[Renal effects and metabolism of sevoflurane in Fisher 3444 rats: an in-vivo and in-vitro comparison with methoxyflurane]

A Round Trip: The Japanese Contribution to the Development of Sevoflurane

Sevoflurane was first synthesized independently by Richard Wallin and Bernard Regan at Travenol Laboratories Incorporated and Ross Terrell and Louise Croix at Airco, Inc in the late 1960s, and subsequent animal studies and a phase-1 human trial of the agent published in 1981 showed promising results. Further research in the United States was halted, however, because of concerns regarding potential nephrotoxicity and the introduction of less degradable alternatives. Interest in sevoflurane resumed in Japan when Maruishi Pharmaceutical Company, Limited (Ltd) (Maruishi) decided to continue its development in 1982. They secured approval by the Japanese Ministry of Health, Labor and Welfare for its clinical use in January 1990. Because of its low blood:gas partition coefficient and resulting rapid action, sevoflurane quickly became the anesthetic of choice of Japanese anesthesiologists. In 1992 Abbott Laboratories, now AbbVie, Inc (Abbott, North Chicago, IL) finalized a licensing agreement with Maruishi to seek the US Food and Drug Administration approval for sevoflurane sales in the United States. Approved in June 1995, sevoflurane is now marketed by Abbott in 120 countries and has been administered >120 million times. This report details the Japanese contribution to the development of sevoflurane.

Sevoflurane has no adverse effects on renal function in cirrhotic patients: a comparison with propofol

BACKGROUND

Cirrhotic patients are prone to developing renal dysfunction after anaesthesia and surgery. However, no consensus has been reached whether sevoflurane could have adverse effects on renal function in cirrhotic patients. We hypothesised that the use of sevoflurane for general anaesthesia would lead to post-operative renal dysfunction in cirrhotic patients undergoing liver resection.

METHODS

A total of 200 patients undergoing liver resection were randomly assigned to a propofol or sevoflurane group. The influence of sevoflurane or propofol on renal function was evaluated by the maximal change, the difference between the pre-operative baseline and the highest values of serum creatinine and blood urea nitrogen measured at day 1, 3 and 6 post-operatively.

RESULTS

The maximal change in serum creatinine after liver resection was -4.52 (5.78) μmol/l and -3.37 (7.34) μmol/l with P = 0.398, and that in blood urea nitrogen was 0.41 (1.49) mmol/l and 0.93 (1.54) mmol/l with P = 0.098 between the sevoflurane group (n = 52) and the propofol group (n = 50), respectively.

CONCLUSIONS

Sevoflurane does not seem to impair post-operative renal function in cirrhotic patients undergoing liver resection.

Minimum alveolar concentration of halogenated volatile anaesthetics in left ventricular hypertrophy and congestive heart failure in rats

BACKGROUND

Although many physiological and pathological conditions affect minimal alveolar concentration (MAC), there are no reliable data on the MAC for halogenated anaesthetics during left ventricular hypertrophy (LVH) and congestive heart failure (CHF). The aim of this experimental study was to determine the MAC values of halothane, isoflurane, and sevoflurane in rats, at early and later stages of cardiomyopathic hypertrophy.

METHODS

LVH was induced by ascending aortic stenosis in 3-4-week-old rats. LVH and CHF in each animal were assessed weekly by echocardiography. MAC of halothane, isoflurane, and sevoflurane was determined using the tail-clamp technique in spontaneously breathing rats from each group. Response vs no-response data were analysed using logistic regression analysis. Data are medians (95% confidence interval).

RESULTS

The MAC of halothane [1.30% (1.26-1.34)], isoflurane [1.52% (1.48-1.57)], and sevoflurane [2.93% (2.78-3.07)] in rats with LVH was not different from sham-operated rats [respectively, 1.23% (1.20-1.26), 1.52% (1.47-1.56), and 2.90% (2.79-3.00)]. Conversely, the MAC of halothane [1.44 (1.39-1.50)] and isoflurane [1.74 (1.69-1.78)], but not sevoflurane [2.99 (2.93-3.06)], was significantly increased in rats with CHF.

