Effect of Injection Pressure of Infiltration Anesthesia to the Jawbone.

To obtain effective infiltration anesthesia in the jawbone, high concentrations of local anesthetic are needed. However, to reduce pain experienced by patients during local anesthetic administration, low-pressure injection is recommended for subperiosteal infiltration anesthesia. Currently, there are no studies regarding the effect of injection pressure on infiltration anesthesia, and a standard injection pressure has not been clearly determined. Hence, the effect of injection pressure of subperiosteal infiltration anesthesia on local anesthetic infiltration to the jawbone was considered by directly measuring lidocaine concentration in the jawbone. Japanese white male rabbits were used as test animals. After inducing general anesthesia with oxygen and sevoflurane, cannulation to the femoral artery was performed and arterial pressure was continuously recorded. Subperiosteal infiltration anesthesia was performed by injecting 0.5 mL of 2% lidocaine containing 1/80,000 adrenaline, and injection pressure was monitored by a pressure transducer for 40 seconds. After specified time intervals (10, 20, 30, 40, 50, and 60 minutes), jawbone and blood samples were collected, and the concentration of lidocaine at each time interval was measured. The mean injection pressure was divided into 4 groups (100 ± 50 mm Hg, 200 ± 50 mm Hg, 300 ± 50 mm Hg, and 400 ± 50 mm Hg), and comparison statistical analysis between these 4 groups was performed. No significant change in blood pressure during infiltration anesthesia was observed in any of the 4 groups. Lidocaine concentration in the blood and jawbone were highest 10 minutes after the infiltration anesthesia in all 4 groups and decreased thereafter. Lidocaine concentration in the jawbone increased as injection pressure increased, while serum lidocaine concentration was significantly lower. This suggests that when injection pressure of subperiosteal infiltration anesthesia is low, infiltration of local anesthetic to the jawbone may be reduced, while transfer to oral mucosa and blood may be increased.

Lidocaine Concentration in Oral Tissue by the Addition of Epinephrine.

The vasoconstrictive effect due to the addition of epinephrine to local anesthetic has been clearly shown by measuring blood-flow volume or blood anesthetic concentration in oral mucosal tissue. However, there are no reports on the measurement of anesthetic concentration using samples directly taken from the jawbone and oral mucosal tissue. Consequently, in this study, the effect of lidocaine concentration in the jawbone and oral mucosal tissue by the addition of epinephrine to the local anesthetic lidocaine was considered by quantitatively measuring lidocaine concentration within the tissue. Japanese white male rabbits (n = 96) were used as test animals. General anesthesia was induced by sevoflurane and oxygen, and then cannulation to the femoral artery was performed while arterial pressure was constantly recorded. Infiltration anesthesia was achieved by 0.5 mL of 2% lidocaine containing 1 : 80,000 epinephrine in the upper jawbone (E(+)) and 0.5 mL of 2% of epinephrine additive-free lidocaine (E(0)) under the periosteum. At specified time increments (10, 20, 30, 40, 50, and 60 minutes), samples from the jawbone, oral mucosa, and blood were collected, and lidocaine concentration was directly measured by high-performance liquid chromatography. No significant differences in the change in blood pressure were observed either in E(+) or E(0). In both E(+) and E(0) groups, the serum lidocaine concentration peaked 10 minutes after local anesthesia and decreased thereafter. At all time increments, serum lidocaine concentration in E(+) was significantly lower than that in E(0). There were no significant differences in measured lidocaine concentration between jawbone and mucosa within either the E(+) or the E(0) groups at all time points, although the E(0) group had significantly lower jawbone and mucosa concentrations than the E(+) group at all time points when comparing the 2 groups to each other. Addition of epinephrine to the local anesthetic inhibited systemic absorption of local anesthetic into the blood such that a high concentration could be maintained in the tissue. Epinephrine-induced vasoconstrictive effect was observed not only in the oral mucosa but also in the jawbone.

Intravenous sedation for implant surgery: midazolam, butorphanol, and dexmedetomidine versus midazolam, butorphanol, and propofol.

