Anaesthesia and myocardial ischaemia/reperfusion injury

Role of the protein kinase A signaling pathway and identification of mediators in the cardioprotective effects of enteral lactoferrin for ischemia-reperfusion injury in an isolated rat heart model

OBJECTIVE

Lactoferrin is an iron-binding glycoprotein. Enteral lactoferrin attenuates myocardial ischemia-reperfusion (IR) injury, but the underlying mechanism remains unknown. The aim of this study was to investigate protein kinase A (PKA) signaling pathway activation and levels of serum glucagonlike peptide-1 (GLP-1), secreted by intestinal endocrine L cells, and adiponectin, secreted by adipose tissue, after enteral lactoferrin administration.

METHODS

Hearts (N = 32) were excised from Wistar rats and perfused using a Langendorff system. To assess the role of the PKA pathway in the cardioprotective effects of lactoferrin, an inhibitor of PKA (H89) was applied before no-flow ischemia. Rats were randomly divided into four groups: control, lactoferrin (LF), control+H89, and LF+H89. The control and control+H89 groups were administered normal saline by gavage, and the LF and L +H89 groups were administered bovine lactoferrin (1000 mg/kg) by gavage 15 min before intraperitoneal pentobarbital injection. Muscle sampling was performed at the end of reperfusion. When rats were sacrificed, blood was sampled to measure hormone levels. The primary outcome was maximum left ventricular pressure derivative (LV dP/dt max) 15 min after reperfusion.

RESULTS

LV dP/dt max at 10 and 15 min after reperfusion was significantly higher in the LF group than in the control group (P < 0.05), and the effect was diminished by H89. The PKA pathway was significantly activated in the LF group. Enteral lactoferrin increased serum GLP-1 but not serum adiponectin levels.

CONCLUSIONS

Enteral lactoferrin induces cardioprotective effects against myocardial IR injury via the PKA signaling pathway and increases serum GLP-1 levels.

Cardioprotective effects of enteral vs. parenteral lactoferrin administration on myocardial ischemia-reperfusion injury in a rat model of stunned myocardium

BACKGROUND

Lactoferrin, an iron-binding glycoprotein, is known to have protective effects against intestinal and cerebral ischemia-reperfusion (IR) injuries; however, its cardioprotective effects against the stunned myocardium are unknown. This study aimed to test the hypothesis that lactoferrin has cardioprotective effects against stunned myocardium.

METHODS

Using isolated rat hearts (Langendorff system), we determined the effects of lactoferrin administered enterally and by direct cardiac perfusion. Rat hearts were perfused using the Langendorff system, and two experiments were performed. In experiment 1, the hearts were divided into the enteral lactoferrin (E-LF) 7.5 m, 15 m, 30 m, and 60 m groups, where lactoferrin (1000 mg/kg) was administered enterally 7.5, 15, 30, and 60 min, respectively, before perfusion; and a control group, where saline was administered 30 min before perfusion. In experiment 2, hearts were allocated to the perfusate lactoferrin (P-LF) 15 and 100 groups, where 15 mg/L and 100 mg/L lactoferrin were respectively added to the perfusate, and a control group. Each group was perfused for 20 min prior to 15 min of no-flow ischemia with pacing, followed by 20 min of reperfusion. The primary outcome was the maximum left ventricular derivative of pressure development (LV dP/dt max) 15 min after reperfusion. Myocardial phospho-protein kinase B (p-Akt) was assayed using western blotting.

RESULTS

The LV dP/dt max 15 min after reperfusion in the E-LF 15 and 30 m groups was significantly higher than that in the control group. However, the effects disappeared in the E-LF 60 m group. In the second experiment, there were no significant differences in LV dP/dt max. Myocardial p-Akt was not significantly activated in any lactoferrin group.

CONCLUSION

Cardioprotection was observed 15-30 min after enteral lactoferrin but not by direct cardiac perfusion with lactoferrin. Myocardial p-Akt was not associated with the cardioprotective effect. The cardioprotective effect may be induced by enteral lactoferrin-induced substances.

Is Greater Than 0.5 MAC Inhalational Agent Use Post-Bypass Related to Need for Inotropic and/or Vasoconstrictor Support?

Background and Aims: We hypothesized that maintaining a patient on moderate–high doses of potent inhalational agent for greater than 30 min during the post-bypass period would be an independent predictor of initiation and usage of either inotropic and/or vasopressor infusions. Setting and Design: This study is a retrospective design and approved by the institutional review board. The setting was a single-center, academic tertiary care hospital in Detroit, Michigan. Materials and Methods: Three-hundred, ninety-seven elective cardiac surgery patients were identified for chart review. Electronic medical records were reviewed to collect demographics and perioperative data. Statistics used include a propensity score regression adjusted analysis utilizing logistic regression models and a multivariable model. Results: A propensity score regression adjusted analysis was performed and then applied in both univariate and multivariate logistic regression models with a p value of <0.05 reaching statistical significance. Fifty-six percent of the participants had an exposure of greater than 30 min of a minimum alveolar concentration of isoflurane greater than 0.5 (ETISO ≥ 0.5MAC, 30 min) in the post-bypass period. After adjusting for propensity score, this was found to be a significant predictor of inotrope and/or vasoconstrictor use post-bypass (OR 2.49, 95% CI 1.15–5.38, p = 0.021). In the multivariate model, pulmonary hypertension (OR 5.9; 95% CI 1.33–26.28; p = 0.02), Euroscore II (2.73; 95% CI 1.35–5.5; p = 0.005), and cardiopulmonary bypass hours (OR 1.86; 95% CI 1.02–3.4; p = 0.042) emerged as significant. Conclusions: This study showed that an ETISO ≥ 0.5MAC, 30 min exposure during the immediate post-bypass period during elective cardiac surgery was an independent predictor of a patient being started on inotrope or vasoconstrictor infusions. Further research should consider a prospective design and examine depth of anesthesia during the post-bypass period.

