Volatile Anesthetics Research Articles

Age-dependent cerebral vasodilation induced by volatile anesthetics is mediated by NG2+ vascular mural cells.

Anesthesia can influence cerebral blood flow by altering vessel diameter. Using in vivo two-photon imaging, we examined the effects of volatile anesthetics, sevoflurane and isoflurane, on vessel diameter in young and adult mice. Our results show that these anesthetics induce robust dilation of cortical arterioles and arteriole-proximate capillaries in adult mice, with milder effects in juveniles and no dilation in infants. This anesthesia-induced vasodilation correlates with decreased cytosolic Ca2+ levels in NG2+ vascular mural cells. Optogenetic manipulation of these cells bidirectionally regulates vessel diameter, and their ablation abolishes the vasodilatory response to anesthetics. In immature brains, NG2+ mural cells are fewer in number and express lower levels of Kir6.1, a subunit of ATP-sensitive potassium channels. This likely contributes to the age-dependent differences in vasodilation, as Kir6.1 activation promotes, while its inhibition reduces, anesthesia-induced vasodilation. These findings highlight the essential role of NG2+ mural cells in mediating anesthesia-induced cerebral vasodilation.

The climate crisis - actions to prioritize for anaesthesiologists.

Climate change is the biggest threat to human health and survival in the twenty-first century. Emissions associated with healthcare contribute to climate change and there are many personal and professional actions that can reduce carbon emissions. This review highlights why action is necessary and what anaesthetists and healthcare workers can do. Encouraging continuing research regarding sustainable anaesthesia and expanding education at all levels to include climate action is key. Professionally, actions include limiting use of single-use equipment, reducing reliance on volatile gas inhalational anaesthesia, and adopting low fresh gas flow techniques. Personal actions such as climate-conscious travelling, spending, and eating are important, especially when shared to create climate positive movements. This article shows that, while patient safety and quality of care must remain healthcare's top priority, considering the climate implications of care is part of that duty. Many actions that reduce the carbon impact of care simultaneously improve the quality of care and reduce financial cost. More research into sustainable healthcare is needed. Departments and hospitals and must create environments in which climate conversations are welcomed and can result in positive advancements.

Ca2+ signaling of pancreatic acinar cells in malignant hyperthermia susceptibility

BackgroundMalignant hyperthermia susceptibility (MHS) and acute pancreatitis (AP) share a common cellular pathomechanism that is Ca2+-overload of the muscle fiber and the pancreatic acinar cell (PAC). In the muscle, gain-of-function mutations of the ryanodine receptor (RyR1) make the Ca2+-release mechanism hypersensitive to certain ligands, including Ca2+, volatile anaesthetics and succinylcholine, creating a medical emergency when the patient is exposed to these drugs. As RyR1 was shown to contribute to Ca2+-overload in PAC, we presumed that pancreata of MHS individuals are more prone to AP. Accordingly, a recent case study reported coincidence of MHS with recurrent AP, indicating a pathological link between the two diseases. MethodsWe tested if MHS poses a risk for AP in mice carrying the Y522S MHS mutation.Fluorescent Ca2+ imaging was performed in PACs. Conventional histopathological analysis and plazma amylase measurement was performed using a cerulein-induced pancreatitis mouse model. ResultsThe intracellular Ca2+-signals of PACs from MHS mice were slightly bigger then in wild type when stimulated with 0.2 and 2 μM carbachol (cch) or with 1 and 5 mM bile acid (taurocholic acid). Store-operated-Ca2+-entry was also higher in PACs from MHS mice. Nevertheless, histopathological analysis and plasma amylase levels did not indicate more severe AP in MHS. ConclusionsThese results suggest that the Y522S RyR1 mutation alter the Ca2+-homeostasis in PACs, but not as much as to cause or aggravate AP.

Chewing gum to treat postoperative nausea and vomiting in female patients: a multicenter randomized trial.

