One MAC of sevoflurane provides protection against reperfusion injury in the rat heart in vivo

Sevoflurane postconditioning reduces myocardial reperfusion injury in rat isolated hearts via activation of PI3K/Akt signaling and modulation of Bcl-2 family proteins

Sevoflurane postconditioning reduces myocardial infarct size. The objective of this study was to examine the role of the phosphatidylinositol-3-kinase (PI3K)/Akt pathway in anesthetic postconditioning and to determine whether PI3K/Akt signaling modulates the expression of pro- and antiapoptotic proteins in sevoflurane postconditioning. Isolated and perfused rat hearts were prepared first, and then randomly assigned to the following groups: Sham-operation (Sham), ischemia/reperfusion (Con), sevoflurane postconditioning (SPC), Sham plus 100 nmol/L wortmannin (Sham+Wort), Con+Wort, SPC+Wort, and Con+dimethylsulphoxide (DMSO). Sevoflurane postconditioning was induced by administration of sevoflurane (2.5%, v/v) for 10 min from the onset of reperfusion. Left ventricular developed pressure (LVDP), left ventricular end-diastolic pressure (LVEDP), maximum increase in rate of LVDP (+dP/dt), maximum decrease in rate of LVDP (-dP/dt), heart rate (HR), and coronary flow (CF) were measured at baseline, R30 min (30 min of reperfusion), R60 min, R90 min, and R120 min. Creatine kinase (CK) and lactate dehydrogenase (LDH) were measured after 5 min and 10 min reperfusion. Infarct size was determined by triphenyltetrazolium chloride staining at the end of reperfusion. Total Akt and phosphorylated Akt (phospho-Akt), Bax, Bcl-2, Bad, and phospho-Bad were determined by Western blot analysis. Analysis of variance (ANOVA) and Student-Newman-Keuls' test were used to investigate the significance of differences between groups. The LVDP, + or - dP/dt, and CF were higher and LVEDP was lower in the SPC group than in the Con group at all points of reperfusion (P<0.05). The SPC group had significantly reduced CK and LDH release and decreased infarct size compared with the Con group [(22.9 + or - 8)% vs. (42.4 + or - 9.4)%, respectively; P<0.05]. The SPC group also had increased the expression of phospho-Akt, Bcl-2, and phospho-Bad, and decreased the expression of Bax. Wortmannin abolished the cardioprotection of sevoflurane postconditioning. Sevoflurane postconditioning may protect the isolated rat heart. Activation of PI3K and modulation of the expression of pro- and antiapoptotic proteins may play an important role in sevoflurane-induced myocardial protection.

Cyclosporine A administered during reperfusion fails to restore cardioprotection in prediabetic Zucker obese rats in vivo

BACKGROUND AND AIMS

Hyperglycaemia blocks sevoflurane-induced postconditioning, and cardioprotection in hyperglycaemic myocardium can be restored by inhibition of the mitochondrial permeability transition pore (mPTP). We investigated whether sevoflurane-induced postconditioning is also blocked in the prediabetic heart and if so, whether cardioprotection could be restored by inhibiting mPTP.

METHODS AND RESULTS

Zucker lean (ZL) and Zucker obese (ZO) rats were assigned to one of seven groups. Animals underwent 25 min of ischaemia and 120 min of reperfusion. Control (ZL-/ZO Con) animals were not further treated. postconditioning groups (ZL-/ZO Sevo-post) received sevoflurane for 5 min starting 1min prior to the onset of reperfusion. The mPTP inhibitor cyclosporine A (CsA) was administered intravenously in a concentration of 5 (ZO CsA and ZO CsA+Sevo-post) or 10 mg/kg (ZO CsA10+Sevo-post) 5 min before the onset of reperfusion. At the end of reperfusion, infarct sizes were measured by TTC staining. Blood samples were collected to measure plasma levels of insulin, cholesterol and triglycerides. Sevoflurane postconditioning reduced infarct size in ZL rats to 35±12% (p<0.05 vs. ZL Con: 60±6%). In ZO rats sevoflurane postconditioning was abolished (ZO Sevo-post: 59±12%, n.s. vs. ZO Con: 58±6%). 5 mg and 10 mg CsA could not restore cardioprotection (ZO CsA+Sevo-post: 59±7%, ZO CsA10+Sevo-post: 57±14%; n.s. vs. ZO Con). In ZO rats insulin, cholesterol and triglyceride levels were significant higher than in ZL rats (all p<0.05).

CONCLUSION

Inhibition of mPTP with CsA failed to restore cardioprotection in the prediabetic but normoglycaemic heart of Zucker obese rats in vivo.

Sevoflurane postconditioning converts persistent ventricular fibrillation into regular rhythm

BACKGROUND AND OBJECTIVE

Recent studies showed that ischaemic postconditioning converted persistent ventricular fibrillation to sinus rhythm. The influence of anaesthetic postconditioning on ventricular fibrillation has not yet been determined. In the present study, we studied the possible effect of sevoflurane postconditioning on persistent reperfusion-induced ventricular fibrillation in the isolated rat heart model.