Total Intravenous Anesthesia for Myocardial Protection and Preconditioning

Perioperative myocardial injury is common after any major surgical procedure even with best possible anesthesia and surgical management. Organ preservation during surgical procedure prevents morbidity and mortality. The effect of ischemic preconditioning on myocardial as well as other organ protection is well known. A variety of other agents also shown to have preconditioning thus protective effect on myocardium during anesthesia and surgery. The beneficial effect of volatile anesthetic preconditioning is well studied. However, the effect of intravenous anesthetic agents on this context is still way to go. This review is an attempt to look into the latest available research regarding the preconditioning and myocardial protective effect of intravenous anesthetic agents.

Precondition of sevoflurane upregulates TIMP3 expression to alleviate myocardial ischemia/reperfusion injury

BACKGROUND

Previous studies have pointed out that sevoflurane (Sef) preconditioning could relieve myocardial ischemia/reperfusion (I/R) injury, but the mechanisms is still unknown.

METHODS

C57BL/6 mice model of myocardial I/R injury was established to evaluate the function of Sef. Briefly, Sef was inhaled before I/R operation. The levels of TIMP3, oxidative damage-related factors, and mitogen activated protein kinases (MAPKs) pathway-related factors were measured by qRT-PCR and western blot. Myocardial infarction (MI) area was detected by triphenyl tetrazolium chloride (TTC) staining assay.

RESULTS

Sef preconditioning reduced MI area in myocardial I/R injury mice and upregulated TIMP3 expression in myocardial tissues of I/R mice. In addition, downregulation of TIMP3 reversed the alleviating effects of Sef pretreatment on myocardial oxidative damage and inhibited the effect of Sef pretreatment on MAPKs pathway activity.

CONCLUSION

Sef preconditioning ameliorated myocardial I/R injury by modulating MAPKs pathway activity via upregulating TIMP3.

From Ganglion Cell to Photoreceptor Layer: Timeline of Deterioration in a Rat Ischemia/Reperfusion Model

Neuronal damage and impaired vision in different retinal disorders are induced, among other factors, by ischemia/reperfusion (I/R). Since the mechanisms and the progression of ischemic injury are still not completely clarified, a timeline of this retinal degeneration is needed. In this study, we investigated protein and mRNA alterations at 2, 6, 12, and 24 h as well as 3 and 7 days after ischemia to determine the course of an ischemic insult through the whole retina. Moreover, functional analyses were performed at later stages. We detected a significant functional loss of cells in the inner nuclear layer and photoreceptors at 3 and 7 days. Additionally, the thickness of the whole retina was decreased at these points in time, indicating a severe degradation of all retinal layers. Immunohistological and qRT-PCR analyses of retinal ganglion cells (RGCs), glial cells, AII amacrine, cone and rod bipolar as well as cone and rod photoreceptor cells confirmed this first assumption. Our results show that all investigated cell types were damaged by ischemia induction. Especially RGCs, cone bipolar cells, and photoreceptor cones are very sensitive to I/R. These cells were lost shortly after ischemia induction with a progressive course up to 7 days. In addition, Müller cell gliosis was observed over the entire period of time. These results provide evidence, that I/R induces damage of the whole retina at early stages and increases over time. In conclusion, our study could demonstrate the intense impact of an ischemic injury. The ischemic defect spreads across the whole retina right up to the outer layers in the long-term and thus seems to impair the visual perception already during the stimulus processing. In addition, our findings indicate that the cone pathway seems to be particularly affected by this damage.

Optimal pathways involved in the treatment of sevoflurane or propofol for patients undergoing coronary artery bypass graft surgery

The cardio-protection mechanisms of sevoflurane and propofol still remain unclear in patients undergoing coronary artery bypass grafting (CABG). We designed the present study to identify the optimal pathways through integrating differential co-expressed network (DCN)-based guilt by association (GBA) principle based on the expression data of E-GEOD-4386 downloaded from EMBL-EBI. Differentially expressed genes (DEGs) were firstly identified and then DCN and sub-DCN were established. The seed pathways were predicted through GBA principle using the area under the curve (AUC) for pathway categories, and the pathway terms with AUC >0.9 were defined as the seed pathways. KEGG pathway analysis was applied to the DEGs based on DAVIA to detect significant pathways. The final optimal pathways were identified based on the traditional pathway analysis and network-based pathway inference approach. There were 83 common, 99 sevoflurane-specific and 4 propofol-specific DEGs in the expression profile of artial samples. Finally, 8 and 4 pathway terms having the AUC >0.9 were identified and determined as the seed pathways in the propofol and sevoflurane group, respectively. TNF signaling pathway, NF-κB signaling pathway, as well as NOD-like receptor signaling pathway were the common optimal ones in these two groups. Only the pathway of cytokine-cytokine receptor interaction was unique to sevoflurane, and no pathway was specific to propofol. Our results suggested that sevoflurane and propofol might synergistically possess some cardio-protective properties in patients undergoing CABG.

