The organ toxicity of inhaled anesthetics

Volatile anesthetic agents for life-threatening pediatric asthma: A multicenter retrospective cohort study and narrative review

BACKGROUND

Volatile anesthetic agents are described as rescue therapy for children invasively ventilated for critical asthma. Yet, data are currently limited to case series.

AIMS

Using the Virtual Pediatric Systems database, we assessed children admitted to a pediatric intensive care unit invasively ventilated for life-threatening asthma and hypothesized ventilation duration and mortality rates would be lower for subjects exposed to volatile anesthetics compared with those without exposure.

METHODS

We performed a multicenter retrospective cohort study among nine institutions including children 5-17 years of age invasively ventilated for asthma from 2013 to 2019 with and without exposure to volatile anesthetics. Primary outcomes were ventilation duration and mortality. Secondary outcomes included patient characteristics, length of stay, and anesthetic-related adverse events. A subgroup analysis was performed evaluating children intubated ≥2 days.

RESULTS

Of 203 children included in study, there were 29 (14.3%) with and 174 (85.7%) without exposure to volatiles. No differences in odds of mortality (1.1, 95% CI: 0.3-3.9, p > .999) were observed. Subjects receiving volatiles experienced greater median difference in length of stay (4.8, 95% CI: 1.9-7.8 days, p < .001), ventilation duration (2.3, 95% CI: 1-3.3 days, p < .001), and odds of extracorporeal life support (9.1, 95% CI: 1.9-43.2, p = .009) than those without volatile exposure. For those ventilated ≥2 days, no differences were detected in mortality, ventilation duration, length of stay, arrhythmias, or acute renal failure. However, the odds of extracorporeal life support remained greater for those receiving volatiles (7.6, 95% CI: 1.3-44.5, p = .027). No children experienced malignant hyperthermia or hepatic failure after volatile exposure.

CONCLUSIONS

For intubated children for asthma, no differences in mechanical ventilation duration or mortality between those with and without volatile anesthetic exposure were observed. Although volatiles may represent a viable rescue therapy for severe cases of asthma, definitive, and prospective trials are still needed.

Risk assessment of occupational exposure to anesthesia Isoflurane in the hospital and veterinary settings

Despite the modern ventilation and waste anesthetic gas (WAG) scavenging systems, occupational exposure to common volatile anesthesia, isoflurane, can occur in the hospital and veterinary settings, but limited information exists on potential exposure and health risk of isoflurane. We assessed exposure dose rates and risks among clinicians and veterinary professionals from occupational exposure to isoflurane. Through a critical review of open literature (1965 to 2020), we summarized potential adverse effects and exposure scenarios of isoflurane among the professional groups, including anesthetists, nurses, operating room personnel, researchers, and/or veterinarians. Deterministic United States National Research Council/Environmental Protection Agency's risk assessment framework (hazard identification, dose-response relationship, exposure assessment and risk characterization) was used to compute inhalation Reference Doses (RfDs), Average Daily Doses (ADDs), and Hazard Quotient (HQ) values-an established measure of non-carcinogenic (systemic) risks-from exposure to isoflurane to workers in hospital and veterinary settings. We identified the central nervous system as the main target for isoflurane, and that isoflurane has dose-dependent effects on cardiac hemodynamics, can impair pulmonary functions and potentially cross the utero-placental barrier leading to congenital malformation in fetus. Based on the modelled RfDs (range 0.8003-7.55 mg/kg-day) and ADDs (range 0.071-1.9617 mg/kg-day), we estimated 56 different HQ values, of which 5 HQs were higher than 1 (range 1.099-2.4512) under high exposure scenarios. Our results suggest a significant non-carcinogenic risk from isoflurane exposures among workers in the occupational settings. The findings underscore the need to significantly minimize isoflurane release to protect workers' health in the hospital and veterinary environments.

TIVA versus Inhalational Agents for Pediatric Cardiac Intensive Care

The field of pediatric intensive care has come a long way, especially with the recognition that adequate sedation and analgesia form an imperative cornerstone of patient management. With various drugs available for the same, the debate continues as to which is the better: total intravenous anesthesia (TIVA) or inhalational agents. While each have their own advantages and disadvantages, in the present era of balance toward the IV agents, we should not forget the edge our volatile agents (VAs) might have in special scenarios. And ultimately as anesthesiologists, let us not forget that be it knob and dial, or syringe and plunger, our aim is to put pain to sleep and awaken a new faith to breathe.

Anaesthesia and ICU sedation with sevoflurane do not reduce myocardial injury in patients undergoing cardiac surgery: A randomized prospective study

BACKGROUND

To evaluate the effect of anaesthesia and ICU sedation with sevoflurane to protect the myocardium against ischemia-reperfusion injury associated to cardiac surgery assessed by troponin release.

METHODS

We performed a prospective, open-label, randomized study in cardiac surgery with cardiopulmonary bypass. Patients were randomized to an algorithm-based intervention group and a control group. The main outcome was the perioperative kinetic of cardiac troponin I (cTnI). The secondary outcomes included composite endpoint, GDF-15 (macrophage inhibitory cytokine-1) value, arterial lactate levels, and the length of stay (LOS) in the ICU.

RESULTS

Of 82 included patients, 81 were analyzed on an intention-to-treat basis (intervention group: n = 42; control group: n = 39). On inclusion, the intervention and control groups did not differ significantly in terms of demographic and surgical data. The postoperative kinetics of cTnI did not differ significantly between groups: the mean difference was 0.44 ± 1.09 μg/ml, P = .69. Incidence of composite endpoint and GDF-15 values were higher in the sevoflurane group than in propofol group. The intervention and control groups did not differ significantly in terms of ICU stay and hospital stay.

CONCLUSION

The use of an anaesthesia and ICU sedation with sevoflurane was not associated with a lower incidence of myocardial injury assessed by cTnI. Sevoflurane administration was associated with higher prevalence of acute renal failure and higher GDF-15 values.

Comparison of the Postoperative Liver Function Between Total Intravenous Anesthesia and Inhalation Anesthesia in Patients with Preoperatively Elevated Liver Transaminase Levels: A Retrospective Cohort Study

Background

Anesthesia and surgery may deteriorate liver function in patients with elevated liver enzyme levels; therefore, in these patients, choosing anesthetics with less hepatotoxicity is important.