Postoperative nausea and vomiting (PONV) is common after general anesthesia, with consequences for patient outcomes, satisfaction with care and healthcare costs. Our aim was to compare a new treatment, chewing gum, with a widely-used intravenous agent, ondansetron, to treat PONV in female patients in the post anesthesia care unit (PACU). We conducted a multicenter, randomized, controlled non-inferiority trial in 17 hospitals in Australia and New Zealand. Female patients aged ≥12 years undergoing volatile anesthetic-based general anesthesia for laparoscopic or breast surgery were enrolled. Protocolized anti-emetic prophylaxis was administered. Patients who developed PONV in the PACU were randomized to either 15 min of chewing gum or 4 mg of intravenous ondansetron. The primary outcome was cessation of nausea, retching or vomiting, with no recurrence nor rescue medication for 2 h after administration of the randomized intervention (i.e., complete response). Of 865 enrolled patients, 218 were randomized. In a per-protocol analysis, 50 of 105 (47.6%) ondansetron-treated patients compared with 31 of 103 (30.1%) chewing gum-treated patients achieved the primary outcome (absolute risk difference [95% confidence interval (CI)] -17.3 [-30.4 to -4.3] %), not reaching our prespecified non-inferiority limit. Time to complete response was longer for patients randomized to chewing gum (hazard ratio [95% CI] 0.53 [0.34, 0.83]), and they were more likely to receive antiemetics in the 24 h after surgery (absolute risk difference [95% CI] 14.07 [1.65, 26.49]). Chewing gum cannot be recommended as an alternative to ondansetron for treatment of PONV in female patients administered antiemetic prophylaxis.

Clinical audit on management of Post Operative Nausea and Vomiting

Postoperative nausea and vomiting (PONV) are common complications following surgery, affecting up to 30% of patients despite advances in anaesthesia and surgical techniques. It can be distressing for patients and may lead to complications such as dehydration, electrolyte imbalances, wound dehiscence, and delayed recovery. Several factors contribute to PONV, including patient-related factors (such as age, gender, history of motion sickness, and smoking), anaesthesia-related factors (type and duration of anaesthesia, use of volatile anaesthetics, opioids, and muscle relaxants), and surgical factors (type and duration of surgery, intraoperative hypotension, and use of certain drugs like opioids and nitrous oxide). It can be determined by APFEL score which says that female sex, non-smokers, history of motion sickness and post operative use of opioids have high chances of PONV. Although PONV is a very detrimental disorder, it can last for several hours to days. Not only it depends on the anaesthetic factors it is also affected by surgical stress. PONV is said to the most important factor resulting to delayed recovery and prolonged hospital stay.

Effect of Propofol and Isoflurane on Hemodynamic changes during Spinal Surgery Under General Anesthesia

