Nephrotoxicity of Sevoflurane Versus Desflurane Anesthesia in Volunteers

Urinary excretion of alpha-GST and albumin in rheumatoid arthritis patients treated with methotrexate or other DMARDs alone or in combination with NSAIDs

OBJECTIVE

To evaluate the effect of methotrexate (MTX) and other disease-modifying anti-rheumatic drugs (DMARDs) alone or in combination with non-steroidal anti-inflammatory drugs (NSAIDs) on the urinary excretion of alpha-glutathione S-transferase (alpha-GST) and albumin in rheumatoid arthritis (RA) patients.

METHODS

Nineteen RA patients starting treatment with MTX were followed for 1 year with measurements of urinary alpha-GST, urinary albumin, and urinary and plasma creatinine at the start of treatment, and after 16, 28, and 52 weeks. A larger group of RA patients (n = 72) undergoing long-term treatment with different DMARDs was compared with 79 healthy controls regarding urinary alpha-GST and albumin. alpha-GST was quantified by an enzyme immunoassay. Urine albumin was measured turbidimetrically.

RESULTS

The urine-alpha-GST/urine-creatinine ratio and the urine-albumin/urine-creatinine ratio did not change during 52 weeks of treatment with MTX. The long-term DMARD-treated RA patients and the healthy controls were comparable with regard to the urine-alpha-GST/urine-creatinine ratio and the urine-albumin/urine-creatinine ratio. All patients had preserved renal function as assessed by plasma creatinine, and none had proteinuria using urine dipstick methods.

CONCLUSION

DMARD-treated RA patients with normal serum creatinine had no detectable renal injuries assessed by the urinary excretions of alpha-GST and albumin.

Kidney transplantation: recent developments and recommendations for anesthetic management

Kidney transplantation is the treatment of choice for patients with end-stage renal disease. After receiving a transplant, survival rates are higher and comorbidities may resolve. As a consequence, more patients with significant comorbidities such as advanced cardiovascular disease will present for transplantation. This review highlights commonly encountered issues in patients undergoing kidney transplantation and recommendations are made for their anesthetic management.

Hepatitis After Sevoflurane Exposure in an Infant Suffering from Primary Hyperoxaluria Type 1

An 11-mo-old child with primary hyperoxaluria was scheduled for a nephroureteromia procedure. Anesthesia was induced and maintained with sevoflurane. Two days after the operation, a hepatomegaly was diagnosed, and a considerable increase in liver enzymes was observed. These pathologic findings disappeared without treatment within 7 days. In a subsequent operation 2 wk later, general anesthesia was performed (sevoflurane was avoided). After the second operation, no pathologic findings could be detected. Nothing in this patient's disease or the conduct of the anesthesia suggested a cause for the injury other than an idiosyncratic response to sevoflurane.

Cytotoxicity of S-conjugates of the sevoflurane degradation product fluoromethyl-2,2-difluoro-1-(trifluoromethyl) vinyl ether (Compound A) in a human proximal tubular cell line

Fluoromethyl-2,2-difluoro-1-(trifluoromethyl)vinyl ether (FDVE) is a fluorinated alkene formed by degradation of the volatile anesthetic sevoflurane in anesthesia machines. FDVE is nephrotoxic in rats but not humans. Rat FDVE nephrotoxicity is attributed to FDVE glutathione conjugation and bioactivation of subsequent FDVE-cysteine S-conjugates, in part by renal beta-lyase. Although FDVE conjugation and metabolism occur in both rats and humans, the mechanism for selective toxicity in rats and lack of effect in humans is incompletely elucidated. This investigation measured FDVE S-conjugate cytotoxicity in cultured human proximal tubular HK-2 cells, and compared this with known cytotoxic S-conjugates. HK-2 cells were incubated with FDVE and its GSH, cysteine S-mercapturic acid, cysteine S-sulfoxide, and mercapturic acid sulfoxide conjugates (0.1-2.7 mM) for 24 h. Cytotoxicity was determined by lactate dehydrogenase (LDH) release, total LDH, and the ability of viable cells to reduce a tetrazolium-based compound (MTT). FDVE was cytotoxic only at concentrations >/=0.9 mM. No increase in LDH release was observed with either FDVE-GSH conjugate. The FDVE-cysteine conjugates S-(1,1-difluoro-2-fluoromethoxy-2-(trifluoromethyl) ethyl)-L-cysteine (DFEC) and (Z)-S-(1-fluoro-2-fluoromethoxy-2-(trifluoromethyl) vinyl)-L-cysteine ((Z)-FFVC) caused significant differences in LDH release and MTT reduction only at 2.7 mM; (Z)-FFVC was slightly more cytotoxic. Both S-(1,1-difluoro-2-fluoromethoxy-2-(trifluoromethyl) ethyl)-L-cysteine sulfoxide (DFEC-SO) and (Z)-N-acetyl-S-(1-fluoro-2-fluoromethoxy-2-(trifluoromethyl) vinyl)-L-cysteine sulfoxide ((Z)-N-Ac-FFVC-SO) caused slightly greater changes in LDH release or total LDH than the corresponding equimolar DFEC and (Z)-N-acetyl-S-(1-fluoro-2-fluoromethoxy-2-(trifluoromethyl) vinyl)-L-cysteine ((Z)-N-Ac-FFVC) conjugates. In contrast to FDVE S-conjugates, S-(1,2-dichlorovinyl)-L-cysteine was markedly cytotoxic, at concentrations as low as 0.1 mM. These results show that human proximal tubular cells are relatively resistant to FDVE and FDVE S-conjugate cytotoxicity. This may partially explain the lack of FDVE nephrotoxicity in humans.