Classic Papers Revisited: An Early Study of Cardioprotection by Volatile Anesthetics

Recovery of Contractile Function of Stunned Myocardium in Chronically Instrumented Dogs Is Enhanced by Halothane or Isoflurane. By Warltier DC, al-Wathiqui MH, Kampine JP, and Schmeling WT. Anesthesiology 1988; 69:552–65. Reprinted with permission.

Following brief periods (5–15 min) of total coronary artery occlusion and subsequent reperfusion, despite an absence of tissue necrosis, a decrement in contractile function of the postischemic myocardium may nevertheless be present for prolonged periods. This has been termed “stunned” myocardium to differentiate the condition from ischemia or infarction. Because the influence of volatile anesthetics on the recovery of postischemic, reperfused myocardium has yet to be studied, the purpose of this investigation was to compare the effects of halothane and isoflurane on systemic and regional hemodynamics following a brief coronary artery occlusion and reperfusion. Nine groups comprising 79 experiments were completed in 42 chronically instrumented dogs. In awake, unsedated dogs a 15-min coronary artery occlusion resulted in paradoxical systolic lengthening in the ischemic zone. Following reperfusion active systolic shortening slowly returned toward control levels but remained approximately 50% depressed from control at 5 h. In contrast, dogs anesthetized with halothane or isoflurane (2% inspired concentration) demonstrated complete recovery of function 3–5 h following reperfusion. Because the anesthetics directly depressed contractile function, additional experiments were conducted in which a 15-minute coronary artery occlusion was produced during volatile anesthesia; however, each animal was allowed to emerge from the anesthetized state at the onset of reperfusion. Similar results were obtained in these experiments, demonstrating total recovery of contractile function within 3–5 h following reperfusion. Thus, despite comparable degrees of contractile dysfunction during coronary artery occlusion in awake and anesthetized dogs, the present results demonstrate that halothane and isoflurane produce marked improvement in the recovery of segment function following a transient ischemic episode. Therefore, volatile anesthetics may attenuate postischemic left ventricular dysfunction occurring intraoperatively and enhance recovery of regional wall motion abnormalities during reperfusion.

Immunomodulatory effects of anesthetics in obese patients

Anesthesia and surgery have an impact on inflammatory responses, which influences perioperative homeostasis. Inhalational and intravenous anesthesia can alter immune-system homeostasis through multiple processes that include activation of immune cells (such as monocytes, neutrophils, and specific tissue macrophages) with release of pro- or anti-inflammatory interleukins, upregulation of cell adhesion molecules, and overproduction of oxidative radicals. The response depends on the timing of anesthesia, anesthetic agents used, and mechanisms involved in the development of inflammation or immunosuppression. Obese patients are at increased risk for chronic diseases and may have the metabolic syndrome, which features insulin resistance and chronic low-grade inflammation. Evidence has shown that obesity has adverse impacts on surgical outcome, and that immune cells play an important role in this process. Understanding the effects of anesthetics on immune-system cells in obese patients is important to support proper selection of anesthetic agents, which may affect postoperative outcomes. This review article aims to integrate current knowledge regarding the effects of commonly used anesthetic agents on the lungs and immune response with the underlying immunology of obesity. Additionally, it identifies knowledge gaps for future research to guide optimal selection of anesthetic agents for obese patients from an immunomodulatory standpoint.

A clinical review of inhalation anesthesia with sevoflurane: from early research to emerging topics

A large number of studies during the past two decades have demonstrated the efficacy and safety of sevoflurane across patient populations. Clinical researchers have also investigated the effects of sevoflurane, its hemodynamic characteristics, its potential protective effects on several organ systems, and the incidence of delirium and cognitive deficiency. This review examines the clinical profiles of sevoflurane and other anesthetic agents, and focuses upon emerging topics such as organ protection, postoperative cognitive deficiency and delirium, and novel ways to improve postanesthesia outcomes.

Cardioprotection Effects of Sevoflurane by Regulating the Pathway of Neuroactive Ligand-Receptor Interaction in Patients Undergoing Coronary Artery Bypass Graft Surgery

This study was designed to identify attractor modules and further reveal the potential biological processes involving in sevoflurane-induced anesthesia in patients treated with coronary artery bypass graft (CABG) surgery. Microarray profile data (ID: E-GEOD-4386) on atrial samples obtained from patients receiving anesthetic gas sevoflurane prior to and following CABG procedure were downloaded from EMBL-EBI database for further analysis. Protein-protein interaction (PPI) networks of baseline and sevoflurane groups were inferred and reweighted according to Spearman correlation coefficient (SCC), followed by systematic modules inference using clique-merging approach. Subsequently, attract method was utilized to explore attractor modules. Finally, pathway enrichment analyses for genes in the attractor modules were implemented to illuminate the biological processes in sevoflurane group. Using clique-merging approach, 27 and 36 modules were obtained from the PPI networks of baseline and sevoflurane-treated samples, respectively. By comparing with the baseline condition, 5 module pairs with the same gene composition were identified. Subsequently, 1 out of 5 modules was identified as an attractor based on attract method. Additionally, pathway analysis indicated that genes in the attractor module were associated with neuroactive ligand-receptor interaction. Accordingly, sevoflurane might exert important functions in cardioprotection in patients following CABG, partially through regulating the pathway of neuroactive ligand-receptor interaction.