Background: Hemodynamic stability are vital requirements of up-to-date anesthesia. Both propofol and isoflurane meet these criteria though the clinical effects like postoperative nausea vomiting after administering propofol and isoflurane have been studied in various surgeries but have not been much evaluated or studied in patients undergoing major surgical procedures like spine surgeries, There’ is definite advantage of one technique over the other. Isoflurane has a low blood gas partition coefficient, which contributes to rapid induction and emergence from anaesthesia than with other volatile anesthetics in current clinical use. Propofol has been established as the intravenous agent that provides faster and smoother recovery & peri operative hemodynamic stability. Objective: To compare the effects of isoflurane and propofol regarding hemodynamic status in spinal surgery under general anaesthesia. Methods: After getting ethical approval, a randomized controlled trial study design was performed where patients were selected in the pre-anesthetic checkup room based on inclusion and exclusion criteria for those who were scheduled for spine surgeries under general anesthesia is admitted in the Department of Neurosurgery in East West Medical College from January 2023 – December 2024. A total number of 40 patients were selected. 20 patients were enrolled each in group A and group B by lottery method in a sealed envelope. They were divided into two groups by randomization; Group A and Group B. A written informed consent was taken from all selected patients. Patients were advised to fast for at least 8 hours before intervention. In Group A, anesthesia is maintained with propofol infusion, nitrous oxide (66%), and oxygen (33%) while in Group B, anesthesia is maintained with Isoflurane, nitrous oxide (66%), and oxygen (33%). All patients were given N2O in oxygen and 1.25% inspired concentration of Isoflurane (MAC -1.15). In Group A propofol infusion at rate of 80 μg/kg/min (fixed from the beginning). All data was collected at –Just after starting, 15 minutes, 30-minute, 1 hour, and >1 hour interval per operatively. Data was compiled, edited and plotted in tabular and figure form. P value was determined as significant when it was <0.05. Results: 40 patients yielded the following results. The mean age of Group A and B were 32.56±12.55 years and 34.6±12.5 years. Mean difference of heart rate was lower in Group A than that of Group B. Other parameters in both groups were confined to good and acceptable categories. But interestingly, there was a statistically significant difference found between Group A and Group B in Systolic Blood Pressure (SBP) & Diastolic Blood Pressure (DBP). The scoring was far better in Group A than Group B. Mean SBP was higher in Group B than Group A (p= >0.05). Similarly, mean DBP was also higher in Group B than Group A (p = >0.05). Conclusion: Propofol is better for maintaining hemodynamic status than Isoflurane for Spine surgery under General anaesthesia. EWMCJ Vol. 12, No. 1&2, January-July 2024: 21-26

Subunit-specific mechanisms of isoflurane-induced acute tonic inhibition in dentate gyrus granule neuron.

Prolonged exposure to volatile anesthetics may raise the risk of developing cognitive impairment by acting on gamma-a Aminobutyric acid A receptors (GABAAR). The dentate gyrus plays an important role in the hippocampus and has a high potential for neural plasticity. However, it is unknown whether prolonged anesthesia induces a change in acute phasic or tonic inhibition in dentate gyrus granule cells (DGGCs) by acting on GABAAR. In order to verify the effects of volatile anesthetics on the current in DGGCs, a whole-cell patch was applied to record acute brain slices, and this study indicated that 4h but not 2h of isoflurane (ISO) exposure induced significantly larger tonic currents in DGGCs other than hippocampal CA1 pyramidal and thalamic relay neurons. Furthermore, this study demonstrated that the increased tonic current in DGGCs was dependent on the δ subunit-containing GABAARs by using transgenic δ subunit knockout mice. In conclusion, the δ subunit specific GABAAR is the key element that increased acute tonic inhibition in DGGCs of mice after prolonged ISO exposure, which may be one of the mechanisms of ISO neurotoxicity to the developing brain.

Structural identification of the RY12 domain of RyR1 as an ADP sensor and the target of the malignant hyperthermia therapeutic dantrolene.

Malignant hyperthermia (MH) is a life-threatening pharmacogenetic condition triggered by volatile anesthetics, which activate pathogenic RyR1 mutants. The small molecule therapeutic dantrolene has long been used to treat MH. However, the binding site and mechanism of dantrolene remain unclear. Here, we present cryo-EM structures of RyR1 bound to dantrolene and the MH trigger agent 4-chloro-m-cresol (4CmC), revealing the dantrolene and 4CmC binding sites in atomic detail. Dantrolene binds stacked with ATP or ADP in the RY12 domain at the corner of the receptor, inducing a conformational change in this domain which is allosterically coupled to pore closure. Functional analyses revealed that ATP or ADP was required for dantrolene inhibition, and a single point mutation that disrupts the peripheral ATP binding site abolished ATP/ADP-dependent dantrolene inhibition. Strikingly, in the absence of dantrolene, this site selectively binds two ADP molecules, suggesting a possible role in ATP/ADP ratio sensing.

