The minimum alveolar concentration of sevoflurane in cats

Eight adult cats of either sex were studied. The minimal alveolar concentration (MAC) for sevoflurane in the cats was found to be 2.58 ± 0.30% (mean ± SD). The ratios of MAC values between sevoflurane and halothane, enflurane and isoflurane in cats were very similar to those ratios found in humans and dogs. This observation suggests that the results of this study are correct and allows us to estimate unknown MAC values for sevoflurane in other species using known MAC values for other anesthetic agents.(Doi M, Yunoki H, Ikeda K: The minimum alveolar concentration of sevoflurane in cats. J Anesth 2: 113–114, 1988)     

Postanesthetic respiratory depression in humans: A comparison of sevoflurane,isoflurane and halothane

The postanesthetic respiratory depression with sevoflurane, isoflurane and halothane was studied in twenty-one patients. They were divided into three groups of seven patients each. One group underwent sevoflurane anesthesia, another group isoflurane and the third group halothane. Following extubation, the decrease in blood concentration of the anesthetic agent was most rapid with sevoflurane and slowest with halothane. Twenty minutes following extubation, resting ventilation and ventilatory response to carbon dioxide returned to the preanesthetic state with sevoflurane and isoflurane anesthesia. With halothane anesthesia, however, the depressive respiratory effects of halothane remained; depressed ventilatory response to carbon dioxide, decreased tidal volume and increased respiratory frequency. Although halothane has been reported to have the least depressive respiratory effect of the three, its elimination was slowest. Thus the respiratory effects of halothane persisted up to and past the twenty minute mark, far longer than with sevoflurane or isoflurane.(Doi M, Ideda K: Postanesthetic respiratory depression in humans: A comparison of sevoflurane, isoflurane and halothane. J Anesth 1: 137–142, 1987)     

Airway irritation produced by volatile anaesthetics during brief inhalation: comparison of halothane,enflurane, isoflurane and sevoflurane

Eleven male volunteers were studied to compare the airway irritation produced by the four anaesthetic agents: halothane, enflurane, isoflurane and sevoflurane at two concentrations, equivalent to one and two MAC. Tidal volume, respiratory frequency and functional residual capacity changes induced by 15 sec inhalation of the anaesthetics were measured using respiratory inductive plethysmograph. Appearance of the cough reflex was also observed. The order of subjective airway irritation was evaluated by the volunteers. Inhalation of the anaesthetic agents induced a decrease in tidal volume, increase in respiratory frequency and decrease in functional residual capacity. Significant changes were considered to have occurred if tidal volume and respiratory frequency changed by more than 30% from the resting values for at least ten seconds, or if functional residual capacity changed by more than 30% of the value at resting tidal volume, for at least ten seconds. Each change was induced most frequently by isoflurane followed by enflurane, halothane and, least frequently, by sevoflurane. The orders of appearance of the cough reflex and of subjective airway irritation were similar. Sevoflurane did not elicit a cough reflex. It is concluded that sevoflurane was the least irritant anaesthetic and is considered to be the most suitable for inhalational induction of anaesthesia. Sept volontaires du sexe masculin font partie dune étude visant à comparer les ejfets irritants de quatre agents anesthésiques sur les voies respiratoires: l’halothane, l’enflurane, l’ isoflurane et le sévoflurane, à deux concentration qui équivalent soit à MAC 1, soit à MAC 2. On mesure les changements de volume courant, de fréquence respiratoire et de capacité résiduelle fonctionnelle à l’aide d’un pléthysmographie à induction. On note l’apparition du réflexe de toux. De plus, on évalue le degré subjectif d’irritation éprouvé par les sujets. L’inhalation d’agents anesthésiques cause une baisse du volume courant, une augmentation de la fréquence respiratoire et une diminution de la capacité résiduelle fonctionnelle. On considère significatifs les changements de volume courant et de fréquence respiratoire de plus de 30% des valeurs de repos pour au moins dix secondes, les changements de capacité résiduelle fonctionnelle de plus de 30% de sa valeur au volume courant de repos pour au moins dix secondes. Les changements sont initiés principalement par l’isoflurane, suivi par l’enflurane, l’halothane et moins fréquemment par le sévoflurane. L’ordre d’apparition du réflexe de toux et de l’impression subjective d’irritation des voies aériennes est identique. Le sévoflurane ne provoque pas de réflexe de toux. On conclut que le sévoflurane est le moins irritant des anesthesiques et qu’on peut le considerer comme celui qui convient le mieux à l’induction de l’anesthésie par inhalation.     

