ABSTRACT
BACKGROUND: For many drugs, dosing scalars such as ideal body weight (IBW) and lean body mass are recommended over the use of total body weight (TBW) during weight-based dose calculations. Doses based on TBW are frequently used, and this may cause under- or over-dosing. Because dexmedetomidine (DEX) overdosing could increase the incidence of side effects, and spinal anesthesia may increase sensitivity to a sedative agent, determining an appropriate dose is critical. METHODS: Eighty patients were randomly divided into 2 groups, the IBW and TBW groups. Patients received a loading dose of DEX 1 µg/kg IBW or TBW for 10 min, followed by a continuous infusion at 0.5 µg/kg/h IBW or TBW after the induction of spinal anesthesia. The patients' vital signs, bispectral index (BIS), peripheral capillary oxygen saturation, time to reach a BIS of 80, airway obstruction score, and coughing were monitored and recorded at 0, 10, 30, and 50 min after the start of the loading dose injection. RESULTS: The changes in BIS, airway obstruction score, the incidence of side effects, and time to reach a BIS of 80 did not show statistically significant differences between the two groups. However, airway obstruction and/or coughing occurred in both groups, and the average BIS in both groups was lower than the target BIS of 60-80 at 30 and 50 min. CONCLUSIONS: A loading dose of DEX 1 µg/kg for 10 min, and a maintenance dose of DEX 0.5 µg/kg/h of either IBW or TBW, may induce excessive sedation, airway obstruction, and/or coughing under spinal anesthesia.