Volatile Anesthetic-Induced Cardiac Protection: Molecular Mechanisms, Clinical Aspects, and Interactions With Nonvolatile Agents

Heart rate variability as a predictor of intraoperative autonomic nervous system homeostasis

The aim of the proof-of-concept study is to investigate the level of concordance between the heart rate variability (HRV), the EEG-based Narcotrend Index as a surrogate marker for the depth of hypnosis, and the minimal alveolar concentration (MAC) of the inhalation anesthetic sevoflurane across the entire course of a surgical procedure. This non-blinded cross-sectional study recorded intraoperative HRV, Narcotrend Index, and MAC in 31 male patients during radical prostatectomy using the Da-Vinci robotic-assisted surgical system at Mannheim University Medical Center. The degree of concordance was calculated using repeated measures correlation with the R package (rmcorr) and presented using the rmcorr coefficient (rrm). The Narcotrend Index correlates significantly across all measures with the time-dependent parameter of HRV, the standard deviation of the means of RR intervals (SDNN) (rrm = 0.2; p < 0.001), the frequency-dependent parameters low frequency (LF) (rrm = 0.09; p = 0.04) and the low frequency/high frequency ratio (LF/HF ratio) (rrm = 0.11; p = 0.002). MAC correlated significantly negatively with the time-dependent parameter of heart rate variability, SDNN (rrm = -0.28; p < 0.001), the frequency-dependent parameter LF (rrm = -0.06; p < 0.001) and the LF/HF ratio (rrm = -0.18; p < 0.001) and the Narcotrend Index (rrm = -0.49; p < 0.001) across all measures. HRV mirrors the trend of the Narcotrend Index used to monitor depth of hypnosis and the inhibitory influence of the anesthetic sevoflurane on the autonomic nervous system. Therefore, HRV can provide essential information about the homeostasis of the autonomic nervous system during general anesthesia. DRKS00024696, March 9th, 2021.

Comparison Between the Protective Effect of Isoflurane and Propofol on Myocardium During Coronary Artery Bypass Grafting: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

OBJECTIVE

Intravenous non-volatile anaesthetics like propofol are commonly used in cardiac surgeries across several countries. Volatile anaesthetics like isoflurane may help in protecting the myocardium and minimize ischaemia-reperfusion injury. Hence, we did this review to compare the cardioprotective effect of isoflurane and propofol among patients undergoing coronary artery bypass grafting (CABG).

METHODS

We conducted a search in the databases Medical Literature Analysis and Retrieval System Online (or MEDLINE), Embase, PubMed Central®, ScienceDirect, Google Scholar, and Cochrane Library from inception until April 2021. We carried out a meta-analysis with random-effects model and reported pooled risk ratio (RR) or standardized mean difference (SMD) with 95% confidence interval (CI) depending on the type of outcome.

RESULTS

We analysed 13 studies including 808 participants. Almost all were low-quality studies. For cardiac index, the pooled SMD was 0.14 (95% CI: -0.22 to 0.50); for cardiac troponin I, pooled SMD was 0.10 (95% CI: -0.28 to 0.48). For mortality, the RR was 3.00 (95% CI: 0.32 to 28.43); for MI, pooled RR was 1.58 (95% CI: 0.59 to 4.20); and for inotropic drug use, pooled RR was 1.04 (95% CI: 0.90 to 1.21). For length of intensive care unit stay, the pooled SMD was 0.13 (95% CI: -0.29 to 0.55), while pooled SMD for mechanical ventilation time was -0.02 (95% CI: -0.54 to 0.51).

CONCLUSION

Isoflurane did not have significant cardioprotective effect compared to propofol following CABG. Hence, the anaesthetists need to check some viable alternatives to manage these patients and reduce the rate of postoperative complications.

Comparison of Volatile Anesthetics Versus Propofol on Postoperative Cognitive Function After Cardiac Surgery: A Systematic Review and Meta-analysis

OBJECTIVE

To compare the effects of volatile anesthetics and propofol on neurocognitive function after cardiac surgery.

DESIGN

A systematic review and meta-analysis of randomized controlled trials.

SETTING

A literature search of PubMed, EMBASE, CENTRAL, CINAHL, Scopus, and Web of Science databases was conducted.

PARTICIPANTS

A total of 10 randomized controlled trials comparing volatile anesthetics and propofol in cardiac surgery were included in the study.

INTERVENTIONS

The standardized mean difference and risk ratio were calculated to estimate pooled effect sizes.

MEASUREMENTS AND MAIN RESULTS

The primary outcome was the postoperative neurocognitive function score, and the secondary outcome was the incidence of delirium after cardiac surgery. The analysis did not show significant differences in postoperative neurocognitive function scores (standardized mean difference -0.06, 95% CI -0.81-0.69; p = 0.879). The incidences of delirium (risk ratio 1.10, 95% CI 0.81-1.50) between the volatile anesthetics and propofol groups were not significant (p = 0.533).

