Inhaled anesthetic agents

Involvement of selected circulating ncRNAs in the regulation of cognitive dysfunction induced by anesthesia

Post-operative cognitive dysfunction (POCD) refers to the functional impairment of the nervous system caused by prolonged exposure to anesthetics. It is known that prolonged exposure to anesthetics may increase the risk for the development of several cognitive impairments. The drugs used to induce general anesthesia are generally safe, owing to the CNS's direct and/or indirect self-protective activity against drug-induced damages. Non-coding RNAs have recently started to gain attention to better understand the mechanism of gene regulation correlated to cellular physiology and pathology. In order to provide new insights for the neuroprotective function of highly expressed ncRNAs in the central nervous system, we investigated their expression profile in the circulating exosomes of patients exposed to anesthesia vs healthy controls. The experimental design envisaged the recruitment of 30 adult patients undergoing general anesthesia and healthy controls. The effects of anesthetics have been evaluated on miR-34a and miR-124, on the lncRNAs MALAT-1, HOTAIR, GAS5, BLACAT1, HULC, PANDA, and on YRNAs. NcRNAs miR-34a, miR-124, MALAT-1, HOTAIR, GAS5, BLACAT1, and YRNA1 are significantly overexpressed following anesthesia, while YRNA5 is significantly down regulated. Some of them have neuroprotective function, while other correlate with neurological dysfunctions. Our data suggests that, during anesthesia, the toxic action of some non-coding RNAs could be compensated by other non-coding RNAs, both synthesized by the CNS or also transported into neurons from other tissues. It is reasonable to suppose a mutual action of these molecules likely to secure the CNS from anesthetics, that drive a convoluted cascade of ncRNA-dependent biological counter-responses. Our findings are novel in the field of brain dysfunction, indicating that some of the analyzed ncRNAs, although several of their functions still need to be addressed, could be suggested as potential biomarkers and therapeutic targets in post-operative cognitive dysfunction-related processes.

Anesthetics drug wastage and preventive strategies: Systematic review

BACKGROUND

Surgical Patients and hospitals are now facing financial strain due to direct anesthetic demand as a result of the development of new anesthetic drugs, equipment, and techniques. Up to 15% of a hospital's pharmacy budget is currently allocated to anesthetic drug expenses. Drug wastage during anesthesia practice is a widespread hidden source of healthcare waste that leads to anesthetic drug shortages as well as poor operating room efficiency. On the other hand, despite the fact that it is preventable in the vast majority of cases, it is well described that drug wastage is routinely observed, including in developing countries where the consequences significantly affect both hospitals and patients.

METHODS

This review aims to review the prevalence of anesthetic drug waste across the world and systematically formulate and describe preventive strategies. Relevant publications were identified using systematic searches on databases including Google Scholar, Medline (PubMed), the Cochrane Library, and Embase. In addition, papers were detected and then selected through the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) criteria guidelines and the inclusion and exclusion criteria. Using the predetermined terms and dates from the searching databases, a total of 504 articles were identified. Based on the screening criteria, 16 papers were considered eligible and included in the final review. In addition, the Joanna Briggs Institute (JBI) Manual for Evidence Synthesis was used for evaluating the quality of selected articles. This study is registered on PROSPERO, number CRD42024497044.

RESULTS

Of the sixteen publications from eleven different nations that were considered suitable for inclusion, only two of them addressed the waste of inhalational anesthetics. In more than half of eligible articles, propofol was the frequently wasted drug that contributed to increased financial loss through drug waste. The first most significant factor contributing to the waste of intravenous and inhalational anesthetics was the disposal of multidrug vials following their use for a single patient and high fresh gas flow, respectively.

CONCLUSION

Anesthetic medication waste is a common occurrence worldwide, despite the fact that it is expensive and has a significant negative impact on operating room efficiency. Because the majority of drug waste is avoidable, preventive measures may lower drug waste and improve patient and hospital efficiency.

Effects of propofol versus sevoflurane on surgical field visibility during arthroscopic rotator cuff repair: a randomized trial

BACKGROUND

During arthroscopic rotator cuff repair (ARCR), clear surgical field visibility (SFV) is the basis of successful surgery, but the choice of anesthesia maintenance drugs may have different effects on SFV. In this study, we aimed to compare the effects of propofol- and sevoflurane-based general anesthesia on SFV in patients undergoing ARCR.

METHODS

Patients (n = 130) undergoing elective ARCR in the lateral decubitus position were randomized into either the propofol group or sevoflurane group (65 per group). The duration of surgery and increased pressure irrigation (IPI), Boezaart score, rocuronium consumption and usage of remifentanil were recorded. The time of both spontaneous respiration recovery and extubation and the incidences of postoperative nausea and vomiting and agitation were also recorded.

RESULTS

The Boezaart score, duration of IPI and ratio of the duration of IPI to the duration of surgery (IPI/S ratio) were similar between the groups (P > 0.05). Rocuronium consumption, number of patients requiring remifentanil infusion and total remifentanil consumption were significantly lower in the sevoflurane group (P < 0.05). The spontaneous respiration recovery time was significantly longer in the propofol group (P < 0.05), but there were no differences in the extubation time between the groups(P > 0.05).

CONCLUSIONS

Compared with propofol, sevoflurane provides equally clear SFV while improving the convenience of anesthesia maintenance in ARCR patients with interscalene plexus (ISB) combined with general anesthesia.

TRIAL REGISTRATION

This single-center, prospective, RCT was retrospective registered at Chinese Clinical Trial Registry with the registration number ChiCTR2300072110 (02/06/2023).

Does sevoflurane sedation in pediatric patients lead to "pseudo" leptomeningeal enhancement in the brain on 3 Tesla magnetic resonance imaging?

BACKGROUND

Prominent leptomeningeal contrast enhancement (LMCE) in the brain is observed in some pediatric patients during sedation for imaging. However, based on clinical history and cerebrospinal fluid analysis, the patients are not acutely ill and do not exhibit meningeal signs. Our study determined whether sevoflurane inhalation in pediatric patients led to this pattern of 'pseudo' LMCE (pLMCE) on 3 Tesla magnetic resonance imaging (MRI).

AIM

To highlight the significance of pLMCE in pediatric patients undergoing enhanced brain MRI under sedation to avoid misinterpretation in reports.

METHODS

A retrospective cross-sectional evaluation of pediatric patients between 0-8 years of age was conducted. The patients underwent enhanced brain MRI under inhaled sevoflurane. The LMCE grade was determined by two radiologists, and interobserver variability of the grade was calculated using Cohen's kappa. The LMCE grade was correlated with duration of sedation, age and weight using the Spearman rho rank correlation.

RESULTS

A total of 63 patients were included. Fourteen (22.2%) cases showed mild LMCE, 48 (76.1%) cases showed moderate LMCE, and 1 case (1.6%) showed severe LMCE. We found substantial agreement between the two radiologists in detection of pLMCE on post-contrast T1 imaging (kappa value = 0.61; P < 0.001). Additionally, we found statistically significant inverse and moderate correlations between patient weight and age. There was no correlation between duration of sedation and pLMCE.