CONCLUSIONS

MAC values for halothane, isoflurane, and sevoflurane were unchanged in rats with pressure-induced overload LVH. Conversely, the MAC for halothane and isoflurane, but not sevoflurane, was significantly increased in rats with CHF.

Effect of sevoflurane preconditioning on ischaemia/reperfusion injury in the rat kidney in vivo

BACKGROUND AND OBJECTIVE

Whereas the protective effect of anaesthetic and ischaemic preconditioning has been described for several organs, it is uncertain whether this mechanism is also effective in the kidney. We compared the effect of preconditioning with sevoflurane and preconditioning with short episodes of ischaemia on renal ischaemia/reperfusion injury in the rat in vivo.

METHODS

Fourteen days after right-sided nephrectomy, anaesthetized male Wistar rats were randomly assigned to a sham-operated group (no arterial occlusion, n = 5) or underwent 45 min of left renal artery occlusion (control group, n = 9) followed by 3 days of reperfusion. Two further experimental groups of animals were preconditioned prior to ischaemia either by administering 1 MAC sevoflurane for 15 min followed by 10 min of washout (sevoflurane group, n = 10) or by subjecting the animals to three short episodes of renal ischaemia (ischaemia-preconditioned group, n = 8). Blood creatinine was measured during reperfusion and morphological damage was assessed by histological examination.

RESULTS

Baseline creatinine values were similar in all four groups (0.7 +/- 0.2 mg dL-1; mean +/- SD) and remained unchanged in the sham-operated animals after 3 days (0.8 +/- 0.2 mg dL-1). Creatinine levels increased in the ischaemic preconditioning group (3.3 +/- 1.2 mg dL-1) and sevoflurane preconditioning group (4.0 +/- 1.1 mg dL-1) compared to the control group (1.6 +/- 0.6 mg dL-1). Morphological damage was less severe in the control group, i.e. in animals without preconditioning, than in both preconditioning groups.

CONCLUSION

Neither sevoflurane nor ischaemic preconditioning preserves renal function or attenuates cell damage in the rat in vivo.

Effects of sevoflurane dose and mode of ventilation on cardiopulmonary function and blood biochemical variables in horses

OBJECTIVE

To quantitate effects of dose of sevoflurane and mode of ventilation on cardiovascular and respiratory function in horses and identify changes in serum biochemical values associated with sevoflurane anesthesia.

ANIMALS

6 healthy adult horses.

PROCEDURE

Horses were anesthetized twice: first, to determine the minimum alveolar concentration (MAC) of sevoflurane and second, to characterize cardiopulmonary and serum biochemical responses of horses to 1.0, 1.5, and 1.75 MAC multiples of sevoflurane during controlled and spontaneous ventilation. Results-Mean (+/- SEM) MAC of sevoflurane was 2.84 +/- 0.16%. Cardiovascular performance during anesthesia decreased as sevoflurane increased; the magnitude of cardiovascular depression was more severe during mechanical ventilation, compared with spontaneous ventilation. Serum inorganic fluoride concentration increased to a peak of 50.8 +/- 7.1 micromol/L at the end of anesthesia. Serum creatinine concentration and sorbitol dehydrogenase activity reached their greatest values (2.0 +/- 0.8 mg/dL and 10.2 +/- 1.8 U/L, respectively) at 1 hour after anesthesia and then returned to baseline by 1 day after anesthesia. Serum creatine kinase, aspartate aminotransferase, and alkaline phosphatase activities reached peak values by the first (ie, creatine kinase) or second (ie, aspartate aminotransferase and alkaline phosphatase) day after anesthesia.

CONCLUSIONS AND CLINICAL RELEVANCE

Sevoflurane causes dose-related cardiopulmonary depression, and mode of ventilation further impacts the magnitude of this depression. Except for serum inorganic fluoride concentration, quantitative alterations in serum biochemical indices of liver- and muscle-cell disruption and kidney function were considered clinically unremarkable and similar to results from comparable studies of other inhalation anesthetics.

