Sohshi Iwasaki

Changes in concentrations of free propofol by modification of the solution

Because free propofol is thought to be responsible for pain on injection, we investigated the changes in concentrations of free propofol by modifying two kinds of propofol products in a medium- and long-chain triglyceride (MCT/LCT) emulsion and in an LCT emulsion. The techniques used in this study were 1) mixing 2% lidocaine (10:1), 2) mixing 5% dextrose in acetated Ringer’s solution to reduce pH (10:1), and 3) changing the temperature to 4°, 20°, and 36°C. The propofol preparations were dialyzed for 24 h, and the receptor medium was analyzed using high-performance liquid chromatography. The concentration of free propofol in propofol MCT/LCT was significantly smaller by 30% than that in propofol LCT. Neither mixing lidocaine nor cooling reduced the concentrations of free propofol in both products, but the concentrations were reduced by a decrease in pH and by an increase in temperature. Because mixing lidocaine can induce instability in an emulsion of propofol and warming can rapidly induce microbial growth, injection of lidocaine before propofol administration is recommended to reduce the pain on injection. The concentrations of free propofol in propofol MCT/LCT were significantly smaller (by approximately 30%–45%) than those in propofol LCT during any situation in this study.

Evaluation of a newly developed monitor of deep body temperature

In 1971, Fox and Solman [1] first described the use of an electronic servocontrolled system to achieve almost complete thermal insulation. The temperature measuring probe has two thermistors separated by a thermal insulator, with an electrical heating element mounted at the rear of the probe. The temperatures on the two sides of the insulating layer, as detected by the thermistors, are compared by a differential amplifier. The error signal is used to control the heater current in such a way as to achieve a situation in which no temperature gradient arises across the insulating layer and thus no heat flows out through this layer. This technique is called the “zero-heat-flow” method. As long as a zero-heat-flow condition is maintained, the probe is equivalent to an ideal thermal insulator; i.e., heat loss from the skin surface beneath the probe is prevented and, after a sufficient time, the skin surface temperature will equilibrate with the deep tissue temperature. Monitoring of deep body temperature, especially from the forehead, is now often used in cardiac surgery in Japan. Deep temperature monitoring has also been used in intensive care units [2] and for monitoring of circulatory failure [3]. Although the monitoring of deep body temperature is noninvasive, clinical application of the monitor is limited by the slow initial response time and the slow response time for rapid internal temperature changes. The initial response time of a deep temperature thermometer, extending from the time when the probe is placed on the body surface to the time when the measured temperature become stable, seems to be long. The

Carbon dioxide absorbents containing potassium hydroxide produce much larger concentrations of compound A from sevoflurane in clinical practice.

UNLABELLED: We investigated the concentrations of degraded sevoflurane Compound A during low-flow anesthesia with four carbon dioxide (CO(2)) absorbents. The concentrations of Compound A, obtained from the inspiratory limb of the circle system, were measured by using a gas chromatograph. In the groups administered 2 L/min fresh gas flow with 1% sevoflurane, when the conventional CO(2) absorbents, Wakolime(TM) (Wako, Tokyo, Japan) and Dragersorb(TM) (Drager, Lubeck, Germany), were used, the concentrations of Compound A increased steadily from a baseline to 14.3 ppm (mean) and 13.2 ppm, respectively, at 2 h after exposure to sevoflurane. In contrast, when the other novel types of absorbents containing decreased or no potassium hydroxide/sodium hydroxide, Medisorb(TM) (Datex-Ohmeda, Louisville, CO) and Amsorb(TM) (Armstrong, Coleraine, Northern Ireland), were used, Compound A remained at baseline (<2 ppm) throughout the study. In the groups administered 1 L/min fresh gas flow with 2% sevoflurane, Wakolime(TM) and Dragersorb(TM) produced much larger concentrations of Compound A (35.4 ppm and 34.2 ppm, respectively) at 2 h after exposure to sevoflurane. Medisorb(TM) showed measurable concentrations of Compound A (8.6 ppm at 2 h), but they were significantly smaller than those produced by the two conventional absorbents. In contrast, when Amsorb(TM) was used, Compound A concentrations remained at baseline throughout the study period. IMPLICATIONS: Carbon dioxide absorbents containing potassium hydroxide/sodium hydroxide produce much larger concentrations of Compound A from sevoflurane in clinical practice. An absorbent containing neither potassium hydroxide nor sodium hydroxide produces the smallest concentrations of Compound A.