Biological indices of kidney involvement in personnel exposed to sevoflurane in surgical areas

BACKGROUND

Fluoride, a main metabolite, and one degradation product of sevoflurane (SEV), called Compound A, are known to cause kidney effects in experimental animals. Other than in volunteers and patients, no research is available on exposed workers. The possible effects on the kidney in workers exposed in surgical areas were studied.

METHODS

Subjects exposed to SEV and nitrous oxide (N(2)O) in surgical areas (N = 61) using open (N = 25) or semi-closed (N = 36) circuits were submitted to biological monitoring. The same biological indices were determined in 43 controls also. Sevoflurane (SEVU), nitrous oxide (N(2)OU), total urinary proteins (TUP), N-acetyl-beta-D-glucosaminidase (NAGU), and glutamine synthetase (GSU) were measured in urine.

RESULTS

The mean values of environmental exposure were 31.3 ppm (range 0.9-111.6 ppm) for N(2)O and 0.28 ppm (range 0-1.88 ppm) for SEV. Exposed subjects had significantly higher excretion of TUP; a higher, not significant, excretion of GSU was also observed in subjects using open circuits. A significant correlation was found in all exposed subjects between NAGU and SEVU (r = 0.303, P < 0.05), GSU and N(2)OU (r = 0.382, P < 0.01) and, especially, GSU and SEVU (r = 0.650, P < 0.001). These correlations appeared to be influenced by the use of open circuits; infact, NAGU was well correlated to N(2)OU (r = 0.770, P < 0.001) and SEVU (r = 0.863, P < 0.001); GSU to N(2)OU (r = 0.468, P < 0.05) and SEVU (r = 0.735, P < 0.001).

CONCLUSIONS

Results show that no relevant effect on the kidney is present for the levels of exposure studied. Nevertheless, correlation between dose and response urinary indices supports that SEV, other than N(2)O, may influence kidney function, especially when open circuits are used.

Sevoflurane: an ideal agent for adult day-case anesthesia?

Sevoflurane has several properties which make it potentially useful as a day case anaesthetic. Following induction of anaesthesia with propofol, awakening from sevoflurane is faster compared to isoflurane, faster or similar compared to propofol and comparable (in the majority of studies) to desflurane. Subsequent recovery and discharge is generally similar following all agents. Sevoflurane may also be used to induce anaesthesia, which is generally well-received and causes less hypotension and apnoea compared to propofol. When used as a maintenance anaesthetic, the incidence of postoperative nausea and vomiting after sevoflurane is comparable to other inhaled anaesthetics, but this complication appears more common after inhaled inductions. The tolerability and low solubility of sevoflurane facilitate titration of anaesthesia and may reduce the need for opioid analgesia, which in turn may limit the occurrence of nausea and vomiting.

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.

Sevoflurane degradation by carbon dioxide absorbents may produce more than one nephrotoxic compound in rats

PURPOSE

Degradation of sevoflurane by carbon dioxide absorbents produces compound A, a vinyl ether. In rats, compound A can produce renal corticomedullary necrosis. We tested whether other compounds produced by sevoflurane degradation also could produce corticomedullary necrosis.

METHODS

Two groups of rats were exposed for four hours to sevoflurane 2.5% delivered through a container filled with fresh Sodasorb and heated to 30 degrees C or to 50 degrees C, respectively. Compound A was added to produce an average concentration of 120 ppm in both groups. A third (control) group received 2.5% sevoflurane that did not pass through absorbent, and no compound A was added.

RESULTS

As determined by gas chromatography, the higher temperature produced more volatile breakdown products, including compound A. Median necrosis of the corticomedullary junction in the 50 degrees C group [10% (quartiles 1.0%-7.8%); n = 20] exceeded that in the 30 degrees C group [5% (6.5%-15%); n = 18; P < 0.02], and both exceeded the median necrosis in the control group [0% (0.0%-0.2%); n = 10; P < 0.02]. The respective mean +/- SD values for these three studies were: 12.8 +/- 16.7%, 5.3 +/- 4.4%, and 0.3 +/- 0.5%.

CONCLUSION

Degradation products of sevoflurane other than compound A can cause or augment the renal injury in rats produced by compound A.

Compound A concentration in the circle absorber system during low-flow sevoflurane anesthesia: comparison of Drägersorb Free, Amsorb, and Sodasorb II

STUDY OBJECTIVE

To determine compound A concentrations in a low-flow circuit containing Drägersorb Free (Dräger, Lübeck, Germany), Amsorb (Armstrong, Coleraine, Northern Ireland), and Sodasorb II (W. R. Grace, Lexington, MA).

DESIGN

Randomized study.

SETTING

Hamamatsu University Hospital.

PATIENTS

24 ASA physical status I and II patients scheduled for general anesthesia greater than 3 hours' duration.

INTERVENTIONS

Patients were allocated to three groups of eight patients each to receive either using either Drägersorb Free, Amsorb, or Sodasorb II. Immediately before anesthesia induction, 1 kg of fresh absorbent was placed in the anesthesia canister. Anesthesia was maintained with sevoflurane (end-tidal concentration 1% to 3%) in oxygen and nitrous oxide (FIO(2) > 0.3) at a total flow of 1 L/min.

MEASUREMENTS

Inspiratory compound A concentration in the circuit was measured once every hour.

MAIN RESULTS

Maximum compound A concentrations for Drägersorb Free, Amsorb, and Sodasorb II were 2.4 +/- 0.8 (mean +/- SD) ppm, 3.1 +/- 0.5 ppm, and 28.0 +/- 10.0 ppm (p < 0.01 vs. Drägersorb Free and Amsorb). Concentrations with Drägersorb Free and Amsorb remained at less than 4 ppm throughout the study.