Halogenated inhalational anaesthetics

The halogenated inhalational anaesthetics halothane, enflurane, isoflurane and desflurane can produce metabolic hepatocellular injury in humans to a variable extent. During metabolism of these anaesthetics, tissue acetylation occurs due to the formation of reactive intermediates. Proteins modified by acetylation may constitute neo-antigens with a potential for triggering an antibody-mediated immune response. The likelihood of suffering post-operative immune hepatitis depends on the amount of the anaesthetic metabolized and is thereby considerably less with enflurane, isoflurane or desflurane compared with halothane. Plasma inorganic fluoride concentrations are regularly increased after sevoflurane. Elevated inorganic fluoride concentrations have been associated with nephrotoxicity following methoxyflurane anaesthesia but not after sevoflurane. Another source of concern is the products of degradation from reactions with carbon dioxide absorbents. Most important is compound A, which has been shown to exhibit nephrotoxicity in rodents. However, no significant changes in renal function parameters have been reported in surgical patients.

Absolute configuration and conformational analysis of a degradation product of inhalation anesthetic Sevoflurane: A vibrational circular dichroism study

1,1,1,3,3-pentafluoro-2-(fluoromethoxy)-3-methoxypropane, compound B, is a product obtained in the degradation of the anesthetic Sevoflurane. Enantiopure (+)-B was investigated using vibrational circular dichroism (VCD). Experimental absorption and VCD spectra of (+)-B in CDCl(3) solution in the 2,000-900 cm(-1) region are compared with the ab initio predictions of absorption and VCD spectra obtained from density functional theory using B3LYP/6-31G* basis set for different conformers of (S)-1,1,1,3,3-pentafluoro-2-(fluoromethoxy)-3-methoxypropane. This comparison indicates that (+)-B is of the (S)-configuration in CDCl(3) solution, in agreement with previous literature results. Our results also indicate that this compound adopts six predominant conformations in CDCl(3) solution.

Renal toxicity with sevoflurane: a storm in a teacup?

The inhaled anaesthetic sevoflurane is metabolised into two products that have the potential to produce renal injury. Fluoride ions are produced by oxidative defluorination of sevoflurane by the cytochrome P450 system in the liver. Until recently, inorganic fluoride has been thought to be the aetiological agent responsible for fluorinated anaesthetic nephrotoxicity, with a toxic concentration threshold of 50 micromol/L in serum. However, studies of sevoflurane administration in animals and humans have not shown evidence of fluoride-induced nephrotoxicity, despite serum fluoride concentrations in this range. Compound A (fluoromethyl-2,2-difluoro-1-[trifluoromethyl] vinyl ether) is a breakdown product of sevoflurane produced by its interaction with carbon dioxide absorbents in the anaesthesia machine. The patient then inhales compound A. Compound A produces evidence of transient renal injury in rats. The mechanism of compound A renal toxicity is controversial, with the debate focused on the role of the renal cysteine conjugate beta-lyase pathway in the biotransformation of compound A. The significance of this debate centres on the fact that the beta-lyase pathway is 10- to 30-fold less active in humans than in rats. Therefore, if biotransformation by this pathway is responsible for the production of nephrotoxic metabolites of compound A, humans may be less susceptible to compound A renal toxicity than are rats. In three studies in human volunteers and one in surgical patients, prolonged (8-hour) sevoflurane exposures and low fresh gas flow rates resulted in significant exposures to compound A. Transient abnormalities were found in biochemical markers of renal injury measured in urine. These studies suggested that sevoflurane can result in renal toxicity, mediated by compound A, under specific circumstances. However, other studies using prolonged sevoflurane administration at low flow rates did not find evidence of renal injury. Finally, there are substantial data to document the safety of sevoflurane administered for shorter durations or at higher fresh gas flow rates. Therefore, the United States Food and Drug Administration recommends the use of sevoflurane with fresh gas flow rates at least 1 L/min for exposures up to 1 hour and at least 2 L/min for exposures greater than 1 hour. We believe this is a rational, cautious approach based on available data. However, it is important to note that other countries have not recommended such limitations on the clinical use of sevoflurane and problems have not been noted.