CONCLUSIONS

Unlike noncardiac surgery, there are no differences between volatile anesthetics and propofol regarding postoperative neurocognitive dysfunction after cardiac surgery.

Beneficial Effects of Halogenated Anesthetics in Cardiomyocytes: The Role of Mitochondria

In the last few years, the use of anesthetic drugs has been related to effects other than those initially related to their fundamental effect, hypnosis. Halogenated anesthetics, mainly sevoflurane, have been used as a therapeutic tool in patients undergoing cardiac surgery, thanks to the beneficial effect of the cardiac protection they generate. This effect has been described in several research studies. The mechanism by which they produce this effect has been associated with the effects generated by anesthetic preconditioning and postconditioning. The mechanisms by which these effects are induced are directly related to the modulation of oxidative stress and the cellular damage generated by the ischemia/reperfusion procedure through the overexpression of different enzymes, most of them included in the Reperfusion Injury Salvage Kinase (RISK) and the Survivor Activating Factor Enhancement (SAFE) pathways. Mitochondria is the final target of the different routes of pre- and post-anesthetic conditioning, and it is preserved from the damage generated in moments of lack of oxygen and after the recovery of the normal oxygen concentration. The final consequence of this effect has been related to better cardiac function in this type of patient, with less myocardial damage, less need for inotropic drugs to achieve normal myocardial function, and a shorter hospital stay in intensive care units. The mechanisms through which mitochondrial homeostasis is maintained and its relationship with the clinical effect are the basis of our review. From a translational perspective, we provide information regarding mitochondrial physiology and physiopathology in cardiac failure and the role of halogenated anesthetics in modulating oxidative stress and inducing myocardial conditioning.

Pharmacological Cardioprotection against Ischemia Reperfusion Injury-The Search for a Clinical Effective Therapy

Pharmacological conditioning aims to protect the heart from myocardial ischemia-reperfusion injury (IRI). Despite extensive research in this area, today, a significant gap remains between experimental findings and clinical practice. This review provides an update on recent developments in pharmacological conditioning in the experimental setting and summarizes the clinical evidence of these cardioprotective strategies in the perioperative setting. We start describing the crucial cellular processes during ischemia and reperfusion that drive acute IRI through changes in critical compounds (∆G_ATP, Na⁺, Ca²⁺, pH, glycogen, succinate, glucose-6-phosphate, mitoHKII, acylcarnitines, BH₄, and NAD⁺). These compounds all precipitate common end-effector mechanisms of IRI, such as reactive oxygen species (ROS) generation, Ca²⁺ overload, and mitochondrial permeability transition pore opening (mPTP). We further discuss novel promising interventions targeting these processes, with emphasis on cardiomyocytes and the endothelium. The limited translatability from basic research to clinical practice is likely due to the lack of comorbidities, comedications, and peri-operative treatments in preclinical animal models, employing only monotherapy/monointervention, and the use of no-flow (always in preclinical models) versus low-flow ischemia (often in humans). Future research should focus on improved matching between preclinical models and clinical reality, and on aligning multitarget therapy with optimized dosing and timing towards the human condition.

Prolonged sedation with sevoflurane in comparison to intravenous sedation in critically ill patients - A randomized controlled trial

BACKGROUND

Volatile anesthetics are used more commonly for sedation in the intensive-care-unit (ICU). However, evidence for long-term use remains low. We therefore conducted a randomized-controlled trial comparing sevoflurane with intravenous sedation with particular focus on efficacy and safety.

METHODS

In this prospective, randomized-controlled phase-IIb monocentric clinical-trial ICU patients requiring at least 48 h of sedation were randomized to receive sevoflurane (S) or propofol/midazolam (P). Sedation quality was monitored using the Richmond-Agitation-Sedation-Scale. Following termination of sedation, the time to spontaneous breathing and extubation, opioid consumption, hemodynamics, ICU and hospital length of stay (LOS) and adverse events were recorded.

RESULTS

79 patients were eligible to randomization. Sedation quality was comparable between sevoflurane (n = 39) and propofol (n = 40). However, the use of sevoflurane lead to a reduction in time to spontaneous breathing (26 min vs. 375 min, P < 0.001). Patients sedated with propofol had lower opioid requirements (remifentanil:400 μg/h vs. 500 μg/h, P = 0.007; sufentanil:40 μg/h vs. 30 μg/h, P = 0.007) while hemodynamics, LOS or the occurrence of adverse events did not differ.

CONCLUSION

ICU patients sedated with sevoflurane >48 h may return to spontaneous breathing faster, while the quality of sedation is comparable to a propofol-based sedation regime. Sevoflurane might be considered to be safe for long-term sedation in this patient population, while being non-inferior compared to propofol.

Inhalational or total intravenous anesthetic for cardiac surgery: does the debate even exist?

