Left ventricular performance and cerebral haemodynamics during xenon anaesthesia. A transoesophageal echocardiography and transcranial Doppler sonography study

Ondansetron disintegrating tablets of 8 mg twice a day for 3 days did not reduce the incidence of nausea or vomiting after laparoscopic surgery

BACKGROUND AND OBJECTIVE

Although many antiemetic drugs are available for intravenous use in the hospital setting, few are available after patient discharge. Consequently, nausea and vomiting are frequent complaints from patients at home after ambulatory surgery. We tested the hypothesis that the new 8 mg ondansetron disintegrating tablets will decrease the rate of nausea and vomiting at home after laparoscopic surgery.

METHODS

Ninety-six patients were studied in a randomized double-blind study. Starting the first evening after operation and continuing every 12 h for 3 days, patients received either placebo or ondansetron 8 mg disintegrating tablets orally. The patients returned a questionnaire about postoperative nausea and vomiting, other side-effects, e.g. dizziness, headache, nightmare, anxiety and pain, as well as their overall satisfaction at 24 and 72 h after completion of surgery.

RESULTS

The rates of nausea and vomiting were similar in the two groups, both during the first 24 h (28 versus 48%, placebo and ondansetron, respectively (ns) and during the 24-72 h (21 versus 35% (ns)). The incidence rate of vomiting was 8% (placebo) versus 12% (ondansetron) during the first 24 h (ns) and 9 versus 13% respectively in the 24-72 h (ns). No difference between groups was observed in overall satisfaction, incidence of postoperative pain or other side-effects.

CONCLUSIONS

The use of ondansetron disintegrating tablets of 8 mg twice a day for 3 days did not reduce the incidence of nausea and vomiting in patients undergoing outpatient laparoscopic surgery.

Effects of xenon on mesenteric blood flow

BACKGROUND AND OBJECTIVE

The effects of xenon on mesenteric vascular resistance have not been investigated. Because human beings anaesthetized with xenon show good cardiovascular stability, we believed that the agent would have little or no effect on vascular resistance in the splanchnic bed. We determined the effects of different inhaled xenon concentrations on mesenteric blood flow and mesenteric oxygen consumption in pigs sedated with intravenous propofol.

METHODS

Twenty-three minipigs were instrumented with transit time flow probes around the pulmonary and superior mesenteric arteries as well as with pulmonary artery and portal venous catheters. A 14 h recovery was allowed followed by recordings of baseline values. Xenon was then randomly administered in 0.30, 0.50, and 0.70 end-tidal fractions.

RESULTS

The administration of xenon resulted in an 8% (not dose dependent) decrease in mean arterial pressure (from 99 +/- 15 to 91 +/- 19 mmHg; P < 0.05), a 20% decrease in calculated systemic oxygen consumption (from 0.23 +/- 0.07 to 0.19 +/- 0.04L min(-1); P < 0.01), a 20% reduction in mesenteric oxygen delivery (from 41 +/- 12 to 33 +/- 11 mL min; P < 0.001), a 37% reduction in mesentericmetabolic rate of oxygen (from 11.3 +/- 3.6 to 7.1 +/- 3.2 mL min(-1); P < 0.01) and an 8% decrease in mesenteric artery blood flow (0.22 +/- 0.07 to 0.20 +/- 0.07 L min(-1); P < 0.05) in a dose-dependent fashion. Heart rate, cardiac output, systemic vascular resistance, mesenteric vascular resistance, mesenteric oxygen extraction fraction and portal lactate concentration were not significantly altered by xenon.

CONCLUSIONS

Xenon inhalation in the propofol-sedated pig had no measurable effects on mesenteric vascular resistance. This finding may partly explain the well-known cardiovascular stability observed in patients anaesthetized with xenon. Although mesenteric artery blood flow and mesenteric oxygen delivery decreased during xenon administration, unchanged mesenteric oxygen extraction fraction and portal lactate suggest that metabolic regulation of the splanchnic circulation remained unaltered.

Dopamine stabilizes milrinone-induced changes in heart rate and arterial pressure during anaesthesia with isoflurane

BACKGROUND AND OBJECTIVE

Phosphodiesterase-III inhibitors and dobutamine effectively improve cardiac function in patients with cardiac failure, but they are limited by possible hypotensive effects. We tested the hypothesis that dopamine contributes to stabilizing milrinone-induced haemodynamic changes.