We compared the amnesic action, recovery process, and satisfaction of patients and surgeons after the use of 2 different sedation regimens for 40 patients undergoing scheduled implant surgery. Butorphanol, midazolam, dexmedetomidine (BMD) was administered to 20 patients who were maintained with continuous infusion of dexmedetomidine after the induction with butorphanol and midazolam, and butorphanol, midazolam, propofol (BMP) was administered to 20 patients who were maintained with continuous infusion of propofol after the induction with butorphanol and midazolam. To assess the amnesic action, the memory of local anesthesia, auditory memory, and visual memory were evaluated. The Trieger Dot Test (TDT) was applied during the recovery process. A questionnaire regarding the patient's feelings of the management of sedation was taken from each patient and was also filled out by the surgeon. The comparison between groups was analyzed by the Mann-Whitney U test. No significant differences in the amnesic action and the TDT were noted. Both methods also satisfied the patients and surgeons, as determined by the questionnaire results. In conclusion, both sedation regimens are appropriate for implant surgery.

Lidocaine concentration in mandibular bone after subperiosteal infiltration anesthesia decreases with elevation of periosteal flap and irrigation with saline.

It has been reported that the action of infiltration anesthesia on the jawbone is attenuated significantly by elevation of the periosteal flap with saline irrigation in clinical studies; however, the reason is unclear. Therefore, the lidocaine concentration in mandibular bone after subperiosteal infiltration anesthesia was measured under several surgical conditions. The subjects were 48 rabbits. Infiltration anesthesia by 0.5 mL of 2% lidocaine with 1 : 80,000 epinephrine (adrenaline) was injected into the right mandibular angle and left mandibular body, respectively. Under several surgical conditions (presence or absence of periosteal flap, and presence or absence of saline irrigation), both mandibular bone samples were removed at a fixed time after subperiosteal infiltration anesthesia. The lidocaine concentration in each mandibular bone sample was measured by high-performance liquid chromatography. As a result, elevation of the periosteal flap with saline irrigation significantly decreased the lidocaine concentration in the mandibular bone. It is suggested that the anesthetic in the bone was washed out by saline irrigation. Therefore, supplemental conduction and/or general anesthesia should be utilized for long operations that include elevation of the periosteal flap with saline irrigation.

Analysis of Oxygen Concentration in the Oral Cavity During Intravenous Sedation with Intranasal Oxygen Administration for Dental Treatment.

Purpose: Intravenous sedation (IVS) with propofol (PPF) is commonly performed in dental treatment, particular in patients with dentophobia, with gag reflex, or undergoing implant surgeries, as PPF has the advantages of rapid induction and recovery. However, PPF and other intravenous sedatives may cause respiratory depression. Thus, IVS with PPF requires oxygen administration. But airway burn may occur when high-concentration oxygen is stored in the oral cavity and catches fire. For these reasons, the present study aimed to elucidate the changes in oxygen concentration (OC) under IVS with PPF and oxygen administration. Patients and methods: Nineteen healthy male volunteers participated in the study. None of them had missing teeth, nasal congestion, or temporomandibular joint dysfunction. They were sedated with a continuous PPF infusion dose of 6 mg/kg/hr for 25 min, followed by administration of 3 L/min oxygen via a nasal cannula. The OC was measured at two sites, namely, the median maxillary anterior teeth (MMAT) and median maxillary soft palate (MMSP), before PPF infusion (baseline) and 14, 15-18 (Term 1), 19, and 20-23 (Term 2) min after the start of infusion. Results: Compared with the values at baseline, the OC in the MMSP significantly increased at each time point, whereas the OC in the MMAT significantly increased at Term 2. Furthermore, in the comparison of the OC before and after the use of a mouth prop, the OC exhibited an upward trend, but no statistically significant differences were observed between the two time points in the MMAT and MMSP. In IVS with PPF and oxygen administration, the OC in the pharynx increases as the sedative level deepens. Conclusion: Oxygen administration should be temporarily discontinued, and suction should be performed to decrease the OC in the oral cavity when sparking procedures during IVS with PPF and oxygen administration are performed.

Effect of propofol on salivary secretion from the submandibular, sublingual, and labial glands during intravenous sedation.

Background: Recent animal studies have suggested the role of GABA type A (GABA-A) receptors in salivation, showing that GABA-A receptor agonists inhibit salivary secretion. This study aimed to evaluate the effects of propofol (a GABA-A agonist) on salivary secretions from the submandibular, sublingual, and labial glands during intravenous sedation in healthy volunteers. Methods: Twenty healthy male volunteers participated in the study. They received a loading dose of propofol 6 mg/kg/h for 10 min, followed by 3 mg/kg/h for 15 min. Salivary flow rates in the submandibular, sublingual, and labial glands were measured before, during, and after propofol infusion, and amylase activity was measured in the saliva from the submandibular and sublingual glands. Results: We found that the salivary flow rates in the submandibular, sublingual, and labial glands significantly decreased during intravenous sedation with propofol (P < 0.01). Similarly, amylase activity in the saliva from the submandibular and sublingual glands was significantly decreased (P < 0.01). Conclusion: It can be concluded that intravenous sedation with propofol decreases salivary secretion in the submandibular, sublingual, and labial glands via the GABA-A receptor. These results may be useful for dental treatment when desalivation is necessary.