Adiponectin deficiency is a critical factor contributing to cognitive dysfunction in obese mice after sevoflurane exposure

BackgroundThe number of major operations performed in obese patients is expected to increase given the growing prevalence of obesity. Obesity is a risk factor for a range of postoperative complications including perioperative neurocognitive disorders. However, the mechanisms underlying this vulnerability are not well defined. We hypothesize that obese subjects are more vulnerable to general anaesthesia induced neurotoxicity due to reduced levels of adiponectin. This hypothesis was tested using a murine surgical model in obese and adiponectin knockout mice exposed to the volatile anaesthetic agent sevoflurane.MethodsObese mice were bred by subjecting C57BL/6 mice to a high fat diet. Cognitive function, neuroinflammatory responses and neuronal degeneration were assessed in both obese and lean mice following exposure to 2 h of sevoflurane to confirm sevoflurane-induced neurotoxicity. Thereafter, to confirm the role of adiponectin deficiency in, adiponectin knockout mice were established and exposed to the sevoflurane. Finally, the neuroprotective effects of adiponectin receptor agonist (AdipoRon) were examined.ResultsSevoflurane triggered significant cognitive dysfunction, neuroinflammatory responses and neuronal degeneration in the obese mice while no significant impact was observed in the lean mice. Similar cognitive dysfunction and neuronal degeneration were also observed in the adiponectin knockout mice after sevoflurane exposure. Administration of AdipoRon partially prevented the deleterious effects of sevoflurane in both obese and adiponectin knockout mice.ConclusionsOur findings demonstrate that obese mice are more susceptible to sevoflurane-induced neurotoxicity and cognitive impairment in which adiponectin deficiency is one of the underlying mechanisms. Treatment with adiponectin receptor agonist ameliorates this vulnerability. These findings may have therapeutic implications in reducing the incidence of anaesthesia related neurotoxicity in obese subjects.

A comparative study between dexmedetomidine versus magnesium sulphate for controlled hypotensive anesthesia in rhinoplasty surgeries

Background: Rhinoplasty, a widely performed surgical procedure globally, necessitates hypotensive anesthesia to minimize bleeding, which can otherwise compromise surgical outcomes. Controlled hypotension anesthesia enhances the bloodless surgical area, reduces postoperative edema and ecchymosis, and can shorten the duration of the procedure. Many drugs have been used to attain hypotensive anesthesia, including magnesium sulfate, volatile anesthetics, and beta-adrenergic blocking agents. We compared dexmedetomidine with magnesium sulfate for producing hypotensive anesthesia in patients undergoing rhinoplasty. Methodology: We included 42 patients, aged 18-60 y, undergoing rhinoplasty and allocated into Group D and Group M. Group D received dexmedetomidine 1 µg/kg diluted in 50 mL of normal saline, administered IV over 10 min prior to anesthesia. Group M received magnesium sulfate 40 µg/kg diluted as infusion. Both groups received continued infusions afterwards. General anesthesia was induced with propofol and atracurium, intubation done and maintained on sevoflurane in N2O and O2. Vital signs were monitored continuously. The efficacy of hypotensive anesthesia was assessed, along with the recording of postoperative complications and the surgeons’ satisfaction. Results: Group D and Group M showed no significant variation in mean arterial pressure. However, significant variation was observed in heart rate (P < 0.05). Group D had better operating area score compared to Group M. Surgeons; satisfaction was notably elevated in the Group D than in the Group M (P < 0.05). Opioids needed were significantly less in the Group D in contrast to the Group M. The amount of atropine needed was higher in the Group D than in the Group M (P < 0.05). Conclusion: Dexmedetomidine proved to be better than magnesium sulfate in achieving hypotensive anesthesia together with providing optimal surgical field conditions. Although magnesium sulfate necessitated additional nitroglycerine, dexmedetomidine increased the risk of bradycardia but reduced the analgesic requirements compared to magnesium sulfate. These factors are crucial when considering the use of dexmedetomidine in rhinoplasty surgery. Trial Registry: PACTR202408620568675. Keywords: hypotensive anesthesia; magnesium sulphate; dexmedetomidine Citation: Abd Elhalem SAA, Ahmed Abd ElAala El-Shawarby AE, Hakim KYK, Abdel Rahman YA, Khalifa AAG. A comparative study between dexmedetomidine versus magnesium sulphate for controlled hypotensive anesthesia in rhinoplasty surgeries. Anaesth. pain intensive care 2024;28(5):894−900; DOI: 10.35975/apic.v28i5.2537 Received: August 21, 2024; Reviewed: September 6, 2024; Accepted: September 9, 2024