CONCLUSION

pLMCE is relatively common on post-contrast spin echo T1-weighted MRI of pediatric patients sedated by sevoflurane due to their fragile and immature vasculature. It should not be misinterpreted for meningeal pathology. Knowing pertinent clinical history of the child is an essential prerequisite to avoid radiological overcalling and the subsequent burden of additional investigations.

Comparing the effects of continuous infusion of esmolol and ramosetron alone and in combination on nausea and vomiting after laparoscopic cholecystectomy: A prospective, randomized, double-blind study

BACKGROUND

Postoperative nausea and vomiting (PONV) is a common complication of laparoscopic cholecystectomy. Although PONV is usually mild, severe thing can delay recovery and prolong hospitalization. We aimed to investigate the effects of ramosetron and esmolol, alone and in combination, on PONV, and pain.

METHODS

We enrolled 165 patients in their 20s to 50s who had an American Society of Anesthesiology physical status score of 1 or 2 and were scheduled to undergo laparoscopic cholecystectomy. They were randomly allocated into 3 groups: groups R, E, and E+R. Patients in group R received 0.3 mg of ramosetron following surgery. Those in group E were intravenously administered a bolus of esmolol (1.0 mg/kg) before endotracheal intubation. They were continuously infused with esmolol during the surgery to maintain their heart rate at 60 to 100 beats per minute and mean blood pressure at 60 to 100 mm Hg, followed by a bolus of esmolol (1.0 mg/kg) following surgery. Patients in group E+R were intravenously administered a bolus of esmolol (1.0 mg/kg) before endotracheal intubation, infused esmolol during surgery, and administered 0.3 mg of ramosetron and a bolus of esmolol (1.0 mg/kg) following surgery. We monitored the PONV stages (none, nausea, retching, and vomiting) and symptom severity in 3 postoperative stages (0-30 minutes, 30 minutes to 6 hours, and 6-24 hours), the latter by using the visual analog scale (VAS). We conducted an analysis of variance to compare VAS scores between groups.

RESULTS

Patients in groups E (mean ± standard deviation VAS score, 3.62 ± 1.00) and E+R (3.66 ± 0.71) exhibited less pain (P < .05) until 30 minutes following surgery compared to group R (5.72 ± 1.41). More patients in group E (28/50, 56%) experienced nausea compared to those in groups R (15/50, 30%) and E+R (8/50, 16%) until 30 minutes after surgery (P < .05). However, there were no differences in the severity of retching and vomiting between the groups in any of the phases (P > .05).

CONCLUSION

Despite reducing pain after laparoscopic cholecystectomy, esmolol did not prevent PONV, whether used alone or in combination with ramosetron.

MiR-128-3p Attenuates the Neurotoxicity in Rats Induced by Isoflurane Anesthesia

Isoflurane (ISO) has been widely used in clinical anesthesia, and exposure to ISO leads to cognitive dysfunction. Our paper aimed to investigate the effect of miR-128-3p on cognitive impairment, inflammation, and oxidative stress elicited by ISO anesthesia in Sprague-Dawley (SD) rats. The SD rats were treated with ISO to mimic the ISO-injured situation, and the concentration of miR-128-3p was quantified utilizing real-time PCR. The miR-128-3p's impacts in ISO-engendered rat models on the respects of inflammatory condition and oxidative activities were measured by the commercial kits. The Morris water maze test was adopted to measure the neuro-function regarding miR-128-3p. Additionally, the target was tested by the alternation of luciferase activity. The irritation of ISO suppressed miR-128-3p expression in rats, which was enhanced by the injection of miR-128-3p agomir. The adverse roles of ISO on inflammation, oxidative stress, and cognitive disorders were partially abrogated by an increment of miR-128-3p. A miR-128-3p's interconnection with specificity protein 1 (SP1) was pinpointed, and aggrandized mRNA levels of SP1 were found under ISO state. MiR-128 acted as a regulator in ISO damage in the respects of cognition, inflammation, and oxidative stress. The SP1's link of miR-128-3p was showcased.

Effects of Volatile Anaesthetics and Iron Dextran on Chronic Inflammation and Antioxidant Defense System in Rats

Iron, as an essential microelement, is involved in cell proliferation, metabolism, and differentiation. It also modulates the fate and function of macrophages in hematopoiesis and macrophage-mediated inflammatory responses. On the other hand, anesthetics can affect the inflammatory process by modulating the response to stress or the functions of immune cells. The aim of this paper is to understand how excessive iron intake alters physiological, functional characteristics of peripheral tissues and whether different anesthetics can alter cell metabolism regarding oxidative stress (OS) and inflammation through regulation of macrophage polarization. Y59 rats were injected intraperitoneally with iron dextran solution at a dose of 50 mg/kg or were exposed to inhaled anesthetics sevoflurane and isoflurane and their combination for 28 days every other day. The results show that the use of anesthetics reduces the rat’s organ weight and increases OS in peripheral tissues, leading to M1 macrophage polarization. Excessive iron intake leads to increased OS, inflammation, and an increased ratio of IL-12/IL-10 cytokines to the M1 macrophage phenotype. Iron, in combination with sevoflurane, has a protective effect in tissues showing the M2 phenotype of macrophages. The combination of iron dextran and isoflurane in rats leads to an increase in the erythropoiesis process made possible through the induction of hypoxia.

Longitudinal Impact of WTC Dust Inhalation on Rat Cardiac Tissue Transcriptomic Profiles

First responders (FR) exposed to the World Trade Center (WTC) Ground Zero air over the first week after the 9/11 disaster have an increased heart disease incidence compared to unexposed FR and the general population. To test if WTC dusts were causative agents, rats were exposed to WTC dusts (under isoflurane [ISO] anesthesia) 2 h/day on 2 consecutive days; controls received air/ISO or air only. Hearts were collected 1, 30, 240, and 360 d post-exposure, left ventricle total RNA was extracted, and transcription profiles were obtained. The data showed that differentially expressed genes (DEG) for WTC vs. ISO rats did not reach any significance with a false discovery rate (FDR) < 0.05 at days 1, 30, and 240, indicating that the dusts did not impart effects beyond any from ISO. However, at day 360, 14 DEG with a low FDR were identified, reflecting potential long-term effects from WTC dust alone, and the majority of these DEG have been implicated as having an impact on heart functions. Furthermore, the functional gene set enrichment analysis (GSEA) data at day 360 showed that WTC dust could potentially impact the myocardial energy metabolism via PPAR signaling and heart valve development. This is the first study showing that WTC dust could significantly affect some genes that are associated with the heart/CV system, in the long term. Even > 20 years after the 9/11 disaster, this has potentially important implications for those FR exposed repeatedly at Ground Zero over the first week after the buildings collapsed.

