Effects of changes in end-tidal carbon dioxide tension on oral tissue blood flow and tissue oxygen tension during remifentanil infusion in rabbits.

PURPOSE: The aim of this study was to investigate the effects of end-tidal carbon dioxide tension (ETCO2) changes during remifentanil infusion on mandibular bone marrow tissue blood flow (BBF), masseter muscle tissue blood flow (MBF), mandibular bone marrow tissue oxygen tension (PbO2) and masseter muscle tissue oxygen tension (PmO2) in rabbits. METHODS: Ten male tracheotomized Japan White rabbits were anesthetized and ventilated with sevoflurane. ETCO2 was adjusted to 30 mmHg. After baseline measurement, CO2 was added to the inhaled air, and ETCO2 was increased to 40 and 60 mmHg. Heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), BBF, MBF, PbO2, and PmO2 were recorded with and without remifentanil infusion at 0.4 µg/kg/min. RESULTS: Two-way repeated measures analysis of variance showed no interaction between ETCO2 and remifentanil in all variables. Remifentanil infusion produced decreases in HR, SBP, MAP, BBF and MBF compared with those without remifentanil infusion, while it did not affect DBP, PbO2 and PmO2. Elevation of ETCO2 from 30 to 60 mmHg produced decreases in HR and MBF, and increases in SBP, DBP, MAP and BBF, while it did not affect PbO2 and PmO2. CONCLUSION: PbO2 and PmO2 remained unchanged despite changes in BBF and MBF during ETCO2 change with or without remifentanil infusion.

Decreases in Oral Tissue Blood Flow Induced by Remifentanil Are Not Accompanied by Deterioration of Oral Tissue Oxygen Tension in Rabbits.

PURPOSE: The purpose of this study was to investigate the effects of remifentanil infusion on tissue blood flow and tissue oxygen tension in the mandibular bone marrow and masseter muscle in rabbits. In addition, changes in tissue oxygen consumption in those tissues during remifentanil infusion were investigated. MATERIALS AND METHODS: Sixteen male tracheotomized Japanese White rabbits were anesthetized with sevoflurane under mechanical ventilation. Under oxygen and air inhalation, fraction of inspiratory oxygen was set at 0.4 and remifentanil was infused at a rate of 0.4 µg ∙ kg-1 ∙ min-1. Measurements were performed before remifentanil infusion, 20 minutes after the start of remifentanil infusion, and 20 and 60 minutes after the completion of remifentanil infusion (n = 8). The observed variables included heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), mandibular bone marrow tissue blood flow (BBF), masseter muscle tissue blood flow (MBF), mandibular bone marrow tissue oxygen tension (PbO2), and masseter muscle tissue oxygen tension (PmO2). Another 8 rabbits were observed for arterial pH, lactate, base excess (BE), and tissue oxygen consumption in the region from which the retromandibular vein received venous blood. Measurements were performed before remifentanil infusion and 20 minutes after the start of remifentanil infusion. RESULTS: HR, SBP, DBP, MAP, BBF, and MBF decreased during remifentanil infusion. PbO2 increased 20 minutes after remifentanil infusion and returned to almost the baseline value 60 minutes after remifentanil infusion. PmO2 did not change throughout the experiment. The difference between the arterial oxygen content of the femoral artery and the venous oxygen content of the retromandibular vein decreased during remifentanil infusion. Arterial pH, lactate, and BE did not change during remifentanil infusion. CONCLUSIONS: Remifentanil decreased BBF and MBF but did not decrease PbO2 and PmO2. It is suggested that tissue oxygen consumption decreased during remifentanil infusion.

Comparison of Changes in Respiratory Dynamics Immediately After the Start of Propofol Sedation With or Without Midazolam.

