These studies were conducted to determine the influence of intravenous clonidine on the induction time of midazolam when used for induction of anesthesia and assoeiated hemodynamic effect. Eighty ASA physical status I or II patients were randomly allocated to one of four treatment groups ; normal saline (control, group 1, n=20), clonidine 1.25 ug/kg (group 2, n=20), clonidine 2.5 ug/kg (group 3, n=20), clonidine 5 ug/kg (group 4, n=20). The test drug was admi- nistered 15 min before induction of anesthesia with intravenous midazolam (0.23 mg/kg). After injection of midazolam, induction time (the time from the start of injection to spontaneous closing of eyes and to loss of eye-lash reflex) and apnea ratio were recorded as well as mean arterial pressure, heart rate and oxygen saturation at 3 min intervals up to induction of anesthesia and then at 1 min intervals for 10 min. Significant shortening in induction time were observed in clonidine groups (33+/-8 and 448 sec in group 2, 32+/-7 and 428 sec in group 3, 26+/-8 and 38+/-8 sec in group 4) compared with the control group (68+/-11, 83+/-11 sec in group 1), but there were no significant difference between clonidine groups. Mean arterial pressure and heart rate were significantly decreased by large dose of clonidine (group 3 and 4), but not changed by saline and small dose of clonidine (group 1 and 2). These results suggest that small dose (1.25 ug/kg) of clonidine shortened the induction time of midazolam and did not significantly affect the hemodynamics.
Anesthesia ; Apnea ; Arterial Pressure ; Clonidine* ; Heart Rate ; Hemodynamics ; Humans ; Midazolam* ; Oxygen