Dose-Related Biochemical Markers of Renal Injury After Sevoflurane Versus Desflurane Anesthesia in Volunteers

Renal injury from sevoflurane in noncardiac surgery: a retrospective cohort study

BACKGROUND

Sevoflurane is metabolised into Compound A and fluoride that carry a hypothetical risk of nephrotoxicity. However, a clinically significant association between sevoflurane use and acute kidney injury (AKI) in humans has not been established.

METHODS

We retrospectively reviewed 15 552 patients who underwent noncardiac surgery under general anaesthesia using a volatile agent lasting >3 h between July 2016 and May 2019 at a single centre. Patients were divided into a sevoflurane group or no sevoflurane group (desflurane or isoflurane). The primary outcome was incidence of postoperative AKI, which was defined based on the Kidney Disease: Improving Global Outcomes criteria using creatinine concentration within 48 h postoperatively. Propensity score analysis using inverse probability of treatment weighting and propensity score matching was designed to compare outcomes between groups.

RESULTS

Amongst 13 701 included patients, 11 070 (80.8%) received sevoflurane during anaesthesia. The incidence of AKI was 2.3% (257/11 070) and 2.5% (66/2631) in the sevoflurane and no sevoflurane groups, respectvely (P=0.57). After inverse probability of treatment weighting adjustment, sevoflurane anaesthesia was not significantly associated with postoperative AKI (odds ratio [OR] 1.32; 95% confidence interval [CI]: 0.99-1.76; P=0.059). In the matched cohort, the incidence of AKI was 3.1% (81/2626) and 2.4% (62/2626) in the sevoflurane and no sevoflurane groups, respectively, and sevoflurane anaesthesia was not associated with postoperative AKI (OR 1.32; 95% CI: 0.94-1.86; P=0.11).

CONCLUSIONS

Sevoflurane anaesthesia for >3 h was not associated with postoperative renal injury compared with anaesthesia using other volatile agents.

Transient postoperative glycosuria after isoflurane exposure in two dogs

The present report describes two surgical cases involving the development of sudden glycosuria after isoflurane anaesthesia, despite the dogs having normal blood glucose levels and renal glucose reabsorption. The glycosuria manifested 1 day after surgery and resolved spontaneously within 2 days in both cases. Considering that the surgeries (subcutaneous mandibular mass removal and fracture repair) were unrelated to the kidneys, and there were no remarkable events during anaesthesia, the glycosuria may have been associated with the isoflurane anaesthesia. There have been several previous reports of glycosuria in human patients following transient proximal tubule dysfunction due to volatile anaesthetics. This case report suggests the possibility of transient renal dysfunction following isoflurane anaesthesia in these two clinically healthy dogs. However, considering the observational nature of this report, it can not be excluded that any other procedure performed in these animals was responsible of the observed glycosuria.

A Comparison of the Effects of Prolonged (>10 Hour) Low-flow Sevoflurane, High-flow Sevoflurane, and Low-flow Isoflurane Anaesthesia on Hepatorenal Function in Orthopaedic Patients

This study compared the effects of low-flow sevoflurane, high-flow sevoflurane and low-flow isoflurane on hepatorenal function during and after more than 10 hours of anaesthesia. Twenty-five patients scheduled for elective orthopaedic surgery were categorized into three groups; low-flow sevoflurane (fresh gas flow at 1 litre/min, n=9), high-flow sevoflurane (5 l/min, n=7), or low-flow isoflurane (1 l/min, n=9). Inspiratory compound A concentrations were measured. The groups had similar duration of anaesthesia and exposure to anaesthetic agents. The area under the curve of concentration (mean, SD) of compound A in the low-flow sevoflurane group (359.8, 106.1 ppm.h) was greater than that in the high-flow sevoflurane group (61.1, 29.3 ppm.h; P<0.01). All groups showed normal plasma creatinine and creatinine clearance, and transient postoperative increases in plasma alanine aminotrans-ferase and alpha glutathione-S-transferase, as well as urinary glucose and alpha glutathione-S-transferase, with no significant differences between groups. There were no significant relationships between the area under the curve of concentration of compound A and the biomarkers. These findings suggest that prolonged anaesthesia with low-flow sevoflurane has similar effects on hepatorenal function to prolonged anaesthesia with high-flow sevoflurane and low-flow isoflurane.