OXY-SCORE and Volatile Anesthetics: A New Perspective of Oxidative Stress in EndoVascular Aneurysm Repair-A Randomized Clinical Trial.

An aortic aneurysm (AA) is a life-threatening condition. Oxidative stress may be a common pathway linking multiple mechanisms of an AA, including vascular inflammation and metalloproteinase activity. Endovascular aneurysm repair (EVAR) is the preferred surgical approach for AA treatment. During surgery, inflammation and ischemia-reperfusion injury occur, and reactive oxygen species (ROS) play a key role in their modulation. Increased perioperative oxidative stress is associated with higher postoperative complications. The use of volatile anesthetics during surgery has been shown to reduce oxidative stress. Individual biomarkers only partially reflect the oxidative status of the patients. A global indicator of oxidative stress (OXY-SCORE) has been validated in various pathologies. This study aimed to compare the effects of the main volatile anesthetics, sevoflurane and desflurane, on oxidative status during EVAR. Eighty consecutive patients undergoing EVAR were randomized into two groups: sevoflurane and desflurane. Plasma biomarkers of oxidative damage (protein carbonylation and malondialdehyde) and antioxidant defense (total thiols, glutathione, nitrates, superoxide dismutase, and catalase activity) were measured before surgery and 24 h after EVAR. The analysis of individual biomarkers showed no significant differences between the groups. However, the OXY-SCORE was positive in the desflurane group (indicating a shift towards antioxidants) and negative in the sevoflurane group (favoring oxidants) (p < 0.044). Compared to sevoflurane, desflurane had a positive effect on oxidative stress during EVAR. The OXY-SCORE could provide a more comprehensive perspective on oxidative stress in this patient population.

Desflurane Versus Sevoflurane and Postoperative Cardiac Biomarkers in Older Adults Undergoing Low- to Moderate-Risk Noncardiac Surgery-Secondary Analysis of a Prospective, Observer-Blinded, Randomized Clinical Trial.

Background/Objectives: Previous preclinical studies have shown that desflurane might have the most significant cardioprotective effect of all volatile anesthetics. However, data regarding the cardioprotective effects of desflurane versus sevoflurane are lacking. Therefore, we evaluated the effect of the maintenance of anesthesia using desflurane versus sevoflurane on the postoperative maximum concentrations of cardiac biomarkers in older adults undergoing low- to moderate-risk noncardiac surgery. Methods: In this secondary analysis of a prospective randomized trial, we included all 190 older adults undergoing low- to moderate-risk noncardiac surgery. Patients were randomized to receive desflurane or sevoflurane for the maintenance of anesthesia. We administered desflurane or sevoflurane, aiming at a BIS value of 50 ± 5. The cardiac-specific biomarkers included troponin T, NT-proBNP, and copeptin, which were measured preoperatively, within one hour after surgery, and on the second postoperative day. Results: There were no significant differences between the desflurane and sevoflurane groups in the postoperative maximum concentrations of troponin T (11 ng.L-1 [8; 16] versus 13 ng.L-1 [9; 18]; p = 0.595), NT-proBNP (196 pg.mL-1 [90; 686] versus 253 pg.mL-1 [134; 499]; p = 0.288), or copeptin (19 pmol.L-1 [7; 58] versus 12 pmol.L-1 [6; 41]; p = 0.096). We also observed no significant differences in the troponin T, NT-proBNP, or copeptin concentrations between the desflurane and sevoflurane groups at any measured timepoint (all p > 0.05). Conclusions: In contrast to preclinical studies, we did not observe a significant difference in the postoperative maximum concentrations of cardiac biomarkers. It seems likely that desflurane does not exert significant clinical meaningful cardioprotective effects in older adults. Thus, our results do not support the use of desflurane in patients undergoing low- to moderate-risk noncardiac surgery.