Sevoflurane Attenuates Ischemia-Reperfusion Injury in a Rat Lung Transplantation Model

BACKGROUND

Sevoflurane is one of the most commonly used volatile anesthetic agents with the fastest onset and offset, replacing isoflurane in modern anesthesiology. Preconditioning and postconditioning using volatile anesthetics can attenuate ischemia-reperfusion injury (IRI). However, no previous studies have evaluated the effect of sevoflurane in lung transplantation after cold ischemic injury. We aimed to study the effects of donor and recipient treatment with sevoflurane in a rat lung transplantation model.

METHODS

Lewis rats were allocated to four groups: control, PreC (preconditioning), PostC (postconditioning), and PreC + PostC. Donor rats in the PreC and PreC + PostC groups were exposed to 1.5% sevoflurane for 30 minutes before donor operation. Donor lungs were flushed with Perfadex and stored for 12 hours at 4°C before transplantation. Recipients received orthotopic left lung transplantation. In the PostC and PreC + PostC groups, sevoflurane was initiated 2 minutes before reperfusion and maintained for 30 minutes. Two hours after reperfusion, lung function was evaluated, and samples were collected for histologic, inflammatory, and cell death assessment.

RESULTS

Preconditioning and postconditioning using sevoflurane significantly improved the oxygenation of lung grafts (partial arterial gas pressure of oxygen: 198 mm Hg in control, 406.5 mm Hg in PreC, 472.4 mm Hg in PostC, and 409.7 mm Hg in PreC + PostC, p < 0.0001) and reduced pulmonary edema. Sevoflurane treatment reduced levels of interleukin-1β, interleukin-6, and tumor necrosis factor-α. Moreover, sevoflurane significantly inhibited apoptotic cells by a decrease in cytochrome c release into cytosol and caspase-3 cleavage.

CONCLUSIONS

Preconditioning or postconditioning of lungs using sevoflurane exhibits a significant protective effect against early phase of ischemia-reperfusion injury in a rat lung transplantation model.

NOD2 mediates isoflurane preconditioning-induced protection of myocardial injury

Anesthetic cardioprotection reduces myocardial infarct size following ischemia-reperfusion injury. However, the underlying mechanisms that drive ischemia-reperfusion injury in cardiomyocytes remain unclear. In this study, we report that isoflurane, a commonly used inhaled anesthetic, can protect cardiomyocytes from anoxia/reoxygenation injury by a nucleotide binding oligomerization domain containing 2 (NOD2)-dependent mechanism. The results showed that isoflurane increased cell viability, and decreased autophagosome generation in primary cardiomyocytes under anoxia/reoxygenation conditions. In addition, western blot revealed that isoflurane reduces the expression of NOD2. Overexpression of NOD2 is accompanied by an increased expression of autophagy-related genes, decreased cell viability, and enhanced expression of phosphorylation p38-mitogen-activated protein kinase (p38MAPK), while NOD2 knockdown exerted the opposite effect. Following preconditioning with SB203580, a p38MAPK inhibitor, the inhibitory effect of isoflurane on cardiomyocytes autophagy was further enhanced, which suggests that p38MAPK is involved in the mechanism of cardioprotection provided by isoflurane. These findings reveal a novel mechanism underlying isoflurane-afford protection of myocardial injury.

Sevoflurane anesthesia during acute right ventricular ischemia in pigs preserves cardiac function better than propofol anesthesia

BACKGROUND

The intention of the present study was to evaluate possible cardioprotective properties of inhalation anesthesia with sevoflurane.

METHODS AND MATERIALS

A porcine, open-chest model of right ventricular ischemia was used in 7 pigs receiving inhalation anesthesia with sevoflurane. The model was earlier developed and published by our group, using pigs receiving intravenous anesthesia with propofol. They served as controls. The animals were observed for three hours after the induction of right ventricular ischemia by ligation of the main branches supplying the right ventricular free wall.

RESULTS

In the sevoflurane group, the cardiac output recovered 2 hours after the induction of ischemia and intact right ventricular stroke work was observed. In the propofol group, no such recovery occurred. The release of troponin T was significantly lower than in the sevoflurane group.

CONCLUSIONS

Inhalation anesthesia with sevoflurane seems superior to intravenous anesthesia with propofol in acute right ventricular ischemic dysfunction.

Involvement of Opioid Receptors in the Lipid Rescue of Bupivacaine-Induced Cardiotoxicity

BACKGROUND

Lipid emulsion (LE) has been successfully used for resuscitation of local anesthetic cardiotoxicity caused by bupivacaine overdose. Opioid receptors have been shown to play a key role in cardio protection. We explored whether this rescue action of LE is mediated through opioid receptors.

METHODS

Asystole was induced by bupivacaine (10 mg/kg over 20 seconds, IV) in young male Sprague-Dawley rats, and resuscitation with LE (intralipid 20%; 5 mL/kg bolus and 0.5 mL/kg/min maintenance) was started immediately. The rats were pretreated 2 minutes before inducing asystole with nonselective opioid receptor antagonists such as naloxone and naloxone methiodide, as well as highly selective opioid receptor antagonists for subtype κ, δ, and µ or phosphate buffer solution as a control. Heart rates and ejection fractions were measured using echocardiography.