Managing general anesthesia for low invasive dental procedures while maintaining spontaneous respiration with low concentration remifentanil: a cross-sectional study.

Background: We assessed the relationship between patient age and remifentanil dosing rate in patients managed under general anesthesia with spontaneous breathing using low-dose remifentanil in sevoflurane. Methods: The participants were patients with an American Society of Anesthesiologists Physical Status of 1 or 2 maintained under general anesthesia with low-dose remifentanil in 1.5-2.0% sevoflurane. The infusion rate of remifentanil was adjusted so that the spontaneous respiratory rate was half the rate prior to the induction of anesthesia, and γH (µg/kg/min) was defined as the infusion rate of remifentanil under stable conditions where the respiratory rate was half the rate prior to the induction of anesthesia for ≥ 15 minutes. The relationship between γH and patient age was analyzed statistically by Spearman's correlation analysis. Results: During dental treatment under general anesthesia using low-dose remifentanil in sevoflurane, a significant correlation was detected between γH and patient age. The regression line of y = -0.00079 x + 0.066 (y-axis; γH, x-axis; patient's age) was provided. The values of γH provide 0.064 µg/kg/min at 2 years and 0.0186 µg/kg/min at 60 years. Therefore, as age increases, the dosing rate exhibits a declining trend. Furthermore, in the dosing rate of remifentanil when the patient's respiratory rate was reduced by half from the preanesthetic respiratory rate, the dosing rate provided was around 0.88 mL/h in all ages if the remifentanil was diluted as 0.1 mg/mL. EtCO2 showed 51.0 ± 5.7 mmHg, and SpO2 was controlled within the normal range by this method. In addition, all dental treatments were performed without major problems, such as awakening and body movement during general anesthesia, and the post-anesthetic recovery process was stable. Conclusion: General anesthesia with spontaneous breathing provides various advantages, and the present method is appropriate for minimally invasive procedures.

Ventricular Tachycardia Following Ephedrine During Dexmedetomidine Dental Procedural Sedation.

We present the case of a 46-year-old man who received ephedrine for hypotension after surgery for a mandibular lesion under intravenous (IV) moderate sedation with dexmedetomidine (DEX) and experienced transient ventricular tachycardia (VT). The patient was scheduled to have cystectomy and multiple apicoectomies for the mandibular periapical infection and the simple bone cyst. Other than obesity, snoring, and a nonalcoholic fatty liver, he denied any other significant medical history, medications, or allergies. The surgery was successful; however, his blood pressure dropped after stopping the DEX infusion. Ephedrine was administered IV several times, which resulted in the onset of VT on the electrocardiogram (ECG). His blood pressure could not be measured at the time, but he was able to respond and breathe independently. A defibrillator was immediately made available. The ECG revealed a spontaneous transition from VT to atrial fibrillation with ST depression. Because he was unable to revert to a normal sinus rhythm, the patient was transferred to a general hospital, where he underwent additional testing. No abnormalities were observed in his heart or brain. After DEX administration, its long-lasting alpha-2 adrenoceptor agonist effects can cause vasodilation and inhibition of sympathetic activity, leading to hypotension in some patients. Should that occur, ephedrine can be used to increase blood pressure, but it may also provoke transient coronary artery spasms and lead to VT. Consequently, extreme caution should be exercised in patients who develop hypotension following DEX administration. We also recognize the significance of regular training sessions, such as advanced cardiac life support programs.

Transient cardiac arrest in patient with left ventricular noncompaction (spongiform cardiomyopathy).

Left ventricular noncompaction (LVNC), also known as spongiform cardiomyopathy, is a severe disease that has not previously been discussed with respect to general anesthesia. We treated a child with LVNC who experienced cardiac arrest. Dental treatment under general anesthesia was scheduled because the patient had a risk of endocarditis due to dental caries along with a history of being uncooperative for dental care. During sevoflurane induction, severe hypotension and laryngospasm resulted in cardiac arrest. Basic life support (cardiopulmonary resuscitation) was initiated to resuscitate the child, and his cardiorespiratory condition improved. Thereafter, an opioid-based anesthetic was performed, and recovery was smooth. In LVNC, opioid-based anesthesia is suggested to avoid the significant cardiac suppression seen with a volatile anesthetic, once intravenous access is established. Additionally, all operating room staff should master Advanced Cardiac Life Support/Pediatric Advanced Life Support (including intraosseous access), and more than 1 anesthesiologist should be present to induce general anesthesia, if possible, for this high-risk patient.

