Effects of dexmedetomidine on conditioned pain modulation in humans.

BACKGROUND: Systemic administration of dexmedetomidine (DEX; selective α(2) -adrenoceptor agonist) is found to inhibit diffuse noxious inhibitory control in rats, now referred to as conditioned pain modulation (CPM) in humans. The present study was designed to investigate the effect of intravenous administration of DEX on CPM in humans. METHODS: There were two sequential sessions in this double blind, randomized study. The first session was the control with normal saline infusion (N(1st), L(1st), H(1st)). During the second session, three types of agents were infused: normal saline (N(2nd)); a low plasma concentration of DEX (0.04 ng/mL; L(2nd)); and a high plasma concentration of DEX (0.08 ng/mL; H(2nd)). The amplitude of somatosensory evoked potentials (ampSEP)s and the visual analogue scale of tooth pain (VASt) induced by electrical tooth stimulation were evaluated with and without conditioning CO(2) laser stimulation of the hand. The inhibition rate (% inhibition) was calculated [= (1-[ampSEP or VASt with conditioning stimuli]/[ampSEP or VASt without conditioning stimuli]) × 100] to compare the magnitude of the DEX effects on CPM. RESULTS: The inhibition rates of ampSEPs and VASt in Types N, L and H varied significantly, demonstrating a dose-dependent reduction of CPM effects of ampSEP and VASt during randomized DEX administration, consistent with results from animal studies. CONCLUSIONS: The present study shows that systemic administration of an α(2) -adrenoceptor agonist (DEX), less than the clinical dose, inhibited CPM in humans. These results may provide some mechanistic insight into why many chronic pain patients show impaired CPM.

Blood loss and endocrine responses in hypotensive anaesthesia with sodium nitroprusside and nitroglycerin for mandibular osteotomy.

The purpose of this study was to determine the differences in endocrine responses, blood loss and arterial blood gas profiles between patients subjected to hypotensive anaesthesia or normotensive anaesthesia and those between patients given sodium nitroprusside (SNP) or nitroglycerin (NTG) as the hypotensive agent. 36 patients, who were scheduled to undergo mandibular osteotomy, were recruited for the study. Their hormonal responses, metabolic responses, arterial blood gas profiles and blood loss were determined during hypotensive anaesthesia induced by either SNP or NTG and normotensive anaesthesia induced by sevoflurane (SEV). Blood loss was smaller and the duration of surgery was shorter in the SNP and NTG groups than in the SEV group. The plasma levels of adrenocorticotrophic hormone, cortisol, vasopressin, norepinephrine and dopamine increased during surgery in all 3 groups. There were no significant differences in the hormone levels, among the 3 groups, or between the SNP and NTG groups.

Haemodynamic changes and heart rate variability during midazolam-propofol co-induction.

In a prospective, blind, randomised study, we examined the effects of midazolam-propofol co-induction on haemodynamic (blood pressure, heart rate and stroke volume) and heart rate variability. The latter was measured by spectral analysis using the maximum-entropy method to calculate the following: the low frequency component (LF), which reflects both the cardiac sympathetic and parasympathetic activity, the high frequency component (HF) and entropy, which reflects the cardiac parasympathetic activity, the total power (TP), calculated by the addition of LF and HF, and the LF/HF ratio, which reflects the balance between the cardiac sympathetic and parasympathetic nervous activity. Forty patients were randomly allocated to the propofol group and the midazolam-propofol group, and the parameters described above were calculated at baseline (T1), post induction (T2), after tracheal intubation (T3), and 3 min (T4) and 5 min after intubation (T5). Propofol was administered at 2.5 mg.kg(-1) in the propofol group and midazolam at 0.1 mg.kg(-1) followed by propofol at 1.5 mg.kg(-1) in the midazolam-propofol group for anaesthesia induction. Then, propofol was administered at 4-6 mg.kg(-1)propofol for maintenance in both groups. The midazolam-propofol group showed compensated haemodynamic changes, which were related to significant increases in the LF/HF ratio at T2, T4 and T5 (p = 0.011, 0.038 and 0.034). These results suggest that the midazolam-propofol combination yielded compensated modulatory effects on the cardiovascular system, including preserved baroreflex activity.

Delirium during intravenous sedation with midazolam alone and with propofol in dental treatment.

A 62-year-old man visited our clinic for dental implantation under intravenous sedation. He demonstrated increased psychomotor activity and incomprehensible verbal contact during intravenous sedation. Although delirium caused by midazolam or propofol in different patients has been reported, the present case represents a delirium that developed from both drugs in the same patient, possibly because of the patient's smaller tolerance to midazolam and propofol.

Tracheal intubation using a new CCD camera-equipped device: a report of two cases with a difficult intubation.

In two patients, one with Klippel-Feil syndrome and one with fibrous dysplasia of the maxilla, no part of the larynx could be visualized by direct laryngoscopy. In both cases, the use of an intubation device equipped with a charge-coupled device camera, the endotracheal intubation device (EID), allowed smooth tracheal intubation.

Application of a mandibular nerve block using an indwelling catheter for intractable cancer pain.