PURPOSE OF REVIEW

Perioperative myocardial injury related to cardiac surgery is associated with organ dysfunction and increased mortality. Volatile anesthetics (VA) have been used during cardiac surgery for decades because of their direct and indirect preconditioning and protection against ischemia-reperfusion injury. The current review provides a summary of the latest literature comparing pharmacological preconditioning and the potential benefits of using VA versus total intravenous anesthesia (TIVA) for general anesthesia to improve outcomes after cardiac surgery.

RECENT FINDINGS

Recent literature reports lower mortality and better outcomes when VA is used alone or in combination with remote ischemic preconditioning compared with groups receiving TIVA. However, inconsistent research findings over the years have led to continued debate regarding the anesthetic technique considered more favorable for cardiac surgery.

SUMMARY

Research findings regarding the use of volatile anesthetic versus TIVA for better outcomes after cardiac surgery are inconsistent. Variability in timing, duration, dosing, and type of VA as well as surgical and patient-related factors may have influenced these results. Therefore, either technique can reasonably be adopted depending on provider and institutional preference and used safely in patients undergoing cardiac surgery.

Effect of Volatile Anesthetics on Myocardial Infarction After Coronary Artery Surgery: A Post Hoc Analysis of a Randomized Trial

OBJECTIVE

To investigate the effect of volatile anesthetics on the rates of postoperative myocardial infarction (MI) and cardiac death after coronary artery bypass graft (CABG).

DESIGN

A post hoc analysis of a randomized trial.

SETTING

Cardiac surgical operating rooms.

PARTICIPANTS

Patients undergoing elective, isolated CABG.

INTERVENTIONS

Patients were randomized to receive a volatile anesthetic (desflurane, isoflurane, or sevoflurane) or total intravenous anesthesia (TIVA). The primary outcome was hemodynamically relevant MI (MI requiring high-dose inotropic support or prolonged intensive care unit stay) occurring within 48 hours from surgery. The secondary outcome was 1-year death due to cardiac causes.

MEASUREMENTS AND MAIN RESULTS

A total of 5,400 patients were enrolled between April 2014 and September 2017 (2,709 patients randomized to the volatile anesthetics group and 2,691 to TIVA). The mean age was 62 ± 8.4 years, and the median baseline ejection fraction was 57% (50-67), without differences between the 2 groups. Patients in the volatile group had a lower incidence of MI with hemodynamic complications both in the per-protocol (14 of 2,530 [0.6%] v 27 of 2,501 [1.1%] in the TIVA group; p = 0.038) and as-treated analyses (16 of 2,708 [0.6%] v 29 of 2,617 [1.1%] in the TIVA group; p = 0.039), but not in the intention-to-treat analysis (17 of 2,663 [0.6%] v 28 of 2,667 [1.0%] in the TIVA group; p = 0.10). Overall, deaths due to cardiac causes were lower in the volatile group (23 of 2,685 [0.9%] v 40 of 2,668 [1.5%] than in the TIVA group; p = 0.03).

CONCLUSIONS

An anesthetic regimen, including volatile agents, may be associated with a lower rate of postoperative MI with hemodynamic complication in patients undergoing CABG. Furthermore, it may reduce long-term cardiac mortality.

Pharmacological Conditioning of the Heart: An Update on Experimental Developments and Clinical Implications

The aim of pharmacological conditioning is to protect the heart against myocardial ischemia-reperfusion (I/R) injury and its consequences. There is extensive literature that reports a multitude of different cardioprotective signaling molecules and mechanisms in diverse experimental protocols. Several pharmacological agents have been evaluated in terms of myocardial I/R injury. While results from experimental studies are immensely encouraging, translation into the clinical setting remains unsatisfactory. This narrative review wants to focus on two aspects: (1) give a comprehensive update on new developments of pharmacological conditioning in the experimental setting concentrating on recent literature of the last two years and (2) briefly summarize clinical evidence of these cardioprotective substances in the perioperative setting highlighting their clinical implications. By directly opposing each pharmacological agent regarding its recent experimental knowledge and most important available clinical data, a clear overview is given demonstrating the remaining gap between basic research and clinical practice. Finally, future perspectives are given on how we might overcome the limited translatability in the field of pharmacological conditioning.

Volatile and Intravenous Anesthetics for Brain Protection in Cardiac Surgery: Does the Choice of Anesthesia Matter?

Postoperative neurologic complications have a significant effect on morbidity, mortality, and long-term disability in patients undergoing cardiac surgery. The etiology of brain injury in patients undergoing cardiac surgery is multifactorial and remains unclear. There are several perioperative causative factors for neurologic complications, including microembolization, hypoperfusion, and systemic inflammatory response syndrome. Despite technologic advances and the development of new anesthetic drugs, there remains a high rate of postoperative neurologic complications. Moreover, despite the strong evidence that volatile anesthesia exerts cardioprotective effects in patients undergoing cardiac surgery, the neuroprotective effects of volatile agents remain unclear. Several studies have reported an association of using volatile anesthetics with improvement of biochemical markers of brain injury and postoperative neurocognitive function. However, there is a need for additional studies to define the optimal anesthetic drug for protecting the brain in patients undergoing cardiac surgery.