Case report: proximal tubule impairment following volatile anesthetic exposure

The safety of contemporary volatile anesthetic agents with respect to kidney function is well established, and growing evidence suggests that volatile anesthetics even protect against ischemic nephropathy. However, studies examining effects of volatile anesthetics on kidney function frequently demonstrate transient proteinuria and glycosuria following exposure to these agents, although the cause of these findings has not been thoroughly examined. We describe the case of a patient who underwent a neurosurgical procedure, then experienced glycosuria without hyperglycemia that resolved within days. Following a second neurosurgical procedure, the patient again developed glycosuria, now associated with ketonuria. Further examination demonstrated nonalbuminuric proteinuria in conjunction with urinary wasting of phosphate and potassium, indicative of proximal tubule impairment. We suggest that transient proximal tubule impairment may play a role in the proteinuria and glycosuria described following volatile anesthetic exposure and discuss the relationship between these observations and the ability of these agents to protect against ischemic nephropathy.

Effect of sevoflurane anesthesia on the severity of renal histopathologic changes in rabbits pretreated with gentamicin: A controlled, investigator-blinded, experimental study

BACKGROUND

Inorganic fluoride and compound A are potential nephrotoxic products of sevoflurane, a halogenated inhalational general-anesthetic drug.

OBJECTIVE

The aim of this study was to microscopically examine the effect of sevoflurane on the severity of renal histopathologic changes in rabbits pretreated with gentamicin.

METHODS

In this controlled, investigator-blinded, experimental study at the Firat University School of Medicine, Elazig, Turkey, male New Zealand white rabbits (age range, 6-8 months; weight range, 2600-3400 g) were randomly divided into 4 groups of equal size. The gentamicin group received IM gentamicin 10 mg/kg · d(-1) for 10 days. Rabbits in the sevoflurane group received pH-balanced saline solution at a volume of 10 mg/kg · d(-1) for 10 days, equivalent to the volume of gentamicin administered to the gentamicin group. On day 11, anesthesia was induced with 8% sevoflurane in 50% oxygen and air using a suitable facemask. When a sufficient depth of anesthesia (loss of eyelash reflex and tolerance to tail-clamp stimuli) was reached (without a muscle relaxant), the rabbits were intubated (3-mm ID) and allowed to breathe spontaneously. End-tidal or end expiratory concentration of sevoflurane was then decreased to 4% and the rabbits were anesthetized at a flow rate of 4 L/min for 4 hours. The rabbits in the gentamicin + sevoflurane group were treated with IM gentamicin at a dosage of 10 mg/kg · d(-1) for 10 days. On day 11, they were exposed to sevoflurane, as described for the sevoflurane group. The control group received IM pH-balanced saline solution for the duration of the study. Twenty-four hours after treatment completion, all rabbits were euthanized and kidney tissue samples were obtained. Histopathologic examinations were then carried out using light microscopy. Changes in renal histopathology were based on the percentage of acute tubular necrosis (ATN) and judged on a scale from none to severe.

RESULTS

Forty male New Zealand white rabbits (mean [SD] age, 7 [0.49] months; mean [SD] weight, 2900 [150] g) were divided into 4 groups of 10 rabbits each. Proximal renal tubule cell injury in the form of ATN (the mean score) was significantly greater in the 3 treatment groups than in the control group (all, P < 0.001), especially at the corticomedullary junction. In the 3 treatment groups, the most severe renal damage observed was rated as mild (10%-25%). More rabbits in the gentamicin + sevoflurane group had mild renal damage (7) than in the gentamicin group (4) or the sevoflurane group (4), but the between-group differences were not statistically significant.

CONCLUSION

In this experimental study of the effects of sevoflurane on the severity of renal histopathologic changes, a higher percentage of rabbits were observed to have greater renal damage in the gentamicin + sevoflurane group than the other groups. However, between-group differences did not reach statistical significance.

Comparison of the renal safety between carbon dioxide absorbent products under sevoflurane anesthesia: a pilot study

Background

The chemical reaction of carbon dioxide absorbent and sevoflurane is known to produce compound A. However, carbon dioxide absorbents are not controlled by the Food and Drug Administration, but are treated as industrial products in some nations. Moreover, carbon dioxide absorbents differ in their capacities to produce compound A, because their chemical compositions differ. In this study, we compared the renal safety between carbon dioxide absorbent products in patients under sevoflurane anesthesia.

