Desflurane-Induced Preconditioning Has a Threshold That Is Lowered by Repetitive Application and Is Mediated by β2-Adrenergic Receptors

Volatile Anesthetic Use Versus Total Intravenous Anesthesia for Patients Undergoing Heart Valve Surgery: A Nationwide Population-Based Study

BACKGROUND

Many studies have suggested that volatile anesthetic use may improve postoperative outcomes after cardiac surgery compared to total intravenous anesthesia (TIVA) owing to its potential cardioprotective effect. However, the results were inconclusive, and few studies have included patients undergoing heart valve surgery.

METHODS

This nationwide population-based study included all adult patients who underwent heart valve surgery between 2010 and 2019 in Korea based on data from a health insurance claim database. Patients were divided based on the use of volatile anesthetics: the volatile anesthetics or TIVA groups. After stabilized inverse probability of treatment weighting (IPTW), the association between the use of volatile anesthetics and the risk of cumulative 1-year all-cause mortality (the primary outcome) and cumulative long-term (beyond 1 year) mortality were assessed using Cox regression analysis.

RESULTS

Of the 30,755 patients included in this study, the overall incidence of 1-year mortality was 8.5%. After stabilized IPTW, the risk of cumulative 1-year mortality did not differ in the volatile anesthetics group compared to the TIVA group (hazard ratio, 0.98; 95% confidence interval, 0.90-1.07; P = .602), nor did the risk of cumulative long-term mortality (hazard ratio, 0.98; 95% confidence interval, 0.93-1.04; P = .579) at a median (interquartile range) follow-up duration of 4.8 (2.6-7.6) years.

CONCLUSIONS

Compared with TIVA, volatile anesthetic use was not associated with reduced postoperative mortality risk in patients undergoing heart valve surgery. Our findings indicate that the use of volatile anesthetics does not have a significant impact on mortality after heart valve surgery. Therefore, the choice of anesthesia type can be based on the anesthesiologists' or institutional preference and experience.

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.

Mitochondria and Pharmacologic Cardiac Conditioning-At the Heart of Ischemic Injury

Pharmacologic cardiac conditioning increases the intrinsic resistance against ischemia and reperfusion (I/R) injury. The cardiac conditioning response is mediated via complex signaling networks. These networks have been an intriguing research field for decades, largely advancing our knowledge on cardiac signaling beyond the conditioning response. The centerpieces of this system are the mitochondria, a dynamic organelle, almost acting as a cell within the cell. Mitochondria comprise a plethora of functions at the crossroads of cell death or survival. These include the maintenance of aerobic ATP production and redox signaling, closely entwined with mitochondrial calcium handling and mitochondrial permeability transition. Moreover, mitochondria host pathways of programmed cell death impact the inflammatory response and contain their own mechanisms of fusion and fission (division). These act as quality control mechanisms in cellular ageing, release of pro-apoptotic factors and mitophagy. Furthermore, recently identified mechanisms of mitochondrial regeneration can increase the capacity for oxidative phosphorylation, decrease oxidative stress and might help to beneficially impact myocardial remodeling, as well as invigorate the heart against subsequent ischemic insults. The current review highlights different pathways and unresolved questions surrounding mitochondria in myocardial I/R injury and pharmacological cardiac conditioning.

Impact of Ca2+-Sensitive Potassium Channels in Levosimendan-Induced Postconditioning

PURPOSE

Small and big conductance Ca²⁺-sensitive potassium (K_Ca) channels are involved in cardioprotective measures aiming at reducing myocardial reperfusion injury. For levosimendan, infarct size-reducing effects were shown. Whether activation of these channels is involved in levosimendan-induced postconditioning is unknown. We hypothesized that levosimendan exerts a concentration-dependent cardioprotective effect and that both types of Ca²⁺-sensitive potassium channels are involved.

