.05). The frequency of hypokalemia (K+ ≤ 3.5 mEq/L) of the clonidine group immediately before the induction of anesthesia was significantly lower than that of the control group (0% vs. 50%). Conclusions: Clonidine premedication was effective in preventing hypokalemic episodes occurring before the induction of anesthesia.