Guideline-oriented perioperative management of patients with bronchial asthma and chronic obstructive pulmonary disease

Increased airway hyperresponsiveness is a major concern in the perioperative management of patients with bronchial asthma and chronic obstructive pulmonary disease. Guidelines using evidence-based medicine are continually being updated and published regarding the diagnosis, treatment, and prevention of these respiratory disorders. Perioperative management in these patients involves: (1) adequate control of airway hyperresponsiveness, including detection of purulent sputum and infection before surgery; (2) evidence-based control of anesthesia; and (3) the aggressive use of beta-2 adrenergic stimulants and the systemic administration of steroids for the treatment of acute attacks. Good preoperative control, including the use of leukotriene antagonists, can reduce the incidence of life-threatening perioperative complications. Awareness of recent guidelines is thus important in the management of patients with airway hyperresponsiveness. This review covers the most recent guidelines for the perioperative management of patients with bronchial asthma and chronic obstructive pulmonary disease.

Design of oxygen delivery systems influences both effectiveness and comfort in adult volunteers

PurposeThe aim of this investigation was to compare the efficiency of four oxygen delivery systems in healthy volunteers.MethodsThe subjects received oxygen at flow rates of 3.0 and 5.0 L·min−1 via a face mask, nasal cannulae, and two kinds of new open- and microphone-type oxygen delivery systems (OxyArm™ and Mike Cannula) in a random sequence, and values of partial arterial pressures of oxygen (RaO2) were measured. The comfort of these devices was also evaluated.ResultsA significant, oxygen flow dependent increase in PaO2 was obtained with all devices tested. PaO2 was significantly higher when the face mask was used [217.5 ± 19.9 (mean ± SD) mmHg at 5 L·min−1) than when the Mike Cannula was used (177.5 ± 14.8 mmHg). The face mask was the least comfortable and OxyArm was the most comfortable among the devices tested.ConclusionThe results of our evaluation suggest that comfort and clinical performance should be considered when using oxygen delivery devices for patients who require oxygen supplementation.RésuméObjectifLe but de la présente étude était de comparer l’efficacité de quatre systèmes de distribution d’oxygène chez des volontaires sains.MéthodeLes sujets ont reçu, suivant une séquence aléatoire, des débits d’oxygène de 3,0 et 5,0 L·min−1 au moyen d’un masque, d’une canule nasale et de deux nouveaux prototypes ouverts et de type microphone (OxyArm™ et Mike Cannula). Les pressions artérielles partielles (PaO2) ont été mesurées. Le confort a été évalué pour chacun des appareils utilisés.RésultatsUne augmentation significative de la PaO2, dépendante du débit d’oxygène, a été obtenue avec tous les appareils. La PaO2 a été significativement plus élevée avec le masque [217,5 ± 19,9 (moyenne ± écart type) mmHg à 5 L·min−1] qu’avec le Mike Cannula (177,5 ± 14,8 mmHg). Le masque était l’appareil le moins confortable et le OxyArm le plus confortable.ConclusionNos résultats indiquent que le confort et la performance clinique doivent être pris en compte au moment d’utiliser des appareils de distribution d’oxygéne pour un apport complémentaire.

Beta-1 selective adrenergic antagonist landiolol and esmolol can be safely used in patients with airway hyperreactivity.

This study was undertaken to clarify the effects of esmolol and landiolol, beta-1 selective adrenergic antagonists, on hyperreactive airways in both ovalbumin-sensitized guinea pigs and asthmatic patients. In the animal study, asthma was induced by ovalbumin. After control acetylcholine responses for total pulmonary resistance (Raw) and dynamic lung compliance (Cdyn) were obtained, the animals received propranolol, esmolol, or landiolol, and the same protocol was again performed. Sixty inpatients with coronary risk factors and asthma were enrolled in the human study. Under propofol anesthesia, the patients received saline, esmolol, or landiolol. To assess intubation-induced bronchoconstriction, the presence of wheezing was determined. The dose-response curves of Raw and Cdyn to acetylcholine were significantly elevated and declined in the ovalbumin-sensitized model compared with those in the control group. Neither esmolol nor landiolol had any effect on the acetylcholine-induced response curve in these sensitized animals. However, propranolol significantly enhanced Raw and reduced Cdyn in this model. Tracheal intubation increased the incidence of wheezing in asthmatic patients. However, there was no significant difference in the incidence of wheezing among these groups. The ultra-short-acting beta-1 selective adrenergic antagonists esmolol and landiolol can be safely used perioperatively in patients with airway hyperreactivity.

