Hikaru Kohase

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

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, leading to decreased HR and BP, and 2) midazolam induces predominance of sympathetic activity, leading to increased HR and decreased BP. Thirty dental patients were included in a prospective, randomized study. 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 in total power (503 ± 209 ms2/Hz versus 162 ± 92 ms2/Hz) and LF/HF ratio (2.5 ± 1.2 versus 1.0 ± 0.4), 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 significantly change LF/HF ratio (2.3 ± 1.1 versus 2.2 ± 1.4) and increased HR in the sedation period. Compared with baseline, propofol was associated with a significant 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.

Long-term pain control in trigeminal neuralgia with local anesthetics using an indwelling catheter in the mandibular nerve.

ObjectiveThe authors sought to determine the usefulness of long-term continuous trigeminal nerve block with local anesthetics using an indwelling catheter in a patient with trigeminal neuralgia. DesignThe study design included pain control in a patient with trigeminal neuralgia until the time of neurosurgical operation. SettingThe study was conducted in the Dental Hospital of Tokyo Medical and Dental University. PatientThe patient was a 78-year-old woman with trigeminal neuralgia in the right maxillary region. Her pain could not be controlled by carbamazepine and was unbearable. InterventionThe authors estimated the patients pain intensity, quality, and locality using a visual analog scale to determine the effectiveness of continuous nerve block. Outcome MeasuresVisual analog scores were measured during treatment. The treatment term was divided into three periods according to the difference of the catheter location and injection protocol (premandibular nerve block, infuser injection, and patient-controlled analgesia [PCA] pump injection). The authors also examined the patients general condition and blood concentration of drugs. ResultsThe visual analog values were 44.8 ± 3.6, 26.7 ± 3.5, and 11.9 ± 3.1 mm in each period, respectively. The value in the PCA pump infusion period was significantly lower than that in the other periods. No side effects of the local anesthetics were observed on the patients systemic condition. ConclusionsThe authors controlled trigeminal neuralgia pain by blocking the mandibular nerve with local anesthetics administered through an indwelling catheter. Because the continuous nerve block with local anesthetics is reversible and only mildly toxic, this method is beneficial for pain control in patients with trigeminal neuralgia scheduled to undergo microvascular decompression.

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.

Effects of dexmedetomidine on conditioned pain modulation in humans

Systemic administration of dexmedetomidine (DEX; selective α2‐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.

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 intuba‐tion (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−1propofol 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.

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 cytoarchitec-ture. 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.

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.

Phenylephrine suppresses the pain modulation of diffuse noxious inhibitory control in rats.

BACKGROUND:Diffuse noxious inhibitory control (DNIC) is a phenomenon whereby wide dynamic range neurons are selectively and powerfully inhibited through the central nervous system by noxious stimuli heterotopically applied to a body area distant from their excitatory receptive fields. Previous work has shown that systemic administration of an &agr;1-adrenoceptor agonist, phenylephrine (PE), blocked the DNIC. We hypothesized that descending inhibitory pathways mediate the DNIC mechanism and that the neural network of the DNIC loop exists in the middle brainstem, likely in a more rostral part than formerly assumed, possibly the nucleus raphe magnus (RMg). The aim of this study was to determine whether DNIC is directly modulated by PE when administered close to the RMg. METHODS:The experiments were performed on anesthetized male Sprague-Dawley rats. For administration of different drugs close to the RMg, the tip of a 33-gauge cannula was placed into an area close to the RMg as determined using the atlas of Paxinos and Watson. Single square-wave electrical stimuli were applied to the digits of the left hindpaw. The C-fiber reflex response elicited by electrical stimulation within the receptive field of the ipsilateral sural nerve was recorded from the biceps femoris muscle in the absence and presence of noxious tail immersion in warm water at 50°C. The DNIC effect was calculated from a recorded electromyogram as the “inhibition rate.” Saline (0.05 &mgr;L) or PE (0.05 &mgr;g/0.05 &mgr;L) was microinjected close to the RMg through the cannula. The C-fiber reflex evoked by electromyographic activity was recorded the same way. The inhibition rate of the C-fiber reflex was compared before and after administration of drugs. A paired t test was used for statistical comparison between same drug administration groups, and 1-way analysis of variance and Bonferroni multiple comparison were used for statistical analysis between different drugs. At the end of all experiments, the tissue-contacting end of the cannula tip was cauterized with an electric current to localize the drug administration site. The brain was removed, sliced in coronal sections, and stained with hematoxylin and eosin. RESULTS:The C-fiber reflex inhibited by noxious thermal stimuli (DNIC) was significantly blocked after the injection of PE close to the RMg. CONCLUSION:Direct administration of PE close to the RMg inhibited DNIC, thereby affecting and modulating the intrinsic pain inhibition system. These findings suggest that the RMg may be involved in the regulation of DNIC.

Determination of the standard value of circulating blood volume during anesthesia using pulse dye-densitometry: a multicenter study in Japan.

PurposeThe standard value for circulating blood volume (BV) during anesthesia was determined by a multicenter study in Japan. The significance of BV on the reduction of blood pressure after the induction of anesthesia was also examined.MethodsThe study included 184 patients from eight university hospitals. After the induction of anesthesia, pulse dye-densitometry was performed according to a uniform protocol. Factors contributing to reduced blood pressure after induction of anesthesia were examined by multiple logistic regression analysis.ResultsThe mean and standard deviation of BV was 80.0 ± 13.9 ml·kg−1; for females and 84.2 ± 15.3 ml·kg−1 for males (P > 0.05). There was no age difference in terms of BV. After adjusting for the effects of height, weight, and age, the factors predisposing to a reduction in blood pressure of >20 mmHg after induction of anesthesia were found to be age (P < 0.01) and BV (ml·kg−1) ( P < 0.001).ConclusionWe determined the BV of anesthetized patients before surgery in Japan using pulse dye-densitometry. It is suggested that age is not a factor regarding BV, and that blood pressure tends to be reduced in hypovolemic patients after induction of anesthesia.

Endotracheal intubation device with a charge couple device camera.

We developed an orotracheal intubation device equipped with a charge couple device (CCD) camera, providing a wide field of vision. We used this device to perform endotracheal intubations in 62 anesthetized patients undergoing dental treatment and oral surgery. The time required to perform an endotracheal intubation with this system was examined. The use of this system is described below. The wand with the CCD camera was inserted into the oropharyngeal cavity. The oropharynx, including the epiglottis and glottis, could be visualized on the monitor screen. The tube introducer was inserted into the trachea through the vocal cords via the side tube of the wand. The wand with the CCD camera was withdrawn, leaving the tube introducer in the trachea. The endotracheal tube was then inserted into the trachea by using the tube introducer as a guide. The time required for the procedure was determined. The mean total time for the procedure was 41.2 s (maximum, 155 s; minimum, 14 s). There were no significant differences in this procedure when the patients were grouped according to the Cormack and Lehane classification. There was no failure to intubate using this system. Because the device can extensively visualize not only the larynx, glottis, and vocal cords, but also the movement of the tube introducer, on the monitor screen via the CCD camera, endotracheal intubation can be easily performed while the vocal cords are visualized on the monitor screen.