METHODS

Nine patients undergoing major surgery were anaesthetized using nitrous oxide and oxygen supplemented with isoflurane 1-2%. After baseline haemodynamics were recorded, milrinone (25 or 50 microg kg(-1)) was administered over 10min, followed by a continuous infusion (0.5 microg kg(-1) min(-1). The second set of haemodynamic values was measured 50 min after beginning the continuous infusion of milrinone. Dopamine (4 microg kg(-1) min(-1)) was then administered with milrinone.

RESULTS

Milrinone significantly increased the heart rate from 81 +/- 8 to 102 +/- 16beats min(-1), but it decreased the mean arterial pressure from 83 +/- 10 to 66 +/- 10 mmHg and systemic vascular resistance (P < 0.05 for each). The pulmonary capillary wedge pressure, cardiac index and pulmonary vascular resistance did not change significantly. The addition of dopamine to the milrinone infusion significantly decreased the heart rate (94 +/- 12 beats min(-1)) and increased the mean arterial pressure (82 +/- 11 mmHg). Dopamine and milrinone, but not milrinone alone, significantly increased the cardiac index and the rate-pressure product.

CONCLUSIONS

The combination regimen of milrinone and dopamine improved cardiac function, and changes in heart rate and mean arterial pressure induced by milrinone were attenuated by dopamine. The results suggest that a combination regimen of milrinone and dopamine rather than milrinone alone should be used to maintain arterial pressure.

Xenon increases total body oxygen consumption during isoflurane anaesthesia in dogs

BACKGROUND

This study was designed to examine whether the coupling between oxygen consumption (VO2) and cardiac output (CO) is maintained during xenon anaesthesia.

METHODS

We studied the relationship between VO2 (indirect calorimetry) and CO (ultrasound flowmetry) by adding xenon to isoflurane anaesthesia in five chronically instrumented dogs. Different mixtures of xenon (70% and 50%) and isoflurane (0-1.4%) were compared with isoflurane alone (1.4% and 2.8%). In addition, the autonomic nervous system was blocked (using hexamethonium) to study its influence on VO2 and CO during xenon anaesthesia.

RESULTS

Mean (SEM) VO2 increased from 3.4 (0.1) ml kg(-1) min(-1) during 1.4% isoflurane to 3.7 (0.2) and 4.0 (0.1) ml kg(-1) min(-1) after addition of 70% and 50% xenon, respectively (P<0.05), whereas CO and arterial pressure remained essentially unchanged. In contrast, 2.8% isoflurane reduced both, VO2 [from 3.4 (0.1) to 3.1 (0.1) ml kg(-1) min(-1)] and CO [from 96 (5) to 70 (3) ml kg(-1) min(-1)] (P<0.05). VO2 and CO correlated closely during isoflurane anaesthesia alone and also in the presence of xenon (r2=0.94 and 0.97, respectively), but the regression lines relating CO to VO2 differed significantly between conditions, with the line in the presence of xenon showing a 0.3-0.6 ml kg(-1) min(-1) greater VO2 for any given CO. Following ganglionic blockade, 50% and 70% xenon elicited a similar increase in VO2, while CO and blood pressure were unchanged.

CONCLUSIONS

Metabolic regulation of blood flow is maintained during xenon anaesthesia, but cardiovascular stability is accompanied by increased VO2. The increase in VO2 is independent of the autonomic nervous system and is probably caused by direct stimulation of the cellular metabolic rate.

Xenon and nitrous oxide do not depress cardiac function in an isolated rat heart model

PURPOSE

To examine the inotropic and chronotropic effects of xenon (Xe) and nitrous oxide (N2O) compared with nitrogen (N2) on isolated rat hearts. The differences between Xe and N2O were also compared.

METHODS

The effects of Xe, N2O and N2 on coronary perfusion pressure (CPP), heart rate, left ventricular developed pressure (LVDP) and double product (DP) were examined in isolated rat hearts perfused at constant flow (10 mL x min(-1)). Following stabilization and baseline measurement with 95% O2 (plus 5% CO2), the heart was exposed to buffer equilibrated with one of three test gases; 50% N2 with 45% O2 (Group N2: n=9), 50% Xe with 45% O2 (Group Xe: n=9), or 50% N2O with 45% O2 (Group N2O: n=9) for 30 min. Measurements were performed in the last minute of exposure to the test gases.

RESULTS

Gas exposure in all three groups decreased O2 delivery (-50%), CPP (-11%), LVDP (-30%) and DP (-44%) compared with baseline values (P <0.001). However, there were no differences among the groups.

