Simultaneous assessment of both lung morphometry and gas exchange function within a single breath‐hold by hyperpolarized 129Xe MRI

During the measurement of hyperpolarized ¹²⁹Xe magnetic resonance imaging (MRI), the diffusion‐weighted imaging (DWI) technique provides valuable information for the assessment of lung morphometry at the alveolar level, whereas the chemical shift saturation recovery (CSSR) technique can evaluate the gas exchange function of the lungs. To date, the two techniques have only been performed during separate breaths. However, the request for multiple breaths increases the cost and scanning time, limiting clinical application. Moreover, acquisition during separate breath‐holds will increase the measurement error, because of the inconsistent physiological status of the lungs. Here, we present a new method, referred to as diffusion‐weighted chemical shift saturation recovery (DWCSSR), in order to perform both DWI and CSSR within a single breath‐hold. Compared with sequential single‐breath schemes (namely the ‘CSSR + DWI’ scheme and the ‘DWI + CSSR’ scheme), the DWCSSR scheme is able to significantly shorten the breath‐hold time, as well as to obtain high signal‐to‐noise ratio (SNR) signals in both DWI and CSSR data. This scheme enables comprehensive information on lung morphometry and function to be obtained within a single breath‐hold. In vivo experimental results demonstrate that DWCSSR has great potential for the evaluation and diagnosis of pulmonary diseases.     

Effect of xenon on cerebral autoregulation in pigs

There are little data on the effect of anaesthetic concentrations of xenon on cerebral pressure autoregulation. In this study, we have investigated the effect of 79% xenon inhalation on cerebral pressure autoregulation and CO2 response in pigs. Ten pigs were randomly allocated to receive xenon 79% or halothane anaesthesia, respectively, in a crossover designed study. Halothane was used to validate the experimental set-up. Transcranial Doppler was performed to determine the mean flow velocities in the middle cerebral artery (vMCA) during defined cerebral perfusion pressures and during normo-, hyper- and hypoventilation. The results showed that the inhalation of 79% xenon preserved cerebral autoregulation during conditions of normo-, hyper- and hypoventilation and at different cerebral perfusion pressures in pigs. These results suggest that with the inhalation of xenon, in the highest concentration suitable for a safe clinical use, cerebral autoregulation is preserved.     

Xenon has no effect on cytokine balance and adhesion molecule expression within an isolated cardiopulmonary bypass system

Background. Although almost inert chemically, xenon is not unreactivebiologically. It interacts with receptors involved in the expressionof cytokines and adhesion molecules. The effect of xenon onthe immune function in whole blood has not been studied. Methods. We examined the effects of 70% xenon in oxygen on cytokinebalance and expression of adhesion molecules in an isolatedcardiopulmonary bypass (CPB) system, which simulates an evolvinginflammatory response. Whole blood from 10 healthy male volunteerswas circulated in a CBP system supplied with either 70% xenonin oxygen, or oxygen-enriched air – FO₂=0.3 (control).We took samples of blood after 30, 60 and 90 min of simulatedCBP. We measured interleukin (IL)-1ß, tumour necrosisfactor (TNF)     

Xenon expenditure and nitrogen accumulation in closed-circuit anaesthesia

The high price of xenon has prevented its use in routine, clinic anaesthetic practice. Xenon therefore has to be delivered by closed-circuit anaesthesia. The accumulation of nitrogen is a significant problem within the closed circuit and necessitates flushing, which in turn increases gas expenditure and costs. In previous investigations, nitrogen concentrations between 12% and 16% have been reported in closed-circuit anaesthesia. In order to avoid such nitrogen accumulation, we denitrogenised seven pigs using a non-rebreathing system and connected the animals to a system primed with a xenon/oxygen mixture. In comparison, seven pigs were anaesthetised with xenon using a standard low-flow anaesthetic procedure. Anaesthesia time was 2 h. Nitrogen concentrations in the closed system ranged from 0.08 to 7.04% and were not significantly different from those observed during low-flow anaesthesia. Closed-circuit anaesthesia reduced the xenon expenditure 10-fold compared with low-flow anaesthesia.     

Blood flow in human temporal muscle during tooth grinding and clenching as measured by 133Xenon clearance

abstract — Six healthy human subjects performed grinding and clenching of teeth, to assess if pain releasing and strenuous muscular exercise causes a decrease or total stop of the blood flow through the temporal muscles, as measured by ¹³³Xenon clearance. The mean blood flow/volume of muscle tissue was 25.4 ml×min⁻¹×l⁻¹ during rest, whereas the mean flow was 101.8 ml×min⁻¹×l⁻¹ during grinding, and 62.9 ml×min⁻¹×l⁻¹ during clenching. It is suggested that facial pains induced by strenuous exercise of the jaw muscles are not due to ischemia. On the contrary, the blood flow seems to increase about 300% during grinding and about 150% during clenching.     