PURPOSE: The aim of this study was to compare changes in respiratory dynamics starting immediately after administration of propofol alone or a combination of propofol and midazolam. MATERIALS AND METHODS: Twenty-seven healthy adult volunteers participated in a randomized crossover study of undergoing sedation with propofol alone (P group) or with a combination of propofol and midazolam (PM group). In the P group, continuous infusion of propofol through a target-controlled infusion (TCI) pump was started with the target effect site (ES) concentration set at 1.2 µg/mL. In the PM group, participants received a bolus administration of midazolam 0.02 mg/kg simultaneously with the start of continuous infusion of propofol through a TCI pump with the target ES concentration set at 0.8 µg/mL. The variables measured included the bispectral index (BIS) value, tidal volume (VT), percutaneous arterial oxygen saturation (SpO2), respiratory rate (RR), end-tidal carbon dioxide tension (ETCO2), estimated ES propofol concentration, and minute volume. RESULTS: BIS value, VT, SpO2, and ETCO2 decreased after sedative administration in the 2 groups. RR increased in the 2 groups. These changes occurred sooner in the PM group than in the P group. The ratio of change in VT to change in BIS value decreased in the 2 groups and was markedly smaller in the PM group than in the P group. Ratios of changes in SpO2, RR, and ETCO2 to change in BIS value increased in the 2 groups and were larger in the PM group than in the P group. CONCLUSION: Changes in respiratory dynamics occurred sooner in the PM group than in the P group. In the PM group, although VT began to decrease before the change in BIS value, the increase in RR caused the rate of decrease in SpO2 to be smaller than the rate of decrease in BIS value.

Remifentanil Reduces Blood Loss During Orthognathic Surgery.

Remifentanil is reported to reduce oral tissue blood flow. We performed a retrospective investigation using logistic regression analysis of anesthesia records to investigate whether the use of remifentanil infusion in a balanced anesthesia technique was useful as a primary technique to reduce blood loss during orthognathic surgery. Subjects were 80 patients who underwent Le Fort I osteotomy and sagittal split ramus osteotomy of the mandible. The variables included gender, age, weight, type of maintenance anesthetic, type and dose or infusion rate of opioid, mean systolic blood pressure (SBP-mean), coefficient of variation of systolic blood pressure (CVSBP) during surgery, mean heart rate (HR-mean), duration of surgery, total blood loss, volume of infusion used, amount of local anesthetic used, body temperature, and urine output. Gender, type of maintenance anesthetic, type of opioid, SBP-mean, CVSBP, HR-mean, and duration of surgery were used as candidates for independent variables. Logistic regression analysis was performed for the selected independent variables with the total blood loss as the dependent variable. The factors associated with the reduction of blood loss were the use of remifentanil (odds ratio, 3.112; 95% CI, 1.166-8.307; P = .023) and smaller CVSBP (odds ratio, 2.747; 95% CI, 1.07-7.053; P = .036). Use of remifentanil and smaller CVSBP were associated with a reduction of blood loss during orthognathic surgery.

Effect of Topical Anesthesia Using an Adhesive Patch and Anesthetic Solution.

We analyzed trigeminal somatosensory evoked potentials (TSEP) to the alveolar mucosa to investigate the efficacy of an amide local anesthetic, 2% lidocaine hydrochloride with 12.5 µg/mL epinephrine (Lido treatment) as a topical anesthetic. Eighteen consenting healthy adult volunteers were enrolled. A volume of 0.06 mL of Lido, 0.06 g of 20% benzocaine, or 0.06 mL of physiological saline (control) was instilled onto a hemostatic adhesive patch, which was then applied to the alveolar mucosa at the maxillary right canine for 5 minutes. An electrical stimulus approximately 5 times that of the sensory threshold was applied using a surface stimulation electrode. The trigeminal somatosensory evoked potential was recorded immediately, 5 minutes, and 10 minutes after removal of the patch. Positive P125 and P310 peaks and negative N100 and N340 peaks were observed as a result of the electrical stimulation. A significant decrease in the percentage change in amplitude of N100-P125 was observed in the Lido treatment immediately, 5 minutes, and 10 minutes after patch removal. In the Lido treatment, trigeminal somatosensory evoked potential amplitude at N100-P125 decreased significantly, suggesting that topical anesthesia produced by an amide local anesthetic may have a topical anesthetic effect as potent as that produced by an ester local anesthetic.

Comparison of the Effect of Electrical Stimulations on the Chin Skin on Autonomic Nervous Activities During Propofol Sedation With or Without Midazolam.