Methods

This retrospective study investigated the effect of total intravenous anesthesia (TIVA) versus inhalation anesthesia (INHA) on the postoperative liver function in patients with preoperatively elevated liver enzyme levels (aspartate transaminase [AST] or alanine transaminase [ALT] >40 U/L) who underwent non-hepatic surgery under general anesthesia. We compared the changes in enzyme levels within 24 hrs before and after surgery.

Results

In 730 patients (TIVA: n=138; INHA: n=592), the baseline characteristics were comparable, except for higher comorbidity rates in the TIVA group. The median anesthesia and operation times were significantly longer in the TIVA group because approximately 50% of the TIVA group (vs 19.7% of the INHA group) underwent neurosurgery, which had a relatively longer operation time than other surgeries. Intraoperative hypotensive events and vasopressor use were more frequent in the TIVA group. After 1:4 propensity score matching (TIVA: n=94; INHA: n=376), the baseline characteristics and surgical variables were comparable, except for longer anesthesia time. Before matching, postoperative AST and ALT changes were significantly lower in the TIVA group than in the INHA group. After matching, only the ALT change was significantly lower after TIVA than after INHA [median (interquartile range), -16.7 (-32 to -4) % vs -12.0 (-28.6-6.5) %, P=0.025].

Conclusion

TIVA may be safer for patients with preoperatively elevated liver transaminase levels.

A prospective study of the incidence of drug-induced liver injury by the modern volatile anaesthetics sevoflurane and desflurane

BACKGROUND

Volatile anaesthetics are known to cause drug-induced liver injury, a hepatotoxic reaction characterised by antibodies to trifluoroacetylated lipid and protein adducts and cytochrome p450 2E1. The incidence of volatile anaesthetic drug-induced liver injury from older agents has been described, but modern agents have not been prospectively studied.

AIM

To determine prospectively the incidence of volatile anaesthetic drug-induced liver injury from sevoflurane and desflurane.

METHODS

Adult surgical patients with a predicted post-operative stay of at least 4 days were recruited. If volatile anaesthetic was administered, liver biochemistry was performed regularly. Medications, observations and other investigations were documented. Patients with abnormal liver biochemistry were classified as likely volatile anaesthetic drug-induced liver injury or not based on clinical assessment, Roussel Uclaf Causality Assessment Method score, and the absence of other likely pathology. Some patients were also tested for antibodies to both trifluoroacetylated lipid and protein adducts, and cytochrome p450 2E1.

RESULTS

A total of 209 patients were recruited, of which 121 were included for analysis. Post-operative liver biochemistry was abnormal in 62 patients (51.2%); further classified as not volatile anaesthetic drug-induced liver injury in 47 cases (38.8%), and likely volatile anaesthetic-drug induced liver injury in 15 cases (12.4%). Of the likely volatile anaesthetic drug-induced liver injury patients, only one had severe disease with alanine transaminase greater than five times the upper limit of normal, while four cases had moderate disease with alanine transaminase greater than three times the upper limit of normal. Thus, the incidence of clinically significant volatile anaesthetic drug-induced liver injury was 4.1%. No risk factors were identified.

CONCLUSIONS

Volatile anaesthetic drug-induced liver injury from modern agents seems to be as common (4.1%) as previously reported with older agents (3%), and may identify patients at risk of severe acute liver injury with subsequent re-exposure.

Blood profiles in unanesthetized and anesthetized guinea pigs (Cavia porcellus)

The guinea pig is a common animal model that is used in biomedical research to study a variety of systems, including hormonal and immunological responses, pulmonary physiology, corticosteroid response and others. However, because guinea pigs are evolutionarily a prey species, they do not readily show behavioral signs of disease, which can make it difficult to detect illness in a laboratory setting. Minimally invasive blood tests, such as complete blood counts and plasma biochemistry assays, are useful in both human and veterinary medicine as an initial diagnostic technique to rule in or rule out systemic illness. In guinea pigs, phlebotomy for such tests often requires that the animals be anesthetized first. The authors evaluated hematological and plasma biochemical effects of two anesthetic agents that are commonly used with guinea pigs in a research setting: isoflurane and a combination of ketamine and xylazine. Hematological and plasma biochemical parameters were significantly different when guinea pigs were under either anesthetic, compared to when they were unanesthetized. Plasma proteins, liver enzymes, white blood cells and red blood cells appeared to be significantly altered by both anesthetics, and hematological and plasma biochemical differences were greater when guinea pigs were anesthetized with the combination of ketamine and xylazine than when they were anesthetized with isoflurane. Overall these results indicate that both anesthetics can significantly influence hematological and plasma biochemical parameters in guinea pigs.

Derivation of an occupational exposure limit for an inhalation analgesic methoxyflurane (Penthrox(®))

Methoxyflurane (MOF) a haloether, is an inhalation analgesic agent for emergency relief of pain by self administration in conscious patients with trauma and associated pain. It is administered under supervision of personnel trained in its use. As a consequence of supervised use, intermittent occupational exposure can occur. An occupational exposure limit has not been established for methoxyflurane. Human clinical and toxicity data have been reviewed and used to derive an occupational exposure limit (referred to as a maximum exposure level, MEL) according to modern principles. The data set for methoxyflurane is complex given its historical use as anaesthetic. Distinguishing clinical investigations of adverse health effects following high and prolonged exposure during anaesthesia to assess relatively low and intermittent exposure during occupational exposure requires an evidence based approach to the toxicity assessment and determination of a critical effect and point of departure. The principal target organs are the kidney and the central nervous system and there have been rare reports of hepatotoxicity, too. Methoxyflurane is not genotoxic based on in vitro bacterial mutation and in vivo micronucleus tests and it is not classifiable (IARC) as a carcinogenic hazard to humans. The critical effect chosen for development of a MEL is kidney toxicity. The point of departure (POD) was derived from the concentration response relationship for kidney toxicity using the benchmark dose method. A MEL of 15 ppm (expressed as an 8 h time weighted average (TWA)) was derived. The derived MEL is at least 50 times higher than the mean observed TWA (0.23 ppm) for ambulance workers and medical staff involved in supervising use of Penthrox. In typical treatment environments (ambulances and treatment rooms) that meet ventilation requirements the derived MEL is at least 10 times higher than the modelled TWA (1.5 ppm or less) and the estimated short term peak concentrations are within the MEL. The odour threshold for MOF of 0.13-0.19 ppm indicates that the odour is detectable well below the MEL. Given the above considerations the proposed MEL is health protective.