[Perioperative cardioprotection - From bench to bedside : Current experimental evidence and possible reasons for the limited translation into the clinical setting]

Hintergrund

Ziel der perioperativen Kardioprotektion ist es, die Auswirkungen eines Ischämie- und Reperfusionsschadens zu minimieren. Aus anästhesiologischer Sicht spielt dieser Aspekt insbesondere in der Herzchirurgie bei Patienten mit Einsatz der Herz-Lungen-Maschine, aber auch allgemein bei längerfristigen hypotensiven Phasen oder perioperativen ischämischen Ereignissen im nichtkardiochirurgischen Setting eine wichtige Rolle. Im Laufe der letzten Jahre konnten diverse pharmakologische sowie nichtpharmakologische Strategien der Kardioprotektion identifiziert werden. Die Ergebnisse von Studien an isoliertem Gewebe sowie von tierexperimentellen In-vivo-Studien sind vielversprechend. Eine Translation dieser kardioprotektiven Strategien in die klinische Praxis ist bislang jedoch nicht gelungen. Große klinische Studien konnten keine signifikante Verbesserung des Outcome der Patienten zeigen.

Ziel der Arbeit

Dieser Übersichtsartikel gibt einen Überblick über die aktuelle experimentelle Evidenz pharmakologischer und nichtpharmakologischer Kardioprotektion. Außerdem sollen mögliche Gründe für die limitierte Translation diskutiert werden. Schließlich werden Möglichkeiten aufgezeigt, wie der Schritt „from bench to bedside“ in Zukunft doch noch gelingen könnte.

Material und Methoden

Narrative Übersichtsarbeit.

Ergebnisse und Diskussion

Trotz der vielversprechenden präklinischen experimentellen Ansätze zum Thema Kardioprotektion besteht nach wie vor eine große Diskrepanz zu den Ergebnissen aus großen klinischen Studien in der perioperativen Phase. Mögliche Gründe für die limitierte Translation könnten insbesondere Komorbiditäten und Komedikationen, die Wahl des Anästhesieverfahrens, aber auch die Wahl des Studiendesigns sein. Eine sorgfältige Studienplanung mit Berücksichtigung der genannten Probleme sowie ein simultaner Einsatz mehrerer kardioprotektiver Strategien mit dem Ziel eines additiven bzw. synergistischen Effekts stellen mögliche Ansätze für die Zukunft dar.

Perioperative Cardioprotection: General Mechanisms and Pharmacological Approaches

Cardioprotection encompasses a variety of strategies protecting the heart against myocardial injury that occurs during and after inadequate blood supply to the heart during myocardial infarction. While restoring reperfusion is crucial for salvaging myocardium from further damage, paradoxically, it itself accounts for additional cell death-a phenomenon named ischemia/reperfusion injury. Therefore, therapeutic strategies are necessary to render the heart protected against myocardial infarction. Ischemic pre- and postconditioning, by short periods of sublethal cardiac ischemia and reperfusion, are still the strongest mechanisms to achieve cardioprotection. However, it is highly impractical and far too invasive for clinical use. Fortunately, it can be mimicked pharmacologically, for example, by volatile anesthetics, noble gases, opioids, propofol, dexmedetomidine, and phosphodiesterase inhibitors. These substances are all routinely used in the clinical setting and seem promising candidates for successful translation of cardioprotection from experimental protocols to clinical trials. This review presents the fundamental mechanisms of conditioning strategies and provides an overview of the most recent and relevant findings on different concepts achieving cardioprotection in the experimental setting, specifically emphasizing pharmacological approaches in the perioperative context.

Sevoflurane as opposed to propofol anesthesia preserves mitochondrial function and alleviates myocardial ischemia/reperfusion injury

BACKGROUND

Pharmacological interventions reducing myocardial ischemia and reperfusion (I/R) injury include the administration of anesthetics. Both sevoflurane as well as propofol have been shown to elicit cardiac protection via distinct molecular mechanisms. We investigated the hypothesis that sevoflurane in contrary to propofol anesthesia elicits cardiac protection against I/R-injury via mitochondrial mechanisms of disease.

METHODS

Male New Zealand white rabbits (n = 42) were subjected 30 min of coronary artery occlusion followed by 3 h of reperfusion. After induction with pentobarbital, the animals either received sevoflurane or propofol to maintain general anesthesia. Infarct size was determined gravimetrically after triphenyltetrazolium chlorid-staining. Cardiac mitochondria were isolated and mitochondrial oxygen consumption was measured using a Clark electrode. Mitochondrial respiratory chain complex activities (I-IV) were analyzed utilizing specific assays. Data are mean ± SD.