Effects of xenon anaesthesia on intestinal oxygenation in acutely instrumented pigs

Background. Xenon is a narcotic gas that might be able to replacevolatile anaesthetics or nitrous oxide due to its favourablepharmacological properties, such as providing haemodynamic stability.Intestinal oxygenation is affected by most volatile anaestheticsas a result of cardiodepressive effects. Reducing oxygenationof the gut might be a factor leading to perioperative organdysfunction. This animal study was designed to assess the effectsof xenon on intestinal oxygenation. Methods. After ethical approval, 24 anaesthetized, acutely instrumentedpigs were randomly assigned to three groups: nine animals receivedxenon anaesthesia with inspiratory concentrations of 0, 20,50 and 65% in addition to their basic i.v. anaesthesia, nineanimals served as a study control group, and five animals wereused to assess model stability. Measurement of systemic andregional haemodynamic and oxygenation parameters was made 30min after changing the xenon concentration. Results. Xenon elicited dose-dependent systemic haemodynamicchanges: heart rate and cardiac output decreased by 30%, whilemean arterial pressure was stable. Superior mesenteric arteryblood flow was lower in the xenon group. Vascular resistanceof the superior mesenteric artery increased. The small intestinaloxygen supply decreased with increasing xenon concentration;the mucosal tissue oxygen partial pressure decreased but didnot reach hypoxic (<5 mm Hg) values. Serosal tissue oxygenpartial pressure was maintained. Conclusions. Xenon, in addition to basic i.v. anaesthesia, eliciteda decrease in cardiac output and maintained mean arterial pressure.Intestinal oxygenation was maintained, although regional macrohaemodynamicperfusion decreased. Xenon does not impair intestinal oxygenationunder physiological conditions.      

Treatment of Vitiligo with 308-nm xenon-chloride excimer laser: therapeutic efficacy of different initial doses according to treatment areas

Many preliminary data suggest that the 308-nm excimer laser can be a highly effective therapeutic alternative for treating vitiligo, inducing rapid repigmentation with minimal ultraviolet irradiation. We evaluated the clinical efficacy of the 308-nm excimer laser treatment for various body areas, using different initial UV doses. One hundred forty vitiligo patches from 69 patients were assigned to 4 groups; face and neck, trunk, extremities, and acral and joint areas. They were then treated twice a week, using different initial UV doses. The rate of repigmentation continued to increase with the number of treatments up to 20 sessions, and then showed plateaus between 20 to 30 sessions. On the other hand, the lesions in acral and joint areas showed the worst responses throughout the treatment sessions. Our findings extend previous observations that the 308-nm excimer laser is an effective treatment option for patients with vitiligo. However, further studies will be needed to determine the optimal dosing and administration method, especially for acral and joint areas.     

Racemic ketamine does not abolish cerebrovascular autoregulation in the pig

BACKGROUND: Little is known about the influence of racemic ketamine on autoregulation of cerebral blood flow (CBF), and available reports regarding its influence on cerebral hemodynamics are contradictory. This study was designed to evaluate cerebrovascular responses to changes in the mean arterial pressure (MAP) during ketamine anesthesia. METHODS: In eight normoventilated pigs anesthesia was induced with propofol and maintained by i.v. infusion of ketamine (15.0 mg kg(-1) x h(-1)) during measurements. The intra-arterial xenon clearance technique was used to calculate CBF. Balloon-tipped catheters were introduced in the inferior caval vein and mid-aorta, and increases or decreases by up to 40% in mean arterial pressure (MAP) in random order were achieved by titrated inflation of these balloon catheters. Cerebral blood flow was determined at each MAP level. Regression coefficients of linear pressure-flow curves were calculated in all animals. RESULTS: From the mean baseline level (101 mmHg) MAP was reduced by 20% and 40%, and increased by 26% and 43%. The maximal mean increase and decrease in MAP induced a 12% increase and a 15% decrease, respectively, of CBF from the mean baseline level (52.6 ml.100 g(-1) x min1). The 95% confidence interval (-0.02; 0.38) of the mean regression coefficient of individual pressure-flow curves does not include the regression coefficient (0.64) of a linear correlation between MAP and CBF including origo (correlation coefficient 0.99), which indicates complete lack of cerebrovascular autoregulation. CONCLUSIONS: We conclude that autoregulation of CBF is not abolished during continuous ketamine infusion in normoventilated pigs and that previous divergent conclusions are unlikely to be associated with severe impairment of cerebrovascular autoregulation.     

Xenon anaesthesia for laparoscopic cholecystectomy in a patient with Eisenmenger's syndrome

There are few reports on anaesthesia for patients with Eisenmenger’ssyndrome requiring non-cardiac surgery and none of the use ofxenon. We describe the use of xenon with a closed- circuit systemin a patient with Eisenmenger’s syndrome having a laparoscopiccholecystectomy. Br J Anaesth 2001; 86: 882–6     

Influence of xenon on pulmonary mechanics and lung aeration in patients with healthy lungs

Background

The anaesthetic xenon shows potent organ-protective properties. Due to high density and dynamic viscosity, peak inspiratory pressure (P_max) increases during xenon application. Thus, barotrauma may counteract organ protection. Accordingly, we investigated the influence of xenon on lung mechanics and lung aeration in patients with normal and reduced thoracic wall compliance.