Sevoflurane and Isoflurane—Pharmacokinetics, Hemodynamic Stability, and Cardioprotective Effects During Cardiopulmonary Bypass

Sedation with propofol and isoflurane differs in terms of microcirculatory parameters: A randomized animal study using dorsal skinfold chamber mouse model

OBJECTIVE

This study aimed to explore the effects of sedative doses of propofol and isoflurane on microcirculation in septic mice compared to controls. Isoflurane, known for its potential as a sedation drug in bedside applications, lacks clarity regarding its impact on the microcirculation system. The hypothesis was that propofol would exert a more pronounced influence on the microvascular flow index, particularly amplified in septic conditions.

MATERIAL AND METHODS

Randomized study was conducted from December 2020 to October 2021 involved 60 BALB/c mice, with 52 mice analyzed. Dorsal skinfold chambers were implanted, followed by intraperitoneal injections of either sterile 0.9 % saline or lipopolysaccharide for the control and sepsis groups, respectively. Both groups received propofol or isoflurane treatment for 120 min. Microcirculatory parameters were obtained via incident dark-field microscopy videos, along with the mean blood pressure and heart rate at three time points: before sedation (T0), 30 min after sedation (T30), and 120 min after sedation (T120). Endothelial glycocalyx thickness and syndecan-1 concentration were also analyzed.

RESULTS

In healthy controls, both anesthetics reduced blood pressure. However, propofol maintained microvascular flow, differing significantly from isoflurane at T120 (propofol, 2.8 ± 0.3 vs. isoflurane, 1.6 ± 0.9; P < 0.001). In the sepsis group, a similar pattern occurred at T120 without statistical significance (propofol, 1.8 ± 1.1 vs. isoflurane, 1.2 ± 0.7; P = 0.023). Syndecan-1 levels did not differ between agents, but glycocalyx thickness index was significantly lower in the isoflurane-sepsis group than propofol (P = 0.001).

CONCLUSIONS

Propofol potentially offers protective action against microvascular flow deterioration compared to isoflurane, observed in control mice. Furthermore, a lower degree of sepsis-induced glycocalyx degradation was evident with propofol compared to isoflurane.

A retrospect and outlook on the neuroprotective effects of anesthetics in the era of endovascular therapy

Studies on the neuroprotective effects of anesthetics were carried out more than half a century ago. Subsequently, many cell and animal experiments attempted to verify the findings. However, in clinical trials, the neuroprotective effects of anesthetics were not observed. These contradictory results suggest a mismatch between basic research and clinical trials. The Stroke Therapy Academic Industry Roundtable X (STAIR) proposed that the emergence of endovascular thrombectomy (EVT) would provide a proper platform to verify the neuroprotective effects of anesthetics because the haemodynamics of patients undergoing EVT is very close to the ischaemia–reperfusion model in basic research. With the widespread use of EVT, it is necessary for us to re-examine the neuroprotective effects of anesthetics to guide the use of anesthetics during EVT because the choice of anesthesia is still based on team experience without definite guidelines. In this paper, we describe the research status of anesthesia in EVT and summarize the neuroprotective mechanisms of some anesthetics. Then, we focus on the contradictory results between clinical trials and basic research and discuss the causes. Finally, we provide an outlook on the neuroprotective effects of anesthetics in the era of endovascular therapy.

High-Sensitivity Cardiac Troponin I and T Kinetics Differ following Coronary Bypass Surgery: A Systematic Review and Meta-Analysis

Background

Cardiac troponin I and T are both used for diagnosing myocardial infarction (MI) after coronary artery bypass grafting (CABG), also known as type 5 MI (MI-5). Different MI-5 definitions have been formulated, using multiples of the 99th percentile upper reference limit (10×, 35×, or 70× URL), with or without supporting evidence. These definitions are arbitrarily chosen based on conventional assays and do not differentiate between troponin I and T. We therefore investigated the kinetics of high-sensitivity cardiac troponin I (hs-cTnI) and T (hs-cTnT) following CABG.