RESULTS

LE rescue of bupivacaine cardiotoxicity was prevented by high-dose (1 mg/kg) naloxone but not by lower doses of naloxone (1, 5, and 10 µg/kg), by naloxone methiodide (which does not cross the blood-brain barrier), and by a selective δ- and κ-opioid receptor antagonists at a higher (10 mg/kg) dose. Successful LE rescue was not affected by highly selective µ-opioid receptor antagonists. δ-Opioid receptor antagonist (10 mg/kg) pretreatment also resulted in reduced phosphorylation level of cardiac glycogen synthase kinase-3β in rats that were not resuscitated by LE compared with control.

CONCLUSIONS

Our data highlight the involvement of peripheral δ- and κ-opioid receptors in the rescue action of LE.

Sevoflurane

Sevoflurane has been available for clinical practice for about 20 years. Nowadays, its pharmacodynamic and pharmacokinetic properties together with its absence of major adverse side effects on the different organ systems have made this drug accepted worldwide as a safe and reliable anesthetic agent for clinical practice in various settings.

Role of Endogenous Opioid System in Ischemic-Induced Late Preconditioning

BACKGROUND

Opioid receptors (OR) are involved in myocardial late preconditioning (LPC) induced by morphine and δ1-opioid receptor (δ1-OR) agonists. The role of OR in ischemic-induced LPC is unknown. We investigated whether 1) OR are involved in the trigger and/or mediation phase of LPC and 2) a time course effect on the expression of different opioid receptors and their endogenous ligands exists.

METHODS

Male Wistar rats were randomly allocated to four groups (each group n = 8). Awake animals were ischemic preconditioned by a 5 minutes coronary occlusion. 24 hours later, anesthetized animals underwent 25 minutes coronary occlusion followed by 2 hours of reperfusion. The role of OR was investigated by treatment with intraperitoneal naloxone (Nal) 10 minutes prior to LPC (Nal-LPC; trigger phase) or 10 min prior to sustained ischemia (LPC-Nal; mediation phase).

RESULTS

LPC reduced infarct size from 61±10% in controls to 25±9% (P<0.001). Naloxone during trigger or mediation phase completely abolished LPC-induced cardioprotection (59±9% and 62±9%; P<0.001 vs. LPC). 8, 12 and 24 hours after the ischemic stimulus, expression of δ-OR in the heart was increased, whereas μ-opioid receptor (μ-OR) and κ-opioid receptor (κ-OR) were not. Plasma concentrations of β-endorphin and leu-enkephalin but not dynorphin were increased by LPC.

CONCLUSION

Ischemic LPC is triggererd and mediated by OR. Expression of δ-OR and plasma levels of endogenous opioid peptides are increased after ischemic LPC.

Biomarkers of inflammation in major vascular surgery: a prospective randomised trial

BACKGROUND

Surgery induces inflammation and pro-inflammatory cytokines are associated with post-operative complications. In cardiac surgery, it has been shown that volatile anaesthetics have cardioprotective properties. We explored whether sevoflurane affects the pro-inflammatory response favourably compared with total intravenous anaesthesia (TIVA) after surgery.

METHODS

We measured monocyte chemotactic protein 1 (MCP-1), matrix metalloproteinase 9 (MMP-9), C-reactive protein (CRP), vascular cell adhesion molecule 1 (VCAM-1), interleukin (IL)-6 and IL-8 perioperatively and evaluated if the anaesthetic regimen affected these mediators. Our hypothesis was that sevoflurane-based anaesthesia is associated with a reduced release of biomarkers of inflammation compared with TIVA with propofol/remifentanil.

RESULTS

In the total population, MCP-1, MMP-9, IL-6 and IL-8 increased 30 min after arrival intensive care unit, compared with before surgery (P < 0.001), whereas CRP and VCAM-1 transiently declined (P < 0.001). From 30 min after arrival intensive care unit to 1st post-operative day, MCP-1 and IL-6 levels declined (P < 0.001), CRP and VCAM-1 increased (P < 0.001), whereas MMP-9 and IL-8 were not significantly altered. Pre-operatively there were no significant differences in any variables between the two anaesthetic groups. Lower levels of MCP-1 and IL-8 (P < 0.001) and higher levels of IL-6 and MMP-9 (P = 0.003) were found in the sevoflurane group, compared with the TIVA group 30 min post-operatively. CRP and VCAM-1 levels did not differ. There were no significant differences between the two anaesthetic groups before surgery or at 1st post-operative day.

CONCLUSION

We found an inflammatory response during the observation period, which was modified by the anaesthetic regimen in the early phase. This short-lasting difference is probably too short to support a cardioprotective effect of sevoflurane compared with TIVA in open abdominal aortic surgery.

The effect of sevoflurane versus propofol anesthesia on troponin I after congenital heart surgery, a randomized clinical trial

Background:

The ischemic preconditioning phenomenon can save myocardium against move severe ischemic damages and reduce infarction size and furthermore a heart rhythm disturbance. In this study we examine relationship between troponin I (as a structural myocardial protein) level and anesthetic agents in the children.