METHODS

In a prospective blinded experimental laboratory investigation, hearts of male Wistar rats were randomized and placed on a Langendorff system, perfused with Krebs-Henseleit buffer at a constant pressure of 80 mmHg. All hearts were subjected to 33 min of global ischemia and 60 min of reperfusion. At the onset of reperfusion, hearts were perfused with various concentrations of levosimendan (0.03-1 μM) in order to determine a concentration-response relationship. To elucidate the involvement of K_Ca-channels for the observed cardioprotection, in the second set of experiments, 0.3 μM levosimendan was administered in combination with the subtype-specific K_Ca-channel inhibitors paxilline (1 μM, big K_Ca-channel) and NS8593 (0.1 μM, small K_Ca-channel) respectively. Infarct size was determined by tetrazolium chloride (TTC) staining.

RESULTS

Infarct size in controls was 60 ± 7% and 59 ± 6% respectively. Levosimendan at a concentration of 0.3 μM reduced infarct size to 30 ± 5% (P < 0.0001 vs. control). Higher concentrations of levosimendan did not induce a stronger effect. Paxilline but not NS8593 completely abolished levosimendan-induced cardioprotection while both substances alone had no effect on infarct size.

CONCLUSIONS

Cardioprotection by levosimendan-induced postconditioning shows a binary phenomenon, either ineffective or with maximal effect. The cardioprotective effect requires activation of big but not small K_Ca channels.

Effect of helium pre- or postconditioning on signal transduction kinases in patients undergoing coronary artery bypass graft surgery

BACKGROUND

The noble gas helium induces pre- and postconditioning in animals and humans. Volatile anesthetics induce cardioprotection in humans undergoing coronary artery bypass graft (CABG) surgery. We hypothesized that helium induces pre- and postconditioning in CABG-patients, affecting signaling molecules protein kinase C-epsilon (PKC-ε), p38 mitogen activated protein kinase (p38 MAPK), extracellular signal-regulated kinase 1/2 (ERK-1/2) and heat shock protein 27 (HSP-27) within cardiac tissue, and reducing postoperative troponin levels.

METHODS

After ethical approval and informed consent, 125 elective patients undergoing CABG surgery were randomised into this prospective, placebo controlled, investigator blinded, parallel arm single-centre study. Helium preconditioning (3 × 5 min of 70 % helium and 30 % oxygen) was applied before aortic cross clamping; postconditioning (15 min of helium) was applied before release of the aortic cross clamp. Signaling molecules were measured in right atrial appendix specimens. Troponin-T was measured at 4, 12, 24 and 48 h postoperatively.

RESULTS

Baseline characteristics of all groups were similar. Helium preconditioning did not significantly alter the primary outcome (molecular levels of kinases PKC-ε and HSP-27, ratio of activated p38 MAPK or ERK ½). Postoperative troponin T was 11 arbitrary units [5, 31; area-under-the-curve (interquartile range)] for controls, and no statistically significant changes were observed after helium preconditioning [He-pre: 11 (6, 18)], helium postconditioning [He-post: 11 (8, 15)], helium pre- and postconditioning [He-PP: 14 (6, 20)] and after sevoflurane preconditioning [APC: 12 (8, 24), p = 0.13]. No adverse effects related to study treatment were observed in this study.

CONCLUSIONS

No effect was observed of helium preconditioning, postconditioning or the combination thereof on activation of p38 MAPK, ERK 1/2 or levels of HSP27 and PKC-ε in the human heart. Helium pre- and postconditioning did not affect postoperative troponin release in patients undergoing CABG surgery. Clinical trial number Dutch trial register ( http://www.trialregister.nl/ ) number NTR1226.

Sevoflurane preconditioning in on-pump coronary artery bypass grafting: a meta-analysis of randomized controlled trials

PURPOSE

Sevoflurane preconditioning (SevoPreC) has been proved to prevent organ ischemia/reperfusion (I/R) injury in various animal models and preclinical studies. Clinical trials on cardioprotection by SevoPreC for adult patients undergoing coronary artery bypass graft (CABG) revealed mixed results. The aim of this meta-analysis was to evaluate the cardiac effect of SevoPreC in on-pump CABG.

METHODS

Randomized controlled trials (RCT) comparing the cardiac effect of SevoPreC (compared with control) in adult patients undergoing CABG were searched from PubMed, Embase, and the Cochrane Library (up to November 2015). The primary endpoints were postoperative troponin levels. Additional endpoints were CK-MB levels, mechanic ventilation (MV) duration, intensive care unit (ICU) stay, and hospital length of stay (LOS).