CONCLUSIONS

Because compound A concentrations in the circuit with Drägersorb Free and Amsorb were negligible, sevoflurane can be used at a fresh gas flow of 1 L/min with these two absorbents.

The place of research and the role of academic anaesthetists in anaesthetic departments

The specialty of anaesthesia developed because of its fundamental contribution to health care, including the prevention of pain from surgery, respiratory, and critical care medicine, cardiopulmonary resuscitation and pain medicine. Through these contributions anaesthesia became an important component of the medical profession. To continue our position in medicine, our intellectual foundation must be maintained and augmented mainly via research. No matter what role they play, all members of an anaesthetic department must contribute to the past intellectual development of anaesthesia as a basis for outlining the future approaches in research, including basic science, applied, transitional, clinical, educational and economic research. The challenges to the anaesthetist-scientist include evaluation, funding, conflicts of interest, legal and fraud. The future of the anaesthetic profession is mainly with its intellectual resources, especially research as the basis of improved patient care, and to have a major impact on the future of medicine overall.

Serum fluoride concentrations, biochemical and histopathological changes associated with prolonged sevoflurane anaesthesia in horses

The volatile anaesthetic sevoflurane is degraded to fluoride (F-) and a vinyl ether (Compound A), which have the potential to harm kidney and liver. Whether renal and hepatic injuries can occur in horses is unknown. Cardiopulmonary, biochemical and histopathological changes were studied in six healthy thoroughbred horses undergoing 18 h of low-flow sevoflurane anaesthesia. Serum F- concentrations were measured and clinical laboratory tests performed to assess hepatic and renal function before and during anaesthesia. Necropsy specimens of kidney and liver were harvested for microscopic examination and compared to pre-experimental needle biopsies. Cardiopulmonary parameters were maintained at clinically acceptable levels throughout anaesthesia. Immediately after initiation of sevoflurane inhalation, serum F- levels began to rise, reaching an ongoing 38-45 micromol 1(-1) plateau at 8 h of anaesthesia. Serum biochemical analysis revealed only mild increases in glucose and creatinine kinase and a decrease in total calcium. Beyond 10 h of anaesthesia mild, time-related changes in urine included increased volume, glucosuria and enzymuria. Histological examination revealed mild microscopic changes in the kidney involving mainly the distal tubule, but no remarkable alterations in liver tissue. These results indicate that horses can be maintained in a systemically healthy state during unusually prolonged sevoflurane anaesthesia with minimal risk of hepatocellular damage from this anaesthetic. Furthermore, changes in renal function and morphology observed after sevoflurane inhalation are judged minimal and appear to be clinically irrelevant; they may be the result of anaesthetic duration, physiological stressors, sevoflurane (or its degradation products) or other unkown factors associated with these animals and study conditions.

Sevoflurane low-flow anaesthesia: best strategy to reduce Compound A concentration

BACKGROUND

To define the best strategy to reduce Compound A production in Sevoflurane low-flow anaesthesia by experiments in vitro and in vivo of different absorbers and different anaesthesia machines.

METHODS

In vitro Compound A has been measured at 45 degrees C in vitro following Sevoflurane interactions with potassium hydroxide, sodium hydroxide, soda lime, Dragersorb 800 Plus and Amsorb, a new absorber that does not contain sodium or potassium hydroxide. In vivo Compound A concentration in the anaesthesia circuit (inspiratory branch) has been measured using an indirect sampling method through absorber vials (SKC) with active coal granules, during low flows (500 ml/min) general anaesthesia using soda lime, Dragersorb 800 Plus or Amsorb as absorber. Compound A was also measured during low flows (500 ml/min) general anaesthesia using as carbon dioxide absorber soda lime with different anaesthesia machines.

RESULTS

In vitro at 45 degrees C Compound A concentration with soda lime and Dragersorb 800 Plus was about 10 times higher than with Amsorb. In vivo the Compound A concentrations in the inspiratory branch of the circuit were lower in the group with Amsorb.

CONCLUSION

The Compound A production is minimal with Amsorb as carbon dioxide absorber.

Recent advances in inhalation anesthesia

Both desflurane and sevoflurane offer theoretical and practical advantages over other inhalation anesthetics for horses. The lower solubility of both agents provides improved control of delivery and helps to counteract the confounding influence of the voluminous patient breathing circuit commonly used for anesthetizing horses. The lower solubility should account for faster rates of recovery compared with the older agents; whether or not the quality of recovery differs remains to be objectively evaluated in a broad range of circumstances. The pharmacodynamic effects are, in large part, similar to those of isoflurane (e.g., low arrhythmogenicity) but with some differences. For example, desflurane may be overall more sparing to cardiovascular function (especially during controlled ventilation) compared with isoflurane and sevoflurane, which are roughly similar. Respiratory depression with both new agents is equal to or more depressing than isoflurane, suggesting the use of mechanical ventilation, especially in circumstances of prolonged management (i.e., hours of anesthesia). Both new anesthetics, not surprisingly, are expensive. From this point there are some agent-unique considerations. The anesthetic potency of both agents is less than that of isoflurane, which influences the cost of anesthesia, but also places an upper limit on inspired oxygen concentration (of particular concern with desflurane). Both agents require new vaporizers, but because of the high boiling point and steep vapor-pressure curve of desflurane, new technology was required. This translates into more costly equipment, adding to the cost of desflurane use. In addition, electricity is necessary for the new desflurane vaporizer to function, which limits its portability and adds additional practical considerations in its clinical use. On the other hand, desflurane strongly resists degradation both in vitro and in vivo, but in vitro degradation of sevoflurane by CO2 absorbents may produce renal injury. This may be true especially in association with low fresh-gas inflow rates (used to reduce the cost of using the new agent), and university based practices, where prolonged anesthesia is common.