Comparative Electroencephalographic Profile of a New Anesthetic and Anticonvulsant That Is Selective for the GABAAR Slow Receptor Subtype.

Anesthetics like propofol increase electroencephalography (EEG) power in delta frequencies (0.1-4 Hz), with a decrease of power in bandwidths >30 Hz. Propofol is nonselective for gamma amino butyric acid type A receptor subtypes (GABAAR) as it enhances all 3 GABAAR subtypes (slow, fast, and tonic). Our newly developed anesthetic class selectively targets GABAAR-slow synapses to depress brain responsiveness. We hypothesized that a selective GABAAR-slow agonist, KSEB 01-S2, would produce a different EEG signature compared to the broad-spectrum GABAAR agonist (propofol), and tested this using rat EEG recordings. Male rats were studied after Institutional Animal Care and Use Committees (IACUC) approval from the US Army Medical Research Institute of Chemical Defense and the University of Michigan. Rats were anesthetized using isoflurane (3%-5% induction, 1%-3% maintenance) with oxygen at 0.5 to 1.0 L/min. Stainless steel screws were placed in the skull and used to record subcranial cortical EEG signals. After recovery, either propofol or KSEB 01-S2 was administered and effects on EEG signals were analyzed. As previously reported, propofol produced increased power in delta frequencies (0.1-4 Hz) compared to predrug recordings and produced a decrease in EEG power >30 Hz but no significant changes were seen within ±20 seconds of losing the righting reflex. By contrast, KSEB 01-S2 produced a significant increase in theta frequency percent power (median 14.7%, 16.2/13.8, 75/25 confidence interval; to 34.7%, 35/31.8; P < .015) and a significant decrease in low gamma frequency percent power (16.9%, 18.6/15.8; to 5.45%, 5.5/5.39; P < .015) for all rats at ± 20 seconds of loss of consciousness (LOC). Both anesthetics produced a flattening of chaotic attractor plots from nonlinear dynamic analyses, like that produced by volatile and dissociative anesthetics at LOC. KSEB 01-S2 produced a markedly different EEG pattern, with a selective increase observed in the theta frequency range. KSEB 01-S2 also differs markedly in its activity at the GABAAR-slow receptor subtype, suggesting a possible mechanistic link between receptor subtype specificity and EEG frequency band signatures. Increased theta together with depressed gamma frequencies is interesting because GABAAR slow synapses have previously been suggested to underlie theta frequency oscillations, while fast synapses control gamma activity. These reciprocal effects support a previous model for theta and nested gamma oscillations based on inhibitory connections between GABAAR fast and slow interneurons. Although each anesthetic produced a unique EEG response, propofol and KSEB 01-S2 both increased slow wave activity and flattened chaotic attractor plots at the point of LOC.

Towards sustainability of volatile anaesthetics: capture and beyond

Towards sustainability of volatile anaesthetics: capture and beyond

INhaled Sedation versus Propofol in REspiratory failure in the Intensive Care Unit (INSPiRE-ICU1): protocol for a randomised, controlled trial

IntroductionSedation in mechanically ventilated adults in the intensive care unit (ICU) is commonly achieved with intravenous infusions of propofol, dexmedetomidine or benzodiazepines. Significant limitations associated with each can impact their...

Links between mutations in functionally separate arms of mitochondrial complex I and responses to volatile anesthetics.

