Hypertensive patients receiving nonselective β-adrenergic antagonists are vulnerable to hypertension and bradycardia when injected with dental local anesthetic formulations containing epinephrine. Dexmedetomidine (DEX), an α2-adrenergic agonist, has been reported to prolong and enhance the local anesthetic effects of lidocaine. The cardiovascular effects of the DEX-lidocaine combination have not yet been investigated in the presence of nonselective β-adrenergic antagonists. Therefore, we assessed the cardiovascular effects of the DEX-lidocaine combination in spontaneously hypertensive rats (SHR) treated with a nonselective β-adrenergic antagonist (propranolol). We injected propranolol-treated rats with various concentrations of DEX alone, 100 μg/kg epinephrine alone, or 5 μg/kg DEX combined with 2% lidocaine and measured their blood pressure (BP) and heart rates (HR) to assess the cardiovascular effects. The BP of propranolol-treated SHR was significantly increased by treatment with 100 μg/kg epinephrine alone. The BP and HR of propranolol-treated SHR were not significantly changed by treatment with low concentrations of DEX, but they were significantly decreased by treatment with a high concentration of DEX (50 μg/kg). Moreover, there was no significant difference in the BP and HR of propranolol-treated SHR after the injection of a combination of 5 μg/kg DEX and 2% lidocaine. Thus, the DEX-lidocaine combination may be an acceptable addition to dental local anesthetic solutions from a cardiovascular standpoint for hypertensive patients receiving nonselective β-adrenergic antagonists.
Measurement of the blood pressure (BP) and heart rate (HR) of rats using a sphygmomanometer. The rats were warmed to 37°C to 38°C using a cylinder thermostat and placed in a restrainer. The sphygmomanometer cuff was placed around the tail of each rat to measure the BP and HR.
A schematic depicting the experimental schedule. Propranolol (10 mg/kg) was injected intraperitoneally 15 minutes prior to the experiments. The systolic blood pressure (SBP), diastolic blood pressure (DBP), and heart rate (HR) were measured by placing the sphygmomanometer cuff around the tail of each rat. The baseline values were recorded as control values 5 minutes prior to the experiments. The SBP, DBP, and HR were also monitored immediately after the injection of normal saline, dexmedetomidine (DEX; 0.5, 5, or 50 μg/kg) alone, 100 μg/kg epinephrine alone, or 5 μg/kg DEX combined with 2% lidocaine and every 5 minutes thereafter for 30 minutes.
Cardiovascular effects of treatment with normal saline (NS; n = 10), dexmedetomidine (DEX; 0.5, 5, or 50 μg/kg; n = 10 for each experiment) alone, 100 μg/kg epinephrine (n = 10) alone, or 5 μg/kg DEX combined with 2% lidocaine (n = 10) on propranolol-treated hypertensive rats. White circles represent the NS group; black circles represent the 0.5 μg/kg DEX (0.5D) group; black triangles represent the 5 μg/kg DEX (5D) group; black squares represent the 50 μg/kg DEX (50D) group; black diamonds represent the 100 μg/kg epinephrine (Epi) group; white squares represent the 5 μg/kg DEX combined with 2% lidocaine (5DL) group.
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