Long-duration low-flow sevoflurane and isoflurane effects on postoperative renal and hepatic function

Sevoflurane degradation by carbon dioxide absorbents during low-flow anesthesia forms the haloalkene Compound A, which causes nephrotoxicity in rats. Numerous studies have shown no effects of Compound A formation on postoperative renal function after moderate-duration (3-4 h) low-flow sevoflurane; however, effects of longer exposures remain unresolved. We compared renal function after long-duration low-flow (<1 L/min) sevoflurane and isoflurane anesthesia in consenting surgical patients with normal renal function. To maximize degradant exposure, Baralyme was used, and anesthetic concentrations were maximized (no nitrous oxide and minimal opioids). Inspired and expired Compound A concentrations were quantified. Blood and urine were obtained for laboratory evaluation. Sevoflurane (n = 28) and isoflurane (n = 27) groups were similar with respect to age, sex, weight, ASA status, and anesthetic duration (9.1 +/- 3.0 and 8.2 +/- 3.0 h, mean +/- SD) and exposure (9.2 +/- 3.6 and 9.1 +/- 3.7 minimum alveolar anesthetic concentration hours). Maximum inspired Compound A was 25 +/- 9 ppm (range, 6-49 ppm), and exposure (area under the concentration-time curve) was 165 +/- 95 (35-428) ppm. h. There was no significant difference between anesthetic groups in 24- or 72-h serum creatinine, blood urea nitrogen, creatinine clearance, or 0- to 24-h or 48- to 72-h urinary protein or glucose excretion. Proteinuria and glucosuria were common in both groups. There was no correlation between Compound A exposure and any renal function measure. There was no difference between anesthetic groups in 24- or 72-h aspartate aminotransferase or alanine aminotransferase. These results show that the renal and hepatic effects of long-duration low-flow sevoflurane and isoflurane were similar. No evidence for low-flow sevoflurane nephrotoxicity was observed, even at high Compound A exposures as long as 17 h. Proteinuria and glucosuria were common and nonspecific postoperative findings. Long-duration low-flow sevoflurane seems as safe as long-duration low-flow isoflurane anesthesia.

IMPLICATIONS

Postoperative renal function after long-duration low-flow sevoflurane (with Compound A exposures greater than those typically reported) and isoflurane anesthesia were not different, as assessed by serum creatinine, blood urea nitrogen, and urinary excretion of protein and glucose. This suggests that low-flow sevoflurane is as safe as low-flow isoflurane, even at long exposures.

The effect of ketorolac and sevoflurane anesthesia on renal glomerular and tubular function

We assessed the renal effects of the combination of ketorolac and sevoflurane anesthesia by using sensitive and specific markers of renal proximal and distal tubular and glomerular function. Thirty women (ASA physical status I and II) undergoing breast surgery received either ketorolac 30 mg IM or saline at premedication, at the end, and 6 h after anesthesia maintained with sevoflurane. Peak levels of serum fluoride at 2 h after the end of anesthesia were 30.1 micromol/L (21.0-50.0 micromol/L) in the Ketorolac group and 33.3 micromol/L (13.0-38.0 micromol/L) in the Control group (mean and range, not significant). Urine alpha1-microglobulin indexed to urine creatinine was increased from 2 h after the start of anesthesia until the first postoperative day in the Ketorolac group (peak level, 0.8 +/- 0.4 mg/mmol; upper limit of normal, 0.7 mg/mmol) but did not change in the Control group. Urine glutathione-S-transferase (GST)-alpha indexed to urine creatinine (GST-alpha/creatinine) and GST-pi/creatinine were increased 2 h after anesthesia and returned to baseline values thereafter in both groups. There were no changes in serum cystatin C and urine kallikrein or urine output per hour between groups. The perioperative administration of ketorolac to healthy, well hydrated patients anesthetized with sevoflurane did not produce renal glomerular or tubular dysfunction.

IMPLICATIONS

Ketorolac 90 mg IM, given in divided doses over approximately 10 h to patients anesthetized with sevoflurane with a fresh gas flow rate of 4-6 L/min, did not result in clinically significant changes in renal glomerular or tubular function.

Comparison of plasma alpha glutathione S-transferase concentrations during and after low-flow sevoflurane or isoflurane anaesthesia

BACKGROUND

We evaluated the effect of low-flow sevoflurane anaesthesia, in which compound A is generated, and isoflurane anaesthesia, in which compound A is not generated (n=13 in each group), on hepatocellular integrity using alpha glutathione S-transferase (GST). Alpha GST is a more sensitive and specific marker of hepatocellular damage than is aminotransferase activity and correlates better with hepatic histology.

METHODS

Sevoflurane or isoflurane were delivered without nitrous oxide with a fresh gas flow of 1 l/min. Concentrations of compound A in the circuit were measured hourly, and plasma alpha GST concentrations were measured perioperatively.

RESULTS

Mean duration of anaesthesia was 338+/-92 min in the sevoflurane group and 320+/-63 min in the isoflurane group. Mean compound A concentration in the sevoflurane group was 28.6+/-9.0 ppm. There was no significant difference in alpha GST concentrations between the sevoflurane and isoflurane groups during or after anaesthesia.

CONCLUSION

These results indicate that low-flow sevoflurane and isoflurane anaesthesia have the same effect on hepatic function, as assessed by plasma alpha GST concentrations.