RESULTS

Sevoflurane anesthesia significantly decreased the resulting myocardial infarct size compared to propofol anesthesia (p = 0.0275 vs. propofol). Mitochondria from animals receiving propofol anesthesia showed a significantly reduced mitochondrial respiratory control ratio (p = 0.01909 vs. sham) and impaired activities of respiratory complex I (p = 0.0147 vs. sham; p < 0.01 vs. sevoflurane) as well as respiratory complex IV (p = 0.0181 vs. sham). Mitochondrial dysfunction was absent in sevoflurane anesthesized animals. Furthermore, a significantly higher portion of complex I was found to be in its deactive form during I/R-injury in animals receiving sevoflurane anesthesia (p = 0.0123 vs. propofol).

CONCLUSIONS

Sevoflurane as opposed to propofol anesthesia preserved mitochondrial respiration and elicited cardiac protection against I/R-injury.

Volatile Anesthetics versus Propofol for Cardiac Surgery with Cardiopulmonary Bypass

Background

The aim of this systematic review and meta-analysis was to assess the effect of anesthesia maintenance with volatile agents compared with propofol on both short- and long-term mortality (primary outcomes) and major clinical events in adults undergoing cardiac surgery with cardiopulmonary bypass.

Methods

Randomized clinical trials on the effects of current volatile anesthetics versus propofol in adults undergoing cardiac surgery with cardiopulmonary bypass were searched (1965 to September 30, 2019) in PubMed, the Cochrane Library, and article reference lists. A random effect model on standardized mean difference for continuous outcomes and odds ratio for dichotomous outcomes were used to meta-analyze data.

Results

In total, 37 full-text articles (42 studies, 8,197 participants) were included. The class of volatile anesthetics compared with propofol was associated with lower 1-yr mortality (5.5 vs. 6.8%; odds ratio, 0.76 [95% CI, 0.60 to 0.96]; P = 0.023), myocardial infarction (odds ratio, 0.60 [95% CI, 0.39 to 0.92]; P = 0.023), cardiac troponin release (standardized mean difference, −0.39 [95% CI, −0.59 to −0.18], P = 0.0002), need for inotropic medications (odds ratio, 0.40 [95% CI, 0.24 to 0.67]; P = 0.0004), extubation time (standardized mean difference, −0.35 [95% CI, −0.68 to −0.02]; P = 0.038), and with higher cardiac index/output (standardized mean difference, 0.70 [95% CI, 0.37 to 1.04]; P &lt; 0.0001). The class of volatile anesthetics was not associated with changes in short-term mortality (1.63 vs. 1.65%; odds ratio, 1.04 [95% CI, 0.73 to 1.49]; P = 0.820) and acute kidney injury (odds ratio, 1.25 [95% CI, 0.77 to 2.03]; P = 0.358).

Conclusions

In adults undergoing cardiac surgery with cardiopulmonary bypass, the class of volatile anesthetics was superior to propofol with regard to long-term mortality, as well as to many secondary outcomes indicating myocardial protection.

Editor’s Perspective

What We Already Know about This Topic

What This Article Tells Us That Is New

Molecular Cardioprotection and the Role of Exosomes: The Future Is Not Far Away

Heart disease is the leading cause of death in men and women in the United States. During the past several decades, research into the role of specific intracellular mediators, called exosomes, has advanced the understanding of molecular cardioprotection. Exosomes and the micro-RNAs within them may be potential targets for the development of genetically engineered or biosimilar medications for patients in heart failure or with ischemic cardiac disease. This review discusses anesthetic implications of exosome production and the future micro-RNA applications for cardioprotection.

The Impact of Anesthetic Regimen on Outcomes in Adult Cardiac Surgery: A Narrative Review

Despite improvements in surgical techniques and perioperative care, cardiac surgery still is burdened by relatively high mortality and frequent major postoperative complications, including myocardial dysfunction, pulmonary complications, neurologic injury, and acute kidney injury. Although the surgeon's skills and volume and patient- and procedure-related risk factors play a major role in the success of cardiac surgery, there is growing evidence that also optimizing perioperative care may improve outcomes significantly. The present review focuses on the aspects of perioperative care that are strictly related to the anesthesia regimen, with special reference to volatile anesthetics and neuraxial anesthesia, whose effect on outcome in adult cardiac surgery has been investigated extensively.

Oxygen inhalation improves postoperative survival in ketamine-xylazine anaesthetised rats: An observational study

OBJECTIVE

A simple but reliable and safe anaesthetic procedure is required for surgical interventions in small rodents. Combined ketamine and xylazine injections are often used in rats for less invasive surgery, possibly with spontaneous breathing and without airway management. However, there are important pitfalls to be avoided by special precautions and monitoring, as shown subsequently.

STUDY DESIGN

Observational study.