Materials and Methods:

In this study 84 children under 12 years age before cardiac surgery were divided randomly into two groups of 42 each. For anesthetic maintenance sevoflurane with dose of 0.5-1 MAC was used in Group 1 and 100-150 mg/kg/min of intravenous propofol in Group 2 for maintenance of anesthesia. Troponin I level was assessed 2 before and 1 hour after anesthetic induction. Outcome measures included the serum cardiac troponin I level in children before and after surgery in two study groups.

Results:

There was no significant difference between two groups in indices and both groups were homogenous in this point of view. The troponin I level after surgery was significantly increased in two groups. In the sevoflurane group it was 0.04 ± 0.12 to 0.05 ± 0.09 ng/ml (P value = 0.003) and the propofol group was 0.12 ± 0.26 to 0.19 ± 0.38 ng/ml (P value = 0.001).

Conclusions:

In this study two Anesthetic regimens were compared to assess the mean troponin I level before and after pediatric closed heart surgery, and it was shown that mean troponin level before and after surgery in the sevoflurane group was less than the propofol group. But this result was not statistically significant. These results indicate that although more protective effects of sevoflurane on myocardial injuries during pediatric cardiac surgery is predominant but this effect has no significant difference in the propofol group.

Peri-operative anaesthetic myocardial preconditioning and protection - cellular mechanisms and clinical relevance in cardiac anaesthesia

Preconditioning has been shown to reduce myocardial damage caused by ischaemia–reperfusion injury peri-operatively. Volatile anaesthetic agents have the potential to provide myocardial protection by anaesthetic preconditioning and, in addition, they also mediate renal and cerebral protection. A number of proof-of-concept trials have confirmed that the experimental evidence can be translated into clinical practice with regard to postoperative markers of myocardial injury; however, this effect has not been ubiquitous. The clinical trials published to date have also been too small to investigate clinical outcome and mortality. Data from recent meta-analyses in cardiac anaesthesia are also not conclusive regarding intra-operative volatile anaesthesia. These inconclusive clinical results have led to great variability currently in the type of anaesthetic agent used during cardiac surgery. This review summarises experimentally proposed mechanisms of anaesthetic preconditioning, and assesses randomised controlled clinical trials in cardiac anaesthesia that have been aimed at translating experimental results into the clinical setting.

Remote ischaemic conditioning: cardiac protection from afar

For patients with ischaemic heart disease, remote ischaemic conditioning may offer an innovative, non‐invasive and virtually cost‐free therapy for protecting the myocardium against the detrimental effects of acute ischaemia‐reperfusion injury, preserving cardiac function and improving clinical outcomes. The intriguing phenomenon of remote ischaemic conditioning was first discovered over 20 years ago, when it was shown that the heart could be rendered resistant to acute ischaemia‐reperfusion injury by applying one or more cycles of brief ischaemia and reperfusion to an organ or tissue away from the heart – initially termed ‘cardioprotection at a distance’. Subsequent pre‐clinical and then clinical studies made the important discovery that remote ischaemic conditioning could be elicited non‐invasively, by inducing brief ischaemia and reperfusion to the upper or lower limb using a cuff. The actual mechanism underlying remote ischaemic conditioning cardioprotection remains unclear, although a neuro‐hormonal pathway has been implicated. Since its initial discovery in 1993, the first proof‐of‐concept clinical studies of remote ischaemic conditioning followed in 2006, and now multicentre clinical outcome studies are underway. In this review article, we explore the potential mechanisms underlying this academic curiosity, and assess the success of its application in the clinical setting.

Cellular mechanisms against ischemia reperfusion injury induced by the use of anesthetic pharmacological agents

Ischemia-reperfusion (IR) cycle in the myocardium is associated with activation of an injurious cascade, thus leading to new myocardial challenges, which account for up to 50% of infarct size. Some evidence implicates reactive oxygen species (ROS) as a probable cause of myocardial injury in prooxidant clinical settings. Damage occurs during both ischemia and post-ischemic reperfusion in animal and human models. The mechanisms that contribute to this damage include the increase in cellular calcium (Ca(2+)) concentration and induction of ROS sources during reperfusion. Pharmacological preconditioning, which includes pharmacological strategies that counteract the ROS burst and Ca(2+) overload followed to IR cycle in the myocardium, could be effective in limiting injury. Currently widespread evidence supports the use of anesthetics agents as an important cardioprotective strategy that act at various levels such as metabotropic receptors, ion channels or mitochondrial level. Their administration before a prolonged ischemic episode is known as anesthetic preconditioning, whereas when given at the very onset of reperfusion, is termed anesthetic postconditioning. Both types of anesthetic conditioning reduce, albeit not to the same degree, the extent of myocardial injury. This review focuses on cellular and pathophysiological concepts on the myocardial damage induced by IR and how anesthetic pharmacological agents commonly used could attenuate the functional and structural effects induced by oxidative stress in cardiac tissue.

The role of macrophage migration inhibitory factor in anesthetic-induced myocardial preconditioning

Introduction

Anesthetic-induced preconditioning (AIP) is known to elicit cardioprotective effects that are mediated at least in part by activation of the kinases AMPK and PKCε as well as by inhibition of JNK. Recent data demonstrated that the pleiotropic cytokine macrophage migration inhibitory factor (MIF) provides cardioprotection through activation and/or inhibition of kinases that are also known to mediate effects of AIP. Therefore, we hypothesized that MIF could play a key role in the AIP response.