CONCLUSION

Our data suggest that cardiac contractility was decreased by the effects of reduced O2 delivery, but both Xe and N2O did not cause further cardiac depressant effects compared to N2 in this experimental model.

Xenon washout during in-vitro extracorporeal circulation using different oxygenators

BACKGROUND

Xenon anesthesia is known to have no adverse influence on myocardial contractility and cardiocirculatory function even in cardiac compromised patients. To make use of this advantages for cardiac surgery patients undergoing extracorporeal circulation (ECC) it must be known if oxygenators are diffusible for xenon in order to avoid losses of the very expensive noble gas.

METHODS

Xenon saturated blood was recirculated in an in-vitro ECC. In 8 experiments four common oxygenators were investigated using continuous mass spectrometry at the exhaust port to measure xenon concentrations in the exspired gas.

RESULTS

Xenon concentrations at the exhaust port of the oxygenator increased during filling the oxygenator with blood. Peak level was detected within one minute after onset of ECC. No xenon could be measured two minutes after onset of ECC.

CONCLUSIONS

Using common oxygenators xenon is eliminated during ECC and lost into the atmosphere. To maintain anesthesia during ECC continuous xenon application would be necessary to compensate these losses. Due to its high price it would be too expensive to continue xenon anesthesia during ECC. Therefore it is not practicable to use the today's oxygenators and ECC equipment in xenon anesthesia.

The effects of subanaesthetic concentrations of xenon in volunteers

This study reports the subjective, psychomotor and physiological properties of subanaesthetic concentrations of xenon. Ten healthy male volunteers received either xenon or nitrous oxide in a randomised crossover study design. The subjects breathed either xenon (Xe) or nitrous oxide (N2O) from a closed circuit breathing system, according to a randomised, double-blind protocol. The concentration of xenon required to produce sedation, ranged between 27 and 45% (median 35%). All subjects completed the xenon protocol. Subjects were tested using the Critical Flicker Fusion test and derived electroencephalogram parameters, however, neither test was found to reliably predict sedation. The respiratory rate decreased markedly during sedation with xenon. The subjects did not experience any airway irritability (coughing, breath-holding or laryngospasm) during administration of either gas. One subject required anti-emetic treatment in the N2O group compared to none in the Xe group. Eight subjects reported that they found sedation with xenon pleasant and preferable to nitrous oxide. Xenon sedation was well tolerated and was not associated with any adverse physiological effects, however, it was reported to be subjectively dissimilar to nitrous oxide.

The direct myocardial effects of xenon in the dog heart in vivo

Xenon has minimal hemodynamic side effects, but no data are available on its direct myocardial effects in vivo. We examined myocardial function during the global and regional administration of xenon in the dog heart. Anesthetized (midazolam/piritramide) dogs (n = 8) were instrumented for measurement of left ventricular pressure, cardiac output, and blood flow in the left anterior descending coronary artery (LAD) and circumflex coronary artery. Regional myocardial function was assessed by sonomicrometry in the antero-apical and the postero-basal wall. Hemodynamics were recorded during baseline conditions and during inhalation of 50% or 70% xenon, respectively. Subsequently, a bypass containing a membrane oxygenator was installed from the carotid artery to the LAD, allowing xenon administration only to the LAD-dependent myocardium. No changes in myocardial function were observed during inhalation of xenon. The regional administration of 50% xenon had no significant effect on regional myocardial function (systolic wall thickening and mean velocity of systolic wall thickening). Seventy percent xenon reduced systolic wall thickening by 7.2% +/- 4.0% and mean velocity of systolic wall thickening by 8.2% +/- 4.0% in the LAD-perfused area (P < 0.05). There were no changes of global hemodynamics, coronary blood flow, and regional myocardial function in the circumflex coronary artery-dependent myocardium. Xenon produces a small but consistent direct negative inotropic effect in vivo.

IMPLICATIONS

Regional administration of xenon direct to the left anterior descending-perfused myocardium resulted in a small but consistent negative inotropic effect of the noble gas in the dog heart in vivo.

Xenon produces minimal haemodynamic effects in rabbits with chronically compromised left ventricular function

BACKGROUND

Xenon has only minimal haemodynamic side-effects on normal myocardium and might be a preferable anaesthetic agent for patients with heart failure. We studied the haemodynamic changes caused by 70% xenon in rabbits with chronically compromised left ventricular (LV) function.