ANIMALS

Twenty-four anaesthetic procedures for bile duct ligation, sham operation or carotid artery dilatation in 20 male Sprague-Dawley rats, preoperatively weighing between 440 and 550 g.

METHODS

Intolerable high mortality rates occurred in the first 7 postoperative days while establishing a new experimental model in rats using ketamine-xylazine anaesthesia. Rats were spontaneously breathing ambient air during the first 12 surgeries without airway management. An observed high mortality rate in these animals led to a change in the trial protocol: the insufflation of 2 litres of oxygen per minute via nose cone during the following 12 rat surgeries. Retrospective comparison of the outcome (without oxygen vs. with oxygen insufflation) was conducted.

RESULTS

The perioperative mortality rate could be significantly reduced from 58% (7/12) to 17% (2/12) (p = 0.036) by oxygen insufflation via nose cone. Significantly different levels of intraoperative oxygen saturation (SpO2; 89 ± 4% [without oxygen] vs. 97 ± 0.5% [with oxygen], p < 0.0001), but no significant differences in heart rate (HR; 267 ± 7 beats minute-1 [bpm] [without oxygen] vs. 266 ± 6 bpm [with oxygen], p = 0.955) were observed.

CONCLUSIONS AND CLINICAL RELEVANCE

In summary, rats under ketamine-xylazine anaesthesia are susceptible to hypoxia. This may lead to increased delayed mortality related to hypoxia induced lung failure. Apparently, this is an underestimated problem. We highly recommend using additional oxygen insufflation in spontaneously breathing rats under ketamine-xylazine anaesthesia with basic monitoring such as measurement of oxygen saturation.

Comparison of the Effects of Target-Controlled Infusion of Propofol and Sevoflurane as Maintenance of Anesthesia on Hemodynamic Profile in Kidney Transplantation

Background

Target-controlled infusion (TCI) propofol and sevoflurane are common agents for general anesthesia, including for kidney transplantation procedure. This study compared the effect of TCI propofol and sevoflurane on intraoperative hemodynamic profile in kidney transplant patients.

Methods

A single-blinded prospective study was performed in 46 kidney transplant recipients who were randomized into receiving TCI propofol or sevoflurane as anesthetics maintenance. Hemodynamic parameters such as mean arterial pressure (MAP), cardiac index (CI), stroke volume index (SVI), and systemic vascular resistance index (SVRI) were measured at baseline before induction, postintubation, first surgical incision, every 15 minutes after the first incision, reperfusion, and 15 minutes after reperfusion. Data were analyzed using unpaired t-test, paired t-test, and general linear model.

Results

Intraoperative MAP, CI, SVI, and SVRI changes were similar in both groups (p = 0.480, 0.216, 0.086, and 0.054). In comparison to the baseline value, TCI propofol and sevoflurane groups showed significant reductions of MAP at postintubation (p=0.010; p < 0.001) and during the first surgical incision (p=0.009; p < 0.001); significant reduction of CI at postintubation (p=0.003; p < 0.001) and during the first surgical incision (p < 0.001; p < 0.001); significant reduction of SVI at postintubation (p=0.013; p=0.008), during the first surgical incision (p=0.008; p=0.003), and 15 minutes after reperfusion (p=0.010; p=0.005); and significant increasing of SVRI during the first surgical incision (p=0.007; p=0.005). The TCI propofol group showed significantly lower SVRI compared to the sevoflurane group postintubation (p=0.029) and during the first surgical incision (p=0.026).

Conclusion

Intraoperative hemodynamic profile was similar between the TCI propofol and sevoflurane group during kidney transplant surgery. The TCI propofol group had higher CI and SVI but showed significantly lower SVRI as compared to the sevoflurane group. The incidence of postanesthesia agitation, postoperative outcome, and complication were not significantly different between the two groups.

Effects of Volatile versus Total Intravenous Anesthesia on Occurrence of Myocardial Injury after Non-Cardiac Surgery