Occupational exposure to volatile anaesthetics: epidemiology and approaches to reducing the problem

Long term occupational exposure to trace concentrations of volatile anaesthetics is thought to have adverse effects on the health of exposed personnel. In contrast with halothane--an agent likely to cause mutagenic effects and proven to be teratogenic--isoflurane and enflurane have not so far been proved to have adverse effects on the health of personnel exposed long term. Data on the newer agents sevoflurane and desflurane are limited. Since possible health hazards from long term exposure to inhalational anaesthetics cannot yet be definitively excluded, many Western countries have established limits for exposure. These usually range from 2 to 10 ppm as a time-weighted average over the time of exposure. A number of investigations have demonstrated that, in operating theatres with modern climate control and waste anaesthetic gas scavenging systems, occupational exposure is unlikely to exceed threshold limits. However, occupational exposure from the use of volatile agents in operating theatres with poor air control--especially during bronchoscopy procedures in paediatric patients--remains a source of concern. This also holds true for both postanaesthesia care units (PACU) and intensive care units (ICU) lacking proper air conditioning and waste gas scavengers. To minimise occupational exposure to volatile anaesthetics, all measures must be taken to provide climate control and properly working scavenging devices, and ensure sufficient personal skill of the anaesthetist, e.g. during inhalational mask induction. Furthermore, low-flow anaesthesia should be used whenever possible. The sole use of intravenous drugs such as propofol instead of volatile agents, were this possible, would eliminate occupational exposure, but may result in environmental pollution by toxic metabolites (e.g. phenol).

The in vitro performance of carbon dioxide absorbents with and without strong alkali apparatus

We report the in vitro longevity of a conventional soda lime carbon dioxide absorbent and an absorbent free from strong alkali (Amsorb). Although the times taken to breakthrough of carbon dioxide (> 0.5%) within an in vitro low flow breathing system were shorter with the alkali-free absorbent, we found that the size and shape of the absorbent container was the major factor in determining the efficiency of the carbon dioxide absorbents.

The effects of low-flow sevoflurane and isoflurane anesthesia on renal function in patients with stable moderate renal insufficiency

Sevoflurane degrades to Compound A, which is nephrotoxic in rats. Therefore, the renal effects of Compound A is an area of intense debate. We investigated the effects of low-flow sevoflurane and isoflurane anesthesia on renal function in patients with stable renal insufficiency. Seventeen patients with a serum creatinine level of more than 1.5 mg/dL were anesthetized with sevoflurane or isoflurane at a total flow of 1 L/min. Serum creatinine and blood urea nitrogen were measured before anesthesia and again 1, 2, 3, 5, 7, and 14 days after anesthesia. The 24-h creatinine clearance was measured before anesthesia and 7 days after anesthesia. There were no significant differences in the blood urea nitrogen levels, serum creatinine concentrations, or creatinine clearance before and after anesthesia within each group. These results suggest that sevoflurane and isoflurane have similar effects on renal function in patients with moderately impaired renal function. Further study of the effects of low-flow sevoflurane anesthesia on impaired renal function with a larger sample size than ours is required to resolve the issue of sevoflurane safety in patients with renal insufficiency.

IMPLICATIONS

The serum creatinine and blood urea nitrogen data indicate that, for exposures of <130 ppm/h in Compound A inspired area under the curve, renal effects of low-flow sevoflurane are similar to those of isoflurane in patients with stable renal insufficiency.

Quantitative Determination of Vapor-Phase Compound A in Sevoflurane Anesthesia Using Gas Chromatography–Mass Spectrometry

Background: During low-flow or closed-circuit anesthesia with the fluorinated inhalation anesthetic sevoflurane, compound A, an olefinic degradation product with known nephrotoxicity in rats, is generated on contact with alkaline CO2 adsorbents. To evaluate compound A formation and thus potential sevoflurane toxicity, a reliable and reproducible assay for quantitative vapor-phase compound A determination was developed.

Methods: Compound A concentrations were measured by fully automated capillary gas chromatography–mass spectrometry with cryofocusing. Calibrators of compound A in the vapor phase were prepared from liquid volumetric dilutions of stock solutions of compound A and sevoflurane in ethyl acetate. 1,1,1-Trifluoro-2-iodoethane was chosen as an internal standard. The resulting quantitative method was fully validated.

Results: A linear response over a clinically useful concentration interval (0.3–75 μL/L) was obtained. Specificity, sensitivity, and accuracy conformed with current analytical requirements. The CVs were 4.1–10%, the limit of detection was 0.1 μL/L, and the limit of quantification was 0.3 μL/L. Analytical recoveries were 100.6% ± 10.1%, 102.5% ± 7.3%, and 99.0% ± 4.1% at 0.5, 10, and 75 μL/L, respectively. The method described was used to determine compound A concentrations during simulated closed-circuit conditions. Some of the resulting data are included, illustrating the practical applicability of the proposed analytical approach.

Conclusions: A simple, fully automated, and reliable quantitative analytical method for determination of compound A in air was developed. A solution was established for sampling, calibration, and chromatographic separation of volatiles in an area complicated by limited availability of sample volume and low concentrations of the analyte.

Sevoflurance: approaching the ideal inhalational anesthetic. a pharmacologic, pharmacoeconomic, and clinical review

Sevoflurane is a safe and versatile inhalational anesthetic compared with currently available agents. Sevoflurane is useful in adults and children for both induction and maintenance of anesthesia in inpatient and outpatient surgery. Of all currently used anesthetics, the physical, pharmacodynamic, and pharmacokinetic properties of sevoflurane come closest to that of the ideal anesthetic (200). These characteristics include inherent stability, low flammability, non-pungent odor, lack of irritation to airway passages, low blood:gas solubility allowing rapid induction of and emergence from anesthesia, minimal cardiovascular and respiratory side effects, minimal end-organ effects, minimal effect on cerebral blood flow, low reactivity with other drugs, and a vapor pressure and boiling point that enables delivery using standard vaporization techniques. As a result, sevoflurane has become one of the most widely used agents in its class.