We report a case in which a mandibular nerve block using an indwelling catheter was employed for pain management in a terminal case of orofacial cancer. The patient was a 74-year-old female weighing 27 kg. She had a 27-month history of mouth floor and tongue cancer. The cancer recurred and spread to bilateral face and neck. The severest pain mainly originated from the right mandibular region. Two steps of pain relief were performed for the patient. First, pain control using 1% lidocaine or 0.25% bupivacaine administered intermittently or continuously through an indwelling catheter in the mandibular nerve was performed for 1 week to estimate the amount of pain relief thereby obtained. Second, a neurolytic block was applied to the mandibular nerve through the catheter. After the neurolytic block, the total dosage of morphine and diclofenac remained unchanged for 2 months. We conclude from the present case that this technique is an excellent means of obtaining long-term pain control in patients with intractable orofacial cancer pain.

Decreased bispectral index as an indicator of syncope before hypotension and bradycardia in two patients with needle phobia.

We report two cases who exhibited a decrease in their bispectral index (BIS) score, associated with syncope during venipuncture in patients with suspected needle phobia. In case 1, the reduction in BIS score occurred during the development of hypotension and bradycardia and may well have been caused by cerebral hypoperfusion. In case 2, the patient lost consciousness with decreasing BIS score before hypotension and bradycardia; this patient's condition could not be completely explained by cerebral hypoperfusion as a result of a vasovagal reflex because the patient's blood pressure and heart rate remained normal during the syncopal episode.

Benign hyperthermia following prolonged TIVA with propofol.

PURPOSE: Propofol is widely used for general anesthesia because of its rapid onset and recovery. We had four cases that had higher body temperatures toward the end of anesthesia. The etiology of the hyperthermia is discussed. CLINICAL FEATURES: Four patients (three male, one female, 22-26 yr of age, weighing 53-57 kg) with facial deformities were anesthetized with propofol infusion (3-10 mg x kg(-1) x hr(-1)) and fentanyl (400-1,300 microg) without nitrous oxide, immobilized with vecuronium bromide (18-37 mg) or pancuronium bromide (31 mg). In order to reduce blood loss and improve the surgical view, tri-nitro-glycerin (TNG) was used in all cases. Osteotomy of maxilla and mandible or sagittal split ramus osteotomy of mandible was successfully performed. Although their body temperatures were normal preoperatively and stable during the operation, toward the end of anesthesia (one hour), they increased to over 38 degrees C. The room temperature was decreased and the water blanket on the operating table was also decreased. In addition, cool crystalloid solution was infused. Body temperature returned to normal in the ward and no complications due to the high temperature were seen postoperatively. It is thought that lighter anesthesia was masked by continuous infusion of propofol and TNG-induced hypotension and that benign hyperthermia occurred toward the end of anesthesia. CONCLUSION: Propofol reduces blood pressure, which suggests deep anesthesia. However, care must be taken to maintain the optimum depth of anesthesia during propofol anesthesia, especially when deliberate hypotensive anesthesia is induced.

[Dental treatment for the handicapped by a combination of public community, dental association and university hospital--a system of Suginoki Dental Clinic].

Suginoki Dental Clinic, which is managed by Suginami Dental Association, financially supported by Suginami City, and technically assisted by the University Hospital, Tokyo Medical and Dental University, was established for dental treatment of handicapped persons living in Suginami City, Tokyo who are difficult to be treated by private practitioners. It has one full-time dentist, 12 part-time dentists, two dental hygienists, one nurse, and one clerk; one of the part-time dentists practices twice a week there. Since December 1994, 406 patients visited the clinic and the total cases was 9,273 in December 1999; 99 cases were mentally retarded, 36 autism, and 30 epileptic patients in the younger group; and 65 cases were cerebrovascular disease and 27 cardiac malfunction patients in the older group. Almost all the patients needed special care such as monitoring, intravenous sedation, nitrous oxide sedation, and general anesthesia. Four cases underwent general anesthesia, and no complication was seen among the cases. It was concluded that the clinic has been successful due to a good relationship among the Dental Association, Suginami City, and the dental hospital.

[Transient global amnesia after general anesthesia].

A 61 year old male patient with left mandibular cyst, received marsupialization of the left mandible under general anesthesia. Four hours after the end of anesthesia, his memory for the past 4 months and short term memory plastisity were impaired. No neurological abnormalies were found at that time. On the 2nd postoperative day, he recovered his lost memory for the past 4 months. The memory of events between 6 hours before operation and next morning, however, remained lost. It is suggested that the memory disorder is the TGA due to various causes including transient hypertension, operative stress, postoperative pain and diazepam.

Dual brain stem projection from the cortical masticatory area in guinea-pig.

The cortical masticatory area (CMA) in the guinea pig is subdivided into the anterior and posterior parts (A-CMA and P-CMA), based on the pattern of the CMA-induced rhythmical digastric EMG burst and the cytoarchitecture. The anterograde tracing of horseradish peroxidase from the A-CMA and P-CMA revealed, in addition to a common projection to the region around the trigeminal motor nucleus and the parvicellular reticular formation bilaterally, a massive projection to the ipsilateral superior colliculus (SC) from the A-CMA but not from the P-CMA. The results suggest a dual brain stem projection system from the CMA: the direct pyramidal route from the P-CMA and the SC-mediated indirect route from the A-CMA.

Resetting of cortically induced rhythmical jaw movements by stimulation of the cerebellar interpositus nucleus in the guinea pig.

Effects of stimulation of the cerebellar interpositus nucleus on fictive rhythmical jaw movements induced by stimulation of the cortical masticatory area were studied in ketamine-anesthetized, paralyzed guinea pigs. A short pulse-train applied to the interpositus nucleus caused a phase shift in cortically induced rhythmical jaw movements. A phase transition curve indicated that interpositus stimulation can reset the cortically induced rhythmical jaw movements.