Methods

Eighty patients with no preexisting renal disease undergoing elective gynecologic surgery were randomly assigned to receive sevoflurane or isoflurane anesthesia with one of four carbon dioxide absorbent products (Sodasorblime®, Sodalyme®, Sodasorb®, Spherasorb®) at the same fresh gas flow of 2 L/min. The renal safety was evaluated by changes of blood urea nitrogen (BUN), creatinine and urine N-acetyl-b-glucoseaminidase (NAG)-creatinine ratio at 24 hours and 72 hours after surgery from preoperative level.

Results

There was no significant difference in the renal safety indicators between carbon dioxide absorbents during sevoflurane anesthesia (P > 0.05). However, the BUN and urine NAG-creatinine ratios at 72 hours after surgery were higher in isoflurane anesthesia in some carbon dioxide absorbent groups (P = 0.03 and 0.04, respectively).

Conclusions

We could not find significant differences of renal safety indicators with carbon dioxide absorbents. Although the adverse effect of carbon dioxide absorbents on renal function was not proved, consideration should be given to their contol by the regulation on their efficacy and safety because carbon dioxide absorbents can produce compound A.

Effect of sevoflurane on grafted kidney function in renal transplantation

BACKGROUND

The objective of this retrospective study was to determine if there are any differences in grafted kidney function in recipients of kidney transplantation (KT) when donors and recipients were anesthetized with sevoflurane compared to desflurane.

METHODS

Seventy-three pairs of donors-recipients were anesthetized with sevoflurane (Sevo group) and 71 pairs were anesthetized with desflurane (Des group). We retrospectively investigated the blood urea nitrogen (BUN) levels, creatinine (Cr) levels, and estimated glomerular filtration rates (eGFR) of the recipients in both groups for 1 year postoperatively. We tested non-inferiority for serum creatinine at discharge and 1 year after KT. Short-term (1 year) outcomes of KT were assessed by the incidence of delayed graft function (DGF), acute rejection episodes (ARE), and graft failure.

RESULTS

There were no differences in BUN, Cr, eGFR, or outcomes of KT at 1 year postoperatively. Specifically, the 95% confidence interval for the difference in creatinine levels between the Sevo and Des groups was less than the margin of equivalence at the time of discharge and 1 year after surgery. The occurrences of DGF, ARE, and graft failure were comparable between the groups.

CONCLUSIONS

Compared to desflurane, sevoflurane had no adverse effects on grafted renal function or on the short-term outcome of renal transplantation.

Biochemical Effects of Low-Flow Anesthesia with Inhalation agents in Patients undergoing Laparoscopic Surgery

This study was designed to investigate the effects of low-flow anesthesia with sevoflurane and desflurane on renal and hepatic functions in patients undergoing laparoscopic abdominal surgery. Twenty patients with ASA I or II (American Society of Anesthesiologists classification) physical scores were included in the study. There were no significant differences between sevoflurane and desflurane groups with respect to age, weight, body mass index, duration of the operation and the anesthesia. In both groups, renal function parameters such as urea, BUN, creatinine and calculated creatinine clearance did not show significant differences at 24 and 48 hours. Homocysteine levels, which showed renal metabolic function, did not change significantly at 24 and 48 hours when compared to baseline levels in both groups. Transaminases were not significantly different between the two groups from baseline to 24 and 48 hours. These differences between the preoperative and postoperative values of biochemical parameters were similar for both anesthetic groups (p>0.05). Low-flow anesthesia did not cause impairment in terms of renal and hepatic functions.

The effects of desflurane and sevoflurane on hepatic and renal functions after right hepatectomy in living donors*

We compared postoperative hepatic and renal functions between the two inhalational anesthetics, desflurane and sevoflurane in living donors undergoing right hepatectomy. Seventy-four adult donors were randomly allocated into Des group (n = 37) and sevo group (n = 37). Before the induction of anesthesia, morphine sulfate 400 microg was injected intrathecally. Anesthesia was maintained with one minimum alveolar concentration (MAC) of deflurane or sevoflurane plus continuous intravenous remifentanil. Liver and renal function tests were performed and analysed at preoperative period, immediately after operation, and on 1st, 2nd, 3rd, 5th, 7th, and 30th postoperative days (PODs). Aspartate aminotransferase (AST) showed significant elevations from the day of surgery to POD 3 and alanine aminotransferase (ALT) was significantly elevated on POD 1 and POD 3 in the sevo group. Albumin level was significantly lower on POD 2 in the sevo group. Creatinine was significantly higher on POD 3 and POD 30 and estimated glomerular filtration ratio was significantly lower on POD 3 and POD 30 in the sevo group. No patient developed hepatic or renal failures. The results of our study showed better postoperative hepatic and renal function test with desflurane than sevoflurane at equivalent dose of 1 MAC in living donors undergoing right hepatectomy, but further study is required to evaluate clinical importance.