The cardioprotective effects of volatile anesthetics versus total intravenous anesthesia (TIVA) are controversial, especially in patients undergoing non-cardiac surgery. Using current generation high-sensitivity cardiac troponin (hs-cTn), we aimed to evaluate the effect of anesthetics on the occurrence of myocardial injury after non-cardiac surgery (MINS). From February 2010 to December 2016, 3555 patients without preoperative hs-cTn elevation underwent non-cardiac surgery under general anesthesia. Patients were grouped according to anesthetic agent; 659 patients were classified into a propofol-remifentanil total intravenous anesthesia (TIVA) group, and 2896 patients were classified into a volatile group. To balance the use of remifentanil between groups, a balanced group (n = 1622) was generated with patients who received remifentanil infusion in the volatile group, and two separate comparisons were performed (TIVA vs. volatile and TIVA vs. balanced). The primary outcome was occurrence of MINS, defined as rise of hs-cTn I ≥ 0.04 ng/mL within postoperative 48 hours. The secondary outcomes were 30-day mortality, postoperative acute kidney injury (AKI), and adverse events during hospital stay (mortality, type I myocardial infarction (MI), and new-onset arrhythmia). In propensity-matched analyses, the occurrence of MINS was lower in the TIVA group compared to the volatile group (OR 0.642; 95% CI 0.450–0.914; p = 0.014). However, after balancing the use of remifentanil, there was no difference between groups in the risk of MINS (OR 0.832; 95% CI 0.554–1.251; p-value = 0.377). There were no significant associations between the two groups in type 1 MI, new-onset atrial fibrillation, in-hospital and 30-day mortality before and after balancing the use of remifentanil. However, the incidence of postoperative AKI was lower in the TIVA group (OR 0.362; 95% CI 0.194–0.675; p-value = 0.001). After balancing the use of remifentanil, volatile anesthesia and TIVA showed comparable effects on MINS in patients undergoing non-cardiac surgery without preoperative myocardial injury. Further studies are needed on the benefit of remifentanil infusion.

Anesthetic-induced Myocardial Conditioning: Molecular Fundamentals and Scope

BACKGROUND

The pre- and post-conditioning effects of halogenated anesthetics make them most suitable for cardiac surgery. Several studies have demonstrated that the mechanism of drug-induced myocardial conditioning is enzyme-mediated via messenger RNA and miRNA regulation. The objective of this study was to investigate the role that miRNAs play in the cardioprotective effect of halogenated anesthetics. For such purpose, we reviewed the literature to determine the expression profile of miRNAs in ischemic conditioning and in the complications prevented by these phenomena.

METHODS

A review was conducted of more than 100 studies to identify miRNAs involved in anesthetic-induced myocardial conditioning. Our objective was to determine the miRNAs that play a relevant role in ischemic disease, heart failure and arrhythmogenesis, which expression is modulated by the perioperative administration of halogenated anesthetics. So far, no studies have been performed to assess the role of miRNAs in anesthetic-induced myocardial conditioning. The potential of miRNAs as biomarkers and miRNAs-based therapies involving the synthesis, inhibition or stimulation of miRNAs are a promising avenue for future research in the field of cardiology.

RESULTS

Each of the cardioprotective effects of myocardial conditioning is related to the expression of several (not a single) miRNAs. The cumulative evidence on the role of miRNAs in heart disease and myocardial conditioning opens new therapeutic and diagnostic opportunities.

CONCLUSION

Halogenated anesthetics regulate the expression of miRNAs involved in heart conditions. Further research is needed to determine the expression profile of miRNAs after the administration of halogenated drugs. The results of these studies would contribute to the development of new hypnotics for cardiac surgery patients.

An innovative technique to improve safety of volatile anesthetics suction from the cardiopulmonary bypass circuit

Context:

Myocardial injury during cardiac surgery on cardiopulmonary bypass (CPB) is a major determinant of morbidity and mortality. Preclinical and clinical evidence of dose- and time-related cardioprotective effects of volatile anesthetic drugs exist and their use during the whole surgery duration could improve perioperative cardiac protection. Even if administering volatile agents during CPB are relatively easy, technical problems, such as waste gas scavenging, may prevent safe and manageable administration of halogenated vapors during CPB.

Aims:

The aim of this study is to improve the safe administration of volatile anesthesia during CPB.

Settings and Design:

Tertiary teaching hospital.

Subjects and Methods:

We describe an original device that collects and disposes of any volatile anesthetic vapors present in the exit stream of the oxygenator, hence preventing its dispersal into the operating theatre environment and adaptively regulates pressure of oxygenator chamber in the CPB circuit.

Results:

We have so far applied a prototype of this device in more than 1300 adult cardiac surgery patients who received volatile anesthetics during the CPB phase.

Conclusions:

Widespread implementation of scavenging system like the one we designed may facilitate the perfusionist and the anesthesiologist in delivering these cardioprotective drugs with beneficial impact on patients’ outcome without compromising on safety.

The effect of inhalational anaesthesia during deceased donor organ procurement on post-transplantation graft survival

Many deceased by neurologic criteria donors are administered inhalational agents during organ recovery surgery-a process that is characterised by warm and cold ischaemia followed by warm reperfusion. In certain settings, volatile anaesthetics (VA) are known to precondition organs to protect them from subsequent ischaemia-reperfusion injury. As such, we hypothesised that exposure to VA during organ procurement would improve post-graft survival. Lifebanc (organ procurement organisation [OPO] for NE Ohio) provided the investigators with a list of death by neurologic criteria organ donors cared for at three large tertiary hospitals in Cleveland between 2006 and 2016-details about the surgical recovery phase were extracted from the organ donors' medical records. De-identified data on graft survival were obtained from the United Network for Organ Sharing (UNOS). The collated data underwent comparative analysis based on whether or not VA were administered during procurement surgery. Records from 213 donors were obtained for analysis with 138 exposed and 75 not exposed. Demographics, medical histories, and organ procurement rates were similar between the two cohorts. For the primary endpoint, there were no significant differences observed in either early (30-day) or late (five-year) graft survival rates for kidney, liver, lung, or heart transplants. Our findings from this retrospective review of a relatively small cohort do not support the hypothesis that the use of VA during the surgical procurement phase improves graft survival. Reviews of larger datasets and/or a prospective study may be required to provide a definitive answer.