The Safety Profile of General and Local Anaesthetic Agents: Data Collected during 20 Years of Spontaneous Reporting Activities in the Campania Region (Southern Italy)

Background: General and local anaesthetics are widely used during surgery. These drugs have peculiar safety profiles, being commonly associated with mild and reversible local adverse drug reactions (ADRs), but also with more severe and systemic ADRs, including respiratory and cardiovascular depression and anaphylaxis. Methods and Objectives: We carried out a descriptive analysis of Individual Case Safety Reports (ICSRs) sent to the Campania Regional Centre of Pharmacovigilance (Southern Italy) from 2001 to 2021 that reported general or local anaesthetics as suspected drugs, with the aim of describing their overall characteristics, focussing on the ADRs’ seriousness and distribution by System Organ Class (SOC) and Preferred Term (PT). Results: A total of 110 ICSRs documenting general or local anaesthetics were sent to the Italian pharmacovigilance database during 20 years of spontaneous reporting activities in the Campania region. ADRs mainly occurred in patients with a median age of 48 years and in a slightly higher percentage of men. ADRs were more commonly classified as not serious and had a favourable outcome. In terms of ADRs’ distribution by SOC and PT, both general and local anaesthetics were associated with general and cutaneous disorders, with common ADRs that included lack of efficacy, rash, and erythema. In addition, general anaesthetics were associated with the occurrence of respiratory ADRs, while local anaesthetics were associated with the occurrence of nervous ADRs. Conclusion: Even though a limited number of ICSRs documenting anaesthetics-induced ADRs were retrieved from the Italian spontaneous reporting database in the Campania region, we believe that the continuous monitoring of these drugs is highly recommended, especially among the frail population.

Prolonged Volatile Anesthetic Exposure Exacerbates Cognitive Impairment and Neuropathology in the 5xFAD Mouse Model of Alzheimer's Disease

BACKGROUND

Alzheimer's disease (AD) is a progressive neurodegenerative disease which shows a set of symptoms involving cognitive changes and psychological changes. Given that AD is the most common form of dementia in aging population and the increasing demand for anesthesia/surgery with aging, there has been significant interest in the exact impact of volatile anesthetics on cognitive function and pathological alterations in AD population.

OBJECTIVE

This study aimed to investigate behavioral changes and neuropathology in the 5xFAD mouse model of Alzheimer's disease with short-term exposure or long-term exposure to desflurane, sevoflurane, or isoflurane.

METHODS

In this study, we exposed 5xFAD mouse model of AD to isoflurane, sevoflurane, or desflurane in two different time periods (30 min and 6 h), and the memory related behaviors as well as the pathological changes in 5xFAD mice were evaluated 7 days after the anesthetic exposure.

RESULTS

We found that short-term exposure to volatile anesthetics did not affect hippocampus dependent memory and the amyloid-β (Aβ) deposition in the brain. However, long-term exposure to sevoflurane or isoflurane significantly increased the Aβ deposition in CA1 and CA3 regions of hippocampus, as well as the glial cell activation in amygdala. Besides, the PSD-95 expression was decreased in 5xFAD mice with exposure to sevoflurane or isoflurane and the caspase-3 activation was enhanced in isoflurane, sevoflurane, and desflurane groups.

CONCLUSION

Our results demonstrate the time-dependent effects of common volatile anesthetics and implicate that desflurane has the potential benefits to prolonged anesthetic exposure in AD patients.

Longitudinal impact on rat cardiac tissue transcriptomic profiles due to acute intratracheal inhalation exposures to isoflurane

Isoflurane (ISO) is a widely used inhalation anesthetic in experiments with rodents and humans during surgery. Though ISO has not been reported to impart long-lasting side effects, it is unknown if ISO can influence gene regulation in certain tissues, including the heart. Such changes could have important implications for use of this anesthetic in patients susceptible to heart failure/other cardiac abnormalities. To test if ISO could alter gene regulation/expression in heart tissues, and if such changes were reversible, prolonged, or late onset with time, SHR (spontaneously hypertensive) rats were exposed by intratracheal inhalation to a 97.5% air/2.5% ISO mixture on two consecutive days (2 hr/d). Control rats breathed filtered air only. On Days 1, 30, 240, and 360 post-exposure, rat hearts were collected and total RNA was extracted from the left ventricle for global gene expression analysis. The data revealed differentially-expressed genes (DEG) in response to ISO (compared to naïve control) at all post-exposure timepoints. The data showed acute ISO exposures led to DEG associated with wounding, local immune function, inflammation, and circadian rhythm regulation at Days 1 and 30; these effects dissipated by Day 240. There were other significantly-increased DEG induced by ISO at Day 360; these included changes in expression of genes associated with cell signaling, differentiation, and migration, extracellular matrix organization, cell-substrate adhesion, heart development, and blood pressure regulation. Examination of consistent DEG at Days 240 and 360 indicated late onset DEG reflecting potential long-lasting effects from ISO; these included DEG associated with oxidative phosphorylation, ribosome, angiogenesis, mitochondrial translation elongation, and focal adhesion. Together, the data show acute repeated ISO exposures could impart variable effects on gene expression/regulation in the heart. While some alterations self-resolved, others appeared to be long-lasting or late onset. Whether such changes occur in all rat models or in humans remains to be investigated.

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.

Expression Signature of lncRNAs and mRNAs in Sevoflurane-Induced Mouse Brain Injury: Implication of Involvement of Wide Molecular Networks and Pathways

Sevoflurane, one of the most commonly used pediatric anesthetics, was found to cause developmental neurotoxicity. To understand specific risk groups and develop countermeasures, a better understanding of its mechanisms is needed. We hypothesize that, as in many other brain degeneration pathways, long non-coding RNAs (lncRNAs) are involved in the sevoflurane-induced neurotoxicity. Postnatal day 7 (PD7) mice were exposed to 3% sevoflurane for 6 h. To quantify neurotoxicity in these mice, we (1) detected neural apoptosis through analysis of caspase 3 expression level and activity and (2) assessed long-term learning ability via the Morris water maze at PD60. To elucidate specific mechanisms, profiles of 27,427 lncRNAs and 18,855 messenger RNAs (mRNAs) in mouse hippocampi were analyzed using microarray assays. Sevoflurane-induced abnormal lncRNA and mRNA expression-associated function pathways were predicted by bioinformatic analysis. We found that sevoflurane induced significant neurotoxicity, causing acute neuroapoptosis and abnormal expression of 148 mRNAs and 301 lncRNAs on PD7 in mouse hippocampus. Additionally, exposed mice exhibited impaired memory on PD60. Bioinformatic analysis predicted that the dysregulated mRNAs, which are highly correlated with their co-expressed dysregulated lncRNAs, might be involved in 34 neurodegenerative signaling pathways (e.g., brain cell apoptosis and intellectual developmental disorder). Our study reveals for the first time that neonatal exposure to 3% sevoflurane induces abnormal lncRNA and mRNA expression profiles. These dysregulated lncRNAs/mRNAs form wide molecular networks that might contribute to various functional neurological disease pathways in the hippocampus, resulting in the observed acute apoptosis and impaired long-term memory.

Effects of milrinone on cerebral perfusion and postoperative cognitive function in spine surgery: Secondary analysis of a CONSORT-compliant randomized controlled trial

OBJECTIVE

To compare the effects of milrinone, sodium nitroprusside (SNP), and nitroglycerin (NTG) on induced hypotension, cerebral perfusion, and postoperative cognitive function in elderly patients undergoing spine surgery.