Methods

A systematic search was applied to MEDLINE and EMBASE databases including the search terms “coronary artery bypass grafting” AND “high-sensitivity cardiac troponin.” Studies reporting hs-cTnI or hs-cTnT on at least 2 different time points were included. Troponin concentrations were extracted and normalized to the assay-specific URL.

Results

For hs-cTnI and hs-cTnT, 17 (n = 1661 patients) and 15 studies (n = 2646 patients) were included, respectively. Preoperative hs-cTnI was 6.1× URL (95% confidence intervals: 4.9–7.2) and hs-cTnT 1.2× URL (0.9–1.4). Mean peak was reached 6–8 h postoperatively (126× URL, 99–153 and 45× URL, 29–61, respectively). Subanalysis of hs-cTnI illustrated assay-specific peak heights and kinetics, while subanalysis of surgical strategies revealed 3-fold higher hs-cTnI than hs-cTnT for on-pump CABG and 5-fold for off-pump CABG.

Conclusion

Postoperative hs-cTnI and hs-cTnT following CABG surpass most current diagnostic cutoff values. hs-cTnI was almost 3-fold higher than hs-cTnT, and appeared to be highly dependent on the assay used and surgical strategy. There is a need for assay-specific hs-cTnI and hs-cTnT cutoff values for accurate, timely identification of MI-5.

Meta-Analysis Evaluating High-Sensitivity Cardiac Troponin T Kinetics after Coronary Artery Bypass Grafting in Relation to the Current Definitions of Myocardial Infarction

Various definitions of myocardial infarction type 5 after coronary artery bypass grafting (CABG) have been proposed (myocardial infarction [MI-5], also known as peri-procedural MI), using different biomarkers and different and arbitrary cut-off values. This meta-analysis aims to determine the expected release of high-sensitivity cardiac troponin T (hs-cTnT) after CABG in general and after uncomplicated surgery and off-pump CABG in particular. A systematic search was applied to 3 databases. Studies on CABG as a single intervention and reporting on postoperative hs-cTnT concentrations on at least 2 different time points were included. All data on hs-cTnT concentrations were extracted, and mean concentrations at various points in time were stratified. Eventually, 15 studies were included, encompassing 2,646 patients. Preoperative hs-cTnT was 17 ng/L (95% confidence interval [CI] 13 to 20 ng/L). Hs-cTnT peaked at 6 to 8 hours postoperatively (628 ng/L, 95% CI 400 to 856 ng/L; 45x upper reference limit [URL]) and was still increased after 48 hours. In addition, peak hs-cTnT concentration was 614 ng/L (95% CI 282 to 947 ng/L) in patients with a definite uncomplicated postoperative course (i.e., without MI). For patients after off-pump CABG compared to on-pump CABG, the mean peak hs-cTnT concentration was 186 ng/L (95% CI 172 to 200 ng/L, 13 × URL) versus 629 ng/L (95% CI 529 to 726 ng/L, 45 × URL), respectively. In conclusion, postoperative hs-cTnT concentrations surpass most of the currently defined cut-off values for MI-5, even in perceived uncomplicated surgery, suggesting thorough reassessment. Hs-cTnT release differences following on-pump CABG versus off-pump CABG were observed, implying the need for different cut-off values for different surgical strategies.

Inased (inhaled sedation in ICU) trial protocol: a multicentre randomised open-label trial

INTRODUCTION

The use of sedation in intensive care units (ICUs) is necessary and ubiquitous. The impact of sedation strategy on outcome, particularly when delivered early after initiation of mechanical ventilation, is unknown. Evidence is increasing that volatile anaesthetic agents could be associated with better outcome. Their use in delirium prevention is unknown.

