Adding Dexmedetomidine to Articaine Increases the Latency of Thermal Antinociception in Rats.

Articaine is a low-toxicity local anesthetic that is widely used in dentistry. Typically, epinephrine is added to prolong the duration of articaine local anesthesia; however, epinephrine exhibits adverse effects. Low-dose dexmedetomidine (DEX), an α2-adrenoreceptor agonist, reportedly prolongs local anesthesia without notable adverse cardiovascular effects. The purpose of this study was to assess whether a combination of low-dose DEX and articaine would provide a low-toxicity local anesthetic option for dental procedures without adverse cardiovascular effects. Thus, this study investigated whether DEX could prolong the local anesthetic effect of articaine using a rat model of pain. Adult male Wistar rats (N = 44; 11 per group) received a 50-µL subcutaneous injection into the plantar surface of the hind paws; injections were composed of either normal saline, 4% articaine (2 mg articaine), combined 5 µg/kg DEX and 4% articaine (1.25 µg DEX + 2 mg articaine), or combined epinephrine (1:100,000) and 4% articaine (0.9 µg epinephrine + 2 mg articaine). Subsequent acute pain perception was determined by paw withdrawal movement in response to infrared radiant heat stimulation of the plantar region. Paw withdrawal latency was tested at 5-minute intervals. Paw withdrawal latency values at 35 and 40 minutes were 3.83 ± 1.76 and 3.29 ± 1.43 seconds for articaine alone, 7.89 ± 2.72 and 7.25 ± 3.37 seconds for DEX and articaine, and 8.95 ± 2.28 and 8.17 ± 3.01 seconds for epinephrine and articaine. DEX prolonged the paw withdrawal latency of articaine for up to 35 minutes (p = .015) but not 40 minutes after injection (p = .052) when compared to articaine alone. The combination of DEX and articaine can provide effective local anesthesia for up to 35 minutes after injection.

Are Wireless Electronic Stethoscopes Useful for Respiratory Rate Monitoring During Intravenous Sedation?

PURPOSE: Wireless stethoscopes can measure respiratory rate noninvasively and continuously, but there are no reports of their use during dental treatment. This study evaluated the usefulness of wireless stethoscopes during dental procedures requiring intravenous sedation (IVS). MATERIALS AND METHODS: This study was a prospective cohort study. The study sample consisted of dental patients who received IVS by propofol or midazolam administration at the Nippon Dental University Hospital (Tokyo, Japan). The predictor was respiratory rate measured using the wireless stethoscope (BrRR), and the outcome variable was respiratory rate measured during capnography (RR). Pearson correlation coefficients and paired-samples t tests were used for data analysis. A P value less than .05 was considered statistically significant. RESULTS: The study sample consisted of 12 patients. BrRR and RR were significantly and positively correlated (r = 0.93, P < .01). The mean ± standard deviation of BrRR was 14.16 ± 2.67 and that of RR was 14.32 ± 2.77. There was no significant difference between the 2 groups (P = .27). CONCLUSIONS: The results of this study suggest that wireless stethoscopes are suitable for monitoring respiratory rate during dental procedures requiring IVS because their use is as accurate as capnography.

A Combination of Dexmedetomidine and Lidocaine Is a Cardiovascularly Safe Dental Local Anesthetic for Hypertensive Rats Treated With a Nonselective ß-Adrenergic Antagonist.

Hypertensive patients receiving nonselective ß-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 ß-adrenergic antagonists. Therefore, we assessed the cardiovascular effects of the DEX-lidocaine combination in spontaneously hypertensive rats (SHR) treated with a nonselective ß-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 ß-adrenergic antagonists.

Dexmedetomidine Increases the Latency of Thermal Antinociception in Rats.

Recent reports have stated that dexmedetomidine (DEX), an α2-adrenoreceptor agonist, enhances the local anesthetic effects of ropivacaine and prolongs its effective duration. However, little is known about the effect of a combination of DEX and lidocaine on anesthetic duration. Therefore, we investigated whether DEX can prolong the local anesthetic effect of lidocaine, using the thermal paw withdrawal test in Wistar rats in order to measure local anesthetic duration. We subcutaneously injected 50 µL of either normal saline, 2% lidocaine, a combination of 0.5 µg/kg DEX and 2% lidocaine, or a combination of 2% lidocaine with 1:80,000 epinephrine into the plantar surface of the left hind paw of the rats. The plantar region was stimulated using heat. We measured the perceived acute pain according to paw movement in response to stimulation. We found DEX significantly prolonged the paw withdrawal latency of lidocaine. Moreover, we found that DEX can prolong the local anesthetic duration of lidocaine as much as 1:80,000 epinephrine, up to 35 minutes after injection. In conclusion, this study concluded that a combination of DEX and lidocaine may be useful as a local anesthetic, similar to a combination of epinephrine and lidocaine, for short procedures.