METHODS

Sixty patients >60 years scheduled for lumbar fusion surgery were assigned to receive milrinone (group M), SNP (group S), or NTG (group N). The administration of the study drug was initiated immediately after perivertebral muscle retraction and was stopped after completion of interbody fusion. Target blood pressure was a decrease of 30% in systolic blood pressure from baseline or mean blood pressure of 60 to 65 mm Hg. The regional cerebral venous oxygen saturation (rSVO2), as a measure of cerebral perfusion, and the change in perioperative Mini-Mental State Examination (MMSE) score, as a measure of postoperative cognitive function, were assessed.

RESULTS

During the administration of the study drug, the overall and lowest intraoperative rSVO2 values were significantly higher (P = .01 and P = .01, respectively), and the duration of rSVO2 <60% was shorter in group M than in the other groups (P = .03). In group M, intraoperative rSVO2 was not different from the basal value, whereas in groups S and N, rSVO2 was significantly lower than the basal value during the administration of the study drug, but then returned to the basal value after terminating the study drug. Basal MMSE scores were comparable among the 3 groups. The MMSE score on postoperative day 5 was higher in group M than the other groups.

CONCLUSIONS

Milrinone used to induce hypotension resulted in better intraoperative cerebral perfusion and postoperative cognitive function compared to SNP and nitroglycerin.

Toxin-Induced Coma and Central Nervous System Depression

Many medications and toxins may induce central nervous system (CNS) depression. Even when the intention is to induce CNS depression, other nervous system adverse effects may occur, such as with anesthetics. Pain medications produce characteristic CNS toxicities. Sedative hypnotics may induce altered mentation among systemic toxicities. Stimulants may mimic coma when discontinued abruptly. Acute and chronic carbon monoxide poisoning can lead to altered mental status and prolonged cognitive difficulties. Some medications and environmental toxins can mimic brain death. High clinical suspicion and early recognition of these effects is vital to treatment, most of which is supportive.

Isoflurane inhibits a Kir4.1/5.1-like conductance in neonatal rat brainstem astrocytes and recombinant Kir4.1/5.1 channels in a heterologous expression system

All inhalation anesthetics used clinically including isoflurane can suppress breathing; since this unwanted side effect can persist during the postoperative period and complicate patient recovery, there is a need to better understand how isoflurane affects cellular and molecular elements of respiratory control. Considering that astrocytes in a brainstem region known as the retrotrapezoid nucleus (RTN) contribute to the regulation of breathing in response to changes in CO2/H+ (i.e., function as respiratory chemoreceptors), and astrocytes in other brain regions are highly sensitive to isoflurane, we wanted to determine whether and how RTN astrocytes respond to isoflurane. We found that RTN astrocytes in slices from neonatal rat pups (7-12 days postnatal) respond to clinically relevant levels of isoflurane by inhibition of a CO2/H+-sensitive Kir4.1/5.1-like conductance [50% effective concentration (EC50) = 0.8 mM or ~1.7%]. We went on to confirm that similar levels of isoflurane (EC50 = 0.53 mM or 1.1%) inhibit recombinant Kir4.1/5.1 channels but not homomeric Kir4.1 channels expressed in HEK293 cells. We also found that exposure to CO2/H+ occluded subsequent effects of isoflurane on both native and recombinant Kir4.1/5.1 currents. These results identify Kir4.1/5.1 channels in astrocytes as novel targets of isoflurane. These results suggest astrocyte Kir4.1/5.1 channels contribute to certain aspects of general anesthesia including altered respiratory control.NEW & NOTEWORTHY An unwanted side effect of isoflurane anesthesia is suppression of breathing. Despite this clinical significance, effects of isoflurane on cellular and molecular elements of respiratory control are not well understood. Here, we show that isoflurane inhibits heteromeric Kir4.1/5.1 channels in a mammalian expression system and a Kir4.1/5.1-like conductance in astrocytes in a brainstem respiratory center. These results identify astrocyte Kir4.1/5.1 channels as novel targets of isoflurane and potential substrates for altered respiratory control during isoflurane anesthesia.

HSP90 inhibitor 17AAG attenuates sevoflurane-induced neurotoxicity in rats and human neuroglioma cells via induction of HSP70

Background

17AAG has been extensively studied for its antitumor effects that protect cells from lethal stress by maintaining protein stability. The role of 17AAG in sevoflurane-induced neuronal injury has never been studied. We aim to investigate the effect of 17AAG on sevoflurane-induced neurotoxicity in vivo and in vitro.

Methods

Sevoflurane-induced hippocampal neuron injury model was established in aged Sprague–Dawley rats. Pretreatment of vehicle or 17AAG was administered prior to sevoflurane inhalation. H4 neuroglioma cells were pretreated with vehicle or 17AAG and exposed to sevoflurane. Apoptosis, oxidative stress, expression of interleukin-6 (IL-6), and activation of the nuclear factor-κB (NF-κB) signaling pathway in H4 cells were examined by Hoechst assay, flow cytometry, Western blot, and immunofluorescent staining. RNA interference against HSPA1A was performed to test the function of HSP70 in neuroprotection.

Results

Exogenous 17AAG reduced sevoflurane-induced apoptosis and oxidative stress in rat hippocampal neurons and in H4 cells. In H4 cells, 17AAG suppressed sevoflurane-induced upregulation of IL-6 and activation of NF-κB signaling. 17AAG enhanced sevoflurane-induced upregulation of HSP70 in rat hippocampal neurons and in H4 cells. Conversely, silencing of HSPA1A in H4 cells blocked the cytoprotective effect of 17AAG against sevoflurane-induced apoptosis and oxidative stress, and prevented upregulation of IL-6 and activation of NF-κB signaling.

Conclusions

17AAG protects against sevoflurane-induced neurotoxicity in vivo and in vitro via HSP70-dependent inhibition of apoptosis, oxidative stress, and pro-inflammatory signaling pathway.

Pharmacologic Modulation of Noxious Stimulus-evoked Brain Activation in Cynomolgus Macaques Observed with Functional Neuroimaging

Maintaining effective analgesia during invasive procedures performed under general anesthesia is important for minimizing postoperative complications and ensuring satisfactory patient wellbeing and recovery. While patients under deep sedation may demonstrate an apparent lack of response to noxious stimulation, areas of the brain related to pain perception may still be activated. Thus, these patients may still experience pain during invasive procedures. The current study used anesthetized or sedated cynomolgus macaques and functional magnetic resonance imaging (fMRI) to assess the activation of the parts of the brain involved in pain perception during the application of peripheral noxious stimuli. Noxious pressure applied to the foot resulted in the bilateral activation of secondary somatosensory cortex (SII) and insular cortex (Ins), which are both involved in pain perception, in macaques under either propofol or pentobarbital sedation. No activation of SII/Ins was observed in macaques treated with either isoflurane or a combination of medetomidine, midazolam, and butorphanol. No movement or other reflexes were observed in response to noxious pressure during stimulation under anesthesia or sedation. The current findings show that despite the lack of visible behavioral symptoms of pain during anesthesia or sedation, brain activation suggests the presence of pain depending on the anesthetic agent used. These data suggest that fMRI could be used to noninvasively assess pain and to confirm the analgesic efficacy of currently used anesthetics. By assessing analgesic efficacy, researchers may refine their experiments, and design protocols that improve analgesia under anesthesia.