Efficacy of the methoxyflurane as bridging analgesia during epidural placement in laboring parturient

Background:

Establishing an epidural in an agitated laboring woman can be challenging. The ideal pain control technique in such a situation should be effective, fast acting, and short lived. We assessed the efficacy of inhalational methoxyflurane (Penthrox™) analgesia as bridging analgesia for epidural placement.

Materials and Methods:

Sixty-four laboring women who requested epidural analgesia with pain score of ≥7 enrolled in an observational study, 56 of which completed the study. The parturients were instructed to use the device prior to the onset of uterine contraction pain and to stop at the peak of uterine contraction, repeatedly until epidural has been successfully placed. After each (methoxyflurane inhalation-uterine contraction) cycle, pain, Richmond Agitation Sedation Scale (RASS), nausea and vomiting were evaluated. Maternal and fetal hemodynamics and parturient satisfaction were recorded.

Results:

The mean baseline pain score was 8.2 ± 1.5 which was reduced to 6.2 ± 2.0 after the first inhalation with a mean difference of 2.0 ± 1.1 (95% confidence interval 1.7-2.3, P < 0.0001), and continued to decrease significantly over the study period (P < 0.0001). The RASS scores continuously improved after each cycle (P < 0.0001). Only 1 parturient from the cohort became lightly sedated (RASS = −1). Two parturients vomited, and no significant changes in maternal hemodynamics or fetal heart rate changes were identified during treatment. 67% of the parturients reported very good or excellent satisfaction with treatment.

Conclusion:

Penthrox™ provides rapid, robust, and satisfactory therapy to control pain and restlessness during epidural placement in laboring parturient.

Analgesic use of inhaled methoxyflurane: Evaluation of its potential nephrotoxicity

Methoxyflurane is a volatile, halogenated analgesic, self-administered in a controlled low dose from the Penthrox(®) inhaler for short-term pain relief. It was formerly used in significantly higher doses to produce anaesthesia, when it caused a specific type of dose-related renal tubular damage. The pathogenesis of the renal damage and clinical use of methoxyflurane are discussed here with evidence that a low but effective analgesic dose is not associated with the risk of renal adverse effects. The maximum dose employed to produce analgesia is limited to methoxyflurane 6 mL/day and 15 mL/week, producing a minimum alveolar concentration (MAC) of 0.59 MAC-hours. Renal damage is due to the metabolism of methoxyflurane and release of fluoride ions. Exposure of humans to methoxyflurane ≤2.0 MAC-hours, resulting in serum fluoride ≤40 µmol/L, has not been associated with renal tubular toxicity. The safety margin of analgesic use of methoxyflurane in the Penthrox ((®)) inhaler is at least 2.7- to 8-fold, based on methoxyflurane MAC-hours or serum fluoride level, with clinical experience suggesting it is higher. It is concluded from clinical experience in emergency medicine, surgical procedures and various experimental and laboratory investigations that the analgesic use of methoxyflurane in subanaesthetic doses in the Penthrox inhaler does not carry a risk of nephrotoxicity.

Proanthocyanidin-rich date seed extract protects against chemically induced hepatorenal toxicity

A hydroacetone extract was prepared from seeds of Phoenix dactylifera L. var. Khalas, which is an industrial by-product of date processing. The proanthocyanidin nature of the extract (coded as DTX) was characterized by phytochemical and nuclear magnetic resonance (NMR) analyses. The total phenol/proanthocyanidin content and antioxidant activity of DTX were estimated by Folin-Ciocalteu, vanillin-sulfuric acid, and 2,2-diphenyl-1-picrylhydrazyl (DPPH) assays, respectively. The hepatorenal protective activity of DTX was evaluated using CCl4-induced toxicity model in rats, in comparison with silymarin (SYL). Results of the histopathological examination and measurements of various hepatorenal serum indices and tissue biochemical markers demonstrated that DTX displayed marked protective potential against CCl4-induced liver and kidney injury at 100 mg/kg/rat. Relative to the control CCl4-intoxicated group, pretreatment with DTX significantly (P<.001) suppressed the elevated serum levels of alanine aminotransferase and aspartate aminotransferase (ALT and AST), alkaline phosphatase (ALP), γ-glutamyl transferase (GGT), total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), bilirubin, creatinine, and calcium, whereas it significantly (P<.001) increased the diminished serum levels of high-density lipoprotein cholesterol (HDL-C) and total protein (TP). Moreover, DTX significantly decreased malondialdehyde (MDA) formation and increased TP synthesis in hepatorenal tissues compared with the intoxicated control. The improvement in biochemical parameters by DTX was observed in a dose-dependent manner and confirmed by restoration of normal histological features. The acute toxicity test of DTX in rats revealed safety of the extract. This study reveals that DTX enhances the recovery from xenobiotics-induced toxicity initiated by free radicals.

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.

Isoflurane enhanced hemorrhagic transformation by impairing antioxidant enzymes in hyperglycemic rats with middle cerebral artery occlusion

BACKGROUND AND PURPOSE

Because the potential neuroprotective effect of isoflurane is controversial, we attempted to study whether isoflurane after treatment provides neuroprotection in a rat model of hyperglycemia-induced ischemic hemorrhagic transformation.

METHODS

Rats received an injection of 50% dextrose (6 mL/kg intraperitoneally) and had a middle cerebral artery occlusion 30 minutes later. Four groups were included: sham-operated, ischemia/reperfusion, isoflurane treatment, and vehicle groups. In the treatment group, after 2 hours of ischemia, 2% isoflurane was administered at the onset of reperfusion. We measured the level of blood glucose at 0, 2.5, 4.5, and 6.5 hours after dextrose injection. Infarct and hemorrhagic volumes, neurological scores, oxidative stress (malondialdehyde, 4-hydroxy-2-nonenal, and nitrotyrosine) and the activities of superoxide dismutase and catalase were measured at 24 hours after ischemia.