RESULTS

Six trials with eight comparisons enrolling a total of 384 study patients reporting postoperative troponin levels were identified. Compared with controls, SevoPreC decreased postoperative myocardial troponin levels [standardized mean difference (SMD) = -0.38; 95 % CI, -0.74 to -0.03; P = 0.04; I ² = 63.9 %]. However, no significant differences were observed in postoperative CK-MB levels [weighted mean difference (WMD) = -1.71; P = 0.37; I ² = 37.7 %], MV duration (WMD = -0.53; P = 0.47; I ² = 0.0 %), ICU stay (WMD = -0.91; P = 0.39; I ² = 0.9 %), and hospital LOS (WMD = 0.08; P = 0.86; I ² = 8.0 %).

CONCLUSION

Available evidence from the present systematic review and meta-analysis suggests that sevoflurane preconditioning may reduce troponin levels in on-pump CABG. Future high-quality, large-scale clinical trials should focus on the early and long-term clinical effect of SevoPreC in on-pump CABG.

Comparison of isoflurane and sevoflurane in cardiac surgery: a randomized non-inferiority comparative effectiveness trial

Purpose

Volatile anesthetics possess cardioprotective properties, but it is unknown if the cardioprotective effects extend equally to all members of the class. Although sevoflurane is a relatively newer anesthetic than isoflurane, its introduction into practice was not preceded by a head-to-head comparison with isoflurane in a trial focusing on clinically important outcomes. Our objective was to determine whether sevoflurane was non-inferior to isoflurane on a clinically important primary outcome in a heterogeneous group of adults undergoing cardiac surgery.

Methods

This was a pragmatic randomized non-inferiority comparative effectiveness clinical trial in 464 adults having coronary artery bypass graft and/or single valve surgery during November 2011 to March 2014. The intervention was maintenance of anesthesia with sevoflurane (n = 231) or isoflurane (n = 233) administered at a dose of 0.5-2.0 MAC throughout the entire operation. All caregivers were blinded except for the anesthesiologist and perfusionist. The primary outcome was a composite of intensive care unit (ICU) length of stay ≥ 48 hr and all-cause 30-day mortality. We hypothesized that sevoflurane would be non-inferior to isoflurane (non-inferiority margin < 10% based on an expected event rate of 25%). Secondary outcomes included prolonged ICU stay, 30- and 365-day all-cause mortality, inotrope or vasopressor usage, new-onset hemodialysis or atrial fibrillation, stroke, and readmission to the ICU.

Results

No losses to follow-up occurred. The primary outcome occurred in 25% of sevoflurane patients and 30% of isoflurane patients (absolute difference, −5.4%; one-sided 95% confidence interval, 1.4), thus non-inferiority was declared. Sevoflurane was not superior to isoflurane for the primary outcome (P = 0.21) or for any secondary outcomes.

Conclusion

Sevoflurane is non-inferior to isoflurane on a composite outcome of prolonged ICU stay and all-cause 30-day mortality. Sevoflurane is not superior to isoflurane on any other of the clinically important outcomes. This trial was registered at clinicaltrials.gov; NCT01477151.

Adding Emulsified Isoflurane to Cardioplegia Solution Produces Cardiac Protection in a Dog Cardiopulmonary Bypass Model

This study investigated whether caridoplegia solution with Emulsified Isoflurane (EI) could improve cardiaoprotection in a dog CPB model of great similarity to clinical settings. Adult dogs were randomly assigned to receive one of the following cardioplegia solutions: St. Thomas with EI (group ST+EI), St. Thomas with 30% Intralipid (group ST+EL) and St. Thomas alone (group ST). The aorta was cross-clamped for two hours followed by reperfusion for another two hours, during which cardiac output was measured and dosages of positive inotropic agent to maintain normal hemodynamics were recorded. Serum level of cardiac troponin I (cTnI) and CK-MB were measured. Deletion of cardiac mitochondrial DNA was examined at the end of reperfusion. Compared with ST, ST+EI decreased the requirement of dopamine support while animals receiving ST+EI had a significantly larger cardiac output. ST+EI reduced post-CPB release of cTnI and CK-MB. Mitochondrial DNA loss was observed in only one of the tested animals from group ST+EI while it was seen in all the tested animals from group ST+EL and ST. Addition of emulsified isoflurane into cardioplegia solution protects against myocardial ischemia reperfusion injury. This protective effect might be mediated by preserving mitochondrial ultrastructure and DNA integrity.