Comparison of the Effects of Milrinone, Sodium Nitroprusside, and Nitroglycerine for Induced Hypotension in Elderly Patients Undergoing Spine Surgery: A Randomized Controlled Trial

BACKGROUND

The use of induced hypotension is limited because of concerns about hypoperfusion to major organs in elderly patients. The aim of this study was to compare the effects of milrinone with those of other vasodilating hypotensive agents on induced hypotension in elderly patients undergoing spine surgery.

METHODS

In total, 60 patients older than 60 years who underwent lumbar fusion surgeries were randomized to groups M (milrinone), S (sodium nitroprusside), and N (nitroglycerine). The study drug was infused after perivertebral muscle retraction until complete interbody fusion occurred. The infusion dose was adjusted to achieve a fall of 30% in systolic blood pressure or mean blood pressure to 60 to 65 mm Hg. Intraoperative blood loss, grade of the surgical field, and urine output were recorded.

RESULTS

Intraoperative blood loss per fused spine level was 288.5±94.4 mL in group M, 399.8±60.3 mL in group S, and 367.0±122.5 mL in group N (P=0.002). The grade of the surgical field was similar among the 3 groups (P=0.439). Hourly urine output was 1.4±0.5 mL in group M, 0.7±0.3 mL in group S, and 0.9±0.4 mL in group N (P<0.001).

CONCLUSIONS

The use of milrinone for induced hypotension led to less intraoperative blood loss and higher urine output than the use of sodium nitroprusside or nitroglycerine in elderly patients undergoing spine surgery.

Evaluation of waste anesthetic gas surveillance program and isoflurane exposures during animal and human surgery

Prolonged occupational exposure to waste anesthetic gases may have the potential to cause adverse health effects. Workplace exposure surveillance programs are intended to reduce health risk by evaluating exposures to waste anesthetic gases during surgical procedures. Both the personal breathing-zone and area measurements are used to assess occupational exposure in the operating theater. Direct-reading instruments provide real-time measurements and are useful for identifying leaks and evaluating on-the-spot corrective actions. Passive diffusion monitors quantify occupational exposures over time during surgery. The aim of this study was to evaluate a waste anesthetic gas surveillance program to understand occupational exposures and further improve data collection strategy. For this study, 76 survey reports from 2012 through 2014 were retrospectively reviewed to assess occupational exposures to isoflurane in 58 unique procedural rooms operated by the National Institutes of Health. The surveys included industrial hygiene assessments performed during animal and human surgical procedures. The survey reports were evaluated qualitatively and data from these reports was transcribed for quantitative analysis. Variations in sample strategy were observed between surveys and were attributed to ambiguity in the written surveillance program. The study also evaluated the relationship between isoflurane concentrations and sampling method, sampling location, patient type, or scavenging method. Isoflurane exposures were significantly higher among procedures performed on rodents compared to the patients with a large body mass (humans, non-human primates, and swine) (P < 0.05) and in procedures using the charcoal canister exhaust system compared with the central vacuum exhaust system. In addition, individuals performing the surgical procedure experienced elevated occupational exposures measured by both direct-reading instrument and passive diffusion monitors, that is, exposure was significantly higher as measured at the breathing-zone compared with any area within the room (P < 0.05). The study identified several inconsistencies and shortcomings in the surveillance program. Isoflurane concentrations measured during rodent procedures requires further review of work practices and engineering controls. Overall, the findings provide insights to further improve data collection, monitoring, and control of isoflurane exposures.

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.

The effect of sevoflurane and isoflurane anesthesia on single unit and local field potentials

Volatile general anesthetics are used commonly in adults and children, yet their mechanisms of action are complex and the changes in single unit firing and synaptic activity that underlie the broad decreases in neuronal activity induced by these drugs have not been well characterized. Capturing such changes throughout the anesthesia process is important for comparing the effects of different anesthetics and gaining a better understanding of their mechanisms of action and their impact on different brain regions. Using chronically implanted electrodes in the rabbit somatosensory cortex, we compared the effects of two common general anesthetics, isoflurane, and sevoflurane, on cortical neurons. Single unit activity and local field potentials (LFP) were recorded continuously before and during anesthetic delivery at 1 MAC, as well as during recovery. Our findings show that although isoflurane and sevoflurane belong to the same class of volatile general anesthetics, their effects upon cortical single units and LFP were quite different. Overall, the suppression of neuronal firing was greater and more uniform under sevoflurane. Moreover, the changes in LFP frequency bands suggest that effect of anesthesia upon beta oscillations does not necessarily depend on the level of single unit activity, but rather on the changes in GABA/glutamate neurotransmission induced by each drug.

Interpreting Neuroendocrine Hormones, Corticosterone, and Blood Glucose to Assess the Wellbeing of Anesthetized Rats during Euthanasia

Current recommendations for assessing animal wellbeing during euthanasia suggest that measuring neuroendocrine hormones-such as ACTH, noradrenaline, and adrenaline-is preferable to measuring corticosterone and blood glucose because of the sensitivity of neuroendocrine hormones to the acute stress associated with rapid methods of euthanasia. However, these neuroendocrine hormones can be stimulated in ways that confound interpretation of welfare assessment in euthanasia studies. Although this property does not negate the usefulness of neuroendocrine hormones as tools of assessment, it is important to differentiate the stress associated with the induction of anesthesia before the loss of consciousness (an animal wellbeing concern) with the physiologic responses that occur after the loss of consciousness (not an animal wellbeing concern). In this study, rats were anesthetized by using a ketamine-xylazine combination. Once the rats achieved a surgical plane of anesthesia, they were exposed to O₂, CO₂, or isoflurane, followed by terminal blood collection to assess concentrations of ACTH, noradrenaline, corticosterone, and blood glucose. Compared with animals exposed to O₂ or isoflurane, rats exposed to CO₂ had significant increases in their serum concentrations of ACTH and noradrenaline, but blood glucose and corticosterone did not differ between groups. These findings indicate that noradrenaline and ACTH should be used with caution to assess animal wellbeing when the method of euthanasia might confound that assessment.

Brain tissue oxygen regulation in awake and anesthetized neonates

Inhaled general anesthetics are used commonly in adults and children, and a growing body of literature from animals and humans suggests that exposure to anesthesia at an early age can impact brain development. While the origin of these effects is not well understood, it is known that anesthesia can disrupt oxygen regulation in the brain, which is critically important for maintaining healthy brain function. Here we investigated how anesthesia affected brain tissue oxygen regulation in neonatal rabbits by comparing brain tissue oxygen and single unit activity in the awake and anesthetized states. We tested two common general anesthetics, isoflurane and sevoflurane, delivered in both air and 80% oxygen. Our findings show that general anesthetics can greatly increase brain tissue PO₂ in neonates, especially when combined with supplemental oxygen. Although isoflurane and sevoflurane belong to the same class of anesthetics, notable differences were observed in their effects upon neuronal activity and spontaneous respiration. Our findings point to the need to consider the potential effects of hyperoxia when supplemental oxygen is utilized, particularly in children and neonates.