Methods

Cardiomyocytes were isolated from rats and subjected to isoflurane preconditioning (4 h; 1.5 vol. %). Subsequently, MIF secretion and alterations in the activation levels of protective kinases were compared to a control group that was exposed to ambient air conditions. MIF secretion was quantified by ELISA and AIP-induced activation of protein kinases was assessed by Western blotting of cardiomyocyte lysates after isoflurane treatment.

Results

In cardiomyocytes, preconditioning with isoflurane resulted in a significantly elevated secretion of MIF that followed a biphasic behavior (30 min vs. baseline: p = 0.020; 24 h vs. baseline p = 0.000). Moreover, quantitative polymerase chain reaction demonstrated a significant increase in MIF mRNA expression 8 h after AIP. Of note, activation of AMPK and PKCε coincided with the observed peaks in MIF secretion and differed significantly from baseline.

Conclusions

These results suggest that the pleiotropic mediator MIF is involved in anesthetic-induced preconditioning of cardiomyocytes through stimulation of the protective kinases AMPK and PKCε.

The effect of intravenous anesthetics on ischemia-reperfusion injury

The effects of intravenous anesthetics on ischemia-reperfusion injury (IRI) have been investigated in both animals and clinical studies. The protective effects and the dosages of the intravenous anesthetics on IRI were discussed in this paper. The prevention of the tissue injury after the IRI was demonstrated with intravenous anesthetics in some studies. In the future, the studies should be focused on the dosage of the anesthetics related to diminishing the tissue injuries. Further studies might be required in order to investigate the effects of the anesthetics on molecular levels.

Thrombomodulin's lectin-like domain reduces myocardial damage by interfering with HMGB1-mediated TLR2 signalling

AIMS

Thrombomodulin (TM), via its lectin-like domain (LLD), exhibits anti-inflammatory properties partly by sequestering the pro-inflammatory cytokine, high-mobility group box 1 (HMGB1). Since myocardial damage after ischaemia and reperfusion is mediated by inflammation, we evaluated the cardioprotective effects of the LLD of TM. Using an in vivo mouse model of transient ischaemia and in vitro models of cardiomyocyte hypoxia, we assessed the ability of the LLD to suppress HMGB1-mediated activation of the receptors, receptor for advanced glycation endproducts (RAGEs) and Toll-like receptors (TLRs) 2 and 4.

METHODS AND RESULTS

Thirty-minute myocardial ischaemia was induced in isoflurane-anaesthetized mice followed by 24 h of reperfusion in wild-type (WT) mice, in mice lacking the LLD of TM (TM(LeD/LeD) mice), and in WT with systemic overexpression of the LLD of TM induced by hydrodynamic transfection. Infarct size, HMGB1 protein, and apoptotic cells were significantly increased in TM(LeD/LeD) mice when compared with WT. Neonatal rat cardiomyocytes transfected with TLR2-, TLR4-, and RAGE-siRNA were exposed to hypoxia (0.8% O2) and reoxygenation (21% O2). HMGB1 augmented hypoxia-induced apoptosis in TLR2- but not in RAGE- or TLR4-suppressed cells. Administration of HMGB1- and TLR2-blocking antibodies in TM(LeD/LeD) mice prior to myocardial ischaemia diminished apoptosis. Therapeutic systemic gene therapy using the LLD reduced the infarct size and HMGB1 protein levels 24 h after reperfusion.

CONCLUSION

The LLD of TM suppresses HMGB1-induced and TLR2-mediated myocardial reperfusion injury and apoptosis in vitro and in vivo.

Pharmacologic therapy that simulates conditioning for cardiac ischemic/reperfusion injury

Cardiovascular disease remains a leading cause of deaths due to noncommunicable diseases, of which ischemic heart disease forms a large percentage. The main therapeutic strategy to treat ischemic heart disease is reperfusion that could either be medical or surgical. However, reperfusion following ischemia is known to increase the infarct size further. Newer strategies such as ischemic preconditioning (IPC), ischemic postconditioning, and remote IPC have been shown to condition the myocardium to ischemia-reperfusion injury and thus reduce the final infarct size. Research over the past 3 decades has deepened our understanding of cellular and subcellular pathways that mediate ischemia-reperfusion injury. This in turn has resulted in the development of several pharmacological agents that act as conditioning agents, which reduce the final myocardial infarct size following ischemia-reperfusion. This review discusses many of these agents, their mechanisms of action, and the animal and clinical evidence behind them.

Diabetes, perioperative ischaemia and volatile anaesthetics: consequences of derangements in myocardial substrate metabolism

Volatile anaesthetics exert protective effects on the heart against perioperative ischaemic injury. However, there is growing evidence that these cardioprotective properties are reduced in case of type 2 diabetes mellitus. A strong predictor of postoperative cardiac function is myocardial substrate metabolism. In the type 2 diabetic heart, substrate metabolism is shifted from glucose utilisation to fatty acid oxidation, resulting in metabolic inflexibility and cardiac dysfunction. The ischaemic heart also loses its metabolic flexibility and can switch to glucose or fatty acid oxidation as its preferential state, which may deteriorate cardiac function even further in case of type 2 diabetes mellitus.Recent experimental studies suggest that the cardioprotective properties of volatile anaesthetics partly rely on changing myocardial substrate metabolism. Interventions that target at restoration of metabolic derangements, like lifestyle and pharmacological interventions, may therefore be an interesting candidate to reduce perioperative complications. This review will focus on the current knowledge regarding myocardial substrate metabolism during volatile anaesthesia in the obese and type 2 diabetic heart during perioperative ischaemia.