Risk Perception of Septic Shock with Multiple Organ Failure Due to Acute Exacerbation of an Infectious Dental Disease.

In general dental conditions such as dental caries and periodontal disease, a combination of adverse conditions can cause potentially life-threatening periodontal abscess. We treated a patient in whom an oral infection developed into septic shock, resulting in patient death. A 78-year-old woman experienced spontaneous pain around a moving tooth. Pus discharge was observed, the area was sterilized, and an analgesic was prescribed. A few days later, the swelling spread to the buccal region leading to difficulty while eating. Upon systemic status and blood examination at our dental hospital, depressed consciousness due to dehydration and septic shock were suspected. Oxygenation and infusion of acetate linger with antibiotics were immediately performed. Furthermore, a blood examination revealed malnutrition and a severe infection; therefore, the patient was transferred to a nearby general hospital. However, the patient died the next day because of advanced disseminated intravascular coagulation and multiple organ failure. When an oral infection is suspected in an elderly patient, antibiotics should be quickly administered, the patient's local and systemic state should be confirmed, and sterilization should be performed daily. If no improvement is observed, medical attention should be quickly sought.

A comparison of intravenous sedation with two doses of dexmedetomidine: 0.2 µg/kg/hr Versus 0.4 µg/kg/hr.

The present study investigated the physiologic and sedative effects between two different continuous infusion doses of dexmedetomidine (DEX). Thirteen subjects were separately sedated with DEX at a continuous infusion dose of 0.2 µg/kg/hr for 25 minutes after a loading dose of 6 µg/kg/hr for 5 minutes (0.2 group) and a continuous infusion dose of 0.4 µg/kg/hr for 25 minutes after a loading dose of 6 µg/kg/hr for 5 minutes (0.4 group). The recovery process was then observed for 60 minutes post infusion. The tidal volume, mean arterial pressure, and heart rate in both groups decreased significantly during infusion, but they were within a clinically acceptable level. A Trieger dot test plot error ratio in the 0.4 group was significantly higher than that in the 0.2 group until 15 minutes post infusion. Sedation appears to be safe at the infusion doses of DEX studied. However, increasing maintenance infusion doses of DEX from 0.2 µg/kg/hr to 0.4 µg/kg/hr delays some recovery parameters.

Immunohistochemical Analysis of Nerve Distribution in Mandible of Rats.

After review of the literature, there appears to be no report on the histology of the mandibular nerve fiber distribution. Therefore, using a Wistar rat model, immunohistochemical staining with protein gene product (PGP) and calcitonin gene-related peptide (CGRP) antibody for all nerves and only the pain-sensitive nerves, respectively, was performed. We also statistically compared the nerve distribution density by mandibular region. The section of the mandible from the alveolar crest to the mandibular canal was compartmentalized to several regions. Subsequently, nerve distribution density by region was measured microscopically in both the PGP- and CGRP-positive nerves. Furthermore, the ratio of CGRP- to PGP-positive nerves was measured in each region and statistically compared. In both the PGP- and CGRP-positive nerves, the nerve distribution density significantly increased vertically toward the mandibular canal from the alveolar crest and horizontally toward the periodontal ligament from the periosteum. From the CGRP- to PGP-positive nerve ratio, the pain-sensitive nerve accounted for approximately >70% in each region. Pain would therefore be more likely to develop when surgical invasiveness deepens toward the mandibular canal or periodontal ligament. Therefore, sufficient local anesthetic infiltration and/or combined use of conduction anesthesia or periodontal ligament injection may be required. These results may aid in the development of more effective surgical and anesthetic techniques for mandibular surgery.

Analysis of Dose Escalation of Propofol Associated With Frequent Sedation.

