No abstract

40 patients (24 male, 16 female, aged 21-59 years) of American Society of Anesthesiologists class I or II who were undergoing routine surgery took part in a randomised, double-blind comparison of the anaesthetic efficacy and potency of xenon and nitrous oxide and their effects on the circulatory and respiratory systems. During anaesthesia, for each rise in blood pressure of more than 20% of the preanaesthetic (baseline) value, the patient received 0.1 mg fentanyl. The total amount of fentanyl required per patient was used as an index of the anaesthetic potency of the study gases. Patients in the xenon group required on average only 0.05 mg fentanyl, whereas those in the nitrous oxide group required 0.24 mg fentanyl; the duration of anaesthesia was similar in the two groups. Changes in blood pressure were significantly greater throughout the study in the nitrous oxide than in the xenon group. Thorax-lung compliance fell during the study period in the nitrous oxide group but not in the xenon group. Thus, xenon is a potent and effective anaesthetic which can be safely used under routine conditions.

Little is known about the haemodynamic effects of inhaled xenon on regional organ perfusion. The aim of this study was to investigate the effect of 79% xenon ventilation on organ perfusion in pigs. We investigated 10 pigs, which were randomly allocated to receive either xenon 79% or total intravenous anaesthesia (TIVA)/oxygen anaesthesia. Microspheres were used to determine organ perfusion. The following regions of interest were investigated: cerebral cortex, medulla oblongata, brainstem, cerebellum, liver, kidney, small intestine, colon, muscle, skin and heart. The results demonstrated a significant increase in regional perfusion in the brainstem (+63%), cerebral cortex (+38%), medulla oblongata (+35%) and cerebellum (+34%). All other organs showed no significant change in regional perfusion. We conclude that xenon should be used with caution in clinical situations associated with pathological increases in intracranial pressure, e.g. neurosurgical procedures, head injury, cerebral mass lesions or stroke.

Higher oxygen content in liver venous blood observed during xenon anesthesia was not induced by changes in hepatic perfusion distribution or by an impairment of liver metabolic capacity. However, it can be explained by similar results known from inhalation anesthesia. Additionally, the effect can be caused by the reduction of plasma catecholamine concentrations during xenon anesthesia.

SummaryLittle is known about the haemodynamic effects of inhaled xenon on regional organ perfusion. The aim of this study was to investigate the effect of 79% xenon ventilation on organ perfusion in pigs. We investigated 10 pigs, which were randomly allocated to receive either xenon 79% or total intravenous anaesthesia (TIVA)/oxygen anaesthesia. Microspheres were used to determine organ perfusion. The following regions of interest were investigated: cerebral cortex, medulla oblongata, brainstem, cerebellum, liver, kidney, small intestine, colon, muscle, skin and heart. The results demonstrated a significant increase in regional perfusion in the brainstem (163%), cerebral cortex (138%), medulla oblongata (135%) and cerebellum (134%). All other organs showed no significant change in regional perfusion. We conclude that xenon should be used with caution in clinical situations associated with pathological increases in intracranial pressure, e.g. neurosurgical procedures, head injury, cerebral mass lesions or stroke.

This study was designed to determine the relative analgesic efficacy and safety of single intramuscular injections of ketorolac (10 mg or 30 mg) and morphine (10 mg) in patients of either sex with moderate to severe pain after major surgery. In a single-dose, randomised, double-blind study of parallel design, pain was assessed immediately before injection of test medication and at regular intervals for 8 h thereafter. One hundred and seventeen patients (109 undergoing cardiac surgery; 8 lung surgery) were randomized to one of the three treatment groups. Pain intensity was assessed using a 5-point verbal scale before administration of study drugs. Postadministration, at 30 min and hourly for 8 h, pain intensity and pain relief were assessed, again using the 5-point verbal scale. Additionally, as a measure of analgesia, forced expiratory volume (FEV1) was obtained in all patients. Vital signs including blood pressure, pulse, temperature, respiratory rate and blood gases (PaCO2) were recorded prior to and after study medication. Based on hourly pain intensity differences and hourly pain relief observations, ketorolac 10 mg was generally more effective than morphine 10 mg, and ketorolac 30 mg was generally more effective than ketorolac 10 mg. The results of this study show that ketorolac is an effective and safe (with regard to arterial pressure, blood gases and lung function) analgesic for relief of postoperative pain after major surgery in stable patients. No clinically significant adverse effects occurred during the study. One cannot exclude an influence on patients with organ system dysfunction or on parameters not measured in this study.

The rate of oxygen consumption was measured in 2-day Zucker preobese (fa/fa), homozygous (Fa/Fa) lean, and lean rats of unknown genotype (Fa/?) over the ambient temperature range of 26-35 degrees C. Significant differences in body mass were found among the three groups at this early age, the preobese pups having the greatest body mass. To account for body mass differences, the oxygen consumption data were expressed in terms of metabolic body size (ml O2 consumed X g body mass-2/3 X h-1). This mass-independent rate of oxygen consumption was significantly lower in the preobese pups than in the homozygous lean (Fa/Fa) pups at both thermoneutral (33-34 degrees C) and cold (26-27 degrees C) ambient temperatures at which, respectively, minimal and maximal rates of oxygen consumption were observed. This reduction in energy expenditure occurs before the establishment of hyperphagia or decreased levels of activity in the preobese pups. These data support the view that attenuated energy expenditure is a significant contributor to the early development of obesity in the Zucker fatty rat and point to the possibility of defective brown adipose tissue-mediated thermogenesis in the preobese pup.

During Xenon anesthesia, elevated ICP is not increased further and is partially reversible by hyperventilation. Our study suggests that inhalation of 75% Xenon seems not to be contraindicated in patients with elevated ICP.