Hydroxyl radical formation during inhalation anesthesia in the reperfused working rat heart

PURPOSE

To determine whether isoflurane, sevoflurane and halothane influenced hydroxyl radical production in the ischemic rat heart.

METHODS

Twenty-four male Wistar rats were divided into four groups; control (C), isoflurane 1.4% (I), sevoflurane 2.5% (S) and halothane 1% (H). The hearts were perfused with modified Krebs-Henseleit bicarbonate buffer by a working heart model for 10 min. Then, whole heart ischemia was induced by severely restricting coronary perfusion for 15 min. Reperfusion of the hearts after this ischemic period lasted for 20 min. The coronary effluent was collected before and during ischemia and at 1, 5, 10, 20 min after reperfusion. At the end of reperfusion, hearts were removed and prepared for measurement. Hydroxyl radicals were identified by their reaction with salicylic acid to yield dihydroxybenzoic acids (DHBAs).

RESULTS

Before and after ischemia, there were no differences in coronary flow and heart rate among the four groups, but cardiac output and LV dP/dt maximum in the anesthetic groups were lower than in the control group. Hydroxyl radical products in the heart were significantly lower in the I group than the other groups (e.g. C vs I, 278.1 +/- 24.3 vs 219.3 +/- 14.4 microM x g(-1), P < 0.05). The concentrations of DHBAs in the coronary effluent at some points in the I and H groups were less than in the C and S groups.

CONCLUSION

These results indicate that isoflurane and halothane (to a lesser extent), reduce hydroxyl radical production in the ischemic heart, but sevoflurane does not.

Minimum alveolar anesthetic concentration of volatile anesthetics in normal and cardiomyopathic hamsters

Minimum alveolar anesthetic concentrations (MAC) values of volatile anesthetics in cardiovascular diseases remain unknown. We determined MAC values of volatile anesthetics in spontaneously breathing normal and cardiomyopathic hamsters exposed to increasing (0.1%-0.3% steps) concentrations of halothane, isoflurane, sevoflurane, or desflurane (n = 30 in each group) using the tail-clamp technique. MAC values and their 95% confidence interval were calculated using logistic regression. In normal hamsters, inspired MAC values were: halothane 1.15% (1.10%-1.20%), isoflurane 1.62% (1.54%-1.69%), sevoflurane 2.31% (2.22%-2.40%), and desflurane 7.48% (7.30%-7.67%). In cardiomyopathic hamsters, they were: halothane 0.89% (0.83%-0.95%), isoflurane 1.39% (1.30%-1.47%), sevoflurane 2.00% (1.85%-2.15%), and desflurane 6.97% (6.77%-7.17%). Thus, MAC values of halothane, isoflurane, sevoflurane, and desflurane were reduced by 23% (P < 0.05), 14% (P < 0.05), 13% (P < 0.05), and 7% (P < 0.05), respectively in cardiomyopathic hamsters.

IMPLICATIONS

Minimum alveolar anesthetic concentrations of volatile anesthetics were significantly lower in cardiomyopathic hamsters than in normal hamsters.

Sevoflurane is equivalent to isoflurane for attenuating bupivacaine-induced arrhythmias and seizures in rats

The effects of sevoflurane on bupivacaine toxicity have not been defined. The purpose of this study was to investigate the effects of sevoflurane and isoflurane on bupivacaine-induced arrhythmias and seizures in rats. Thirty-seven Sprague-Dawley rats received bupivacaine intravenously at a constant rate of 2 mg.kg-1.min-1 until both arrhythmias and seizures occurred while electrocardiogram (ECG) and electroencephalogram (EEG) recordings were made. The cumulative doses of bupivacaine inducing arrhythmias and seizures were determined in the presence of 1 minimum alveolar anesthetic concentration (MAC) of sevoflurane (sevoflurane group, n = 14) or isoflurane (isoflurane group, n = 10) and in the absence of anesthetic (control group, n = 13). The cumulative doses of bupivacaine inducing arrhythmias and seizures were larger in the sevoflurane and isoflurane groups than in the control group and were similar in the sevoflurane and isoflurane groups. These results indicate that sevoflurane and isoflurane attenuate bupivacaine-induced arrhythmias and seizures in rats.