Patients with dental phobia frequently require intravenous sedation to complete dental treatment. We encountered a case of a patient who received frequent sedation by propofol, which required escalation in the dosage of propofol required. The patient was a healthy young female with severe dental phobia, and the dental procedures were initiated under intravenous sedation. Intravenous sedation was administered to the patient more than 100 times over 9 years, and the dosages were analyzed. The mean dosage of propofol administered per hour was 6.9 ± 2.4 mg/kg/h, and the dosage tended to increase with frequency (0.06-0.1 mg/kg/h in each administration). Increased dosage was needed with a shorter interval between sedations after 30 episodes of sedation. Regarding the mean dosage of propofol per hour, the step-down method exhibited the highest increase in dosage rate of 0.18 mg/kg/h per administration followed by target-controlled infusion at 0.07 mg/kg/h per administration and combination sedation at 0.06 mg/kg/h per administration. We discuss factors that may be associated with acute tolerance to propofol when frequent propofol sedations are provided.

Intravenous sedation with low-dose dexmedetomidine: its potential for use in dentistry.

This study investigated the physiologic and sedative parameters associated with a low-dose infusion of dexmedetomidine (Dex). Thirteen healthy volunteers were sedated with Dex at a loading dose of 6 mcg/kg/h for 5 minutes and a continuous infusion dose of 0.2 mcg/kg/h for 25 minutes. The recovery process was observed for 60 minutes post infusion. The tidal volume decreased significantly despite nonsignificant changes in respiratory rate, minute ventilation, oxygen saturation, and end-tidal carbon dioxide. The mean arterial pressure and heart rate also decreased significantly but within clinically acceptable levels. Amnesia to pin prick was present in 69% of subjects. A Trieger dot test plot error ratio did not show a significant change at 30 minutes post infusion despite a continued significant decrease in bispectral index. We conclude that sedation with a low dose of Dex appears to be safe and potentially efficacious for young healthy patients undergoing dental procedures.

A Histological Study of Vasoconstriction by Local Anesthetics in Mandible.

To assess the effect of epinephrine-containing local anesthetics on vasoconstriction, we immunohistochemically measured the intravascular lumen area in different regions of the mandible. Twelve male Wistar rats were used. General anesthesia was induced and maintained with sevoflurane. Infiltration anesthesia was performed with 0.2 mL of epinephrine-free 2% lidocaine (E-) near the left mandibular first molar and with 0.2 mL of epinephrine-containing 2% lidocaine (E+) near the right mandibular first molar. After decalcification, the specimens were paraffinized, and thin sections were prepared and immunohistologically stained with an antismooth muscle actin antibody. The intravascular lumen area was measured in the mucosa, periodontal membrane, Haversian/Volkmann's canal, and bone marrow. A Mann-Whitney U test was used for statistical processing, and p < .05 was considered to indicate a statistically significant difference. In the oral mucosa and the periodontal membrane, E+ had a significantly smaller vascular lumen area than E-. In the Haversian/Volkmann's canal and the bone marrow, no significant intergroup difference was observed in the intravascular lumen area. We postulate that this is due to a low smooth muscle content of blood vessels in the mandible and suggest that the vasoconstrictive effect of epinephrine-containing local anesthetics within the mandible is ineffective.

The Effect of Dexmedetomidine on Oral Mucosal Blood Flow and the Absorption of Lidocaine.

Dexmedetomidine (DEX) is a sedative and analgesic agent that acts via the alpha-2 adrenoreceptor and is associated with reduced anesthetic requirements, as well as attenuated blood pressure and heart rate in response to stressful events. A previous study reported that cat gingival blood flow was controlled via sympathetic alpha-adrenergic fibers involved in vasoconstriction. In the present study, experiment 1 focused on the relationship between the effects of DEX on alpha adrenoreceptors and vasoconstriction in the tissues of the oral cavity and compared the palatal mucosal blood flow (PMBF) in rabbits between general anesthesia with sevoflurane and sedation with DEX. We found that the PMBF was decreased by DEX presumably because of the vasoconstriction of oral mucosal vessels following alpha-2 adrenoreceptor stimulation by DEX. To assess if this vasoconstriction would allow decreased use of locally administered epinephrine during DEX infusion, experiment 2 in the present study monitored the serum lidocaine concentration in rabbits to compare the absorption of lidocaine without epinephrine during general anesthesia with sevoflurane and sedation with DEX. The depression of PMBF by DEX did not affect the absorption of lidocaine. We hypothesize that this is because lidocaine dilates the blood vessels, counteracting the effects of DEX. In conclusion, despite decreased palatal blood flow with DEX infusion, local anesthetics with vasoconstrictors should be used in implant and oral surgery even with administered DEX.