Effects of sevoflurane vs. propofol on mitochondrial functional activity after ischemia-reperfusion injury and the influence on clinical parameters in patients undergoing CABG surgery with cardiopulmonary bypass

The aim of the study was to evaluate the effects of sevoflurane and propofol on the activity of mitochondrial function related to ischemia-reperfusion injury, myocardial damage biomarkers release and clinical parameters in the postoperative period. Seventy-two patients scheduled for elective coronary artery bypass graft surgery with cardiopulmonary bypass were randomized into two groups: 36 patients received sevoflurane during anesthesia (Group S) and 36 patients received propofol (Group P). To investigate the functional activity of mitochondria, we used skinned fibers prepared from biopsies of right atrial tissue before cardioplegia and after the aorta cross-clamp removal (within 10-15 minutes after reperfusion). Patients’ clinical data (length of stay in ICU, hemodynamic parameters, duration of mechanical ventilation (MV) and the amount of lactate and troponin I in the blood serum) were evaluated postoperatively. The results showed that, before cardioplegia and after reperfusion, there was no significant difference in the mitochondrial routine and State 3 respiration rates between the groups. The effect of cytochrome c was higher in Group P. Troponin I concentration at the 12th hour after the surgery was 2.2 ± 0.8 ng/mL in Group S and 3.5 ± 1.1 ng/mL in Group P (p<0.001). There were no significant differences in the duration of mechanical ventilation, hemodynamic parameters and length of stay in the ICU between the groups. We conclude that sevoflurane slightly protects the mitochondrial outer membrane from ischemia-reperfusion injury and the loss of cytochrome c, yet has the similar effect on clinical parameters in the postoperative period when compared to propofol.

A pilot study investigating the effects of remote ischemic preconditioning in high-risk cardiac surgery using a randomised controlled double-blind protocol

The efficacy of remote ischemic preconditioning (RIPC) in high-risk cardiac surgery is uncertain. In this study, 96 adults undergoing high-risk cardiac surgery were randomised to RIPC (3 cycles of 5 min of upper-limb ischemia induced by inflating a blood pressure cuff to 200 mmHg with 5 min of reperfusion) or control. Main endpoints were plasma high-sensitivity troponin T (hsTNT) levels at 6 and 12 h, worst post-operative acute kidney injury (AKI) based on RIFLE criteria, and noradrenaline duration. hsTNT levels were log-normally distributed and higher with RIPC than control at 6-h post cross-clamp removal [810 ng/ml (IQR 527-1,724) vs. 634 ng/ml (429-1,012); ratio of means 1.41 (99.17% CI 0.92-2.17); P=0.04] and 12 h [742 ng/ml (IQR 427-1,700) vs. 514 ng/ml (IQR 356-833); ratio of means 1.56 (99.17% CI 0.97-2.53); P=0.01]. After adjustment for baseline confounders, the ratio of means of hsTNT at 6 h was 1.23 (99.17% CI 0.88-1.72; P=0.10) and at 12 h was 1.30 (99.17% CI 0.92-1.84; P=0.05). In the RIPC group, 35/48 (72.9%) had no AKI, 5/48 (10.4%) had AKI risk, and 8/48 (16.7%) had either renal injury or failure compared to the control group where 34/48 (70.8%) had no AKI, 7/48 (14.6%) had AKI risk, and 7/48 (14.6%) had renal injury or failure (Chi-squared 0.41; two degrees of freedom; P = 0.82). RIPC increased post-operative duration of noradrenaline support [21 h (IQR 7-45) vs. 9 h (IQR 3-19); ratio of means 1.70 (99.17% CI 0.86-3.34); P=0.04]. RIPC does not reduce hsTNT, AKI, or ICU-support requirements in high-risk cardiac surgery.