RESULTS

Isoflurane had no effects on blood glucose, it failed to reduce infarct, hemorrhage volume, and brain edema, and it enhanced neurobehavioral deficits when compared with the ischemia/reperfusion group at 24 hours after middle cerebral artery occlusion. On the contrary, isoflurane exacerbated these parameters compared with the vehicle group. In addition, it increased the expressions of malondialdehyde, 4-hydroxy-2-nonenal, and nitrotyrosine, and it decreased the activities of superoxide dismutase and catalase compared to the vehicle group.

CONCLUSIONS

Isoflurane after treatment worsened physiological and neurological outcomes in this ischemia hyperglycemia-induced hemorrhagic transformation possibly by impairing the antioxidant defense system.

Inhalational anesthesia: basic pharmacology, end organ effects, and applications in the treatment of status asthmaticus

The potent inhalational anesthetic agents are used on a daily basis to provide intraoperative anesthesia. Given their beneficial effects on airway tone and reactivity, they also have a role in the treatment of status asthmaticus that is refractory to standard therapy. Although generally not of clinical significance, these agents can affect various physiological functions. The potent inhalational anesthetic agents decrease mean arterial pressure and myocardial contractility. The decrease in mean arterial pressure reduces renal and hepatic blood flow. Secondary effects on end-organ function may result from the metabolism of these agents and the release of inorganic fluoride. The following article reviews the history of inhalational anesthesia, the physical structure of the inhalational anesthetic agents, their end-organ effects, reports of their use for the treatment of refractory status asthmaticus in the intensive care unit (ICU) patient, and special considerations for their administration in this setting including equipment for their delivery, scavenging, and monitoring.

The age- and gender-dependent effects of desflurane and sevoflurane on rat liver

OBJECTIVE

This study aimed to investigate the age- and gender-dependent effects of desflurane and sevoflurane on the liver.

MATERIAL AND METHOD

Upon the approval of ethics committee, 84 rats were divided into four groups as 21 young male, 21 young female, 21 old male, and 21 old female rats. Then, each group was further divided into three groups as desflurane, sevoflurane, and control groups. Maintaining the minimum alveolar concentration of 1, desflurane at 6vol% and sevoflurane at 2vol% in 6Lmin(-1) 100% O2 were administered for 2h in a transparent plastic container of 40cmx40cmx70cm. Each liver preparation was evaluated for hydropic degeneration, nuclear polymorphism, portal neutrophile infiltration, portal lymphocyte infiltration, and focal necrosis, and each preparation was assigned injury points of 0-3; thus, the number of histopathologically injured cases, total injury scores of each preparation, and the mean injury scores of each group were determined.

RESULTS

Desflurane and sevoflurane did not significantly increase hepatic injury in the young male rats, while both agents caused significantly more hepatic injury in the young female rats. In the old rats, both desflurane and sevoflurane inflicted more hepatic injury on both genders. In addition, desflurane caused more hepatic injury in the old female rats than in the young female or the old male rats.

CONCLUSION

Hepatic injury associated with desflurane and sevoflurane was mild to moderate, suggesting that both agents can be safely used in routine anaesthesia procedures.

Prolonged sevoflurane inhalation therapy for status asthmaticus in an infant

A 3-month-old boy with retractive breathing from his birth was scheduled for a rigid bronchoscopic examination. Anesthesia was induced and maintained with sevoflurane. The examination revealed a slight laryngomalacia which was not compatible with his severe symptom. During the procedure, no respiratory deterioration occurred. He was once extubated in the operating room, however, developed severe desaturation immediately. He was reintubated at the scene and returned to the ward being mechanically ventilated and sedated. The next day, his respiratory condition worsened gradually. Conventional drugs including theophylline, corticosteroid and beta adrenergic agonist did not improve his deleterious condition. He became bradycardic and was on the verge of circulatory collapse as his lungs were unable to ventilate. Then, we commenced inhalation of sevoflurane using a standard anesthesia machine, which relieved him from ventilatory crisis. Although there were some difficulties in using anesthesia machine in the ICU, we could successfully manage mechanical ventilation. After the beginning of sevoflurane inhalation, his condition improved gradually. Discontinuation of sevoflurane was difficult and it took 94 h to wean from sevoflurane inhalation. Despite long duration of inhalation, no adverse effects of sevoflurane were observed except transient mild increase in liver transaminase. There have been very few reports on application of sevoflurane inhalation for such a long period in infants with bronchospasm. Moreover, measured serum fluoride concentration (24.2 micromol x l(-1)) during inhalation was well below harmful level. Sevoflurane inhalation is worth attempting and safe to treat life-threatening bronchospasm even in infants.

Association between GSTP1 gene polymorphism and serum α-GST concentrations undergoing sevoflurane anaesthesia

BACKGROUND AND OBJECTIVES

The measurement of alpha-glutathione-S-transferase enzyme is one of the most sensitive indicators of hepatocellular function. Variation in the glutathione-S-transferase P1 gene clusters has been intensively investigated and polymorphism has been described. The aim of the study was to assess whether an association exists between glutathione-S-transferase P1 gene polymorphism and serum alpha-glutathione-S-transferase concentrations for the first postoperative day in patients who underwent anaesthesia with sevoflurane.

METHODS

In all, 54 unrelated patients were enrolled in this study. Anaesthesia was induced with thiopental and fentanyl. Vecuronium was used for neuromuscular relaxation before endotracheal intubation. Anaesthesia was maintained with sevoflurane in a gas mixture containing 50% nitrous oxide in oxygen. Peripheral venous blood samples to determine serum alpha-glutathione-S-transferase concentrations were collected before induction (T1), at the end of anaesthesia (T2) and at 24-h postoperatively (T3). Enzyme-linked immunosorbent assay (ELISA) immunoassay was used to measure alpha-glutathione-S-transferase levels. Genomic DNA was isolated from serum samples using a genomic DNA purification kit. In order to detect the variants of glutathione-S-transferase P1, polymerase chain reaction-restriction fragment length polymorphism analysis was employed.