METHODS

Anaesthetized rabbits were thoracotomized and a major coronary artery was ligated to induce ischaemic heart disease. Nine weeks later, rabbits were again anaesthetized (ketamine/propofol), and haemodynamics were measured during inhalation of 70% xenon using echocardiography [LV end-diastolic dimension (LVedD), fractional shortening (FS), velocity of circumferential fibre shortening (VcF), ejection fraction (EF)] in closed-chest animals. Subsequently, rabbits were thoracotomized and instrumented for measurement of LV pressure (tip manometer), LV dP/dtmax and cardiac output (ultrasonic flow probe). Haemodynamics were recorded again during inhalation of 70% xenon.

RESULTS

All rabbits had compromised LV function 9 weeks after coronary artery ligation. Mean LVedD increased from 12.9 (SD 0.9) mm to 17.1 (0.4) mm; EF decreased from 73 (9) to 64 (8)%; FS decreased from 36 (7) to 29 (5)%; VcF decreased from 28.9 (6.8) to 17.6 (4.7) mm s(-1); all P<0.05. Inhalation of 70% xenon had no effect on haemodynamics in closed-chest rabbits, as measured by echocardiography. After invasive instrumentation, small decreases in LV pressure from 78 (20) to 72 (19) mm Hg, LV dP/dtmax from 3081 (592) to 2633 (503) mm Hg s(-1) and cardiac output from 239 (69) to 225 (71) ml min(-1) were observed during xenon inhalation (all P<0.05).

CONCLUSION

These data show that xenon has only minimal negative inotropic effects in rabbits with LV dysfunction after coronary artery ligation.

Why is xenon not more widely used for anaesthesia?

Many authors write favourably about the use of xenon as an anaesthetic, but the clinical use of xenon is still limited to a small number of patients.

Monitoring xenon in the breathing circuit with a thermal conductivity sensor. Comparison with a mass spectrometer and implications on monitoring other gases

OBJECTIVE

To test the accuracy of a thermal conductivity xenon sensor in vitro and in vivo and to test the effect of xenon on other anesthetic gas analyzers as determined by a mass spectrometry gold standard.

METHODS

The xenon concentration was measured with a prototype of a thermal conductivity sensor and a mass spectrometer in vitro and in 6 patients. Further in vitro experiments determined the impact of xenon on the measurements of oxygen, carbon dioxide and desflurane with three commercially available anesthesia gas monitors.

RESULTS

In vitro the thermal conductivity sensor and an associated computer, when calibrated against a mass spectrometer using a third order polynomial calibration curve measured the xenon concentration to a 95% confidence limit of -1.2 to +1.8 vol% compared to mass spectrometry. In vivo and under clinical conditions with a mixture of xenon, O2 and CO2 the 95% confidence limit was -2.5 to +1.6 vol% with a mean bias of -0.5 vol% over a concentration range of 20 to 70 vol%. Xenon induced a clinically relevant bias on the measurements of oxygen (up to 5 vol%), carbon dioxide and desflurane (both twofold overestimation) in a Hewlett-Packard M1025B monitor. In contrast there was only a small bias on the measurements of a Drager PM8060 and a Datex AS3 compact monitor, which was statistically significant (oxygen and desflurane) but clinically irrelevant.

CONCLUSION

Thermal conductivity is a clinically useful technique to measure xenon in the breathing circuit despite its statistically significant but clinically irrelevant error compared to mass spectrometry. Other gases of interest have to be measured with selected monitors explicitly approved or tested for use with xenon.

Cerebral and regional organ perfusion in pigs during xenon anaesthesia

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.

Xenon does not affect human platelet function in vitro

We sought to determine whether xenon affects platelet glycoprotein expression and platelet-related hemostasis in vitro at a clinically relevant concentration. Human whole blood was stimulated with either adenosine diphosphate or the thrombin receptor agonist peptide (TRAP)-6 after incubation with 65% xenon. Halothane at 2 minimum alveolar anesthetic concentration was used as a positive control. Platelet function and activation were evaluated with two-color flow cytometry. The expression of the platelet glycoproteins GPIIb/IIIa, GPIb, and P selectin were detected with fluorochrome-conjugated monoclonal antibodies. In vitro measurement of platelet-related hemostasis under conditions of high shear stress was performed in citrated whole blood with a platelet function analyzer (PFA-100((R))) by using collagen/epinephrine and collagen/adenosine diphosphate cartridges. Xenon did not affect basal or agonist-induced expression of platelet membrane glycoproteins, activation-dependent conformational changes of the GPIIb/IIIa receptor, expression of P selectin, or PFA closure times. In contrast, halothane reduced TRAP-6-induced activation of the GPIIb/IIIa complex. Furthermore, collagen/epinephrine-induced PFA closure time was significantly prolonged. These results demonstrate that xenon does not affect the unstimulated or agonist-induced platelet glycoprotein expression, activation of GPIIb/IIIa, or platelet-related hemostasis.