Protection by remote ischemic preconditioning during coronary artery bypass graft surgery with isoflurane but not propofol - a clinical trial

BACKGROUND

Remote ischemic preconditioning (RIPC) of the myocardium by limb ischemia/reperfusion may mitigate cardiac damage, but its interaction with the anesthetic regimen is unknown. We tested whether RIPC is associated with differential effects depending on background anesthesia. Specifically, we hypothesized that RIPC during isoflurane anesthesia attenuates myocardial injury in patients undergoing coronary artery bypass graft (CABG) surgery, and that effects may be different during propofol anesthesia.

METHODS

In a randomized, single-blinded, placebo-controlled prospective study, serum troponin I concentration (cTnI) (baseline, and 1, 6, 12, 24, 48, and 72 h postoperatively) were measured during isoflurane/sufentanil or propofol/sufentanil anesthesia with or without RIPC (three 5-min periods of intermittent left upper arm ischemia with 5 min reperfusion each) in non-diabetic patients (n = 72) with three-vessel coronary artery disease (ClinicalTrials.gov NCT01406678).

RESULTS

RIPC during isoflurane anesthesia (n = 20) decreased the area under the cTnI time curve (cTnI AUC) (-50%, 190 ± 105 ng/ml × 72 h vs. 383 ± 262 ng/ml × 72 h, P = 0.004), and the peak (7.3 ± 3.6 ng/ml vs. 11.8 ± 5.5, P = 0.004) and serial (P < 0.041) postoperative cTnI when compared to isoflurane alone (n = 19). In contrast, RIPC during propofol anesthesia (n = 14) did not alter the cTnI AUC [263 ± 157 ng/ml × 72 h vs. 372 ± 376 ng/ml × 72 h (n = 19), P = 0.318] or peak postoperative cTnI (10.1 ± 4.5 ng/ml vs. 12 ± 8.2, P = 0.444). None of the patients experienced harm or side effects from the intermittent left arm ischemia.

CONCLUSION

Thus, RIPC during isoflurane but not during propofol anesthesia decreased myocardial damage in patients undergoing CABG surgery. Accordingly, effects of RIPC evoked by upper limb ischemia/reperfusion depend on background anesthesia, with combined RIPC/isoflurane exerting greater beneficial effects under conditions studied.

Clinical application of the cardioprotective effects of volatile anaesthetics: CON--total intravenous anaesthesia or not total intravenous anaesthesia to anaesthetise a cardiac patient?

Although volatile anaesthetics show strong and easily reproducible cardioprotective effects in animal experiments, these effects are less obvious in clinical settings. Indeed, more than a decade after the first human clinical study, the number of publications has increased extensively, but the encouraging results from previous studies in terms of myocardial protection have failed to translate into an improvement in survival or a decrease the incidence of myocardial infarction. No consensus on the modalities of administration of volatile anaesthetics has been agreed and when the experimental protocols are transposed into daily clinical practice, their cardioprotective effects are still weak. The reasons for the disparities between experimental and clinical studies will be reviewed here, especially the role of patients' co-morbidities and medications as well as the limitations of the main positive clinical trials. Recent data showing anti-inflammatory properties of propofol will also be explained. One of the most important clinical benefits of propofol is that it can be used by target-controlled or continuous infusion for anaesthesia and sedation throughout the surgical and critical care periods without the risk of a transition failure. Further large multi-centre clinical investigations are still required.

Clinical application of the cardioprotective effects of volatile anaesthetics: PRO--get an extra benefit from a proven anaesthetic free of charge

Volatile anaesthetic agents have been used in millions of patients around the world and have proved to be both well tolerated and efficient. In recent years, cardioprotective properties of these drugs have been demonstrated unequivocally in numerous experimental investigations, but the beneficial effects of volatile anaesthetics in daily clinical practice are still under debate. In order to elucidate their cardioprotective properties in an unbiased way, the STAIR (Stroke Therapy Academic Industry Roundtable Preclinical Recommendation) criteria proposed as a framework for researchers in the field of neuroprotection can be applied to research conducted in the field of cardioprotection by volatile anaesthetics. All STAIR criteria have already been clearly fulfilled when all experimental and clinical studies are considered. Specifically, a dose-response pattern has been found with a minimal alveolar concentration value and a ceiling effect; volatile anaesthetics show two distinct therapeutic windows after application; important outcome measures such as hospital length of stay have been addressed; and multiple species have been studied by different independent groups of researchers who were largely able to reproduce their findings. Given the numerous confounding factors capable of attenuating or even abolishing the cardioprotective properties of volatile anaesthetics in laboratory investigations, the positive effects found in the majority of clinical trials point to the fact that the cardioprotective effects exerted by volatile anaesthetics are robust and triggered by interactions with several distinct cellular and subcellular targets, thereby providing multiplication and reiteration. The available evidence indicates that volatile anaesthetic agents should be used routinely in clinical practice in order to claim an extra benefit for our patients 'free of charge'.