RESULTS

Early postoperative serum alpha-glutathione-S-transferase levels for all patients were significantly increased when compared with preanaesthetic and 24-h postoperatively (P 0.05).

CONCLUSIONS

Although alpha-glutathione-S-transferase levels were elevated in all patients after sevoflurane anaesthesia, levels remained high at 24 h in patients with glutathione-S-transferase P1 Ile105Val genotypes compared to controls.

Therapeutic applications and uses of inhalational anesthesia in the pediatric intensive care unit

OBJECTIVE

To review the physical properties, end-organ effects, therapeutic applications, and delivery techniques of inhalational anesthetic agents in the pediatric intensive care unit.

DATA SOURCE

A computerized, bibliographic search regarding intensive care unit applications of inhalational anesthetic agents.

MAIN RESULTS

Although the end-organ effects of inhalational anesthetic agents vary depending on the agent, general effects include a dose-related depression of ventilatory and cardiovascular function. With increasing anesthetic depth, there is a decrease in alveolar ventilation with a reduction in tidal volume and an increase in PaCO2 in spontaneously breathing patients. The potent inhalational anesthetic agents decrease mean arterial pressure and myocardial contractility. The decrease in mean arterial pressure reduces renal and hepatic blood flow. Secondary effects on end-organ function may result from the metabolism of these agents and the release of inorganic fluoride. Beneficial effects include sedation, amnesia, and anxiolysis, making these agents effective for sedation during mechanical ventilation. Bronchodilatory and anticonvulsant properties have led to their use as therapeutic agents in patients with refractory status asthmaticus and epilepticus. Issues regarding their delivery in the intensive care unit include equipment for their delivery, scavenging, and monitoring.

CONCLUSIONS

The literature contains reports of the therapeutic use of the potent inhalational anesthetic agents in the pediatric intensive care unit. Potential applications include sedation during mechanical ventilation as well as therapeutic use for the treatment of status asthmaticus and epilepticus.

Prehospital analgesia in adults using inhaled methoxyflurane

OBJECTIVE

For many years, ambulance services throughout Australia have been administering methoxyflurane as a first-line analgesic agent. However, there is a paucity of literature regarding its efficacy, safety and usage profile. The present study was designed to examine the efficacy of methoxyflurane in adults.

METHODS

An observational case series was conducted over a 10 month period. Adults to whom methoxyflurane was administered while traveling by ambulance to an urban teaching hospital were enrolled. Data analysed included indications for use, verbal numerical pain scores, depth of sedation and adverse effects. Data were collected via paramedic, patient and ED staff surveys.

RESULTS

Eighty-three adult patients were enrolled over a 10 month period. A mean reduction in verbal numerical rating scale (VNRS) scores of 2.47 +/- 0.24 (on a 10-point scale) was recorded 5 min post methoxyflurane, with a total reduction of 3.21 +/- 0.24 at time of arrival at the ED. Both VNRS scores were significantly different from baseline (P < 0.0001). Fifteen patients (18.1%, 95% CI 9.8-26.4%) reported mild side-effects either during or shortly after administration. A total of 68 (81.9%, 95% CI 72.0-89.5%) of the paramedics and 60 (72.3%, 95% CI 61.4-81.6%) of the patients interviewed said that they felt satisfied with the level of analgesia provided by methoxyflurane.

CONCLUSION

The use of methoxyflurane as a prehospital analgesic significantly reduced pain in patients, with no significant side-effects attributed to its use. The majority of patients and paramedics interviewed were satisfied with its effects and indicated a willingness to use it again.

Chemical toxicology: reactive intermediates and their role in pharmacology and toxicology

Reactive intermediates formed during the metabolism of drugs have been investigated extensively over the past decades. Today, interest in reactive intermediates in drug discovery is focused on minimising bioactivation in hopes of reducing the risk of causing so-called idiosyncratic toxicity. These efforts are justified based on the 'hapten hypothesis', namely, that on binding to protein, reactive intermediates may elicit an immune response to the modified protein, leading to a cascade of events that ultimately manifests as a toxic outcome. However, the pharmacological action of certain drugs depends on reactive intermediates that modify critical amino acid residues of proteins, typically enzymes, thereby altering their activity. Thus, the notion that reactive intermediates are inherently dangerous is unjustified. When a reactive intermediate is necessary for the desired pharmacological effect of a drug, the selectivity it displays towards the target protein is crucial, as off-target binding may produce unwanted toxicities. On the other hand, reactive intermediates may play no role in toxicity. This review provides a balanced perspective, primarily focusing on the proposed role of reactive intermediates in drug toxicity, while also highlighting examples in which they are involved in causing the desired pharmacology. It is hoped that this knowledge can help scientists involved in drug discovery and development in their challenging task of producing safe and effective drugs.

A pilot study of inhaled methoxyflurane for procedural analgesia in children

BACKGROUND

Methoxyflurane (MF), a potent volatile anesthetic, can be used as an analgesic in subanesthetic concentrations. In Australia, MF is extensively used in children and adults as an analgesic in the prehospital setting via a hand-held inhaler device. We conducted a pilot study to explore its use as a patient controlled analgesic for painful procedures in children in the emergency department (ED).

METHODS

This is a prospective observational case series of children aged 5 years and older requiring procedural analgesia for brief painful procedures. Pain scores, depth of sedation, adverse events and patient, parent and staff satisfaction were assessed as well as consumption of MF measured.

RESULTS

Fourteen patients (aged 6-13 years) received MF mainly for extremity injuries. Amount of MF consumed ranged from 0.36 to 3.06 g per patient inhaled over 4-25 min. There were no serious adverse events. No patient was deeply sedated. Five patients had mild brief self-resolving adverse events including agitation, euphoria, blurry vision, dizziness and cough. Four patients with fractures with initial high pain scores (> or =6) received MF for bridging analgesia with large drops in pain scores. Four patients who required fracture reductions with initial low scores did not achieve adequate analgesia. The remaining six patients had painful procedures undertaken with satisfactory analgesia.