The Gly16 Allele of the Gly16Arg Single-Nucleotide Polymorphism in the β₂-Adrenergic Receptor Gene Augments Perioperative Use of Vasopressors: A Retrospective Cohort Study

BACKGROUND

Arterial hypotension is frequent in patients undergoing anesthesia and may aggravate the outcome. Common genetic variations may influence the cardiovascular response to anesthesia. In this retrospective cohort study, we tested whether variation in the gene encoding the β2-adrenergic receptor (ADRB2) influences perioperative arterial blood pressure and consequently the use of vasopressors.

METHODS

Five hundred seventy-one Danish Caucasians undergoing neurosurgery were genotyped for 5 marker single-nucleotide polymorphisms (SNPs) within ADRB2 (Gly16Arg, Gln27Glu, Thr164Ile, Arg175Arg, and Gly351Gly). A pairwise tagging principle was used to identify ADRB2 haplotypes. Mean arterial blood pressure (MAP) was recorded in the supine awake state and, together with administration of vasopressors (ephedrine and/or phenylephrine), for 30 minutes after induction of general anesthesia (sevoflurane/remifentanil or propofol/remifentanil).

RESULTS

Four hundred thirteen (72%) patients received ephedrine and/or phenylephrine. Only baseline MAP (P < 0.001) and the Arg175Arg SNP (P = 0.01) were associated with nadir perioperative MAP. The Gly16Arg SNP but no other SNPs showed a trend toward an association with the amount of vasopressors used during anesthesia with Arg16 homozygotes receiving less ephedrine equivalents. The Arg16-Gln27-Thr164-Arg175-Gly351 haplotype was associated with approximately 13% lower vasopressor requirements than the most common Gly16-Glu27-Thr164-Arg175-Gly351 haplotype (P = 0.01).

CONCLUSIONS

Gly16 carriers received larger amounts of vasopressor compared with Arg16 homozygotes. This corresponds to previous studies demonstrating that the Gly16 allele in ADRB2 is associated with vasodilation and high cardiac output.

Intraoperative factors associated with delayed recovery of liver function after hepatectomy: analysis of 1969 living donors

BACKGROUND

The safety of healthy living donors who are undergoing hepatic resection is a primary concern. We aimed to identify intraoperative anaesthetic and surgical factors associated with delayed recovery of liver function after hepatectomy in living donors.

METHODS

We retrospectively analysed 1969 living donors who underwent hepatectomy for living donor liver transplantation. Delayed recovery of hepatic function was defined by increases in international normalised ratio of prothrombin time and concomitant hyperbilirubinaemia on or after post-operative day 5. Univariate and multivariate logistic regression analyses were performed to determine the factors associated with delayed recovery of hepatic function after living donor hepatectomy.

RESULTS

Delayed recovery of liver function after donor hepatectomy was observed in 213 (10.8%) donors. Univariate logistic regression analysis showed that sevoflurane anaesthesia, synthetic colloid, donor age, body mass index, fatty change and remnant liver volume were significant factors for prediction of delayed recovery of hepatic function. Multivariate logistic regression analysis showed that independent factors significantly associated with delayed recovery of liver function after donor hepatectomy were sevoflurane anaesthesia (odds ratio = 3.514, P < 0.001), synthetic colloid (odds ratio = 1.045, P = 0.033), donor age (odds ratio = 0.970, P = 0.003), female gender (odds ratio = 1.512, P = 0.014) and remnant liver volume (odds ratio = 0.963, P < 0.001).

CONCLUSIONS

Anaesthesia with sevoflurane was an independent factor in predicting delayed recovery of hepatic function after donor hepatectomy. Although synthetic colloid may be associated with delayed recovery of hepatic function after donor hepatectomy, further study is required. These results can provide useful information on perioperative management of living liver donors.

Drug-induced hepatotoxicity: incidence of abnormal liver function tests consistent with volatile anaesthetic hepatitis in trauma patients

BACKGROUND & AIMS

Volatile anaesthetic drug-induced liver injury can range from asymptomatic alanine transaminase elevations to fatal hepatic necrosis. There is very limited research regarding hepatotoxicity of modern volatile anaesthetic agents. The aim of this study was to determine how common liver injury consistent with volatile anaesthetic hepatitis is, following exposure to isoflurane, desflurane and sevoflurane; and to propose risk factors for its development.

METHODS

Following ethics approval, we conducted a retrospective audit of adult trauma patients with abnormal liver biochemistry following volatile anaesthesia during January 1 to December 31, 2009. The data collected included patient demographics, volatile anaesthetic administration, concurrent medication, perioperative liver biochemistry results and comorbidities. The Council for International Organisations of Medical Sciences/Roussel Uclaf Causality Assessment Method scoring system was used to group cases according to the likelihood of volatile anaesthetic being the causative agent of drug-induced hepatotoxicity.

RESULTS

Forty-seven (3%) of 1556 patients had abnormal post-operative liver biochemistry potentially attributable to volatile anaesthetic. Of the 47, 12 patients (26%) had peak alanine transaminase levels greater than 200 U/L. No significant predictors of volatile anaesthetic drug-induced liver injury following isoflurane, desflurane or sevoflurane anaesthesia could be identified.

CONCLUSION

Volatile anaesthetic drug-induced liver injury in adult trauma patients may be significantly more common than previously noted. This study suggests that about a quarter of patients with volatile anaesthetic drug-induced liver injury develop significant liver injury. Further prospective studies are required to define risk factors and clinical outcomes.

Changes in the gene expression levels of microRNAs in the rat hippocampus by sevoflurane and propofol anesthesia

General anesthesia is commonly used in the surgical arena, but little is known regarding its influence at the genomic and molecular levels. MicroRNAs (miRNAs) belong to a new class of non-coding RNA molecules which influence cell biology. In the present study, it was hypothesized that miRNAs alter gene expression levels under general anesthesia. The aim was to compare the miRNA expression profiles in the rat hippocampus in response to anesthesia with representative volatile (sevoflurane) and intravenous (propofol) anesthetics. Wistar Rats were randomly assigned to either a 2.4% sevoflurane, 600 µg/kg/min propofol or control (without anesthetics) group. Total RNA from hippocampal samples which contained miRNA was subjected to quantitative reverse transcription-polymerase chain reaction and Taqman Low-Density Arrays (TLDA). A total of 373 miRNAs are associated with rats and the TLDA analysis revealed that 279 expressed miRNAs (74.8%) were expressed in all three groups. Significant differences in the levels of 33 of the 279 expressed miRNAs (11.8%) were observed among the three groups in response to the anesthetic agents, and when compared with the control group, significant differences were found in 26 of the 279 expressed miRNAs (9.3%). Following sevoflurane anesthesia, the levels of four miRNAs were significantly increased and those of 12 were significantly reduced. By contrast, following propofol anesthesia, the levels of 11 miRNAs were significantly reduced but no miRNAs exhibited significantly elevated levels. One miRNA was common between the two anesthesia groups, whereas 14 miRNAs were significantly differentially expressed. In conclusion, sevoflurane and propofol exerted different effects on miRNA expression in the rat hippocampus.