Elevation of a periosteal flap with irrigation of the bone for minor oral surgery reduces the duration of action of infiltration anesthesia.

The aim of this study is to assess the difference in duration of action after infiltration anesthesia when elevation of a periosteal flap (EPF) was accomplished with water or saline irrigation versus nonelevation of a periosteal flap (NEPF). The 57 patients in this study were under conscious sedation. A long treatment time of more than 1 hour was used. Instances where peripheral nerve block or opioids were administered and infiltration anesthesia over 2 fields were excluded before the study. Patients were included in either an EPF group (n = 29) or an NEPF group (n = 28). Statistically significant differences were detected in the initial dose of anesthetic (EPF: 4.3 +/- 1.4 mL, NEPF: 1.8 +/- 0.9 mL), the time until initial supplemental anesthesia (EPF: 38 +/- 26 minutes, NEPF: 65 +/- 27 minutes), and the frequency of anesthesia administration (EPF: 2.5 +/- 1.2 times, NEPF: 1.3 +/- 0.7 times). These results suggest that the duration of anesthesia action in EPF decreases to half compared with NEPF, even if the anesthetic was infiltrated in double the amount. Although supplemental anesthesia is required frequently in EPF, it is not efficacious. We speculated that the residual anesthetics in tissue were washed out by irrigation and hemorrhage and that supplemental anesthesia became ineffective because of leakage from the opened flap. Elevation of a periosteal flap reduces the effect of infiltration anesthetics.

Continuous infusion propofol general anesthesia for dental treatment in patients with progressive muscular dystrophy.

Progressive muscular dystrophy may produce abnormal reactions to several drugs. There is no consensus of opinion regarding the continuous infusion of propofol in patients with progressive muscular dystrophy. We successfully treated 2 patients with progressive muscular dystrophy who were anesthetized with a continuous infusion of propofol. In case 1, a 19-year-old, 59-kg man with Becker muscular dystrophy and mental retardation was scheduled for dental treatment under general anesthesia. General anesthesia was maintained by a continuous infusion of 6-10 mg/kg propofol per hour and an inhalational mixture of 67% nitrous oxide and 33% oxygen. No complications were observed during or after the operation. In case 2, a 5-year-old, 11-kg boy with Fukuyama type congenital muscular dystrophy and slight mental retardation was scheduled for dental treatment under general anesthesia. General anesthesia was maintained with a continuous infusion of 6-12 mg/kg propofol per hour and an inhalational mixture of 0.5-1.5% sevoflurane in 67% nitrous oxide and 33% oxygen. No complications were observed during or after the operation. It is speculated that a continuous infusion of propofol in progressive muscular dystrophy does not cause malignant hyperthermia because serum levels of creatine phosphokinase and myoglobin decreased after our anesthetic management. Furthermore, our observations suggest that sevoflurane may have some advantages in patients with progressive type muscular dystrophies other than Duchenne muscular dystrophy and Becker muscular dystrophy. In conclusion, our cases suggest that a continuous infusion of propofol for the patients with progressive muscular dystrophy is a safe component of our anesthetic strategy.

Dexmedetomidine decreases the oral mucosal blood flow.

There is an abundance of blood vessels in the oral cavity, and intraoperative bleeding can disrupt operations. There have been some interesting reports about constriction of vessels in the oral cavity, one of which reported that gingival blood flow in cats is controlled by sympathetic α-adrenergic fibres that are involved with vasoconstriction. Dexmedetomidine is a sedative and analgesic agent that acts through the α-2 adrenoceptor, and is expected to have a vasoconstrictive action in the oral cavity. We have focused on the relation between the effects of α-adrenoceptors by dexmedetomidine and vasoconstriction in oral tissues, and assessed the oral mucosal blood flow during sedation with dexmedetomidine. The subjects comprised 13 healthy male volunteers, sedated with dexmedetomidine in a loading dose of 6 µg/kg/h for 10 min and a continuous infusion of 0.7 µg/kg/h for 32 min. The mean arterial pressure (MAP), heart rate (HR), cardiac output (CO), stroke volume (SV), systemic vascular resistance (SVR), and palatal mucosal blood flow (PMBF) were measured at 0, 5, 10, 12, 22, and 32 min after the start of the infusion. The HR, CO, and PBMF decreased significantly during the infusion even though there were no differences in the SV. The SVR increased significantly but the PMBF decreased significantly. In conclusion, PMBF was reduced by the mediating effect of dexmedetomidine on α-2 adrenoceptors.