CONCLUSIONS

On the basis of this small pilot study of MF use in children in the ED, this agent appears to be a powerful analgesic. MF seems most useful as a self-titrated bridging analgesic agent in patients after extremity trauma. It appears less useful as a procedural agent when patients are unable to anticipate and achieve a sufficient level of analgesia before painful stimulus infliction. Pre- and intraprocedure coaching is an important aspect of its use especially if initial pain scores are low.

Heme oxygenase-1 as a potential therapeutic target for hepatoprotection

Heme oxygenase (HO), the rate limiting enzyme in the breakdown of heme into carbon monoxide (CO), iron and bilirubin, has recently received overwhelming research attention. To date three mammalian HO isozymes have been identified, and the only inducible form is HO-1 while HO-2 and HO-3 are constitutively expressed. Advances in unveiling signal transduction network indicate that a battery of redox-sensitive transcription factors, such as activator protein-1 (AP-1), nuclear factor-kappa B (NF-kappaB) and nuclear factor E2-related factor-2 (Nrf2), and their upstream kinases including mitogen-activated protein kinases play an important regulatory role in HO-1 gene induction. The products of the HO-catalyzed reaction, particularly CO and biliverdin/bilirubin have been shown to exert protective effects in several organs against oxidative and other noxious stimuli. In this context, it is interesting to note that induction of HO-1 expression contributes to protection against liver damage induced by several chemical compounds such as acetaminophen, carbon tetrachloride and heavy metals, suggesting HO-1 induction as an important cellular endeavor for hepatoprotection. The focus of this review is on the significance of targeted induction of HO-1 as a potential therapeutic strategy to protect against chemically-induced liver injury as well as hepatocarcinogenesis.

Inhaled methoxyflurane as a prehospital analgesic in children

OBJECTIVE

Despite widespread use of methoxyflurane as an inhaled analgesic by ambulance services in Australia there are no published data as to its use pattern, efficacy and safety in the prehospital setting. We set out to characterize methoxyflurane use in children in the prehospital setting.

METHODS

An observational case series was conducted over an 8 month period. Children who received methoxyflurane while being transported to a tertiary children's hospital by ambulance were enrolled. We analysed indications for use, verbal numerical pain scores, adverse events and depth of sedation based on paramedic, patient, parent and ED staff surveys and review of ambulance care records.

RESULTS

During the study period 105 patients were enrolled with an age range of 15 months to 17 years (median age 11 years). Methoxyflurane was mainly used for extremity injuries (82%). Paramedic pain scores dropped from a mean of 7.9 (95% confidence interval [CI] 7.5-8.3) prior to methoxyflurane use to 4.5 (95% CI 3.9-5.0) at 2-5 min and to 3.2 (95% CI 2.8-3.7) at 10 min. There were no serious adverse events (one-sided 97.5% CI 0-3%). Mild adverse events occurred in 38 patients (36.2%; 95% CI 27.0-46.1%). Five of 15 (33.3%) patients under 5 years of age were deeply sedated.

CONCLUSION

In the present paediatric case series methoxyflurane appears to be an efficacious analgesic with a low adverse events profile. In young children in particular it can briefly lead to deep sedation.

Clinical assessment of effects of botanical supplementation on cytochrome P450 phenotypes in the elderly: St John's wort, garlic oil, Panax ginseng and Ginkgo biloba

OBJECTIVES

Elderly patients are more likely to ingest prescription medications concurrently with botanical supplements, and may therefore be vulnerable to herb-drug interactions. Phytochemical-mediated modulation of cytochrome P450 (CYP) activity may underlie many herb-drug interactions. Some evidence suggests that CYP activity may decrease in the elderly. If so, herb-mediated changes in CYP activity may take on greater clinical relevance in this population. In this study, single timepoint, phenotypic metabolic ratios were used to determine whether long-term supplementation of St John's wort, garlic oil, Panax ginseng, and Ginkgo biloba affected CYP1A2, CYP2D6, CYP2E1 or CYP3A4 activity in elderly subjects.

METHODS

Twelve healthy volunteers between the ages of 60 and 76 years (mean age 67 years) were randomly assigned to receive each botanical supplement for 28 days followed by a 30-day washout period. Probe drug cocktails of midazolam, caffeine, chlorzoxazone and debrisoquine were administered before and at the end of supplementation. Pre- and post-supplementation phenotypic ratios were determined for CYP3A4, CYP1A2, CYP2E1 and CYP2D6 using 1-hydroxymidazolam/midazolam serum ratios (1-hour), paraxanthine/caffeine serum ratios (6-hour), 6-hydroxychlorzoxazone/chlorzoxazone serum ratios (2-hour) and debrisoquine urinary recovery ratios (8-hour), respectively. The content of purported 'active' phytochemicals was determined for each supplement.

RESULTS

Comparisons of pre- and post-St John's wort phenotypic ratios revealed significant induction of CYP3A4 (approximately 140%) and CYP2E1 activity (approximately 28%). Garlic oil inhibited CYP2E1 activity by approximately 22%. P. ginseng inhibition of CYP2D6 was statistically significant, but the magnitude of the effect (approximately 7%) did not appear to be clinically relevant. None of the supplements tested in this study appeared to affect CYP1A2 activity.

CONCLUSIONS

Elderly subjects, like their younger counterparts, are susceptible to herb-mediated changes in CYP activity, especially those involving St John's wort. Pharmacokinetic herb-drug interactions stemming from alterations in CYP activity may adversely affect drug efficacy and/or toxicity. When compared with earlier studies that employed young subjects, the data suggest that some age-related changes in CYP responsivity to botanical supplementation may exist. Concomitant ingestion of botanical supplements with prescription medications, therefore, should be strongly discouraged in the elderly.

Severe hepatotoxicity after sevoflurane anesthesia in a child with mild renal dysfunction

Sevoflurane, an anesthetic agent with methyl isopropyl fluorinated ether structure, has a very low potential for hepatotoxicity. Nevertheless, a few cases of hepatotoxicity have been reported since its introduction into clinical practice. The underlying pathophysiology may be multifactorial and sometimes nonspecific. We report a case of severe hepatotoxicity after anesthesia with sevoflurane in a child with preexisting mild renal dysfunction.

