Masaki Nagase

Intravenous midazolam suppresses noxiously evoked activity of spinal wide dynamic range neurons in cats.

The effects of intravenously (IV) administered midazolam on noxiously evoked activity of spinal wide dynamic range (WDR) neurons were investigated in decerebrate, spinal-cord-transected cats. Extracellular, single-unit recordings were measured during stimulation by pinching the receptive field on the hind paw and the effect of midazolam at doses of 0.25, 0.5, 1, 2, and 4 mg/kg were measured. Two series of experiments were performed to characterize the analgesic effects of midazolam. In the first, dose-response experiments (n = 59) demonstrated a dose-dependent suppression of the noxiously evoked activity of spinal WDR neurons after midazolam administration. This effect of midazolam was maximal at a dose of 1 mg/kg IV. The second series of experiments (n = 14) demonstrated that a benzodiazepine antagonist, flumazenil (n = 8), promptly reversed the effect of midazolam, while an opioid antagonist, naloxone (n = 6), had no effect on the effect of midazolam. The present study demonstrates that IV administered midazolam suppresses noxiously evoked activity of spinal WDR neurons that is reversible by a benzodiazepine antagonist. This is consistent with an analgesic action of midazolam. (Anesth Analg 1995;80:58-63)

Strychnine poisoning: Natural course of a nonfatal case

A rare case of suicidal strychnine poisoning that resolved naturally without treatment is presented. The patient first complained of chest pain, which was originally thought to be caused by a dissecting aneurysm; however, nystagmus, dysesthesia, spastic paraplesia, and hyperreactivity to stimuli shortly developed. Diagnosis was difficult because the patient did not disclose the drinking of strychnine or the suicidal intent, and no abnormal signs were seen in the various central nervous system examinations. The natural course was observed without treatment because the patients circulatory and respiratory condition was good. Movement disturbances in the upper extremities disappeared after 2 days, nystagmus in 3 days, and dysesthesia and spastic paraplesia in 4 days. The patient was able to stand on the fourth day and walk on the seventh. He was discharged on day 10 without any detectable ill effects.

Optimal administration time of intramuscular midazolam premedication

The optimal administration time for intramuscular injection of midazolam as premedication was studied. Sixty patients ranging in age from 40 to 65 were included. A combination of atropine 0.3–0.5 mg and midazolam 0.08 mg·kg−1 was given to four groups of 15 subjects each in intramuscular injections 45, 30, 15 min, and immediately before entering the operating room. Blood pressure, heart rate, respiratory rate, depression of the root of the tongue, eyelash reflex, degree of sedation, and amnestic effect at the time of arriving the operating room were compared among the groups. There was no difference among the groups in blood pressure, heart rate, and respiratory rate. The depression of the root of the tongue, disappearance of verbal response, and eyelash reflex were found in the 30- and 45-min groups. The degree of sedation and amnestic effect were good except for the group who received midazolam immediately before entering the operating room. From the above results, intramuscular injection of midazolam 0.08 mg·kg−1 with atropine 0.3–0.5 mg is considered best when administered 15 min before entering the operating room.

Rapid induction with 7% sevoflurane inhalation-not the single-breath method.

The usefulness of the rapid anesthesia induction method with 7% sevoflurane, not the single-breath method, was investigated in 88 patients with ASA physical status 1. Anesthesia was induced with 3 l·min−1 nitrous oxide in 3 l·min−1 oxygen and sevoflurane 7% for 3 min (group A), 7% for 5 min (group B), 7% for 7 min (group C), and 5% for 7 min in conventional induction (group D). There were 22 patients in each group. Each sevoflurane concentration was given at the same time as the start of nitrous oxide inhalation except for group D. The changes in blood pressure and heart rate were the smallest in group A. The time for the loss of consciousness was shorter in groups A (47.2 s), B (44.9 s), and C (49.8 s) than in group D (73.4 s). During induction, body movements were seen in 18.2% in group A and 13.6% in the other 3 groups, but no other complications such as coughing, breath holding, or laryngospasm were seen in any group. In conclusion, the anesthesia induction method with 3 min of 7% sevoflurane inhalation was useful for rapid induction.