Synthesis and biological characterisation of 18F-SIG343 and 18F-SIG353, novel and high selectivity σ2 radiotracers, for tumour imaging properties

Background

Sigma2 (σ₂) receptors are highly expressed in cancer cell lines and in tumours. Two novel selective ¹⁸F-phthalimido σ₂ ligands, ¹⁸F-SIG343 and ¹⁸F-SIG353, were prepared and characterised for their potential tumour imaging properties.

Methods

Preparation of ¹⁸F-SIG343 and ¹⁸F-SIG353 was achieved via nucleophilic substitution of their respective nitro precursors. In vitro studies including radioreceptor binding assays in the rat brain membrane and cell uptake studies in the A375 cell line were performed. In vivo studies were carried out in mice bearing A375 tumours including positron emission tomography (PET) imaging, biodistribution, blocking and metabolite studies.

Results

In vitro studies showed that SIG343 and SIG353 displayed excellent affinity and selectivity for σ₂ receptors (Ki(σ₂) = 8 and 3 nM, σ₂:σ₁ = 200- and 110-fold, respectively). The σ₂ selectivity of ¹⁸F-SIG343 was further confirmed by blocking studies in A375 cells, however, not noted for ¹⁸F-SIG353. Biodistribution studies showed that both radiotracers had similar characteristics including moderately high tumour uptake (4%ID/g to 5%ID/g); low bone uptake (3%ID/g to 4%ID/g); and high tumour-to-muscle uptake ratios (four- to sevenfold) up to 120 min. Although radiotracer uptake in organs known to express σ receptors was significantly blocked by pre-injection of competing σ ligands, the blocking effect was not observed in the tumour. PET imaging studies indicated major radioactive localisation in the chest cavity for both ligands, with approximately 1%ID/g uptake in the tumour at 120 min. Metabolite studies showed that the original radiotracers remained unchanged 65% to 80% in the tumour up to 120 min.

Conclusions

The lead ligands showed promising in vitro and in vivo characteristics. However, PET imaging indicated low tumour-to-background ratios. Furthermore, we were unable to demonstrate that uptake in the A375 tumour was σ₂-specific. ¹⁸F-SIG343 and ¹⁸F-SIG343 do not display ideal properties for imaging the σ₂ receptor in the A375 tumour model. However, since the radiotracers show promising in vitro and in vivo characteristics, longer scans using appropriate half-life isotopes and alternative tumour models will be carried out in future studies to fully validate the imaging characteristics of these radiotracers.

Effects of Volatile Anesthetic Choice on Hospital Length-of-stay

Background:

Volatile anesthetic prices differ substantially. But differences in drug-acquisition cost would be inconsequential if hospitalization were prolonged by more soluble anesthetics. The authors tested the hypothesis that the duration of hospitalization is prolonged with isoflurane anesthesia.

Methods:

Initially, the authors queried their electronic records and used propensity matching to generate homogeneous sets of adults having inpatient noncardiac surgery who were given desflurane, sevoflurane, and isoflurane. The authors then conducted a prospective alternating intervention trial in which adults (mostly having colorectal surgery) were assigned to isoflurane or sevoflurane, based on protocol.

Results:

In the retrospective analysis, 2,898 matched triplets were identified among 43,352 adults, each containing one patient receiving isoflurane, desflurane, and sevoflurane, respectively. The adjusted geometric mean (95% CI) hospital length-of-stay for the isoflurane cases was 2.85 days (2.78–2.93); this was longer than that observed for both desflurane (2.64 [2.57–2.72]; P &lt; 0.001) and sevoflurane (2.55 [2.48–2.62]; P &lt; 0.001). In the prospective trial (N = 1,584 operations), no difference was found; the adjusted ratio of means (95% CI) of hospital length-of-stay in patients receiving isoflurane versus sevoflurane was 0.98 (0.88–1.10), P = 0.77, with adjusted geometric means (95% CI) estimated at 4.1 (3.8–4.4) and 4.2 days (3.8–4.5), respectively.

Conclusions:

Results of the propensity-matched retrospective analysis suggested that avoiding isoflurane significantly reduced the duration of hospitalization. In contrast, length-of-stay was comparable in our prospective trial. Volatile anesthetic choice should not be based on concerns about the duration of hospitalization. These studies illustrate the importance of following even the best retrospective analysis with a prospective trial.

Complex modulation of TRPM8 cold receptor by volatile anaesthetics and role in complications of general anaesthesia

The mechanisms by which volatile general anaesthetics (VAs) produce a depression of central nervous system are beginning to be better understood, but little is known about a number of side effects. Here, we show that the cold receptor, TRPM8, is complexly modulated by clinical concentration of VAs in dorsal root ganglion neurons and HEK-293 cells heterologously expressing TRPM8. VAs produced transient enhancement of TRPM8 via a depolarizing shift of its activation towards physiological membrane potentials, followed by a sustained TRPM8 inhibition. Stimulatory action of VAs engaged molecular determinants distinct from those used by the TRPM8 agonist. Transient TRPM8 activation by VAs could explain such side effects as inhibition of respiratory drive, shivering and cooling sensation during the beginning of anaesthesia, whereas the second phase of VA action associated with sustained TRPM8 inhibition may be responsible for hypothermia. Consistent with this, both hypothermia and inhibition of respiratory drive induced by VAs are partially abolished in TRPM8-null animals. Thus, we propose TRPM8 as a new clinical target for diminishing common and serious complications of general anaesthesia.

Repeated exposure to modern volatile anaesthetics may cause chronic hepatitis as well as acute liver injury

Volatile anaesthetic agents are known to cause acute hepatitis and fulminant hepatic failure in susceptible individuals. Four patients were identified with prolonged liver injury due to volatile anaesthetic-induced hepatitis. Three had liver biopsy confirmation and all gave blood for specific diagnostic tests (TFA and CYP 2E1 IgG4 antibodies). The Roussel Uclaf Causality Assessment Method (RUCAM) drug causality scale was used to determine the likelihood of volatile anaesthetics causing the chronic liver injury. We describe four cases of volatile anaesthetic hepatitis in which three evolved into chronic hepatitis. The fourth followed a more typical pattern of acute hepatitis; however, resolution took a few months. These cases all occurred with modern volatile anaesthetics, predominantly sevoflurane, and all cases were proven with specific antibody tests, liver histology and a drug causality scale. This is the first report of chronic liver injury due to volatile anaesthetic exposure.

Non-steroidal anti-inflammatory drugs reduce the stress response during sevoflurane anesthesia

BACKGROUND

Non-steroidal anti-inflammatory drugs are analgesics commonly used for post-operative pain. However, their effect on dosages of inhaled anesthetics during surgery is unclear. We investigated the effect of flurbiprofen axetil and parecoxib sodium on the minimum alveolar concentration of sevoflurane required to blunt stress responses to skin incision under general anesthesia.