PURPOSE: The aim of this study was to compare the effect of electrical stimulations on the chin skin on autonomic nervous activities evaluated by use of power spectrum analysis of heart rate (HR) variability during intravenous sedation using propofol with or without midazolam. MATERIALS AND METHODS: Thirty-eight healthy adult male volunteers underwent intravenous sedation with midazolam and propofol (group MP) and with propofol alone (group P) in a randomized crossover manner. In group MP, the participants received midazolam (0.04 mg/kg) and a target-controlled infusion of propofol with a predicted blood concentration of 1.0 µg/mL. In group P, the predicted blood concentration of propofol was maintained at 1.5 µg/mL. The observed variables were bispectral index value, systolic blood pressure, HR, high-frequency component (HF), low-frequency component (LF), and LF/HF ratio. Measurements were conducted over 100-second periods and carried out before, during, and after emergence from sedation by administering 0.2 mg of flumazenil. The paired t test, Wilcoxon t test, repeated-measures analysis of variance, and Friedman χ(2) r test were used for statistical analyses. RESULTS: The mean age and body weight of the participants were 24.6 ± 2.8 years and 67.0 ± 7.9 kg, respectively. Bispectral index values, systolic blood pressure, and HR showed similar changes in both groups. The LF/HF ratio in group MP during sedation was lower than that before sedation; it also was lower than that in group P during sedation. CONCLUSIONS: Intravenous sedation with a combination of midazolam and propofol inhibited sympathetic nervous activation induced by electrical stimulations to a greater extent than that with propofol alone.

Inhalation of 50% Oxygen Does Not Impair Respiratory Depression During Midazolam Sedation.

PURPOSE: To investigate how inhalation of 50% oxygen during intravenous midazolam sedation affects respiratory variables and thus the availability of oxygen. MATERIALS AND METHODS: Study subjects were 21 healthy adult volunteers (American Society of Anesthesiologists physical status I). They were allocated to undergo midazolam sedation during high-concentration oxygen inhalation (group H) or during normal air inhalation (group N) in a single-blinded randomized crossover design, with an interval of at least 3 days between the 2 sedation sessions. In each experiment, midazolam 0.05 mg/kg was administered, after which the following variables were measured for 40 minutes: oxygen saturation by pulse oximetry (SpO2), end-tidal carbon dioxide partial pressure (ETCO2), respiration rate (RR), tidal volume (VT), and minute volume (MV). Subsequently, flumazenil 0.5 mg was administered, and the same variables were measured for 10 minutes. RESULTS: SpO2 decreased after midazolam administration in the 2 groups. SpO2 in group H was higher than that in group N at all time points. RR increased and VT decreased after midazolam administration in the 2 groups; however, in contrast to SpO2, the levels of these parameters did not meaningfully differ between groups at any time point. MV remained unchanged in the 2 groups. ETCO2 decreased similarly after midazolam administration in the 2 groups. CONCLUSION: Inhalation of 50% oxygen during midazolam sedation did not enhance respiratory depression by midazolam. This suggests that high-concentration oxygen inhalation during midazolam sedation could prevent hypoxia.

Effect of Cuff Pressure Elevation on Internal Diameter of Tracheal Tube in Simulated Trachea.

Application of nitrous oxide during anesthesia causes an increase in tracheal tube cuff pressure over time. The purpose of this study was to investigate the effect of an increase in cuff pressure on 3 types of tube (the Portex, Mallinckrodt, and Parker) commonly used for nasotracheal intubation. A cylindrical vessel was used to simulate a trachea. Cuff pressure was set at 0 cmH2O (R0) or 20 cmH2O (R20) at room temperature, or at 20 cmH2O (H20), 40 cmH2O (H40), 60 cmH2O (H60), or 80 cmH2O (H80) in 38°C hot water and pressure applied for 30 min. The value obtained at R0 was used as a reference (100%) and the rate of change under each condition determined. No change was observed at R20 in any of the 3 groups. In 38°C hot water, internal diameter in the Portex group decreased by 5.4% at H20 and 7.3% at H40, while that in the Mallinckrodt group decreased by 6% at H40. No significant change was observed in internal diameter in the Parker group, even when cuff pressure was increased. The internal diameter in the Portex group was the smallest at all cuff pressures in hot water. When the nasotracheal intubation tubes selected were placed in a simulated trachea and cuff pressure increased, internal diameter in the Portex and Mallinckrodt groups decreased.

Effect of changes in end-tidal carbon dioxide tension on oral tissue blood flow during dexmedetomidine infusion in rabbits.