The effects of prolonged low-flow sevoflurane anesthesia on renal and hepatic function

We assessed the effects of prolonged low-flow sevoflurane anesthesia on renal and hepatic functions by comparing high-flow sevoflurane with low-flow isoflurane anesthesia. Thirty patients scheduled for surgery of > or =10 h in duration randomly received either low-flow (1 L/min) sevoflurane anesthesia (n = 10), high-flow (6-10 L/min) sevoflurane anesthesia (n = 10), or low-flow (1 L/min) isoflurane anesthesia (n = 10). We measured the circuit concentrations of Compound A and serum fluoride. Renal function was assessed by blood urea nitrogen, serum creatinine, creatinine clearance, and urinary excretion of glucose, albumin, protein, and N:-acetyl-beta-D-glucosaminidase. The hepatic function was assessed by serum aspartate aminotransferase, alanine aminotransferase, lactate dehydrogenase, alkaline phosphatase, and total bilirubin. Compound A exposure was 277 +/- 120 (135-478) ppm-h (mean +/- SD [range]) in the low-flow sevoflurane anesthesia. The maximum concentration of serum fluoride was 53.6 +/- 5.3 (43.4-59.3) micromol/L for the low-flow sevoflurane anesthesia, 47.1 +/- 21.2 (21.4-82.3) micromol/L for the high-flow sevoflurane anesthesia, and 7.4 +/- 3.2 (3.2-14.0) micromol/L for the low-flow isoflurane anesthesia. Blood urea nitrogen and serum creatinine were within the normal range, and creatinine clearance did not decrease throughout the study period in any group. Urinary excretion of glucose, albumin, protein, and N:-acetyl-beta-D-glucosaminidase increased after anesthesia in all groups, but no significant differences were seen among the three groups at any time point after anesthesia. Lactate dehydrogenase and alkaline phosphatase on postanesthesia Day 1 were higher in the high-flow sevoflurane group than in the low-flow sevoflurane group. However, there were no significant differences in any other hepatic function tests among the groups. We conclude that prolonged low-flow sevoflurane anesthesia has the same effect on renal and hepatic functions as high-flow sevoflurane and low-flow isoflurane anesthesia.

IMPLICATIONS

During low-flow sevoflurane anesthesia, intake of Compound A reached 277 +/- 120 ppm-h, but the effect on the kidney and the liver was the same in high-flow sevoflurane and low-flow isoflurane anesthesia.

The effect of desflurane on liver function markers in infants and children. Report of a study and a pertinent case report

BACKGROUND

In an open-labelled clinical trial, the effect of desflurane anaesthesia on liver function markers in paediatric patients was monitored.

METHODS

Fifty infants and children, 37 male, scheduled for elective cleft plate surgery were included in the study. Median age was 0.57 (0.25-5.45) years (range), mean desflurane exposure was 2.29 +/- 0.75 MAC-h. Function markers were determined within 24 h prior to and within 24-48 h after anaesthesia. Complete data sets were available for total bilirubin 29, aspartate aminotransferase (ASAT) 36, alanine aminotransferase (ALAT) 35, and for alkaline phosphatase (AP) 28. Pre- and postanaesthetic function tests were compared by means of Wilcoxon's matched-pairs test.

RESULTS

Only for AP could a statistically significant reduction of the postanaesthetic values be observed, while the other parameters showed no significant changes. Postanaesthetic ASAT and ALAT were clearly reduced in three children who had unspecific highly elevated preanaesthetic values. After the study, this observation could be repeated in at least one child, who received a further anaesthesia with desflurane within 3 months.

CONCLUSION

The data suggest that desflurane does not affect excretory or structural liver integrity in infants and children.

Compound A concentrations during low-flow sevoflurane anesthesia correlate directly with the concentration of monovalent bases in carbon dioxide absorbents

Sevoflurane degrades to Compound A, which is nephrotoxic in rats. Potassium hydroxide (KOH) and sodium hydroxide (NaOH) are primary determinants of this degradation reaction. To address this, new carbon dioxide absorbents, such as Amsorb((R)) (A; Armstrong Medical, Coleraine, Northern Ireland), which contains neither KOH nor NaOH, Drägersorb 800 Plus((R)) (D; Dräger, Luebeck, Germany), and Medisorb((R)) (M; Datex-Ohmeda, Bromma, Sweden), which contain some NaOH (1% to 2%) and only trace amounts of KOH (0.003%), were recently developed. We compared Compound A concentrations using these three CO(2) absorbents during low-flow (1 L/min) sevoflurane anesthesia in surgical patients, with those using a conventional CO(2) absorbent, Drägersorb 800 (C). The mean Compound A concentrations +/- SD using C, A, D, and M were 18.7 +/- 2.5, 1.8 +/- 0.7, 13.3 +/- 3.5, and 11.2 +/- 2.6 ppm, respectively, with significant differences (P < 0.001; A versus C, A versus D, A versus M, C versus D, C versus M). Amsorb prevented the degradation of sevoflurane to Compound A, whereas Drägersorb 800 Plus and Medisorb decreased the degradation to Compound A.

IMPLICATIONS

Sevoflurane degradation to Compound A is decreased by lowering the concentration of monovalent bases in the carbon dioxide absorbent (Drägersorb 800 Plus) [Dräger, Luebeck, Germany] and Medisorb) [Datex-Ohmeda, Bromma, Sweden]) and is virtually eliminated in the absence of these bases (Amsorb) [Armstrong Medical, Coleraine, Northern Ireland]).

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

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 Drägersorb(TM) (Dräger, Lübeck, 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 Drägersorb(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.