Individuals with mitochondrial defects, especially those in Complex I of the electron transport chain, exhibit behavioral hypersensitivity and toxicity to volatile anesthetics. In Drosophila melanogaster, mutation of ND23 (NDUFS8 in mammals), which encodes a subunit of the matrix arm of Complex I, sensitizes flies to toxicity from isoflurane but not an equipotent dose of sevoflurane. Also, in ND23 flies, both anesthetics activate expression of stress response genes, but to different extents. Here, we investigated the generality of these findings by examining flies mutant for ND2 (ND2 in mammals), which encodes a subunit of the membrane arm of Complex I. The serial anesthesia array was used to expose ND2del1 and ND2360114 flies to precise doses of isoflurane, sevoflurane, and oxygen. Behavioral sensitivity was assessed by a climbing assay and toxicity by percent mortality within 24 h of exposure. Changes in expression were determined by qRT-PCR of RNA isolated from heads at 0.5 h after anesthetic exposure. Unlike ND2360114, ND2del1 did not affect behavioral sensitivity to isoflurane or sevoflurane. Furthermore, sevoflurane in hyperoxia as well as anoxia caused mortality of ND2del1 but not ND2360114 flies. Finally, the mutations had different effects on induction of stress response gene expression by the anesthetics. Mutations in different arms of Complex I resulted in different behavioral sensitivities and toxicities to isoflurane and sevoflurane, indicating that (i) the anesthetics have mechanisms of action that involve arms of Complex I to different extents and (ii) the lack of behavioral hypersensitivity does not preclude susceptibility to anesthetic toxicity.

Diethyl ether anaesthesia does not block local touch response in Arabidopsis thaliana

Plants can sense and respond to non-damaging mechanical stimulation such as touch, rain, or wind. Mechanical stimulation induces an increase of cytosolic calcium ([Ca2+]cyt), accumulation of phytohormones from the group of jasmonates (JAs) and activation of gene expression, which can be JAs-dependent or JAs-independent. Response to touch shares similar properties with reactions to stresses such as wounding or pathogen attack, and regular mechanical stimulation leads to changes in growth and development called thigmomorphogenesis. Previous studies showed that well-known seismonastic plants such as Venus flytrap (Dionaea muscipula) or sensitive plant (Mimosa pudica) lost their touch-induced motive responses during exposure to general volatile anaesthetic (GVA) diethyl ether. Here, we investigated the effect of diethyl ether anaesthesia on touch response in Arabidopsis thaliana. We monitored [Ca2+]cyt level, accumulation of JAs and expression of touch-responsive genes. Our results showed that none of the investigated responses was affected by diethyl ether. However, diethyl ether alone increased [Ca2+]cyt and modulated JAs-independent touch-responsive genes, thus partially activating touch response non-specifically. Together with our previous studies, we concluded that GVA diethyl ether cannot block the local rise of [Ca2+]cyt but only its systemic propagation dependent on GLUTAMATE LIKE RECEPTOR 3s (GLR3s) channels.

Isoflurane Titration Improves Detection of Hippocampal Lactate by 1H-MRS

Abstract Lactate has increasingly been recognized as both an important fuel source and signaling molecule within the brain. Alterations in brain lactate levels are associated with various neurological diseases. Thus, there is great interest in the in vivo detection and measurement of cerebral lactate levels in animals used for investigation of normal brain function and models of disease. Proton magnetic resonance spectroscopy (1H-MRS) is a non-invasive technique used to measure lactate and other metabolites within the brain. However, lactate can be difficult to detect with conventional 1H-MRS due to its low abundance and spectral overlap with lipids. In addition, volatile anesthetics used during image acquisition increase lactate production, potentially masking any subtle physiological changes in lactate levels. Here we made use of a transgenic mouse model in which expression of lactate dehydrogenase A (Ldha), the rate-limiting enzyme of lactate production, was induced within cortical and hippocampal neurons. Unexpectedly, 1H-MRS analysis under typical isoflurane-induced anesthesia of 4% induction followed by 1.6-2% maintenance, revealed no significant elevation of hippocampal lactate levels in neuronal Ldha induction mice compared to control mice. In contrast, 1H-MRS analysis using an isoflurane titration protocol in which mice were sequentially exposed to 1.6%, 2%, then finally 3% isoflurane, revealed significantly higher hippocampal lactate levels in Ldha transgenic mice compared to controls. In addition, significantly fewer mice were required to detect differences in lactate levels using the isoflurane titration protocol compared to conventional isoflurane-induced anesthesia. Our findings highlight the importance of controlling for the effects of anesthesia when detecting changes in hippocampal lactate levels in vivo and offer a novel protocol for enhanced cerebral lactate detection.