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.

Cardiac Calcium Release Channel (Ryanodine Receptor 2) Regulation by Halogenated Anesthetics

Background

Halogenated anesthetics activate cardiac ryanodine receptor 2–mediated sarcoplasmic reticulum Ca2+ release, leading to sarcoplasmic reticulum Ca2+ depletion, reduced cardiac function, and providing cell protection against ischemia-reperfusion injury. Anesthetic activation of ryanodine receptor 2 is poorly defined, leaving aspects of the protective mechanism uncertain.

Methods

Ryanodine receptor 2 from the sheep heart was incorporated into artificial lipid bilayers, and their gating properties were measured in response to five halogenated anesthetics.

Results

Each anesthetic rapidly and reversibly activated ryanodine receptor 2, but only from the cytoplasmic side. Relative activation levels were as follows: halothane (approximately 4-fold; n = 8), desflurane and enflurane (approximately 3-fold,n = 9), and isoflurane and sevoflurane (approximately 1.5-fold, n = 7, 10). Half-activating concentrations (Ka) were in the range 1.3 to 2.1 mM (1.4 to 2.6 minimum alveolar concentration [MAC]) with the exception of isoflurane (5.3 mM, 6.6 minimum alveolar concentration). Dantrolene (10 μM with 100 nM calmodulin) inhibited ryanodine receptor 2 by 40% but did not alter the Ka for halothane activation. Halothane potentiated luminal and cytoplasmic Ca2+ activation of ryanodine receptor 2 but had no effect on Mg2+ inhibition. Halothane activated ryanodine receptor 2 in the absence and presence (2 mM) of adenosine triphosphate (ATP). Adenosine, a competitive antagonist to ATP activation of ryanodine receptor 2, did not antagonize halothane activation in the absence of ATP.

Conclusions

At clinical concentrations (1 MAC), halothane desflurane and enflurane activated ryanodine receptor 2, whereas isoflurane and sevoflurane were ineffective. Dantrolene inhibition of ryanodine receptor 2 substantially negated the activating effects of anesthetics. Halothane acted independently of the adenine nucleotide–binding site on ryanodine receptor 2. The previously observed adenosine antagonism of halothane activation of sarcoplasmic reticulum Ca2+ release was due to competition between adenosine and ATP, rather than between halothane and ATP.

Attenuation of Isoflurane Preconditioning-Induced Acute Cardioprotection in Hypertensive Hypertrophied Hearts

OBJECTIVES

To evaluate the efficiency of isoflurane-induced anesthetic preconditioning and the role of mitochondrial manganese superoxide dismutase (MnSOD) in hypertensive hypertrophied hearts.

DESIGN

A prospective animal investigation.

SETTING

Medical center hospital research laboratory.

PARTICIPANTS

Male spontaneously hypertensive rats (SHRs) and normotensive control Wistar-Kyoto (WKY) rats.

INTERVENTIONS

All pentobarbital-anesthetized open-chest rats were subjected to a 45-minute left coronary artery occlusion followed by a 120-minute reperfusion. Before ischemia, both SHR and WKY rats were assigned randomly to receive a 30-minute exposure to 0.9% saline or 1.0 minimum alveolar concentration isoflurane.

MEASUREMENTS AND MAIN RESULTS

The myocardial infarct size, assessed as a percentage of the area at risk, was significantly greater in the hypertrophied SHRs than in the WKY rats (65.3%±8.7% v 51.8%±7.2%, p<0.05). Isoflurane preconditioning appreciably reduced the infarct size in the WKY hearts (30.9%±10.5%, p<0.05) but not in the SHR hearts. MnSOD protein expression and enzymatic activity were increased drastically in response to isoflurane exposure in the hearts of the WKY rats (p<0.05) but not in the SHRs.

CONCLUSIONS

Isoflurane-induced anesthetic preconditioning is attenuated in hypertensive hypertrophied hearts. This impairment may be associated with the loss of MnSOD augmentation during ischemia and reperfusion.

[Special aspects of analgosedation in cardiogenic shock patients]

Patients with cardiogenic shock pose a challenge to physicians due to cardiorespiratory instability in addition to the underlying medical condition. If analgosedation and ventilation are indicated, commonly administered drugs themselves often influence hemodynamics and oxygenation. The present article provides an overview of the available substances with consideration of the patients' condition, then monitoring and optimization of analgosedation.