β-blockers and volatile anesthetics may attenuate cardioprotection by remote preconditioning in adult cardiac surgery: a meta-analysis of 15 randomized trials

OBJECTIVE

Clinical trials on cardioprotection by remote ischemic preconditioning (RIPC) for adult patients undergoing cardiac surgery revealed mixed results. Previous meta-analyses have been conducted and found marked heterogeneity among studies. The aim of this meta-analysis was to evaluate the factors affecting cardioprotection by remote preconditioning in adult cardiac surgery.

DESIGN

A meta-analysis of randomized controlled trials.

SETTING

University hospitals.

PARTICIPANTS

Adult subjects undergoing cardiac surgery.

INTERVENTIONS

RIPC.

MEASUREMENTS AND MAIN RESULTS

Fifteen trials with a total of 1,155 study patients reporting postoperative myocardial biomarker (CK-MB or troponin) levels were identified from PubMed, Embase, and the Cochrane Library (up to July 2012). Compared with controls, RIPC significantly reduced postoperative biomarkers of myocardial injury (standardized mean difference = -0.31, p = 0.041; heterogeneity test: I(2) = 83.5%). This effect seemed more significant in valve surgery (standardized mean difference = -0.74, p = 0.002) than in coronary artery surgery (standardized mean difference = -0.23; p = 0.17). Univariate meta-regression analyses suggested that the major sources of significant heterogeneity were β-blockers (%) (coefficient = 0.0161, p = 0.022, adjusted R(2) = 0.37) and volatile anesthetics (coefficient = 0.6617, p = 0.065, adjusted R(2) = 0.22). These results were further confirmed in multivariate regression and subgroup analyses.

CONCLUSIONS

Available data from this meta-analysis further confirmed the cardioprotection conferred by RIPC in adult cardiac surgery. Moreover, the cardioprotective effect may be attenuated when combined with β-blockers or volatile anesthetics.

Failure of remote ischemic preconditioning to reduce the risk of postoperative acute kidney injury in children undergoing operation for complex congenital heart disease: a randomized single-center study

OBJECTIVE

The objective of this study was to evaluate whether remote ischemic preconditioning can protect kidney function in children undergoing operation for complex congenital heart disease.

METHODS

Children (n = 113) aged 0 to 15 years admitted for complex congenital heart disease were randomly allocated according to age to remote ischemic preconditioning and control groups. After exclusion of 8 patients, we conducted the analysis on 105 patients (remote ischemic preconditioning group, n = 54; control group, n = 51). Before surgery, remote ischemic preconditioning was performed as 4 cycles of 5 minutes of ischemia by inflating a cuff around a leg to 40 mm Hg above the systolic pressure. End points were development of acute kidney injury, initiation of dialysis, plasma creatinine, estimated glomerular filtration rate, plasma cystatin C, plasma and urinary neutrophil gelatinase-associated lipocalin, and urinary output. Secondary end points included postoperative blood pressure, inotropic score, and mortality, as well as morbidity reflected by reoperation and stays in the intensive care unit and hospital.

RESULTS

Overall, 57 of the children (54%) had acute kidney injury develop, with 27 (50%) in the remote ischemic preconditioning group and 30 (59%) in the control group (P > .2). Remote ischemic preconditioning was not associated with improvement in either any of the renal biomarkers or any of the secondary end points.

CONCLUSIONS

We found no evidence that remote ischemic preconditioning provided protection of kidney function in children undergoing operation for complex congenital heart disease.

Pathophysiology of myocardial reperfusion injury: preconditioning, postconditioning, and translational aspects of protective measures

Heart diseases due to myocardial ischemia, such as myocardial infarction or ischemic heart failure, are major causes of death in developed countries, and their number is unfortunately still growing. Preliminary exploration into the pathophysiology of ischemia-reperfusion injury, together with the accumulation of clinical evidence, led to the discovery of ischemic preconditioning, which has been the main hypothesis for over three decades for how ischemia-reperfusion injury can be attenuated. The subcellular pathophysiological mechanism of ischemia-reperfusion injury and preconditioning-induced cardioprotection is not well understood, but extensive research into components, including autacoids, ion channels, receptors, subcellular signaling cascades, and mitochondrial modulators, as well as strategies for modulating these components, has made evolutional progress. Owing to the accumulation of both basic and clinical evidence, the idea of ischemic postconditioning with a cardioprotective potential has been discovered and established, making it possible to apply this knowledge in the clinical setting after ischemia-reperfusion insult. Another a great outcome has been the launch of translational studies that apply basic findings for manipulating ischemia-reperfusion injury into practical clinical treatments against ischemic heart diseases. In this review, we discuss the current findings regarding the fundamental pathophysiological mechanisms of ischemia-reperfusion injury, the associated protective mechanisms of ischemic pre- and postconditioning, and the potential seeds for molecular, pharmacological, or mechanical treatments against ischemia-reperfusion injury, as well as subsequent adverse outcomes by modulation of subcellular signaling mechanisms (especially mitochondrial function). We also review emerging translational clinical trials and the subsistent clinical comorbidities that need to be overcome to make these trials applicable in clinical medicine.