Masahiro Umino

Bio: Masahiro Umino is an academic researcher from Tokyo Medical and Dental University. The author has contributed to research in topics: Diffuse noxious inhibitory control & Somatosensory evoked potential. The author has an hindex of 19, co-authored 68 publications receiving 1173 citations. Previous affiliations of Masahiro Umino include Okayama University & The Open University of Japan.

The different effects of intravenous propofol and midazolam sedation on hemodynamic and heart rate variability.

Abstract: Heart rate (HR) and arterial blood pressure (BP) changes have been reported during conscious sedation with propofol and midazolam. One potential mechanism to explain these changes is that propofol and midazolam affect HR and BP via changes in the cardiac autonomic nervous system. Two specific hypotheses were tested by HR variability analysis: 1) propofol induces predominance of parasympathetic activity, leadingtodecreasedHRandBP,and2)midazolaminduces predominance of sympathetic activity, leading to increased HR and decreased BP. Thirty dental patients wereincludedinaprospective,randomizedstudy.HR, BP, low frequency (LF), high frequency (HF), and entropy were monitored during the awake, sedation, and recovery periods and depth of sedation was assessed using the Observer’s Assessment of Alertness/ Sedation score. Propofol induced a significant decrease intotalpower(503209ms 2 /Hzversus16292ms 2 / Hz)andLF/HFratio(2.51.2versus1.00.4),despite the absence of any change in HR during the sedation period compared with baseline. Midazolam decreased normalized HF (34 10% versus 10 4%) but did not significantlychangeLF/HFratio(2.31.1versus2.2 1.4) and increased HR in the sedation period. Comparedwithbaseline,propofolwasassociatedwithasignificant increase in normalized HF in the recovery period (34 11% versus 44 12%) and a significant decrease in HR, whereas midazolam was associated with an increase in LF/HF ratio (2.3 1.1 versus 3.7 1.8) with no change in HR. These results indicated a dominant parasympathetic effect of propofol and a dominant sympathetic effect of midazolam in both periods. These results should be considered during conscious sedation, especially in patients at risk of cardiovascular complications. (Anesth Analg 2005;101:97–102)

Prolonged rhythmic gum chewing suppresses nociceptive response via serotonergic descending inhibitory pathway in humans

Abstract: Serotonergic (5-HT) neurons are implicated in modulating nociceptive transmission. It is established that 5-HT neuronal activity is enhanced by rhythmic behaviors such as chewing and locomotion in animals. We thus hypothesized that 5-HT descending inhibitory pathways may be enhanced by rhythmic behavior of gum chewing in humans. To evaluate this idea, we examined nociceptive flexion reflex (NFR), while a subject chewed gum rhythmically for 20 min. NFR was elicited by electrical stimulation of the sural nerve, and the evoked potential was recorded from the biceps femoris muscle. Visual analogue scale (VAS) was also obtained. To assess 5-HT activity, we determined 5-HT levels quantitatively in platelet poor plasma (PPP) and whole blood (WB) using HPLC system. Both NFR area and VAS were significantly decreased at 5 min after the onset of chewing and these reductions persisted until cessation of chewing. There were no significant changes in NFR and VAS while resting without chewing. The PPP 5-HT level increased significantly just after cessation of chewing and had returned to the pre-chewing level by 30 min after cessation of chewing. The WB 5-HT level obtained 30 min after cessation of chewing was significantly greater than the pre-chewing level. Serotonin transporters have recently been discovered at the blood-brain barrier, suggesting that the rise in blood 5-HT may possibly reflect an increase in 5-HT level within the brain. The present results support our hypothesis that the rhythmic behavior of chewing suppresses nociceptive responses via the 5-HT descending inhibitory pathway.

Comparison of topical anesthesia of 20% benzocaine and 60% lidocaine gel

Abstract: Objective. The purpose of this study was to determine the efficacies of 2 topical anesthetics commonly used in dentistry. Study Design. The alveolar mucosa of the upper incisor apices of 20 healthy male volunteers was applied for 20 minutes with either 20% benzocaine gel or nothing as a control. The second part of experiment was done with 60% lidocaine gel and vehicle as control. Three methods of stimulation were given, and the pain rating score and visual analog scale were measured after each stimulation. Results. Twenty percent benzocaine did not significantly alter pain perception as measured by the pain rating score and visual analog scale with these 3 methods of stimulation. In contrast, 60% lidocaine significantly reduced pain perception according to these measurements. We conclude that 60% lidocaine gel is effective for topical anesthesia before infiltration anesthesia. (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2002;94:157-61)

International association for the study of pain

Abstract: I am delighted to announce the exciting news that we have received just under 900 abstracts for presentation in the scientific program of the VIth World Congress on Pain in Adelaide, April l-6, 1990. This 1s about a 50% increase in the number of abstracts submitted for the 1987 Congress in Hamburg and it represents by far the greatest number of scientific papers ever offered for the an IASP Congress. This surely reflects the healthy state of IASP and is also a very encouraging indlcator of the high level of activity in basic and clinical research in the field of pain throughout the world. Based upon our previous experience with the ratio of congress delegates to scientific abstracts, the Adelaide Congresses promises to be the largest world congress on pain we have so far held.