Effects of inhalation anesthetics halothane, sevoflurane, and isoflurane on human cell lines

Cytotoxic and antiproliferative effects of halothane, isoflurane, and sevoflurane in anesthetic doses on human colon carcinoma (Caco-2), larynx carcinoma (HEp-2), pancreatic carcinoma cells (MIA PaCa-2), poorly differentiated cells from lymph node metastasis of colon carcinoma (SW-620), and normal fibroblasts were investigated. Cells were exposed to anesthetic gas mixture consisting of O(2): N2O (35:60 vol.%), halothane (1.5 vol.%) or isoflurane (2.0 vol.%) or sevoflurane (3.0 vol.%), and CO(2) (5 vol.%), for 2, 4, and 6 h. Cytotoxicity of anesthetics was analyzed by validated tetrazolium dye assay MTT test. All anesthetics expressed cytotoxic effects on treated tumor cells in time and cell line dependent manner. Growth suppression in cells exposed to halothane was enhanced in HEp-2 (to 67.7%), Caco-2 (to 76.3%), and SW620 cells (to 80.9%), and was minimal in normal fibroblasts (to 89.4%). Antiproliferative activity of halothane was measured via radioactive precursors incorporation assay. In Caco-2 cells treated by halothane, decrease in DNA synthesis (52.4%, p=0.001), RNA synthesis (39.2%, p<0.001), and protein synthesis (19.2%, p=0.004) was observed. In HEp-2 cells, DNA and RNA syntheses were decreased to 72.5% and 79.9%, whereas protein synthesis was 14.0% of control (p<0.001). In SW620 cells, protein synthesis after 4 h was 24.4% (p=0.007). A DNA fragmentation was observed in Caco-2 and MIA PaCa-2 cells. Exposition of phosphatidylserine on outer lipid bilayer plasma membrane of tumor cell treated by halothane proved apoptosis as mode of cell death.

Effects of dehydroepiandrosterone administration on rat hepatic metabolism following thermal injury

BACKGROUND

Severe burns cause dramatic alterations in liver and whole-body metabolism. Recently, there has been interest in using dehydroepiandrosterone (DHEA) as a treatment for trauma patients, and enhanced survival and immune function have been reported using DHEA in animal trauma models. The specific effects of DHEA on hepatic metabolism following burn injury have not been explored.

MATERIALS AND METHODS

Male rats received either (1) a burn covering approximately 20% of the total body surface area or a sham burn or (2) burn injury followed by two intraperitoneal injections of DHEA or vehicle. After 4 days, the livers were isolated and perfused in vitro, and 28 metabolite fluxes were measured. Metabolic flux analysis was used to obtain the intracellular metabolic flux distribution and provide an overview of the metabolic state of the livers in each experimental group.

RESULTS

Burn injury decreased the uptake of lactate and the production of beta-hydroxybutyrate and increased the deamination of glutamine to glutamate and asparagine to aspartate. DHEA, compared to vehicle treatment, decreased pentose phosphate pathway (PPP) fluxes and the uptake of several amino acids in burned rats. Furthermore, DHEA treatment restored liver metabolism in burned rats to a state that was very similar to that of the sham control group.

CONCLUSIONS

DHEA administration appears to normalize hepatocellular metabolism in burned rats but also decreases the PPP flux, which may impair the liver's ability to recycle endogenous antioxidants. DHEA treatment combined with exogenous antioxidants should receive further consideration in the management of burn and trauma patients.

Inhaled anesthetics: an historical overview

Inhalational agents have played a pivotal role in anesthesia history. The first publicly demonstrated anesthetic of the modern era, diethyl ether, was an inhalational anesthetic. The attributes of a good agent, ability to rapidly induce anesthesia, with limited side effects has led research efforts for over a hundred and fifty years. The explosion hazard was largely conquered with the development of the halogenated agents in the 1950s. Rapid emergence, with limited nausea and vomiting continue to drive discovery efforts, yet the 'modern' agents continue to improve upon those in the past. The future holds promise, but perhaps the most interesting contrast over time is the ability to rapidly introduce new agents into practice. From James Young Simpson's dinner table one evening to the operating suite the next day, modern agents take decades from first synthesis to clinical introduction.

Preoperative assessment of the patient with liver disease

Patients with liver disease are at appreciable risk when undergoing anesthesia and surgery. Attempts to quantify this risk have been thwarted by the diversity of disease states and illness severity that such patients bring to the operating theater and the myriad of procedures they may undergo. This review discusses the indications and contraindications for surgery in patients with liver disease and attempts to give specific recommendations for optimizing the clinical status of a patient with hepatic dysfunction prior to operative intervention.

Severe desflurane hepatotoxicity after colon surgery in an elderly patient

PURPOSE

To report a case of desflurane hepatotoxicity.

CLINICAL FEATURES

An 81-yr-old woman with a remote history of abdominal surgery developed severe acute liver injury after general anesthesia with desflurane for resection of colonic cancer. Serum alanine aminotransferase and aspartate aminotransferase peaked at postoperative day six (2188 and 425 U*L(-1) respectively), with the development of coagulopathy with an international normalized ratio of 2.29 on postoperative day eight, progressive jaundice with a peak serum total bilirubin of 214 mumol*L(-1) on postoperative day 12 and hepatic encephalopathy on postoperative day ten. Other causes for liver disease were excluded. Treatment with corticosteroids was started. The liver biochemistry normalized completely by postoperative day 30 and the patient was discharged from hospital on postoperative day 21.

CONCLUSIONS

To our knowledge, this represents only the third report of desflurane hepatotoxicity and the first with reversible fulminant liver failure. Our experience suggests that all fluorinated anesthetics may cause acute hepatic damage.

The transplant recipient for nontransplant surgery

The transplant recipient has traded a life-threatening illness for a chronically immunosuppressed state. Subsequent anesthetic management for non-transplant surgical procedures may be challenging. The anesthesia provider must be aware of the degree of post-transplant organ dysfunction and alter anesthesia techniques accordingly. This article reviews the anesthetic concerns for patients who have undergone a variety of organ transplants.

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.