METHODS

One hundred and five adult patients were randomly allocated to four treatment groups, each receiving sevoflurane: control (sevoflurane only), lidocaine (1 mg/kg bolus, followed by continuous infusion of 20 μg/kg/min after intubation), Intravenous (IV) flurbiprofen (1 mg/kg before skin incision), and IV parecoxib (40 mg before skin incision). Following anesthetic induction and stabilization of end-tidal sevoflurane concentration, mean arterial blood pressure and heart rate were recorded 2 min before and at 5-min intervals after skin incision. The stable end-tidal sevoflurane concentration was calculated using an up-and-down method.

RESULTS

The minimum alveolar concentration of sevoflurane required to blunt the stress responses to skin incision in the control, lidocaine, flurbiprofen, and parecoxib groups was 4.63 ± 0.08%, 2.67 ± 0.08%, 3.33 ± 0.08%, and 3.80 ± 0.11%, respectively. These figures for the later three groups were all significantly less than that of the control group (P = 0.021, P = 0.037, and P = 0.011, respectively); that of the flurbiprofen group was significantly less than the parecoxib (P = 0.034).

CONCLUSION

The non-steroidal anti-inflammatory drugs flurbiprofen axetil and parecoxib sodium decreased the minimum alveolar concentration of sevoflurane required to blunt the stress response to skin incision during general anesthesia.

Evaluating methods of mouse euthanasia on the oocyte quality: cervical dislocation versus isoflurane inhalation

Cervical dislocation is a commonly used method of mouse euthanasia. Euthanasia by isoflurane inhalation is an alternative method which allows the sacrifice of several mice at the same time with an anaesthesia, in the aim to decrease pain and animal distress. The objective of our study was to assess the impact of these two methods of euthanasia on the quality of mouse oocytes. By administering gonadotropins, we induced a superovulation in CD1 female mice. Mice were randomly assigned to euthanasia with cervical dislocation and isoflurane inhalation. Oviducts were collected and excised to retrieve metaphase II oocytes. After microscopic examination, oocytes were classified into three groups: intact, fragmented/cleaved and atretic. Intact metaphase II oocytes were employed for biomedical research. A total of 1442 oocytes in the cervical dislocation group were compared with 1230 oocytes in the isoflurane group. In the cervical dislocation group, 93.1% of the oocytes were intact, versus 65.8% in the isoflurane group ( P ≤ 0.001). In light of these results, we conclude that cervical dislocation is the best method of mouse euthanasia for obtaining intact oocytes for biomedical research.

Role of immune reactions in drug-induced liver injury (DILI)

Although some drugs cause drug-induced liver injury (DILI) through direct damage to hepatocytes or intereference with bile secretion, others cause delayed, often idiosyncratic, DILI with clinical features, such as mild lymphocytic infiltrate, that are reminiscent of allergic reactions involving activation of the adaptive immune system. Even in cases of direct drug-induced hepatotoxicity, infiltration of inflammatory cells into the liver is often observed, suggesting a role for the innate immune system (e.g., neutrophils, macrophages, and so on). Therefore, a variety of hypotheses for the pathogenesis of DILI center around a pathogenic role of drug- (or drug-metabolite-) specific adaptive immune cells, as well as hepatic-injury-induced innate immune responses in the development, progression, and/or resolution of DILI.

Reduced respiratory neural activity elicits phrenic motor facilitation

We hypothesized that reduced respiratory neural activity elicits compensatory mechanisms of plasticity that enhance respiratory motor output. In urethane-anesthetized and ventilated rats, we reversibly reduced respiratory neural activity for 25-30 min using: hypocapnia (end tidal CO(2)=30 mmHg), isoflurane (~1%) or high frequency ventilation (HFV; ~100 breaths/min). In all cases, increased phrenic burst amplitude was observed following restoration of respiratory neural activity (hypocapnia: 92±22%; isoflurane: 65±22%; HFV: 54±13% baseline), which was significantly greater than time controls receiving the same surgery, but no interruptions in respiratory neural activity (3±5% baseline, p<0.05). Hypocapnia also elicited transient increases in respiratory burst frequency (9±2 versus 1±1bursts/min, p<0.05). Our results suggest that reduced respiratory neural activity elicits a unique form of plasticity in respiratory motor control which we refer to as inactivity-induced phrenic motor facilitation (iPMF). iPMF may prevent catastrophic decreases in respiratory motor output during ventilatory control disorders associated with abnormal respiratory activity.

Evaluation of antioxidant parameters in rats treated with sevoflurane

BACKGROUND AND OBJECTIVES

Sevoflurane is a halogenated fluorinated ether that undergoes hepatic biotransformation through cytochrome P4502E1. Halogenated ethers undergoing biotransformation by P4502E1 can produce reactive oxygen species (ROS), weakening the antioxidant defense mechanism. The objective of this study was to investigate the relationship between the activity of erythrocyte antioxidant enzymes and sevoflurane.

METHODS

Animals were divided in four groups: Group 1 - control: 100% oxygen (1 L.min(-1) for 60 min during five consecutive days); Group 2 - 4.0% sevoflurane in 100% oxygen (1 L.min(-1) for 60 minutes during five consecutive days); Group 3 - isoniazid (i.p.), 50 mg.kg(-1)/ day for four consecutive days, followed by 100% oxygen (1 L.min(-1) for 60 minutes during four consecutive days); Group 4 - intraperitoneal isoniazid, 50 mg.kg(-1) daily for four days, followed by 4.0% sevoflurane in 100% oxygen (1 L.min(-1) for 60 minutes during five days). Twelve hours after the last exposure to sevoflurane, animals were sacrificed and their blood was collected through the portal vein for analysis of antioxidant enzymes.

RESULTS

An increase in the activity of glucose-6-phosphate dehydrogenase and a decrease in the activity of catalase were observed, especially in the group of animals pre-treated with isoniazid. Changes in the activity of glutathione peroxidase were not observed.

CONCLUSIONS

The interaction between sevoflurane and cytochrome P450 2E1 with enzymatic inducers can lead to oxidative stress with prolonged and repetitive exposure.

Drug-induced acute liver failure and gastrointestinal complications

The objective of this article is to describe adverse drug events related to the liver and gastrointestinal tract in critically ill patients. PubMed and other resources were used to identify information related to drug-induced acute liver failure, gastrointestinal hypomotility, constipation, diarrhea, gastrointestinal bleeding, and pancreatitis in critically ill patients. This information was reviewed, and data regarding pathophysiology, common drug causes, and guidelines for prevention and management were collected and summarized. In cases in which data in critically ill patients were unavailable, data were extrapolated from other patient populations. Drug-induced acute liver failure can be caused by many drugs routinely used in the intensive care unit and may be associated with significant morbidity and mortality. Drug-related hypomotility and constipation and drug-related diarrhea are reported with many drugs, and these are common adverse drug events in critically ill patients that can substantially complicate the care of these patients. Drug-induced gastrointestinal bleeding and drug-induced pancreatitis occur less frequently, can range in disease severity, and can be associated with morbidity and mortality. Many drugs used in critically ill patients are associated with adverse drug events related to the liver and gastrointestinal tract. Critical care clinicians should be aware of common drug causes of drug-induced acute liver failure, gastrointestinal hypomotility, constipation, diarrhea, gastrointestinal bleeding, and pancreatitis, and should be familiar with the prevention and management of these diverse conditions.