The infusion rate of most disposable, non-electric infusion pumps decreases under hypobaric conditions.

PurposeTo examine the delivery rates of four disposable, nonelectric infusion pumps during hypobaric conditions.MethodsFour models categorized by three different driving forces, one vacuum unit (Coopdech Syringector), one spring unit (Linear-fuser), and two elastomeric balloon-powered units (Multirate Infuser LV and Large DIB), were tested. Each infusion pump was placed in an airtight container, and the pressure in the container was decreased to 1,000, 900, and 800 hPa. The catheter tip of each pump was exposed either to atmospheric pressure (1,000 hPa) or to similar hypobaric conditions (800–1,000 hPa).ResultsUnder normal atmospheric pressure, each pump showed an accurate delivery rate in the range of −2% to +8% of the set infusion rate (4.0–5.0 mL·hr−1). With the catheter tip exposed to atmospheric pressure, the infusion rate of each pump was reduced from 35% in the case of the Large DIB to 64% in the case of the Coopdech Syringector, depending on the magnitude of change in hypobaric pressure. When the pressure acting on the catheter tip was reduced to a level similar to that exerted on the pump body, infusion rate was reduced (by 19%–27%) in all three types of pump, and the Large DIB showed no significant difference in performance compared to normal atmospheric pressure.ConclusionThe infusion rates of disposable infusion pumps are reduced under hypobaric conditions. Even though we still do not know how the epidural pressure changes under hypobaric conditions, clinicians should be aware that the infusion rate of disposable infusion pumps is decreased under hypobaric conditions.RésuméObjectifVérifier les vitesses d’administration de quatre pompes à perfusion non électriques jetables utilisées dans des conditions hypobares.MéthodeNous avons testé quatre modèles classés selon trois différentes catégories d’éléments moteurs, un appareil à aspiration (Coopdech Syringector), un appareil à charnière (Linearfuser) et deux appareils élastomères à ballonnet d’entraînement (Multirate Infuser LV et Large DIB). Chaque pompe a été placée dans un contenant hermétique dont la pression interne a été abaissée à 1 000, 900 et 800 hPa. La pointe du cathéter de chacune des pompes a été exposée soit à la pression atmosphérique (1 000 hPa) soit à des conditions hypobares similaires (800– 1 000 hPa).RésultatsSoumise à une pression atmosphérique normale, chaque pompe a affiché une vitesse d’administration précise allant de −2 % à +8 % de la vitesse de perfusion préalablement définie (4,0– 5,0 mL·hr− 1). Si la pointe du cathéter était exposée à la pression atmosphérique, la vitesse de perfusion de chaque pompe était réduite de 35 %, dans le cas du Large DIB,jusqu’à 64 %, pour le Coopdech Syringector, en fonction de l’importance du changement de pression hypobare. Si la pression sur la pointe du cathéter était réduite au niveau de celle qui était exercée sur le corps de la pompe, la vitesse de perfusion était réduite (de 19 % à 27 %) pour les trois types de pompes. La performance du Large DIB n’a pas présenté de différence significative, comparée à la performance sous pression atmosphérique normale.ConclusionLes vitesses de perfusion des pompes jetables sont réduites dans des conditions hypobares. Même si nous ne pouvons encore expliquer les changements de pression péridurale observés dans des conditions hypobares, il faut savoir que la vitesse de perfusion des pompes jetables diminue dans de telles conditions.