Effect of bupivacaine on sevoflurane-induced preconditioning in isolated rat hearts

Volatile anesthetics protect the heart against ischemia-reperfusion injury. As an adjunct to general anesthesia, local and regional application of bupivacaine is often used. However, systemic plasma levels of bupivacaine might be cardiodepressant and interfere with sevoflurane-induced cardioprotection. Effects of bupivacaine on sevoflurane-induced cardioprotection were assessed in isolated Langendorff-perfused rat hearts subjected to 35 min of global ischemia followed by 60 min reperfusion. Hearts (n=40) were randomized to different groups: 1. CONTROL; 2. Bupivacaine: addition of 0.125 or 1.0 μg/ml bupivacaine to the perfusate for 40 min prior to ischemia-reperfusion; 3. Sevoflurane: preconditioning induced by three times 5-min episodes of sevoflurane (2.5 vol.%) prior to ischemia-reperfusion; 4. Bupivacaine-sevoflurane: combined application of bupivacaine and sevoflurane. After ischemia-reperfusion, cardioprotection was assessed from infarct size and recovery of ventricular function, and phosphorylation levels of glycogen synthase kinase 3β (GSK3β) and 5'AMP activated protein kinase (AMPK) were determined. Infarct size was reduced in the sevoflurane and bupivacaine-sevoflurane groups (Sevo: 23±7% and Bupi-Sevo: 23±5% vs.

CONTROL

59±6%, P<0.05). In the bupivacaine group infarct size was reduced as well (34±3%). In the sevoflurane and bupivacaine-sevoflurane groups the recovery of left ventricular function (+dP/dt) was improved (Sevo: 59±2% and Bupi-Sevo: 59±2% vs.

CONTROL

47±3%, P<0.05), but not in the bupivacaine group (48±3%). AMPK and GSK3β phosphorylation were increased by sevoflurane but not by bupivacaine. Sevoflurane-induced cardioprotection was not affected by bupivacaine in the non-cardiotoxic range. Bupivacaine alone also reduced infarct size. Both anesthetics activated different signaling kinases, indicating the existence of different cardioprotective intracellular signaling cascades.

Activation of adenosine-monophosphate-activated protein kinase abolishes desflurane-induced preconditioning against myocardial infarction in vivo

OBJECTIVES

Myocardial ischemia is accompanied by a rapid activation of adenosine-monophosphate-activated protein kinase (AMPK). However, it is unclear whether this represents a potentially beneficial or detrimental event in the course of ischemic injury. The role of AMPK activation in the cardioprotective setting of desflurane-induced preconditioning has not been investigated to date. Hence, the current study was undertaken to address the role of AMPK activation during desflurane-induced preconditioning in vivo.

DESIGN

A prospective randomized vehicle-controlled study.

SETTING

A university research laboratory.

SUBJECTS

Male New Zealand white rabbits (n = 44).

INTERVENTIONS

The animals were subjected to a 30-minute coronary artery occlusion (CAO) followed by 3 hours of reperfusion. Desflurane (1.0 minimum alveolar concentration) was administered for 30 minutes and discontinued 30 minutes prior to CAO. Different groups of animals received the AMPK activator, 5-aminoimidazole-4-carboxamide-1-b-riboside (AICAR), alone or in combination with desflurane. Infarct size was determined gravimetrically; AMPK activity and myocardial glycogen content were measured using specific assays. Phosphorylation of the AMPK substrate, acetyl-CoA carboxylase, was assessed by immunoblotting. Data are mean ± standard error of the mean.