Formation and toxicity of anesthetic degradation products

Toxic degradation products are formed from a range of old and modern anesthetic agents. The common element in the formation of degradation products is the reaction of the anesthetic agent with the bases in the carbon dioxide absorbents in the anesthesia circuit. This reaction results in the conversion of trichloroethylene to dichloroacetylene, halothane to 2-bromo-2-chloro-1,1-difluoroethylene, sevoflurane to 2-(fluoromethoxy)-1,1,3,3,3-pentafluoro-1-propene (Compound A), and desflurane, isoflurane, and enflurane to carbon monoxide. Dichloroacetylene, 2-bromo-2-chloro-1,1-difluoroethylene, and Compound A form glutathione S-conjugates that undergo hydrolysis to cysteine S-conjugates and bioactivation of the cysteine S-conjugates by renal cysteine conjugate beta-lyase to give nephrotoxic metabolites. The elucidation of the mechanisms of formation and bioactivation of degradation products has allowed for the safe use of anesthetics that may undergo degradation in the anesthesia circuit.

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.

Acute toxic renal failure

Acute renal failure (ARF) is a common problem in intensive care medicine. Even modest degrees of ARF not requiring dialysis treatment increase the risk of death approximately fivefold. Despite the widespread appreciation of the role of nephrotoxic drugs in their contribution to ARF, these drugs continue to have an ongoing aetiological role. Potentially nephrotoxic drugs include non-steroidal anti-inflammatory drugs, radiocontrast agents, antimicrobial and anaesthetic agents. Endogenous compounds such as myoglobin and haemoglobin may furthermore cause toxic nephropathy. Tubular injury initiated by toxins often results from a combination of acute renal vasoconstriction and direct cellular toxicity due to intracellular accumulation of the toxin, or, alternatively, may be mediated immunologically in case of interstitial nephritis. Patients with reduced renal functional reserve, cardiovascular co-morbidity, diabetes mellitus, and advanced age are at increased risk. Awareness of the range of toxins on the one hand and simple measures such as adequate pre-hydration of the patient and drug monitoring on the other hand may be sufficient to avoid drug-induced ARF or minimize its clinical severity in susceptible patients.

Kidney-Specific Proteins in Elderly Patients Undergoing Cardiac Surgery with Cardiopulmonary Bypass: Retracted

In cardiac surgery, acute renal failure (ARF) is more likely in elderly patients than in younger patients. We assessed whether kidney function is different between elderly and younger cardiac surgery patients by measuring kidney-specific proteins. Forty consecutive patients aged <60 yr and 40 patients aged >70 yr without preoperative kidney dysfunction undergoing elective cardiac surgery with cardiopulmonary bypass (CPB) were included. Creatinine clearance and fractional excretion of sodium, as well as urine concentrations of N-acetyl-beta-D-glucosaminidase, alpha-1-microglobulin, glutathione transferase-pi (GST-pi), and glutathione transferase-alpha (GST-alpha) were measured after induction of anesthesia, at the end of surgery, and at the first and second postoperative days (PODs) on the intensive care unit. Patients' ages were 54 +/- 4 and 77 +/- 3 yr, respectively. Preoperative creatinine concentrations were without significant differences between the two groups. Fractional excretion of sodium was significantly higher after bypass in the elderly than in the younger patients. Urine concentrations of all kidney-specific proteins increased after CPB in the elderly (e.g., GST-pi from 16.2 +/- 3.4 to 27.7 +/- 3.9 microg/L), whereas they remained almost unchanged in the younger patients. Concentrations of all kidney-specific proteins were significantly larger in the elderly than in the younger patients even at the second POD. Although none of our patients suffered ARF requiring dialysis, increased post-CPB urine concentrations of kidney-specific proteins in the elderly suggest discrete and transient alterations in kidney integrity in comparison with a younger patient population undergoing cardiac surgery.