Sevoflurane versus isoflurane for maintenance of anesthesia: are serum inorganic fluoride ion concentrations of concern?

Sevoflurane administration can result in increased serum inorganic fluoride ion concentrations, which have been associated with inhibition of renal concentrating ability. We measured serum fluoride levels, renal function, and recovery variables as a function of time in ASA grade I-III patients administered general anesthesia with isoflurane or sevoflurane for at least 1 h. Fifty patients were exposed to sevoflurane (< or = 2.4% inspired concentration) or isoflurane (< or = 1.9% inspired concentration) for maintenance of anesthesia as part of a multicenter trial. Blood was collected for determination of serum fluoride ion concentration, electrolytes, blood urea nitrogen, and creatinine at various time points pre- and postoperatively. Mean serum fluoride levels were significantly increased in sevoflurane versus isoflurane groups at all time points; the mean peak serum levels were 28.2 +/- 14 mumol/L at 1 h for sevoflurane and 5.08 +/- 4.35 mumol/L at 12 h for isoflurane. Sevoflurane-mediated increases in serum fluoride levels peaked at 1 h and, in general, decreased rapidly after discontinuation of the anesthesia. Three of 24 patients exposed to sevoflurane had one or more fluoride levels > 50 mumol/L. One of these patients had a serum inorganic fluoride ion level > 50 mumol/L at 12 h after sevoflurane, and an additional patient had fluoride levels > 33 mumol/L for up to 24 h after sevoflurane discontinuation. Those two patients also demonstrated an increase in serum blood urea nitrogen and creatinine at 24 h after sevoflurane administration compared with baseline. The elimination half-life of serum fluoride ion was 21.6 h. The results of this study suggest the possibility of sevoflurane induced nephrotoxicity.

Cardiovascular and pulmonary effects of sevoflurane anesthesia in horses

The effects of 1.0, 1.5, and 2.0 minimum alveolar concentration (MAC) of sevoflurane on hemodynamic, pulmonary and blood chemistry variables were measured during spontaneous and controlled ventilation in healthy horses. Sevoflurane was the only anesthetic drug administered to the horses. In a dose-dependent manner, sevoflurane significantly decreased (P < .05) mean arterial blood pressure, cardiac output, and stroke volume. There was a progressive decrease in peripheral vascular resistance and an increase in heart rate as the concentration of sevoflurane was increased, but the differences were not significant. During spontaneous ventilation there was a dose-dependent decrease in respiratory rate that caused a decrease in the minute volume. As the dose of sevoflurane increased, the arterial carbon dioxide tension also increased (P < .05). All blood chemistries remained within normal limits. Recovery from anesthesia was without incident. In conclusion, sevoflurane induces a dose-dependent decrease in hemodynamic variables and pulmonary function in horses that is not greatly different from that of other approved inhalant anesthetics.

Comparison of the alteration of cardiac function by sevoflurane, isoflurane, and halothane in the isolated working rat heart

OBJECTIVES

Despite its widespread use, little is known about sevoflurane's physiologic effects. The direct myocardial effects of sevoflurane were compared with both halothane and isoflurane.

DESIGN

Administration of minimum alveolar concentration (MAC) fractions of anesthetic (0 to 3.0) was systematically varied to decrease the possibility of time-related effects on measured parameters.

SETTING

Isolated rat hearts were perfused using a working heart model where the parameters affecting myocardial work were carefully controlled and monitored.

PARTICIPANTS

To avoid confounding effects of prior anesthetic administration, hearts were removed from rats, after decapitation, in the absence of anesthetic.

INTERVENTIONS

In the first series, isolated perfused rat hearts were exposed to one of the three anesthetics in doses of 0 to 1.5 times MAC. In the second series, hearts were exposed to either sevoflurane or isoflurane in doses of 0 to 3.0 times MAC. The following variables were measured: the rate of change of left ventricular pressure; aortic flow rate; cardiac output; left ventricular end-diastolic pressure; the time constant of isovolumetric relaxation; and coronary vascular resistance. Oxygen consumption was measured during the first series.