A decrease in arterial carbon dioxide tension induces an increase in masseter muscle blood flow and a decrease in mandibular bone marrow blood flow during general anesthesia. In addition, dexmedetomidine infusion reduces oral tissue blood flow. In this study we investigated how end-tidal carbon dioxide tension (ET-CO2 ) changes influence on oral tissue blood flow during continuous dexmedetomidine infusion in rabbits. Eleven male Japan White rabbits were anesthetized with sevoflurane. Then, ET-CO2 was set at 30 mmHg and adjusted to 40 and 60 mmHg, and heart rate, systolic blood pressure, diastolic blood pressure, mean arterial pressure, common carotid artery blood flow, mandibular bone marrow blood flow, masseter muscle blood flow, and blood flow in other oral tissues were measured. Following this, the ET-CO2 was returned to 30 mmHg and dexmedetomidine was infused over 60 min. The measurements were repeated. Most parameters increased, regardless of whether or not dexmedetomidine was present, and heart rate and masseter muscle blood flow decreased in an ET-CO2 -dependent manner. Dexmedetomidine infusion suppressed ET-CO2 -dependent masseter muscle blood flow change. Masseter muscle blood flow during ET-CO2 at 30 mmHg with dexmedetomidine was the same as that during ET-CO2 at 40 mmHg without dexmedetomidine. Our findings suggest that dexmedetomidine infusion and slight hypocapnia under general anesthesia suppress an increase in masseter muscle blood flow as well as reducing mandibular bone marrow blood flow. These results may be of significance for decreasing bleeding during oral and maxillofacial surgery.

Effects of Volatile Anesthetics on Oral Tissue Blood Flow in Rabbits: A Comparison Among Isoflurane, Sevoflurane, and Desflurane.

PURPOSE: The aim of this study was to compare the concentration-dependent effects of isoflurane, sevoflurane, and desflurane on oral tissue blood flow. MATERIALS AND METHODS: Thirty male Japan White rabbits were randomized to receive 1 of 3 volatile anesthetics: isoflurane (group Iso), sevoflurane (group Sevo), or desflurane (group Des). The end-tidal concentration of each volatile anesthetic was regulated to 0.5, 1, and 1.5 minimum alveolar concentrations (MACs). The observed variables were heart rate, systolic blood pressure, diastolic blood pressure, mean arterial pressure, common carotid arterial blood flow, tongue mucosal blood flow, mandibular bone marrow blood flow (BBF), masseter muscle blood flow (MBF), upper alveolar tissue blood flow, and lower alveolar tissue blood flow (LBF). RESULTS: The blood pressure in each group tended to decrease depending on the concentration of each volatile anesthetic, with the smallest effect in group Des. BBF and MBF in group Iso were higher than those in group Des at 1 MAC, and MBF and LBF in group Iso were highest at 1.5 MAC. CONCLUSION: The results of this study suggest that each volatile anesthetic produced unique effects on blood flow in oral tissues and circulatory parameters. Among the 3 volatile anesthetics, desflurane produced the smallest effects on oral tissue blood flow.

Intraoperative Blood Loss During Orthognathic Surgery: A Comparison of Remifentanil-Based Anesthesia With Sevoflurane or Isoflurane.

PURPOSE: The aim of the present study was to compare the blood loss with remifentanil-based anesthesia with sevoflurane or isoflurane during orthognathic surgery. PATIENTS AND METHODS: In this randomized controlled clinical trial, the patients who were scheduled for orthognathic surgery were divided into 2 groups: the sevoflurane (Sevo) group and isoflurane (Iso) group. Anesthesia was maintained using end-tidal concentrations of 1.4% sevoflurane or 0.9% isoflurane. Remifentanil was continuously infused at 0.05 to 0.5 µg/kg/min to maintain the mean blood pressure (MBP) at 60 to 65 mm Hg. The intraoperative blood loss was compared between the 2 groups. The Student t test for unpaired samples was used for statistical analysis. P < .05 was considered statistically significant. RESULTS: The study sample included 19 men and 45 women (n = 64). The mean age was 25 years (range 16 to 50). The intraoperative blood loss tended to be greater in the Iso group (n = 32; 4.79 ± 3.22 mL/kg) than in the Sevo group (n = 32; 4.00 ± 1.98 mL/kg). However, the difference between the 2 groups was not significant. CONCLUSION: In a comparison of intraoperative blood loss during remifentanil-based anesthesia with sevoflurane or isoflurane during orthognathic surgery, no difference was observed between the 2 groups.

Concomitant administration of nitrous oxide and remifentanil reduces oral tissue blood flow without decreasing blood pressure during sevoflurane anesthesia in rabbits.