Evaluation of combined antibiotic-omeprazole therapies in Helicobacter pylori-infected Mongolian gerbils

Mongolian gerbils are a laboratory host for gastric colonization with Helicobacter pylori, showing gastritis followed by typical gastric ulcer after infection with H. pylori. In such gerbils, we evaluated combined therapies of amoxicillin (AMPC) and clarithromycin (CAM) as antibiotics, and omeprazole (OPZ) as a H⁺/K⁺ adenosine triphosphatase (ATPase) inhibitor. The gerbils were orally inoculated with 2 × 10⁸ bacilli of ^{H. pylori} ATCC 43504. Four weeks after inoculation, the infected gerbils were orally treated singly with OPZ, AMPC, and CAM, and their insufficient efficacy on bacterial clearance was confirmed by a polymerase chain reaction technique, and by a culture method. In contrast, combined therapy of OPZ plus either AMPC or CAM showed significant bacterial clearance, demonstrating the efficacy of this combined therapy in the gerbil model. Mongolian gerbils are suggested to be useful for the pharmacological evaluation of anti-H. pylori compounds. Received Mar. 11, 1997; accepted June 27, 1997     

Influence of tumor size on anesthetic management for pheochromocytoma resection

The relationship between tumor size and the complexity of anesthetic management was studied using several values: plasma catecholamine concentrations, requirement of vasoactive agents, surgical time, blood loss, plasma glucose concentrations, and hemodynamic variables. Ten patients with clinical and laboratory diagnosis of pheochromocytoma were prospectively studied. Each anesthesia was maintained using inhalational anesthetic agents. Control of arterial blood pressure (ABP), heart rate (HR), and pulmonary artery blood pressure (PABP) was attempted with only titrating the inhalational anesthetics and adenosine triphosphate (ATP). If the titration of both the inhalational anesthetic and ATP failed to control ABP, HR, or PABP, then phentolamine, propranolol, trinitroglycerine, or norepinephrine was additionally used. Tumor weight was significantly correlated with amount of blood loss, surgical time, duration of ATP requirement, maximal dose of ATP infusion used, maximal plasma glucose concentration, and plasma total catecholamine concentration. However, the tumor weight was not correlated with hemodynamic variables. Patients who required propranolol generally had a significantly larger tumor than those who did not. In conclusion, surgical removal of large pheochromocytoma required more complicated anesthetic management than that of small pheochromocytoma.     

Bispectral index decreased to "10" during propofol anesthesia despite the appropriate serum concentration of propofol

We report a case showing a bispectral index (BIS) value "10" during anesthesia maintained with propofol. Vital signs of the patient including blood pressure and heart rate were stable and the depth of anesthesia was considered as adequate. The serum concentration of propofol measured later was 2.5 and 2.2 microg ml(-1) when BIS indicated 10 and 35, respectively. The age of patient was 81 and the BIS values in elderly might decrease in accordance with the reduction of brain function.     

Frequently repeated fick cardiac output measurements during anesthesia

A computer-based system was developed for monitoring cardiac output using the Fick principle during general anesthesia. The variables of the oxygen-consumption Fick equation were measured using the following system: oxygen uptake by an originally developed respiratory gas monitoring system, arteriovenous oxygen saturation difference by pulse and fiberoptic oximetry, and hemoglobin concentration by an in vitro oximeter. Fick cardiac output and systemic vascular resistance were calculated every 30 seconds. Fick cardiac output was compared with thermodilution cardiac output in 11 anesthetized patients. A total of 208 corresponding cardiac output measurements showed a range of 2 to 9 L · min^-1. The correlation coefficient between the thermodilution and Fick cardiac outputs was 0.961, with a regression equation of Fick cardiac output = 1.058 thermodilution cardiac output 0.359. The difference between the thermodilution and Fick cardiac outputs was 0.103 ± 0.395. The Fick cardiac output was significantly lower than the thermodilution cardiac output, especially in the low flow range. We demonstrated that this new monitoring system was clinically feasible and sufficiently accurate, under the limited circumstances of our study. The integration of routinely used equipment has made possible a frequently repcatable method for estimating cardiac output in patients.     

The effect of halothane or sevoflurane anesthesia on the extracellular concentration of dopamine and its metabolites examined by in vivo microdialysis techniques

BACKGROUND: Volatile anesthetics induce changes in the extracellular concentration of dopamine (DA) metabolites in the rat striatum and their metabolism might be modified in different manners by different anesthetics. Although, we have studied DA metabolism during anesthesia using in vivo microdialysis techniques, time dimensional changes were not assessed concerning the difference between anesthetics. In the current investigation, the rats were anesthetized with halothane or sevoflurane, which has different blood solubility, and investigated the effect of anesthetics and time-related development on DA metabolism. METHODS: The rats were implanted with a microdialysis probe in the striatum and perfusate was introduced to HPLC every 20 min. Anesthesia was induced with halothane or sevoflurane for 20 or 60 min, and methamphetamine 2 mg x kg(-1) was administered during or after inhalation. RESULTS: Both anesthetic agents increased the concentration of DA metabolites, and dose and time dependency was more obvious with sevoflurane than with halothane. The increase of metabolites was prolonged after halothane anesthesia (20 min), but the effect of methamphetamine administered immediately after anesthesia on DA release was not enhanced by halothane anesthesia. Sevoflurane, not halothane anesthesia, antagonized methamphetamine-induced decrease of metabolites. CONCLUSIONS: Not only the difference of blood solubility between halothane and sevoflurane and anesthetic effect of time dependency, but also another pharmacological property affects DA metabolism, including the change in the activity of dopamine transporter during inhalation of anesthetics.