You Don't Always Get What You Want!

Mutations in several genes of Caenorhabditis elegans confer altered sensitivities to volatile anesthetics. A mutation in one gene, gas-1(fc21), causes animals to be immobilized at lower concentrations of all volatile anesthetics than in the wild type, and it does not depend on mutations in other genes to control anesthetic sensitivity. gas-1 confers different sensitivities to stereoisomers of isoflurane, and thus may be a direct target for volatile anesthetics. The authors have cloned and characterized the gas gene and the mutant allele fc21. Genetic techniques for nematodes were as previously described. Polymerase chain reaction, sequencing, and other molecular biology techniques were performed by standard methods. Mutant rescue was done by injecting DNA fragments into the gonad of mutant animals and scoring the offspring for loss of the mutant phenotype. The gas-1 gene was cloned and identified. The protein GAS-1 is a homologue of the 49-kd (IP) subunit of the mitochondrial NADH-ubiquinone-oxidoreductase (complex I of the respiratory chain). gas-1(fc21) is a missense mutation replacing a strictly conserved arginine with lysine. The function of the 49-kd (IP) subunit of complex I is unknown. The finding that mutations in complex I increase sensitivity of C. elegans to volatile anesthetics may implicate this physiologic process in the determination of anesthetic sensitivity. The hypersensitivity of animals with a mutation in the gas-1 gene may be caused by a direct anesthetic effect on a mitochondrial protein or secondary effects at other sites caused by mitochondrial dysfunction.

Estimation of carbon emissions associated with tibial plateau levelling osteotomies in 10 dogs

ObjectiveTo describe a method of estimating the carbon emissions resulting from 10 clinical canine surgical procedures. Study designProspective observational cohort study. AnimalsA total of 10 adult client-owned dogs presenting to two private referral centres in the UK for tibial plateau levelling osteotomy (TPLO) using either isoflurane or sevoflurane for maintenance of anaesthesia. MethodsSingle-use consumables, pharmaceuticals and waste streams were recorded. Volatile anaesthetic use was calculated based on fresh gas flow (FGF) and vaporizer setting. Travel of owners and staff involved in the procedure was recorded (the latter adjusted by procedure length relative to working day). Energy use was calculated based on the clinic’s monthly usage adjusted for floor area of rooms used. Overnight hospitalisation, kennelling consumables and a revisit for postoperative radiography were excluded. Carbon accounting was performed using published carbon conversion factors (‘bottom-up analysis’) if available, or conversion factors based on cost (‘top-down’). Data are presented as median (range) and totals per emission category. ResultsCarbon emissions from all cases amounted to 667.2 kgCO2e. In these two clinics, median carbon emissions from a canine TPLO were 63.5 (47.6–93) kgCO2e, which is equivalent to driving 372 km (231 miles) in an average UK passenger car. Travel accounted for 30.1% of carbon emissions. Volatile anaesthetics accounted for 21.4% of carbon emissions, with other pharmaceuticals accounting for 24.0%. Consumables, building energy and waste disposal accounted for 19.7%, 3.9% and 0.9% of carbon emissions, respectively. Conclusionsand clinical relevanceand clinical relevance Likely carbon hotspots for canine orthopaedic procedures include travel and pharmaceuticals, particularly volatile anaesthetic agents. Carbon reductions should focus on reducing travel emissions, streamlining pharmaceutical use and lower-carbon anaesthetic techniques. Future research should focus on improving carbon accounting methodology and widening the range of cases assessed.