Suppressive effect of spinal dorsal-horn neuronal activity by local spinal-cord cooling is reversed by naloxone in cats

AbstractPurpose. The purpose of this study was to assess the effect of local spinal cord cooling on spinal dorsal-horn neuronal activity, with special emphasis on the role of endogenous opioid. Methods. Decerebrate, spinal-cord-transected cats (n= 30) were subjected to local spinal-cord irrigation, using 0.9 N saline solution (15°C; n= 15, and 35°C; n= 15) for 90 min. The extracellular, single-cell activity of spinal dorsal-horn neurons responding to noxious stimulation was recorded. Sixty-one minutes after induction of local spinal-cord irrigation, naloxone (0.1 mg·kg−1) was administered intravenously. Local spinal-cord blood flow was measured using the hydrogen clearance technique. Results. Local spinal cord cooling produced significant suppression of both spontaneous and evoked activity (33.1 ± 7.7% and 31.4 ± 5.5%, respectively; mean ± SE). Naloxone reversed this suppression immediately. Local spinal-cord blood flow was significantly reduced during spinal-cord cooling, but naloxone did not change local spinal-cord blood flow. Conclusion. The results demonstrate that endogenous opioids may play an important role in dorsal-horn neuronal suppression induced by local spinal-cord cooling.

Sevoflurane anesthesia for renal transplanted patient—comparison with normal renal function subjects

There are many studies on serum inorganic fuor ide (F-) levels and renal function in sevofurane anesthesia [1-3] because sevoflurane produces F and may cause renal dysfunction. It is not clear, however, what the effect of sevoflurane anesthesia is on a transplanted kidney. In this report, we investigate the serum and urinary F levels and renal function of a patient with a transplanted kidney who underwent sevoflurane anesthesia and compared the results with those of two patients with normal renal function.

The sticker-type skin-surface temperature indicator in anesthesia

The sticker-type skin-surface temperature indicator ProChecker (Kyowa Medex Tokyo, Japan) is a skinsurface temperature monitor that enables continuous and long-duration measurement of body temperature by merely attaching it to the body surface [1]. ProChecker indicates temperature in increments of 2 ~ and body temperature can be read by changes in color at a precision of 0.5 ~ (Fig. 1). We studied the usefulness of ProChecker as a surface temperature monitor during anesthesia by comparing the skin surface temperature measured by Prochecker with the rectal temperature measured by thermometer. The present study included 18 patients (age 11-75 years, body weight 42-70 kg) who underwent laparotomy under general anesthesia. Informed consent was obtained from eac]h patient. To measure the skin surface temperature, ProChecker and the PTP-50 sensor of the thermocouple thermometer PTW-100A (Unique Medical, Tokyo, Japan) were placed side by side on the center of the forehead and on the forearm. The rectal temperature was measured using an electronic thermometer ETC-21A (Top, Tokyo, Japan). During surgery, all temperatures were monitored continuously and recorded at any points where a change in temperature occurred. The differences between the temperatures measured with ProChecker and with the thermocouple thermometer were investigated. Correlations between temperatures were obtained by the least squares method. A value of less than 0.05 was considered significant.

Interactions of nicardipine to inhalation anesthetics sevoflurane and isoflurane

The hemodynamic effects and pharmacokinetics of nicardipine under general anesthesia were compared between two different volatile anesthetics, sevoflurane and isoflurane. Sixteen adult neurosurgery patients were divided into sevoflurane and isoflurane groups. Anesthesia was maintained with either sevoflurane or isoflurane (0.5–1.5%) and nitrous oxide in oxygen. When the blood pressure was stabilized [0.5 minimum alveolar concentration (MAC) in both anesthetics] during surgery, nicardipine 1 mg, i.v. was administered. Plasma catecholamines and nicardipine concentration were measured, and the pharmacokinetics of nicardipine were calculate. The decrease in blood pressure and the increase in heart rate 30 min after nicardipine administration were significant in the isoflurane group but not in the sevoflurane group. Although plasma catecholamine levels increased after nicardipine administration in the isoflurane group, no significant changes were observed in the sevoflurane group. The sevoflurane group had a significantly longer elimination half-life, a larger area under the plasma concentration curve, and smaller clearance of nicardipine compared to the isoflurane group. In summary, the effects of nicardipine on blood pressure and heart rate were significantly longer under isoflurane anesthesia than under sevoflurane anesthesia. However, the etabolism and excretion of nicardipine were significantly delayed under sevoflurane anesthesia.

The effect of pentobarbital sodium on the dorsal horn of the spinal cord

The effect of intravenously administered pentobarbital sodium on the activity of single unit in Rexed lamina V of the transected feline lumbar spinal cord was studied using an extracellular microelectrode recording technique. Pentobarbital sodium 1.0 mg·kg−1, 2.5 mg·kg−1, and 5.0 mg·kg−1 administered intravenously suppressed both the spontaneous and the evoked activity in Rexed lamina V cells, known to respond principally to noxious stimuli, in a dose-dependent manner. The maximum depression of cell activity occurred within 5 min after intravenous administration. The recovery of cell activity occurred within 70 min after intravenous administration of pentobarbital sodium. We conclude that pentobarbital sodium intravenously administered has a suppressive effect on single unit activity of cells in Rexed lamina V and probably has an analgesic effect. Its suppressive effect is dose-dependent.