MEASUREMENTS AND MAIN RESULTS

In the first series, all systolic variables were reduced in the presence of halothane when compared with either isoflurane or sevoflurane. Halothane affected diastolic function to a greater degree than either sevoflurane or isoflurane, as measured by the rate of relaxation and end-diastolic pressure. In the second series, at a dose of 3.0 times MAC, both sevoflurane and isoflurane decreased systolic and diastolic function, with a greater reduction in cardiac output, and peak aortic flow and higher left ventricular end-diastolic pressures observed with isoflurane. Coronary resistance and oxygen consumption were not affected by any of the anesthetics.

CONCLUSIONS

These data suggest that sevoflurane depresses cardiac function less than either halothane in doses of 1.0 and 1.5 x MAC or isoflurane at doses of 3 x MAC.

Biotransformation of sevoflurane

Several characteristics of sevoflurane biotransformation are apparent from the preceding investigations. Metabolism is rapid, with fluoride and HFIP appearing in plasma within minutes after the start of sevoflurane administration (38-40,51). Peak plasma fluoride concentrations generally occur within approximately 1 h after the termination of sevoflurane administration in most patients, regardless of the dose or duration of exposure (ranging from 0.35-9.5 MAC-h) (39,48). Peak plasma inorganic fluoride concentrations are proportional to sevoflurane dose, measured in MAC-h (42-44). Inorganic fluoride concentrations decline rapidly after termination of sevoflurane administration, with concentrations well below peak levels by the first postoperative day. HFIP is rapidly conjugated, with more than 85% circulating in plasma as the glucuronide. Plasma HFIP concentrations peak later than fluoride concentrations, but both metabolites are eliminated at similar rates (52). Metabolism of sevoflurane does not contribute to the termination of clinical drug effect (52), unlike more extensively metabolized drugs such as halothane (55). Sevoflurane is metabolized by P-450 2E1, so pathophysiologic factors and drug interactions altering P-450 2E1 activity will also influence sevoflurane metabolism (52). The extent of metabolism of sevoflurane, 2% to 5%, is less than that of all other volatile anesthetics except isoflurane and desflurane. It has been proposed that the ideal anesthetic should resist biotransformation because anesthetic toxicity is related to anesthetic metabolism (67,68). Experience to date suggests that biotransformation of sevoflurane has not been causally related to either hepatic or renal toxicity. Sevoflurane does not result in formation of fluoroacetylated liver neoantigens or other reactive metabolites. Although both sevoflurane and methoxyflurane may produce plasma fluoride concentrations in excess of 50 microM, they have not produced the same nephrotoxic effects. Clearly, anesthetic metabolism and anesthetic toxicity can no longer be considered synonymous. The introduction of sevoflurane into clinical practice will hopefully stimulate new investigations into biochemical mechanisms of anesthetic toxicity and continued clinical investigations regarding the relationship between anesthetic metabolism and organ toxicity.

Inhalational anesthetics: desflurane and sevoflurane

This article reviews the physico-chemical properties and performance characteristics of the two new potent inhaled anesthetics, desflurane and sevoflurane. Both drugs provide a greater degree of control of anesthetic depth and a more rapid immediate recovery from anesthesia than is currently available with other inhaled agents because of their decreased solubility. Desflurane is currently in widespread clinical use in the United States and parts of Europe. Compared with sevoflurane, it has the additional advantage of being extremely resistant to degradation and biotransformation. However, its pungent odor and tendency to irritate the respiratory tract make it unsuitable for inhalational inductions, and it has been linked to CO production in CO2 absorbents. The sympathetic nervous system activation that occurs with desflurane limits its use in patients with cardiac disease. Otherwise, its hemodynamic and physiologic effects are similar to those seen with isoflurane. Studies of the economics of using desflurane are mixed, although it may offer the advantage of shorter postoperative recovery time. Sevoflurane is currently in widespread clinical use in Japan and parts of South America. The FDA Advisory Panel has recently recommended approval of sevoflurane in the United States, and we can expect the drug to be clinically available in the United States in the second quarter of 1995. Compared with desflurane, sevoflurane has the additional advantage of being nonirritating to the airway; inhalational induction of anesthesia with sevoflurane is achieved rapidly and easily. The instability of sevoflurane with CO2 absorbents and its in vivo biotransformation produce potentially toxic byproducts. These byproducts, including Compound A and fluoride, have been extensively studied, and although the possibility for iatrogenic sequelae from sevoflurane exists, the likelihood of long-term toxicity appears quite low. Phase IV studies are indicated to determine the safety of administering sevoflurane (1) to renally impaired patients and (2) to any patient with fresh gas flows less than 2 L/min. Sevoflurane is otherwise very well tolerated and appears to offer the advantage of rapid and smooth induction and emergence from general anesthesia.