Anaesthetic implications of anticancer chemotherapy

In anaesthetic practice we deal with cancer patients who are scheduled for operations on tumours or other manifestations of malignant disease. Those patients are often debilitated and have significant weight loss accompanied with hypoproteinaemia, anaemia and coagulation disorders. Oncological patients usually present to the anaesthetist before tumour disease surgery, but they are also candidates for elective operations (e.g. hernia repair) and urgent/emergency surgery (e.g. trauma, fractures and ileus). Chemotherapeutic agents given to these patients are potentially noxious, can affect the conduct of anaesthesia and, furthermore, may aggravate the patient's condition. In this review the most commonly used cytostatic drug regimens and their common side-effects are listed. Some preclinical studies on anaesthetic and cytostatic drug metabolism and interactions are emphasized, as well as clinically relevant perioperative alterations that may affect anaesthetic management in cancer patients. An anaesthetist may have to modify a routine anaesthetic regimen in cancer patients especially if anticancer chemotherapeutics were given. Clinically silent toxic drug effects may become apparent during operation, trauma or in the early postoperative course in such patients. Altered reactions to commonly used anaesthetics in patients receiving chemotherapeutics and an impaired stress reaction may occur in such patients. Special attention must be drawn to protection against opportunistic infections.

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.

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.

Increased cytotoxicity of carbon tetrachloride in a human hepatoma cell line overexpressing cytochrome P450 2E1

Cytotoxic free radicals generated during the metabolism of carbon tetrachloride by cytochrome P450 2E1 (CYP2E1) are thought to cause hepatotoxicity. Here, the cytotoxic effects of carbon tetrachloride in a liver cell line expressing CYP2E1 (HLE/2E1) are compared with those in the mother cell line (HLE). The effects of carbon tetrachloride on the gene expression of HSP70, a potential marker of oxidative stress, were also examined. The viability of HLE/2E1 cells after exposure to carbon tetrachloride was significantly decreased compared with that of HLE cells. Northern blot analysis revealed that the HSP70 mRNA level was significantly increased after carbon tetrachloride treatment in both cell lines, while the magnitude of its increase was much greater in HLE/2E1 cells than in HLE cells. These results suggest that the oxidative stress induced by CYP2E1 plays an important role in the increase in cytotoxicity of carbon tetrachloride in CYP2E1-overexpressing cells.

Hepatobiliary scintigraphy for evaluating the hepatotoxic effect of halothane and the protective effect of catechin in comparison with histo-chemical analysis of liver tissue

Halothane and its metabolites cause liver damage by decreasing liver blood flow and generating free-radical species. Catechin suppresses lipid peroxidation and increases enzyme activity, therefore it seems to be capable of protecting liver parenchyma against the direct toxic effect of halothane. The aim of this study was to investigate the role of hepatobiliary scintigraphy in detecting liver damage after halothane anaesthesia and the protective effect of catechin in comparison with histo-chemical analysis. Thirty rabbits, divided into three groups (A, controls; B, halothane; and C, catechin+halothane), were investigated. In group A no anaesthesia was administered. Group B only received halothane, while group C was pretreated with catechin and halothane anaesthesia was administered for 2 h. Dynamic scintigrams were taken for 60 min after injecting 99mTc-mebrofenin, and the time of peak uptake (TPU) and the time for half of the activity to clear from the liver (T(1/2)) were calculated. Rabbits were killed, and malondialdehyde (MDA), superoxide dismutase (SOD), glutathione peroxidase (GSH-Px) and catalase (CAT) levels were measured in hepatic tissue. The TPU and T(1/2) values of group A is significantly lower than in groups B and C (P<0.0002 and P<0.0002, respectively, for TPU; and P<0.0002 and P<0.0003, respectively, for T(1/2)). The TPU and T(1/2) values of group B were significantly higher than in group C (P<0.0003 and P<0.0003, respectively). The hepatic MDA level of group A was significantly lower than in groups B and C (P<0.0002 and P<0.0002, respectively). SOD, GSH-Px and CAT levels of group A were significantly higher than in groups B and C (P<0.0002, P<0.0001 and P<0.003, respectively, for group A vs group B; and P<0.0005, P<0.0002 and P<0.03, respectively, for group A vs group C). The MDA level of group B was significantly higher than that in group C (P<0.0002). SOD, GSH-Px and CAT levels of group B were significantly lower than in group C (P<0.0002, P<0.0002 and P<0.003, respectively). According to these results, we suggest that catechin protects liver parenchyma against the toxic effect of halothane and its metabolites, and that, compared to invasive histo-chemical analysis, hepatobiliary scintigraphy is a useful and alternative non-invasive method for detecting the protective effect of catechin on liver parenchyma after halothane anaesthesia.

An in vitro model for evaluation of vaporous toxicity of trichloroethylene and tetrachloroethylene to CHO-K1 cells

Toxicokinetics of trichloroethylene (TCE) and tetrachloroethylene (PER) in culture medium and their toxicity to CHO-K1 cells were investigated by employing an in vitro vapor exposure system. Cells were cultured in a 60 mm petri dish with a 25 mm glass dish glued in the central area. TCE or PER was added to the central glass dish so that it would evaporate and dissolve in the surrounding medium in which cells were growing. The results showed that the concentration of TCE or PER in medium increased significantly within 20 min and then decreased very rapidly with time. After a 24 h incubation, the residual of TCE or PER in the medium was very low, but was displayed in a dose-dependent manner. Treatment of cells with either TCE or PER resulted in a dose- and time-dependent inhibition of cell growth. A significantly increase in the frequency of micronuclei (MN) was also observed with either TCE or PER treatment. Low doses of TCE (5-20 microl) or PER (1-5 microl) significantly enhanced the intracellular glutathione (GSH) level. However, the level of GSH rapidly decreased with higher doses of TCE (40-80 microl) or PER (10-20 microl). Depletion of cellular GSH showed no effect on the sensitivity of cells to TCE or PER treatment. GSH-conjugation has been proposed as an activation mechanism to account for the nephrotoxicity of TCE and PER, however the toxicity of TCE and PER to CHO-K1 cells is probably mediated through a distinct mechanism.