METHODS AND ANALYSIS

This study is an investigator-initiated, prospective, multicentre, two-arm, randomised, control, open-trial comparing inhaled sedation strategy versus intravenous sedation strategy in mechanically ventilated patients in ICU. Two hundred and fifty patients will be randomly assigned to the intravenous sedation group or inhaled sedation group, with a 1:1 ratio in two groups according to the sedation strategy. The primary outcome is the occurrence of delirium assessed using two times a day confusion assessment method for the ICU (CAM-ICU). Secondary outcomes include cognitive and functional outcomes at 3 and 12 months.

ETHICS AND DISSEMINATION

The study has been approved by the Regional Ethics Committee (CPP Ouest) and national authorities (ANSM). The results will be submitted for publication in peer-reviewed journals.

TRIAL REGISTRATION NUMBER

NCT04341350.

Cardioprotective Effect of Anesthetics: Translating Science to Practice

Cardiovascular diseases are the number one cause of mortality in the world, particularly among the aging population. Major adverse cardiac events are also a major contributor to perioperative complications, affecting 2.6% of noncardiac surgeries and up to 18% of cardiac surgeries. Cardioprotective effects of volatile anesthetics and certain intravenous anesthetics have been well-documented in preclinical studies; however, their clinical application has yielded conflicting results in terms of their efficacy. Therefore, better understanding of the underlying mechanisms and developing effective ways to translate these insights into clinical practice remain significant challenges and unmet needs in the area. Several recent reviews have focused on mechanistic dissection of anesthetic-mediated cardioprotection. The present review focuses on recent clinical trials investigating the cardioprotective effects of anesthetics in the past five years. In addition to highlighting the main outcomes of these trials, the authors provide their perspectives about the current gap in the field and potential directions for future investigations.

Sevoflurane‑induced neurotoxicity is driven by OXR1 post‑transcriptional downregulation involving hsa‑miR‑302e

Sevoflurane is a common anesthetic agent used in surgical settings and previous studies have indicated that it exerts a neurotoxic effect. However, the molecular mechanism underlying this side effect is unknown. In addition, the human microRNA‑302 (hsa‑miR‑302) family members have been reported to be involved in neuronal cell development and biology. Thus, the present study aimed to investigate the potential implication of hsa‑miR‑302e in the sevoflurane‑induced cytotoxicity on human hippocampal cells (HN‑h). HN‑h cells were transfected with hsa‑miR‑302e mimic, hsa‑miR‑302e inhibitor or negative controls and subsequently exposed to different concentrations of sevoflurane. An MTT assay was used to assess the cytotoxicity of sevoflurane on HN‑h cells. Cell apoptosis was determined by flow cytometry. The levels of lactate dehydrogenase release, reactive oxygen species, lipid peroxidation and intracellular calcium (Ca2+) were additionally detected. Reverse transcription‑quantitative polymerase chain reaction and western blotting were conducted to determine mRNA and protein expression, respectively. A luciferase assay was performed for validating the targeting of OXR1 by hsa‑miR‑302e. The results indicated that sevoflurane induced a decrease in cell viability, malondialdehyde and reactive oxygen species production, lactate dehydrogenase release, intracellular Ca2+ production, calcium/calmodulin‑dependent protein kinase II phosphorylation and apoptosis. In addition, treatment with sevoflurane induced the expression of hsa‑miR‑302e while the expression of its target, oxidation resistance gene 1 (OXR1), was significantly downregulated. Inhibition of hsa‑miR‑302e expression protected neuronal cells from sevoflurane cytotoxicity. Mechanistic studies demonstrated that OXR1 was a direct target of hsa‑miR‑302e. Furthermore, the overexpression of OXR1 abolished the effect of sevoflurane on neuronal cells. The results of the present study indicated that sevoflurane exerts its neurotoxic effect by regulating the hsa‑miR‑302e/OXR1 axis. Therefore, the manipulation of the hsa‑miR‑302e/OXR1 pathway will be useful for preventing sevoflurane‑induced neurotoxicity.