Serum fluoride concentration and urine osmolality after enflurane and sevoflurane anesthesia in male volunteers

The purpose of this study was to measure the serum fluoride concentration after enflurane or sevoflurane anesthesia and to compare the effects of prolonged anesthesia with these drugs on renal concentrating function in male volunteers. The study was subdivided into three stages; an ascending dose study of 3.0 and 6.0 minimum alveolar anesthetic concentration (MAC) hours of sevoflurane alone, a 6.0-MAC-hour comparison of enflurane and sevoflurane, and a 9.0-MAC-hour comparison of enflurane and sevoflurane. Renal concentrating function was assessed by an 18-h period of fluid deprivation and the serum fluoride concentration was measured at intervals until 60 h postanesthesia. The maximum serum fluoride concentration was greater in the volunteers exposed to sevoflurane and reached a peak in the 9-MAC-hour sevoflurane group of 36.6 microM (SD 4.3) compared with 27.5 microM (SD 2.6) in the 9-MAC-hour enflurane group. However, the rapid decrease in the serum fluoride concentration after sevoflurane was such that there was no difference between the areas under the fluoride concentration-time curves. There were no significant differences between the median maximum urine osmolalities after enflurane or sevoflurane anesthesia. Prolonged anesthesia with enflurane or sevoflurane is not associated with impaired renal concentrating function despite an increase in the serum fluoride concentration.

Correlation between renal function and pharmacokinetic parameters of inorganic fluoride following sevoflurane anesthesia

We studied the correlation between renal function and pharmacokinetic parameters of inorganic fluoride following sevoflurane anesthesia. In 30 neurosurgical patients aged 40-70 years, anesthesia was induced with midazolam and sevoflurane and maintained with sevoflurane and nitrous oxide in oxygen. Serum and urine inorganic fluoride (F^-) levels and β₂-microglobulin (BMG), blood urea nitrogen (BUN), and serum creatinine (Cr) were measured during and after anesthesia. The decrease rate of serum F^- level and the area under the curve (AUC) of serum F^- were calculated. Correlations among sevoflurane dosage, duration of administration, peak serum F^- level, AUC, the decrease rate of serum F^- level, and the maximum values in BUN, Cr, and urine BMG during the study were investigated. Urine BMG increased significantly after surgery but returned to the preoperative level in a week. BUN, Cr, and serum BMG remained within normal ranges during the study. Sevoflurane dosage and duration of administration were significantly correlated with AUC and the maximum value of urine BMG, but not with the peak serum F^- level or the decrease rate of serum F^-. AUC was significantly correlated with the maximum value of urine BMG. In sevoflurane anesthesia, sevoflurane dosage, duration of administration, and AUC affected urine BMG level, but not peak serum F^-.

Sevoflurane anaesthesia for major intra-abdominal surgery

The cardiovascular effects and recovery characteristics of sevoflurane and isoflurane anaesthesia were compared in 30 gynaecological and 20 general surgical patients undergoing elective intra-abdominal surgery. Patients were randomly allocated to receive either sevoflurane or isoflurane as the volatile agent, in a balanced anaesthetic technique including morphine and atropine premedication and thiopentone, fentanyl, vecuronium and nitrous oxide. The concentration of volatile agent was titrated according to clinical variables. Mean heart rate, systolic and diastolic arterial pressure and duration of surgery did not differ between the two groups. Time to emergence from anaesthesia in the gynaecological patients was significantly faster after sevoflurane compared with isoflurane (p < 0.005). Sevoflurane provided stable anaesthesia during major intra-abdominal surgery.