PURPOSE: To determine whether continuous administration of nitrous oxide and remifentanil­either alone or together­alters blood flow in oral tissues during sevoflurane anesthesia. METHODS: Eight male tracheotomized Japanese white rabbits were anesthetized with sevoflurane under mechanical ventilation. Heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), common carotid arterial blood flow (CCBF), tongue mucosal blood flow (TMBF), mandibular bone marrow blood flow (BBF), masseter muscle blood flow (MBF), upper alveolar tissue blood flow (UBF), and lower alveolar tissue blood flow (LBF) were recorded in the absence of all test agents and after administration of the test agents (50 % nitrous oxide, 0.4 µg/kg/min remifentanil, and their combination) for 20 min. RESULTS: Nitrous oxide increased SBP, DBP, MAP, CCBF, BBF, MBF, UBF, and LBF relative to baseline values but did not affect HR or TMBF. Remifentanil decreased all hemodynamic variables except DBP. Combined administration of nitrous oxide and remifentanil recovered SBP, DBP, MAP, and CCBF to baseline levels, but HR and oral tissue blood flow remained lower than control values. CONCLUSIONS: Our findings suggest that concomitant administration of nitrous oxide and remifentanil reduces blood flow in oral tissues without decreasing blood pressure during sevoflurane anesthesia in rabbits.

Tissue Blood Flow During Remifentanil Infusion With Carbon Dioxide Loading.

The aim of this study was to investigate the effect of changes in end-tidal carbon dioxide tension (ETCO2) during remifentanil (Remi) infusion on oral tissue blood flow in rabbits. Eight male tracheotomized Japan White rabbits were anesthetized with sevoflurane under mechanical ventilation. The infusion rate of Remi was 0.4 µg/kg/min. Carbon dioxide was added to the inspired gas to change the inspired CO2 tension to prevent changes in the ventilating condition. Observed variables were systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), heart rate (HR), common carotid artery blood flow (CCBF), tongue mucosal blood flow (TBF), mandibular bone marrow tissue blood flow (BBF), masseter muscle tissue blood flow (MBF), upper alveolar tissue blood flow (UBF), and lower alveolar tissue blood flow (LBF). The CCBF, TBF, BBF, UBF, and LBF values were increased, while MBF was decreased, under hypercapnia, and vice versa. The BBF, UBF, and LBF values were increased, while the MBF value was decreased, under hypercapnia during Remi infusion, and vice versa. The BBF, MBF, UBF, and LBF values, but not the CCBF and TBF values, changed along with ETCO2 changes during Remi infusion.

Survey on choice of intravenous sedative agent at department of dental anesthesiology, Tokyo Dental College Chiba Hospital between 2010 and 2011.

Use of intravenous sedation is increasing in the management of dental patients in consideration of accompanying diseases and patient demand for comfort and safety. We surveyed choice of sedative agent and dosage on the basis of accompanying diseases or conditions in patients receiving treatment at the Department of Dental Anesthesiology, Tokyo Dental College Chiba Hospital between 2010 and 2011. A total of 5,256 patients were reviewed and divided into the following categories: 1) medically compromised patients (MC); 2) minor oral surgery (OS); 3) cerebral palsy (CP); 4) mental retardation (MR); 5) mental disorder (MD); and 6) dental phobia with/without gag reflex. The investigated variables were sex, age, weight, duration of sedation, and dosage of agent. Dosage of midazolam (M), M plus propofol (MP), and P alone was investigated. A total of 2,336 patients were managed by intravenous sedation during the study period. The combination of MP was used in approximately 63-79% of patients in all categories, except MC. Midazolam was used in approximately 47% in the MC group. Propofol was used in approximately 32% of patients in the MR group. Other agents (minor tranquilizers, analgesics, and so on) were used in approximately 12% in the OS group. The dose of M was approximately 0.05-0.06 mg/kg. When MP was administered, the dose of M showed no difference among groups. The dose of P, however, tended to be lower in the MC and CP groups than in the other groups. These results suggest that MP is chosen for intravenous sedation in most types of dental treatment.

Impact of skeletal muscle mass on postoperative complications in oral cancer surgery.