Sevoflurane and anesthesia for neurosurgery: a review

This review assesses the extent to which sevoflurane fulfills the requirements of the ideal inhalational agent for use in neuroanesthetic practice. Sevoflurane's pharmacokinetic profile is outlined. Data from animal and human studies are used to discuss its effects on cerebral hemodynamics, central nervous system monitoring, and cardiovascular parameters. Where possible, sevoflurane is compared with isoflurane, currently considered the inhalational agent of choice in neuroanesthesia. Sevoflurane's potential for toxicity is reviewed.

Clinical and economic factors important to anaesthetic choice for day-case surgery

Clinical and economic factors that are important to consider when selecting anaesthesia for day-case surgery can differ from those for inpatient anaesthesia. Patients undergoing day-case surgery tend to be healthier and have shorter durations of surgery. They expect less anxiety before surgery, amnesia for the surgical experience, a rapid return to normal (normal mentation with minimal pain and nausea) after surgery, and lower expenses. However, the latter 2 expectations can conflict; older generic drugs have lower acquisition costs but often impose longer recovery times. Longer recovery periods can increase costs by prolonging the time to discharge from labour-intensive areas such as the operating suite or the post-anaesthesia recovery unit. The challenge for today's anaesthetist is to use newer drugs judiciously to minimise their expense without compromising the rate or quality of recovery. Several approaches can secure these aims. Most apply the least anaesthetic needed. 'Least anaesthetic' may mean the particular form of anaesthetic (e.g. local infiltration with monitored anaesthesia care versus a general anaesthetic), or may mean the delivery of the smallest effective dose, perhaps guided by anaesthetic monitors such as end-tidal analysers or the bispectral index. For patients requiring general anaesthesia, a combination of several drugs usually secures the closest approach to the ideal. Drug combinations used usually include a short-acting properative anxiolytic (e.g. midazolam), intravenous propofol (a short-acting potent anxiolytic and amnestic agent) for induction of anaesthesia (and sometimes for maintenance) and primary maintenance of anaesthesia with inhaled nitrous oxide combined with a poorly soluble (low solubility produces rapid recovery; the least soluble is desflurane) potent inhaled anaesthetic delivered at a low inflow rate (to minimise cost). Although old, nitrous oxide is inexpensive and has favourable pharmacokinetic and cardiovascular advantages; however, it is limited in its anaesthetic/amnestic potency, and has the capacity to increase nausea. In children, induction of anaesthesia is often accomplished with sevoflurane rather than desflurane; although sevoflurane is modestly more soluble than desflurane, it is non-pungent whereas desflurane is pungent. Moderate- or short-acting opioids (fentanyl is popular) or nonsteroidal anti-inflammatory agents (especially ketorolac), or local anaesthetics are added to secure analgesia during and after surgery. Similarly, when needed, moderate- or short-acting muscle relaxants are selected. Before the end of anaesthesia, an intravenous antiemetic may be given. With this drug combination, patients usually awaken within minutes after anaesthesia and can often move themselves to the vehicle for transport to the recovery unit. These combinations of anaesthetics and techniques minimise use of expensive drugs while expediting recovery (again minimising cost) with minimal or no compromise in the quality of recovery.

The effects of sevoflurane on serum creatinine and blood urea nitrogen concentrations: a retrospective, twenty-two-center, comparative evaluation of renal function in adult surgical patients

Despite mounting clinical evidence that supports its safety, the question of the potential adverse effects of sevoflurane on renal function continues to generate some controversy. This study retrospectively evaluated pooled renal laboratory data from 22 different clinical trials that compared sevoflurane with three widely used anesthetics. The trials examined postoperative changes in serum creatinine and blood urea nitrogen levels from a total of 3, 436 ASA physical status I-IV adult surgical patients administered either sevoflurane (n = 1941) or a control drug (isoflurane, enflurane, or propofol; n = 1495) as the maintenance anesthetic. The incidences of increased serum creatinine and blood urea nitrogen concentrations were similar among patients administered sevoflurane and those administered control drugs. Additionally, no trends specific to sevoflurane were observed with respect to postoperative serum creatinine concentration and fresh gas flow rate, concurrent treatment with nephrotoxic antibiotics, or type of carbon dioxide absorbent.

IMPLICATIONS

Our data for changes in serum creatinine and blood urea nitrogen indicate that, for exposures of less than 4 minimum alveolar anesthetic concentration/h, sevoflurane is not associated with an increased risk of renal toxicity compared with other commonly used anesthetics. For clinical purposes, the pre- to postoperative changes in serum creatinine and blood urea nitrogen are appropriate measures of renal function in surgical patients.

Mouse strain modestly influences minimum alveolar anesthetic concentration and convulsivity of inhaled compounds

In this study, we measured the minimum alveolar anesthetic concentration (MAC) in several mouse strains, including strains used in the construction of genetically engineered mice. This is important because defined genetic modifications are used increasingly to test mechanisms of inhaled anesthetic action, and background variability in MAC can potentially influence the interpretation of these studies. We investigated the effect of strain on MAC for desflurane, isoflurane, halothane, ethanol, the experimental anesthetic 1-chloro-1,2,2-trifluorocyclobutane, and convulsive 50% effective dose (the dose required to produce convulsions in 50% of animals) of the nonimmobilizer 1,2-dichlorohexafluorocyclobutane. These drugs were studied in eight inbred strains, including both laboratory and wild mouse strains (129/J, 129/SvJ, 129/Ola Hsd, C57BL/6NHsd, C57BL/6J, DBA/2J, Spret/Ei, and Cast/Ei), one hybrid strain (B6129F2/J, derived from the C57BL/6J and 129/J strains), and one outbred strain (CD-1). To test our ability to detect effects in a genetically modified mouse, we compared these data with those for a mouse lacking the gamma (neuronal) isoform of the protein kinase C gene (PKCgamma). We also assessed whether amputating the tail tip of mice (a standard method of obtaining tissue for genetic analysis) increased MAC (e.g., by sensitization of the spinal cord). MAC and convulsant 50% effective dose values differed modestly among strains, with a range of 17% to 39% from the lowest to highest values for MAC using conventional anesthetics, and up to 48% using the experimental anesthetic 1-chloro-1,2,2-trifluorocyclobutane. Convulsivity to the nonimmobilizer varied by 47%. Amputating the tail tip did not affect MAC. PKCgamma knockout mice had significantly higher MAC values than control animals for isoflurane, but not for halothane or desflurane, which implies that protein phosphorylation by PKCgamma can alter sensitivity to isoflurane.