Failure of Isoflurane Cardiac Preconditioning in Obese Type 2 Diabetic Mice Involves Aberrant Regulation of MicroRNA-21, Endothelial Nitric-oxide Synthase, and Mitochondrial Complex I

BACKGROUND

Diabetes impairs the cardioprotective effect of volatile anesthetics, yet the mechanisms are still murky. We examined the regulatory effect of isoflurane on microRNA-21, endothelial nitric-oxide synthase, and mitochondrial respiratory complex I in type 2 diabetic mice.

METHODS

Myocardial ischemia/reperfusion injury was produced in obese type 2 diabetic (db/db) and C57BL/6 control mice ex vivo in the presence or absence of isoflurane administered before ischemia. Cardiac microRNA-21 was quantified by real-time quantitative reverse transcriptional-polymerase chain reaction. The dimers and monomers of endothelial nitric-oxide synthase were measured by Western blot analysis. Mitochondrial nicotinamide adenine dinucleotide fluorescence was determined in Langendorff-perfused hearts.

RESULTS

Body weight and fasting blood glucose were greater in db/db than C57BL/6 mice. Isoflurane decreased left ventricular end-diastolic pressure from 35 ± 8 mmHg in control to 23 ± 9 mmHg (P = 0.019, n = 8 mice/group, mean ± SD) and elevated ±dP/dt 2 h after post-ischemic reperfusion in C57BL/6 mice. These beneficial effects of isoflurane were lost in db/db mice. Isoflurane elevated microRNA-21 and the ratio of endothelial nitric-oxide synthase dimers/monomers and decreased mitochondrial nicotinamide adenine dinucleotide levels 5 min after ischemia in C57BL/6 but not db/db mice. MicroRNA-21 knockout blocked these favorable effects of isoflurane, whereas endothelial nitric-oxide synthase knockout had no effect on the expression of microRNA-21 but blocked the inhibitory effect of isoflurane preconditioning on nicotinamide adenine dinucleotide.

CONCLUSIONS

Failure of isoflurane cardiac preconditioning in obese type 2 diabetic db/db mice is associated with aberrant regulation of microRNA-21, endothelial nitric-oxide synthase, and mitochondrial respiratory complex I.

The Impact of Volatile Anesthetic Choice on Postoperative Outcomes of Cardiac Surgery: A Meta-Analysis

OBJECTIVES

To evaluate the impact of volatile anesthetic choice on clinically relevant outcomes of patients undergoing cardiac surgery.

METHODS

Major databases were systematically searched for randomized controlled trials (RCTs) comparing volatile anesthetics (isoflurane versus sevoflurane) in cardiac surgery. Study-level characteristics, intraoperative events, and postoperative outcomes were extracted from the articles.

RESULTS

Sixteen RCTs involving 961 patients were included in this meta-analysis. There were no significant differences between both anesthetics in terms of intensive care unit length of stay (SMD -0.07, 95% CI -0.38 to 0.24, P = 0.66), hospital length of stay (SMD 0.06, 95% CI -0.33 to 0.45, P = 0.76), time to extubation (SMD 0.29, 95% CI -0.08 to 0.65, P = 0.12), S100β (at the end of surgery: SMD 0.08, 95% CI -0.33 to 0.49, P = 0.71; 24 hours after surgery: SMD 0.21, 95% CI -0.23 to 0.65, P = 0.34), or troponin (at the end of surgery: SMD -1.13, 95% CI -2.39 to 0.13, P = 0.08; 24 hours after surgery: SMD 0.74, 95% CI -0.15 to 1.62, P = 0.10). CK-MB was shown to be significantly increased when using isoflurane instead of sevoflurane (SMD 2.16, 95% CI 0.57 to 3.74, P = 0.008).

CONCLUSIONS

The volatile anesthetic choice has no significant impact on postoperative outcomes of patients undergoing cardiac surgery.