IMPLICATIONS

Measurement of kidney-specific proteins demonstrated that patients >70 yr (mean, 77 +/- 3 yr) undergoing cardiac surgery with cardiopulmonary bypass had moderate and transient alterations in kidney integrity compared with patients aged <60 yr (mean, 54 +/- 4 yr). These abnormalities were not detected with standard measures of kidney function (e.g., creatinine concentrations).

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.

Is kidney function altered by the duration of cardiopulmonary bypass?

BACKGROUND

Cardiopulmonary bypass (CPB) is considered responsible for kidney damage. By using sensitive markers of kidney damage we assessed whether the length of CPB influences kidney function.

METHODS

In a prospective study, 50 consecutive cardiac operation patients with CPB times of less than 70 minutes were compared with 50 consecutive patients showing CPB times of more than 90 minutes. Aside from creatinine clearance and fractional excretion of sodium, urine concentrations of N-acetyl-beta-D-glucosaminidase, alpha1-microglobulin, glutathione transferase-pi, and glutathione transferase-alpha were measured after induction of anesthesia at the end of the operation, and on the first and second postoperative days in the intensive care unit.

RESULTS

CPB times were 58 +/- 12 minutes and 116 +/- 18 minutes, respectively. Hemodynamics, volume replacement, and use of catecholamines during cardiopulmonary bypass (CPB) were without significant differences between groups. Concentrations of all kidney-specific proteins increased significantly after CPB, showing the highest significant increases in the CPB more than 90 minutes group (eg, glutathione transferase-alpha CPB > 90 minutes from 3.0 +/- 1.0 to 12.9 +/- 2.9 microg/L; glutathione transferase-alpha CPB < 70 minutes from 2.4 +/- 0.5 to 5.5 +/- 1.2 microg/L). By the second postoperative day, urine concentrations of kidney-specific proteins had returned to almost baseline in the CPB less than 70 minutes patients, but remained slightly elevated in the other group.

CONCLUSIONS

Patients with CPB times more than 90 minutes showed more pronounced kidney damage than patients with CPB times less than 70 minutes as assessed by sensitive kidney-specific proteins. Whether patients with preexisting renal dysfunction undergoing prolonged CPB times would profit from renal protection strategies needs to be elucidated.

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.

Interaction of inhalational anaesthetics with CO2 absorbents

We review the currently available carbon dioxide absorbents: sodium hydroxide lime (=soda lime), barium hydroxide lime, potassium-hydroxide-free soda lime, calcium hydroxide lime and non-caustic lime. In general, all of these carbon dioxide absorbents are liable to react with inhalational anaesthetics. However, there is a decreasing reactivity of the different absorbents with inhalational anaesthetics: barium hydroxide lime >> soda lime > potassium-hydroxide-free soda lime > calcium hydroxide lime and non-caustic lime. Gaseous compounds generated by the reaction of the anaesthetics with desiccated absorbents are those that threaten patients. All measures are comprehensively described to--as far as possible--prevent any accidental drying out of the absorbent. Whether or not compound A, a gaseous compound formed by the reaction of sevoflurane with normally hydrated absorbents, is still a matter of concern is discussed. Even after very high loading with this compound, during long-lasting low-flow sevoflurane anaesthesias, no clinical or laboratory signs of renal impairment were observed in any of the surgical patients. Finally, guidelines for the judicious use of different absorbents are given.

Sevoflurane provides faster recovery and postoperative neurological assessment than isoflurane in long-duration neurosurgical cases

Sevoflurane (SEVO) provides faster emergence than isoflurane (ISO). This advantage is thought to magnify with increased duration of exposure. In addition, SEVO has several of the characteristics of an ideal neuroanesthetic. We designed a prospective, randomized, double-blinded study to compare the recovery profile of SEVO versus ISO in neurosurgery. Sixty patients undergoing intracranial surgery were enrolled. They were randomized to receive SEVO or ISO in 40% oxygen as part of a balanced anesthetic regimen. The anesthetic concentration (0.5 to 1.0 minimum alveolar anesthetic concentration [MAC]) was adjusted to maintain mean arterial blood pressure within 20% of the preinduction baseline. At the end of the surgery, neuromuscular blockade was reversed, anesthetics were discontinued without prior tapering, and fresh gas flow was increased to 10 L/min. Recovery end-points were measured as the time from closure of the anesthetic vaporizer. Mean MAC-hours were identical in both groups (4.7). Patients in the SEVO group demonstrated a shorter time to emergence (P = 0.02) and for response to command (squeeze hand, P = 0.03; move feet, P = 0.01). Patients in the SEVO group obtained a Glasgow coma scale score of >/=10 5 min before patients in the ISO group (P = 0.04). Obtaining an early neurological examination can be critical in neurosurgical patients. The observed difference in emergence between SEVO and ISO could therefore be of clinical importance.