Usefulness of oral hypnotic premedication for volatile induction of anesthesia in adults

AbstractPurpose. We investigated the effects of oral hypnotic premedication for smooth anesthetic induction and for the patients comfort under anesthesia, using sevoflurane without nitrous oxide. Methods. Adult patients were divided into four groups: control (n= 12), triazolam (0.25 mg; n= 12), zopiclone (7.5 mg; n= 12), and clonidine (0.15 mg; n= 12) groups. Each premedication was given to each patient 1 h before the anesthesia. The patients breathed out to residual volume and then the anesthetic mask was fitted. The repeated vital capacity breathing technique was used, with 5% sevoflurane in 10 l·min−1 oxygen. Induction time, specific induction side effects, and acceptability of this technique by the patients were recorded by an independent observer. Results. Induction time in the premedicated groups ranged from 66 ± 12 s (mean ± SD) to 76 ± 14 s, and these values were significantly shorter than that in the control group (92 ± 16 s). The number of patients in whom adverse effects occurred during anesthetic induction was significantly greater in the control group (4 patients; 33%) than in the premedicated groups (1 patient each; 8%). Acceptability of the smell of sevoflurane was significantly higher in the premedicated groups (8–10 patients; 67%–83%) than in the control group (5 patients; 42%). Conclusion. Oral hypnotic premedications with either triazolam (0.25 mg), zopiclone (7.5 mg), or clonidine (0.15 mg) are recommended for smoother volatile anesthetic induction and for the patients comfort in adults.

Usefulness of midazolam premedication for volatile induction of anesthesia in adults

Induction of anesthesia can be achieved rapidly using the vital capacity (“single breath”) technique with 8% sevoflurane, which typically produces loss of consciousness in 45‐55 s [1‐3]. This technique using sevoflurane is associated with minimal complications compared with those using halothane [4,5] or isoflurane [6]. Although sevoflurane has little pungency, patients sometimes complain about the discomfort of the induction. We therefore investigated the effect of premedication with midazolam for smoother induction and for the patient’s comfort. One hundred adult patients with ASA physical status I or II who required general anesthesia for minor surgery were enrolled in this study. Patients with a history of, or evidence from laboratory or physical examination indicating, hepatic, renal, or significant respiratory or cardiovascular disease were excluded from the study. The patients were randomly divided into two groups (by the coin technique): control (n 5 48) and midazolam (n 5 52) groups. Intramuscular injection of midazolam (2‐ 3 mg) was given to the midazolam group 1 h before anesthesia, whereas no premedication was given to the control group. While the patients were breathing room air before the induction of anesthesia, the anesthetic circuit was circulated with 10 l·min 21 oxygen and 5% sevoflurane for 1 min. The patients were instructed to breathe out to residual volume, and then the anesthetic mask was fitted tightly. They were then told to take

The Repolarizing Effects of Volatile Anesthetics on Porcine Tracheal and Bronchial Smooth Muscle Cells

UNLABELLED This study was conducted to determine the effects of volatile anesthetics (potent bronchodilators) on membrane potentials in porcine tracheal and bronchial smooth muscle cells. We used a current-clamp technique to examine the effects of the volatile anesthetics isoflurane (1.5 minimum alveolar anesthetic concentration [MAC]) and sevoflurane (1.5 MAC) on membrane potentials of porcine tracheal and bronchial (third- to fifth-generation) smooth muscle cells depolarized by a muscarinic agonist, carbachol (1 microM). The effects of volatile anesthetics on muscarinic receptor binding affinity were also investigated by using a radiolabeled receptor assay technique. The volatile anesthetics isoflurane and sevoflurane induced significant repolarization of the depolarized cell membranes in the trachea (from -19.8 to -23.6 mV and to -24.8 mV, respectively) and bronchus (from -24.7 to -29.3 mV and -30.4 mV, respectively) without affecting carbachol binding affinity to the muscarinic receptor. The repolarizing effect was abolished by a Ca(2+)-activated Cl(-) channel blocker, niflumic acid. These results indicate that volatile anesthetic-induced repolarization of airway smooth muscle cell membranes might be caused by a change in Ca(2+)-activated Cl(-) channel activity and that the different repolarized effects of the volatile anesthetics could in part contribute to the different effects of volatile anesthetics on tracheal and bronchial smooth muscle contractions. IMPLICATIONS By use of a current-clamp technique, the volatile anesthetics isoflurane and sevoflurane repolarized porcine airway smooth muscle cell membranes depolarized by a muscarinic agonist. This effect might be caused mainly by change in Ca(2+)-activated Cl(-) channel activity, not in K(+) channel activity.