Cobalt Chloride Upregulates Impaired HIF-1α Expression to Restore Sevoflurane Post-conditioning-Dependent Myocardial Protection in Diabetic Rats

Previous studies from our group have demonstrated that sevoflurane post-conditioning (SPC) protects against myocardial ischemia reperfusion injury via elevating the intranuclear expression of hypoxia inducible factor-1 alpha (HIF-1α). However, diabetic SPC is associated with decreased myocardial protection and disruption of the HIF-1 signaling pathway. Previous studies have demonstrated that cobalt chloride (CoCl₂) can upregulate HIF-1α expression under diabetic conditions, but whether myocardial protection by SPC can be restored afterward remains unclear. We established a rat model of type 2 diabetes and a Langendorff isolated heart model of ischemia-reperfusion injury. Prior to reperfusion, 2.4% sevoflurane was used as a post-conditioning treatment. The diabetic rats were treated with CoCl₂ 24 h before the experiment. At the end of reperfusion, tests were performed to assess myocardial function, infarct size, mitochondrial morphology, nitric oxide (NO), Mitochondrial reactive oxygen species (ROS), mitochondrial respiratory function and enzyme activity, HIF-1α, vascular endothelial growth factor (VEGF) and endothelial NO synthase (eNOS) protein levels. In addition, myocardial protection by SPC was monitored after the blood glucose levels were lowered by insulin. The diabetic state was associated with deficient SPC protection and decreased HIF-1α expression. After treating the diabetic rats with CoCl₂, SPC significantly upregulated the expression of HIF-1α, VEGF and eNOS, which markedly improved cardiac function, NO, mitochondrial respiratory function, and enzyme activity and decreased the infarction areas and ROS. In addition, these effects were not influenced by blood glucose levels. This study proved that CoCl₂activates the HIF-1α signaling pathway, which restores SPC-dependent myocardial protection under diabetic conditions, and the protective effects of SPC were independent of blood glucose levels.

Feasibility of Anesthesia Maintenance With Sevoflurane During Cardiopulmonary Bypass: A Pilot Pharmacokinetics Study

OBJECTIVE

Adequate maintenance of hypnosis during anesthesia throughout surgery using sevoflurane alone was investigated. In addition, sevoflurane pharmacokinetics during cardiopulmonary bypass were analyzed.

DESIGN

This was a pilot pharmacokinetic study.

SETTING

Tertiary care university hospital.

PARTICIPANTS

The study comprised 10 patients aged between 18 and 75 years who underwent elective mitral valve surgery.

INTERVENTIONS

The end-tidal and sevoflurane plasma concentrations were measured throughout cardiac surgery procedures involving cardiopulmonary bypass. The sevoflurane plasma concentration was measured using gas chromatography. In addition, the ratio between sevoflurane alveolar concentration and inspired concentration over time (F_A/F_I) was analyzed to describe wash-in and wash-out curves.

MEASUREMENTS AND MAIN RESULTS

Hypnosis was maintained adequately throughout surgery using sevoflurane alone. The bispectral index was maintained between 40 and 60 during cardiopulmonary bypass. The end-tidal sevoflurane was significantly different before and during cardiopulmonary bypass (1.86%±0.54% v 1.30%±0.58%, respectively; p<0.001). However, the sevoflurane plasma concentration was not significantly different before and after cardiopulmonary bypass start-up (40.55 µg/mL [76.62-125.33] before cardiopulmonary bypass and 36.24 µg/mL [56.49-81-42] during cardiopulmonary bypass). This mismatch possibly can be explained by changes that occured after cardiopulmonary bypass start-up, such as reductions of body temperature (36.33°C±0.46°C v 32.98°C±2.38°C, respectively; p<0.001) and hematocrit (35.62%±3.98% v 25.5%±3.08%, respectively; p<0.001). The sevoflurane alveolar concentration varied according to sevoflurane plasma concentration and bispectral index values. No adverse events regarding sevoflurane administration during cardiopulmonary bypass were observed.

CONCLUSIONS

Sevoflurane end-tidal values were reliable indicators of adequate anesthesia during all cardiac surgery procedures involving cardiopulmonary bypass.