IMPLICATIONS

The low-solubility anesthetic, sevoflurane, provides faster recovery and postoperative neurological assessment than isoflurane after long-duration (4.7 MAC-h) intracranial surgery.

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.

Renal tubular injury after infrarenal aortic aneurysm repair

OBJECTIVE

To investigate markers of tubular injury (glutathione-S-transferase [GST] isoforms) as early markers for renal damage in patients undergoing abdominal aortic aneurysm repair.

DESIGN

Prospective study.

SETTING

Regional teaching hospital.

PARTICIPANTS

Eight consecutive patients undergoing elective infrarenal abdominal aortic aneurysm repair.

INTERVENTIONS

All patients received a standard anesthetic technique including a dopamine infusion (3 microg/kg/min) but without supplemental renoprotective agents. Urine and blood samples were taken at induction, at 1 hour and 3 hours after limb reperfusion, and on days 1 and 2 postoperatively. Urine microalbumin and creatinine concentrations were measured using standard assays, and urine pi-GST and alpha-GST enzyme measurements were performed by a commercial immunoassay (Biotrin, Biotrin International Ltd., Co., Dublin, Ireland).

MEASUREMENTS AND MAIN RESULTS

Five patients (63%) showed a postoperative elevation of serum creatinine (median increase from baseline, 35.4%; range, 8.3% to 50.6%) that was associated with significant elevations of urinary microalbumin-to-creatinine, alpha-GST-to-creatinine, and pi-GST-to-creatinine ratios soon after clamp removal. The remaining 3 patients showed no increase in serum creatinine or urine proteins. Peak alpha-GST-to-creatinine levels were different between the 2 groups. The peak levels of GST enzymes were significantly (r(2) > 80%) associated with the percent increase in serum creatinine from baseline.

CONCLUSION

Urinary GST-to-creatinine ratios are a sensitive early biomarker for renal injury after infrarenal abdominal aortic aneurysm repair.

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.

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.

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 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.

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.

Cost comparison of sevoflurane with isoflurane anesthesia in arthroscopic menisectomy surgery

PURPOSE

To determine the "real world" cost of sevoflurane compared with isoflurane in balanced general anesthesia for daycare arthroscopic menisectomy, we prospectively investigated perioperative drug requirement and expense as well as recovery time.

METHODS

Following intravenous induction, 40 consenting adult patients randomly received either sevoflurane- or isoflurane-based anesthesia with a standardized gas inflow rate of 3 l x min. Recovery was assessed in the postanesthetic recovery room (PARR) in a double-blind manner at 15 min intervals using the Aldrete scoring system until patients met discharge criteria.

RESULTS

Patient demographics, anesthetic duration, volatile potency and adjunct drug requirements were similar in the two groups. Total perioperative drug cost per patient was CAN$38.10+/-10.13 (mean +/- SD) for the sevoflurane group and $23.87+/-6.59 for the isoflurane group (P<0.01). Although the nonvolatile drug cost was comparable between the two groups, the volatile drug cost per patient was $19.40+/-8.80 for sevoflurane and $4.50+/-1.90 for isoflurane (P<0.01). This four-fold sevoflurane-to-isoflurane cost difference was the product of two ratios, both based on the volume of liquid anesthetic: the ratio of consumption, 2.1; and the ratio of institutional price, 2.1. Intraoperative hemodynamic response, time until discharge from the PARR and incidences of postoperative nausea and vomiting did not significantly differ between the two groups.

CONCLUSIONS

When used to maintain equipotent balanced general anesthesia for daycare arthroscopic menisectomy, volatile consumption and cost were greater for sevoflurane compared with isoflurane. Nonvolatile perioperative drug cost and recovery times were similar, however, in the two groups.