Serum fluoride concentration after sevoflurane anesthesia in ethanol treated rats: special reference to cytochrome P-450 in the liver

The relationship between serum concentration of inorganic fluoride (F(-)) and cytochrome P-450 content after sevoflurane anesthesia was investigated in ethanol treated rats. Twenty male Wistar rats were randomly divided into 2 isocaloric diet groups of 10 rats each: one group receiving a standard diet and the other an ethanol diet. After 28 days on the diets the animals were administered 2.5% sevoflurane for 2 hr with 30% oxygen and 70% nitrous oxide. Cytochrome P-450 and cytochrome b(5) were induced by the ethanol diet. In the ethanol diet group serum concentration of F(-) was significantly higher than that of the standard diet group after sevoflurane anesthesia. These results suggest that cytochrome P-450 and b(5), which were induced by ethanol, enhanced sevoflurane defluorination.

Gas chromatographic headspace analysis of sevoflurane in blood

We have developed a rapid, simple and precise gas chromatographic headspace analysis for sevoflurane in blood which circumvents problems associated with the high volatility and low blood/gas partition coefficient of this anesthetic drug. Blood standards are easily prepared by volumetric addition of a saturated aqueous solution of sevoflurane. Likewise, internal standardization is achieved using a saturated aqueous solution of halothane. Chromatographic conditions are similar to those commonly used for the analysis of blood ethanol. A simple method is also described for the preparation of stable and precise, aliquots of quality control materials for this assay.

Other new and potentially useful inhalational anesthetics

Sevoflurane and desflurane are volatile inhaled anesthetics that are currently being investigated as possible improvements for the anesthetic management of human patients. Information to date suggests these agents have several advantages over existing clinical agents. For example, the blood/gas partition coefficient for both agents is lower than that of other halogenated anesthetics. Consistent with this physical characteristic is a more rapid induction of and emergence from anesthesia. Both cause a dose-related depression of cardiopulmonary function, which is comparable to isoflurane. Results of studies to date favor desflurane over sevoflurane because it is less soluble in blood, is stable in soda lime, is biodegraded the least of any volatile anesthetic, and is not toxic.

[Desflurane (I 653) and sevoflurane: halogenated anesthetics of the future?]

Sevoflurane is an halogenated methyl isopropyl ether. It is potent, non explosive and non flammable. It reacts with soda lime to form traces of a related ether which has not been shown to have any toxic effect on animals chronically exposed to it in a closed system. Induction of anaesthesia with sevoflurane is rapid and smooth, as predicted by a blood/gas partition coefficient of about 0.6 and an acceptable odour which allows the use of concentrations of up to 10%. Its MAC has been reported to vary between 1.7 and 2.3 vol %. Sevoflurane causes dose-dependent cardiovascular and respiratory depression. Its effect on the cerebral circulation is similar to that of isoflurane. The extent of biotransformation is similar to that of enflurane, but its low solubility and rapid elimination confine this to the period of inhalation. No toxic effects on the kidneys, liver and haematopoietic system have been found. Desflurane is a fluorinated methyl ether, structurally very similar to isoflurane. It is non flammable and non explosive at clinical concentrations. It is more stable in the presence of soda lime than any of the volatile anaesthetic agents available. This agent must be delivered with a thermostated vaporizer within a closed circle system, as its boiling point is 23.5 degrees C. Desflurane is less potent than isoflurane. Its MAC has been estimated to be about 7.2 vol % in man. Desflurane did not lead to any liver, lung or kidney injury in laboratory rats, even during hypoxia and enzyme induction. Desflurane undergoes little biotransformation, although the presence of volatile metabolites or covalent tissue-bound products cannot be excluded.(ABSTRACT TRUNCATED AT 250 WORDS)