BACKGROUND: Sarcopenia is characterized by a progressive and generalized loss of skeletal muscle mass and strength. The aim of this retrospective study was to investigate the impact of skeletal muscle mass on adverse events in free-flap reconstruction for defects after oral cancer resection. RESULTS: Of 120 patients, recipient-site adverse events occurred in 56 patients (46.7%), and recipient-site surgical site infections occurred in 45 patients (37.5%). Skeletal muscle index was significantly associated with recipient-site adverse events in univariate analysis (P < 0.05). Lower body mass index and skeletal muscle index were significantly associated with recipient-site surgical site infection in univariate analysis (P < 0.05). In the multiple logistic regression model, a lower skeletal muscle index was a significant risk factor for recipient-site adverse events and surgical site infections (adverse events odds ratio; 3.17/P = 0.04; surgical site infection odds ratio; 3.76/P = 0.02). CONCLUSIONS: The SMI at level Th12 was an independent factor for postoperative AEs, especially SSI, in OSCC patients with free-flap reconstruction.

Dexmedetomidine dose dependently decreases oral tissue blood flow during sevoflurane and propofol anesthesia in rabbits.

PURPOSE: The aim of the present study was to investigate the effect of dexmedetomidine (DEX) continuous infusion on blood flow in rabbit oral tissues during sevoflurane or propofol anesthesia. METHODS: A total of 24 male tracheotomized Japanese white rabbits were anesthetized with sevoflurane or propofol under mechanical ventilation. An initial loading dose of 6.0 µg/kg/hr DEX was administered for 10 minutes. DEX was then maintained at 0.2, 0.4, and 0.6 µg/kg/hr for 1 hour, respectively. The observed variables were systolic blood pressure, diastolic blood pressure, mean arterial pressure, heart rate, common carotid artery blood flow, tongue mucosal blood flow (TBF), mandibular bone marrow blood flow (BBF), masseter muscle blood flow (MBF), upper alveolar tissue blood flow (UBF), lower alveolar tissue blood flow (LBF), and vascular resistance for each tissue (tongue mucosal vascular resistance, mandibular bone marrow vascular resistance, masseter muscle vascular resistance, upper alveolar tissue vascular resistance, and lower alveolar tissue vascular resistance). RESULTS: The heart rate, systolic blood pressure, mean arterial pressure, common carotid artery blood flow, TBF, BBF, MBF, UBF, and LBF showed dose-dependent decreases during DEX infusion during both sevoflurane and propofol anesthesia. The decreasing ratios in TBF, BBF, MBF, UBF, and LBF were greater than those in heart rate, systolic blood pressure, mean arterial pressure, and common carotid artery blood flow. The vascular resistance of the oral tissues was increased in a dose-dependent manner during DEX infusion in both sevoflurane and propofol anesthesia. CONCLUSION: Our findings suggest that infusion of DEX decreases TBF, BBF, MBF, UBF, and LBF in a dose-dependent manner without significant changes in systemic hemodynamic variables during sevoflurane or propofol anesthesia.

Midazolam increases bite force during intravenous sedation.

PURPOSE: Although there have been many reports on the effects of midazolam on vital function and the recovery profile, little is known about muscle power during sedation. The purpose of this study was to investigate the effects of midazolam on muscle power during moderate sedation. MATERIALS AND METHODS: The subjects were 20 male volunteers classified as American Society of Anesthesiologists physical status I. Each subject underwent 2 experiments in a randomized crossover manner (midazolam and control groups). After baseline data were obtained, midazolam (0.05 mg/kg) was administered. Thirty minutes after midazolam administration, flumazenil (0.5 mg) was administered to antagonize the sedative effects of midazolam in the midazolam group. Heart rate, noninvasive blood pressure, arterial oxygen saturation, respiratory rate, and the bispectral index value were monitored. The Observer's Assessment of Alertness/Sedation scale and the correct-answer rate of the Stroop color word test were assessed. To evaluate muscle power, grip strength and bite force were measured. After baseline measurement, all variables were measured 2, 5, 10, 20, and 30 minutes after midazolam administration and 5, 10, and 20 minutes after flumazenil administration. For statistical comparisons, repeated measures analysis of variance, the Friedman χ(2) test, and the Student t test for paired samples were used. RESULTS: No significant changes were observed for any variable in the control group. In the midazolam group, the bispectral index value and the Observer's Assessment of Alertness/Sedation scale decreased during midazolam sedation. The correct-answer rate of the Stroop color word test decreased 5 and 10 minutes after midazolam administration. Grip strength decreased during midazolam sedation. Bite force increased immediately after midazolam administration and remained increased even after flumazenil administration. CONCLUSIONS: Although the detailed mechanisms are unknown, bite force increases despite the muscle-relaxant action of midazolam during sedation and persists even with flumazenil reversal.