RESULTS

Desflurane significantly reduced the myocardial infarct size (36.7 ± 1.9%, p < 0.05) compared with the control group (61.6% ± 3.0%), concomitant with increased myocardial tissue levels of glycogen (2.09 ± 0.07 μg, p < 0.05). Activation of the AMPK by AICAR alone did not protect against ischemic injury (65% ± 3.3), but did abolish the cardioprotection elicited by desflurane (61.8% ± 4.2%) at the same time as increasing myocardial glycogen consumption (1.42 ± 0.15 μg/mL).

CONCLUSIONS

The results obtained show that the pharmacologic activation of AMPK abolishes cardioprotection elicited by desflurane.

Organ protection by volatile anesthetics in non-coronary artery bypass grafting surgery

The cardioprotective properties of volatile anesthetics have been widely demonstrated by numerous randomized studies and meta-analyses in the setting of cardiac surgery, above of all during coronary artery bypass grafting procedures. Recently, conflicting results have been presented in cardiac non-coronary artery bypass grafting surgery. Unfortunately, despite the existence of a great number of studies comparing a total intravenous anesthetic regimen with an inhalational regimen, at present there are no randomized studies presenting data regarding mortality and important outcomes, such as myocardial infarction, in non-cardiac surgery. In this review we analyze and present the results of the most recent and important studies regarding anesthetic preconditioning in cardiac and in noncardiac surgery. Furthermore, we focus on the emerging data from animal experiments, discussing in particular the molecular mechanisms underlying anesthetic preconditioning.

Comparison of Isoflurane-, Sevoflurane-, and Desflurane-Induced Pre- and Postconditioning Against Myocardial Infarction in Mice In Vivo

The murine in vivo model of acute myocardial infarction is increasingly used to investigate anesthetic-induced preconditioning (APC) and postconditioning (APOST). However, in mice the potency of different volatile anesthetics to reduce myocardial infarct size (IS) has never been investigated systematically nor in a head to head comparison with regard to ischemic preconditioning (IPC) and postconditioning (IPOST). Male C57BL/6 mice were subjected to 45 min of coronary artery occlusion (CAO) and 180 min of reperfusion. To induce APC, 1.0 MAC isoflurane (ISO), sevoflurane (SEVO) or desflurane (DES) was administered 30 min prior to CAO for 15 min. In an additional group, ISO was administered 45 min prior to CAO for 30 min. To induce APOST, 1.0 MAC ISO, SEVO or DES was administered for 18 min starting 3 min prior to the end of CAO. IPC was induced by 3 or 6 cycles of 5 min ischemia/reperfusion, 40 or 60 min prior to CAO, respectively. IPOST was induced by 3 cycles of 30 sec reperfusion/ischemia at the beginning of reperfusion. Area at risk (AAR) and IS were determined with Evans Blue and TTC staining, respectively. IS (IS/AAR) was 50 ± 4% (mean ± SEM) in the control group and was significantly (* P < 0.05) reduced by 3×5 IPC (26 ± 3%*), 6×5 IPC (26 ± 4%*), IPOST (20 ± 2%*), ISO APOST (19 ± 1%*), SEVO APOST (15 ± 1%*), DES APOST (14 ± 2%*) and SEVO APC (27 ± 6%*). ISO APC significantly reduced IS compared to control when administered 30 min (33 ± 4%*), but not when administered 15 min (48 ± 6%). DES APC significantly reduced IS compared to control and to SEVO APC (7 ± 1%*). Within the paradigm of preconditioning, the potency of volatile anesthetics to reduce myocardial infarct size in mice significantly increases from ISO over SEVO to DES, whereas within the paradigm of postconditioning the potency of these volatile anesthetics to reduce myocardial infarct size in mice is similar.

Anaesthesia and myocardial ischaemia/reperfusion injury

Anaesthetists are confronted on a daily basis with patients with coronary artery disease, myocardial ischaemia, or both during the perioperative period. Therefore, prevention and ultimately adequate therapy of perioperative myocardial ischaemia and its consequences are the major challenges in current anaesthetic practice. This review will focus on the translation of the laboratory evidence of anaesthetic-induced cardioprotection into daily clinical practice.