[Xenon anesthesia: from myth to reality]

OBJECTIVE

To analyze the current knowledge concerning xenon anaesthesia.

DATA SOURCES

References were obtained from computerized bibliographic research (Medline), recent review articles, the library of the service and personal files.

STUDY SELECTION

All categories of articles on this topic have been selected.

DATA EXTRACTION

Articles have been analysed for history, biophysics, pharmacology, toxicity and environmental effects and using prospect.

DATA SYNTHESIS

The noble gas xenon has anaesthetic properties that have been recognized 50 years ago. Xenon is receiving renewed interest because it has many characteristics of an ideal anaesthetic. In addition to its lack of effects on cardiovascular system, xenon has a low solubility enabling faster induction of and emergence from anaesthesia than with other inhalational agents. Nevertheless, at present, the cost and arety of xenon limit its widespread use in clinical practice. The developement of closed rebreathing system that allowed recycling of xenon and therefore reducing its waste has led to a recent interest in this gas. Reducing its cost will help xenon to find its place among anaesthetic agents. An European multicentric clinical trial under submission will contribute to the discussion of the opportunity for xenon introduction in anaesthesia.

Xenon administration during early reperfusion reduces infarct size after regional ischemia in the rabbit heart in vivo

The noble gas xenon can be used as an anesthetic gas with many of the properties of the ideal anesthetic. Other volatile anesthetics protect myocardial tissue against reperfusion injury. We investigated the effects of xenon on reperfusion injury after regional myocardial ischemia in the rabbit. Chloralose-anesthetized rabbits were instrumented for measurement of aortic pressure, left ventricular pressure, and cardiac output. Twenty-eight rabbits were subjected to 30 min of occlusion of a major coronary artery followed by 120 min of reperfusion. During the first 15 min of reperfusion, 14 rabbits inhaled 70% xenon/30% oxygen (Xenon), and 14 rabbits inhaled air containing 30% oxygen (Control). Infarct size was determined at the end of the reperfusion period by using triphenyltetrazolium chloride staining. Xenon reduced infarct size from 51%+/-3% of the area at risk in controls to 39%+/-5% (P<0.05). Infarct size in relation to the area at risk size was smaller in the xenon-treated animals, indicated by a reduced slope of the regression line relating infarct size to the area at risk size (Control: 0.70+/-0.08, r = 0.93; Xenon: 0.19+/-0.09, r = 0.49, P<0.001). In conclusion, inhaled xenon during early reperfusion reduced infarct size after regional ischemia in the rabbit heart in vivo.

Comparison of inhalation inductions with xenon and sevoflurane

BACKGROUND

Xenon is an odorless gas with low blood-gas solubility coefficient and without occupational and environmental hazards. This investigation was performed to evaluate the speed of induction, and respiratory and cardiovascular reactions to inhalation induction with xenon compared to an equianesthetic concentration of sevoflurane.

METHOD

Twenty-four adult ASA 1-2 patients premedicated with 0.05 mg/kg of midazolam were instructed to take vital capacity breaths of 1 minimum alveolar concentration (MAC) of either xenon or sevoflurane until they lost consciousness. Induction time, total ventilatory volume, tidal volume, respiratory rate, minute ventilation, end-tidal MAC fraction, cardiovascular parameters and oxygen saturation were recorded. The patients were interviewed on the following day to evaluate their acceptability rating of the inhalation inductions.

RESULTS

Compared to equianesthetic sevoflurane, xenon produced a faster induction of anesthesia (147 +/- 59 versus 71 +/- 21 s, respectively) with smaller decreases in respiratory rate, tidal volume and minute ventilation. Both agents showed comparable cardiovascular stability and oxygen saturation during induction. One patient in the sevoflurane group had breath-holding and movements of extremities and another had only breath-holding. No patients in the xenon group experienced any complications.

CONCLUSION

Xenon produced a faster induction of anesthesia without any complications than sevoflurane. Xenon had smaller decreases in tidal volume and respiratory rate during induction than sevoflurane. Xenon might offer an alternative to sevoflurane for an inhalation induction.