IMPLICATIONS

Anesthetic potency differs by modest amounts among inbred, outbred, wild, and laboratory mouse strains. Absence of the neural form of protein kinase C increases minimum alveolar anesthetic concentration for isoflurane, indicating that protein phosphorylation by the gamma-isoform of protein kinase C (PKCgamma) can influence the potency of this anesthetic.

The elimination of sodium and potassium hydroxides from desiccated soda lime diminishes degradation of desflurane to carbon monoxide and sevoflurane to compound A but does not compromise carbon dioxide absorption

Normal (hydrated) soda lime absorbent (approximately 95% calcium hydroxide [Ca(OH)2], the remaining 5% consisting of a mixture of sodium hydroxide [NaOH] and potassium hydroxide [KOH]) degrades sevoflurane to the nephrotoxin Compound A, and desiccated soda lime degrades desflurane, enflurane, and isoflurane to carbon monoxide (CO). We examined whether the bases in soda lime differed in their capacities to contribute to the production of these toxic substances by degradation of the inhaled anesthetics. Our results indicate that NaOH and KOH are the primary determinants of degradation of desflurane to CO and modestly augment production of Compound A from sevoflurane. Elimination of these bases decreases CO production 10-fold and decreases average inspired Compound A by up to 41%. These salutary effects can be achieved with only slight decreases in the capacity of the remaining Ca(OH)2 to absorb carbon dioxide.

IMPLICATIONS

The soda lime bases used to absorb carbon dioxide from anesthetic circuits can degrade inhaled anesthetics to compounds such as carbon monoxide and the nephrotoxin, Compound A. Elimination of the bases sodium hydroxide and potassium hydroxide decreases production of these noxious compounds without materially decreasing the capacity of the remaining base, Ca(OH)2, to absorb carbon dioxide.

Comparison of renal function following anesthesia with low-flow sevoflurane and isoflurane

STUDY OBJECTIVE

To evaluate postoperative renal function after patients were administered sevoflurane under conditions designed to generate high concentrations of compound A.

STUDY DESIGN AND SETTING

A multicenter (11 sites), multinational, open-label, randomized, comparative study of perioperative renal function in patients who have received low-flow (< or = 1 L/min) sevoflurane or isoflurane.

PATIENTS

254 ASA physical status I, II and III patients requiring endotracheal intubation for elective surgery lasting more than 2 hours.

INTERVENTIONS

After induction, low-flow anesthesia was initiated at a flow rate < or = 1 L/min. Blood and urine samples were studied to assess postoperative renal function.

MEASUREMENTS AND MAIN RESULTS

Measurements of serum BUN and creatinine, and urine glucose, protein, pH, and specific gravity were used to assess renal function preoperatively and up to 3 days postoperatively. Serum inorganic fluoride ion concentration was measured at preinduction, emergence, and 2, 24 and 72 hours postoperatively. Compound A concentrations were measured at two sites for those patients receiving sevoflurane. Adverse experience data were analyzed. One hundred eighty-eight patients were considered evaluable (98 sevoflurane and 90 isoflurane). Peak serum fluoride concentrations were significantly higher after sevoflurane (40 +/- 16 microM) than after isoflurane (3 +/- 2 microM). Serum creatinine and BUN decreased in both groups postoperatively; glucosuria and proteinuria occurred in 15% to 25% of patients. There were no clinically significant differences in BUN, creatinine, glucosuria, and proteinuria between the low-flow sevoflurane and low-flow isoflurane patients.

CONCLUSIONS

There were no statistically significant differences in the renal effects of sevoflurane or isoflurane in surgical patients undergoing low-flow anesthesia for up to 8 hours. Low-flow sevoflurane anesthesia under clinical conditions expected to produce high levels of compound A appears as safe as low-flow isoflurane anesthesia.

[Adsorption of carbon dioxide gas]

OBJECTIVES

To analyse the various methods for carbon dioxide absorption in anaesthesia, the available absorbents and their modes of use.

DATA SOURCES

We searched the Medline and Internet databases for papers using the key words: carbon dioxide absorption, soda-lime, zeolite. We also had correspondence and contacts with soda lime manufacturers.

STUDY SELECTION

All types of articles containing data on CO2 absorption.

DATA EXTRACTION

The articles were analysed for the benefits and adverse effects of the various absorbents.

DATA SYNTHESIS

Carbon dioxide absorption enables the use of low flow anaesthesia, and a decreased consumption of medical gases and halogenated anaesthetics, as well as reduced pollution. Chemical absorbents (soda-lime and barium hydroxide lime (Baralyme) may produce toxic compounds: carbon monoxide with all halogenated anaesthetics and compound A with sevoflurane. Simple measures against desiccation of the lime prevent carbon monoxide production. The toxicity of compound A, shown in the rat, has not been proven in clinical anaesthesia. Recent improvements in manufacture processes have decreased the powdering of lime. Moreover, filters inserted between the anaesthesia circuit and the patient abolish the risk for powder inhalation.