Oral mucosal injection of a local anesthetic solution containing epinephrine enhances muscle relaxant effects of rocuronium.

The purpose of this study was to examine how submucosal injection of a clinically relevant dose of a lidocaine hydrochloride solution containing epinephrine affects the muscle relaxant effects of rocuronium bromide. Sixteen patients scheduled for orthognathic surgery participated in this study. All patients were induced with fentanyl citrate, a target-controlled infusion of propofol and rocuronium bromide. Anesthesia was maintained by total intravenous anesthesia. After nasotracheal intubation, an infusion of rocuronium bromide was started at 7 µg/kg/min, and the infusion rate was then adjusted to maintain a train of four (TOF) ratio at 10 to 15%. The TOF ratio just prior to oral mucosal injection of a 1% lidocaine hydrochloride solution containing 10 µg/mL epinephrine (LE) was taken as the baseline. TOF ratio was observed for 20 minutes, with 1-minute intervals following the start of injection. Mean epinephrine dose was 85.6 ± 18.6 µg and mean infusion rate of rocuronium bromide was 6.3 ± 1.6 µg/kg/min. TOF ratio began to decrease 2 minutes after the injection of LE, reached the minimum value at 3.1 ± 3.6% 12 minutes after the injection, and then began to recover. We conclude that oral mucosal injection of LE enhances the muscle relaxant effects of rocuronium bromide.

Usefulness of lateral cephalometric radiography for successful blind nasal intubation: a prospective study.

Background: This study aimed to investigate the relationship between pharyngeal morphology and the success or failure of blind nasotracheal intubation using standard lateral cephalometric radiography and to analyze the measurement items affecting the difficulty of blind nasotracheal intubation. Methods: Assuming a line perpendicular to the Frankfort horizontal (FH) plane, the reference point (O) was selected 1 cm above the posterior-most end of the hard palate. A line passing through the reference point and parallel to the FH plane is defined as the X-axis, and a line passing through the reference point and perpendicular to the X-axis is defined as the Y-axis. The shortest length between the tip of the uvula and posterior pharyngeal wall (AW), shortest length between the base of the tongue and posterior pharyngeal wall (BW), and width of the glottis (CW) were measured. The midpoints of the lines representing each width are defined as points A, B, and C, and the X and Y coordinates of each point are obtained (AX, BX, CX, AY, BY, and CY). For each measurement, a t-test was performed to compare the tracheal intubation success and failure groups. A binomial logistic regression analysis was performed using clinically relevant items. Results: The items significantly affecting the success rate of blind nasotracheal intubation included the difference in X coordinates at points A and C (Odds ratio, 0.714; P-value, 0.024) and the ∠ABC (Odds ratio, 1.178; P-value, 0.016). Conclusion: Using binomial logistic regression analysis, we observed statistically significant differences in AX-CX and ∠ABC between the success group and the failure group.

Latent changes in the pharyngeal stage of swallowing in non-aspirating older adults.

PURPOSE: The characteristic changes in the swallowing mechanism with aging are collectively termed presbyphagia. Although several studies have investigated presbyphagia in older adults, few have assessed oldest-old adults. We aimed to characterize the latent changes of swallowing function in oldest-old adults and to consider risk ages for presbyphagia. METHODS: We analyzed the records of 85 individuals (44 males and 41 females, aged 25-101 years) who underwent videofluoroscopic swallowing studies. The included participants had penetration and aspiration scores of ≤ 2 and no history of aspiration, pneumonia, or diseases that affect swallowing. They were divided into four age groups: 25-64 years (non-older), 65-74 years (young-old), 75-84 years (middle-old), and ≥ 85 years (oldest-old). We analyzed and compared the pharyngeal delay time (PDT), duration of tongue base and posterior pharyngeal wall contact, duration and dimension of upper esophageal sphincter opening (UES-O), and maximal hyoid bone displacement between the age groups. RESULTS: Among the older groups, the oldest-old showed significantly longer PDT than younger-old adults, and the UES-O tended to be wider in the former. However, no other remarkable differences were found between the oldest-old and other old groups. Statistical comparisons between the < 75 and ≥ 75-year age groups revealed significant age-related changes in the PDT and duration and dimension of UES-O. CONCLUSION: On videofluoroscopic evaluation, physiological changes with aging affected few parameters of swallowing in our cohort. These findings indicate that in non-aspirating oldest-old adults, any deterioration may be adjusted for by compensatory changes to maintain swallowing function.