METHODS

Isolated Langendorff-perfused rat hearts (n=80) were subjected to 40 min of global ischaemia and reperfusion. The hearts with persistent ventricular fibrillation (n=16) present after 15 min of reperfusion were then randomly assigned into one of the two groups: controls (n=8), reperfusion was continued for 25 min without any intervention, and sevoflurane postconditioning (n=8), rat hearts in the sevoflurane postconditioning group were exposed to sevoflurane at a concentration of 8.0% for 2 min followed by 23 min of reperfusion. As for the third group, the rest of the hearts were included in the nonpersistently fibrillating hearts group (n=64). Left ventricular pressures, heart rate, coronary flow, electrogram and infarct size were measured as variables of ventricular function and cellular injury, respectively.

RESULTS

Conversion of ventricular fibrillation into regular rhythm was observed in all hearts subjected to sevofluane postconditioning. Regular beating was maintained by all anaesthetic postconditioned hearts during the subsequent reperfusion. None of the hearts in the control group had normal rhythm at the end of the experiment. At the end of reperfusion, the coronary flow was increased in sevoflurane postconditioned hearts compared with the hearts that did not develop persistent ventricular fibrillation.

CONCLUSION

Sevoflurane postconditioning possesses strong antiarrhythmic effect against persistent reperfusion-induced ventricular fibrillation. Anaesthetic postconditioning may have the potential to be an antiarrhythmic therapy for reperfusion-related arrhythmias.

The use of a volatile anesthetic regimen protects against acute normovolemic hemodilution induced myocardial depression in patients with coronary artery disease

BACKGROUND

Previous studies indicated that acute normovolemic hemodilution (ANH) was associated with a depression of myocardial function in coronary surgery patients with baseline heart rate faster than 90 bpm. It was suggested that this phenomenon could be explained by the occurrence of myocardial ischemia. In the present study, we hypothesized that the cardioprotective properties of a volatile anesthetic regimen might protect against the ANH related myocardial functional impairment.

MATERIALS AND METHODS

Forty elective coronary surgery patients with baseline heart rate faster than 90 bpm were randomly allocated to receive different anesthetic regimens. Group A (n = 20) received midazolam-based anesthesia. Group B (n = 20) received a sevoflurane-based anesthesia. Five-lead electrocardiogram, pulse oximetry, capnography, radial arterial pressure, and Swan Ganz continuous thermodilution cardiac output via right internal jugular vein were monitored. Measurements were obtained before and after ANH. Data were compared using paired t test. All data were expressed as mean +/- SD. Data were considered significant if P < 0.05.

RESULTS

After ANH, systemic vascular resistance was slightly decreased in group A while there was a significant decrease in group B. In group A, cardiac output was slightly decreased from 5.07+/-1.17 l/min to 5.02+/-1.28 l/min after ANH, whereas in group B, cardiac output was significantly increased from 4.84+/-1.21 l/min to 6.02+/-1.28 l/min after ANH.

CONCLUSION

In coronary surgery patients, with baseline heart rate faster than 90 bpm, anesthesia with sevoflurane during ANH was associated with an improvement in myocardial function after ANH, which was not present in patients anesthetized with midazolam.

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.

Expressions of genes encoding drug-metabolizing enzymes are altered after sevoflurane, isoflurane, propofol or dexmedetomidine anesthesia

We previously showed that sevoflurane anesthesia affected the expression ratios of 177 of 10,000 genes in multiple organs of rats by microarray analyses. The maximum number of altered genes was detected in the liver, and included several genes characterized as encoding drug-metabolizing enzymes (DMEs). Here, we investigated whether alterations of pharmacokinetic gene expressions after anesthesia differed between inhalation and intravenous anesthesia, and how long the alterations persisted after awakening from anesthesia. Livers were obtained from rats (n = 6 per group) anesthetized with sevoflurane, isoflurane, propofol or dexmedetomidine for 0 or 6 h, and rats awakened for 24 h after anesthesia for 6 h. The mRNA expression ratios of eight genes encoding DMEs that showed the greatest alterations in the previous study, namely Cyp7a1, Cyp2b15, Por, Nr1i2, Ces2, Ugt1a7, Abcb1a and Abcc2, were measured by quantitative real-time reverse transcriptase-polymerase chain reaction. The expression ratios were mostly increased after 6 h of anesthesia and returned to their control levels at 24 h after awakening from anesthesia. However, the expression ratios of some genes remained elevated for 24 h after awakening from anesthesia. There were differences between inhalation and intravenous anesthesia, and interestingly, between sevoflurane and isoflurane and between propofol and dexmedetomidine.

Sevoflurane- and desflurane-induced human myocardial post-conditioning through Phosphatidylinositol-3-kinase/Akt signalling

BACKGROUND

The role of phosphatidylinositol-3-kinase (PI3K) in sevoflurane- and desflurane-induced myocardial post-conditioning remains unknown.

METHODS

We recorded isometric contraction of isolated human right atrial trabeculae (oxygenated Tyrode's at 34 degrees C, stimulation frequency 1 Hz). In all groups, a 30-min hypoxic period was followed by a 60-min reoxygenation period. At the onset of reoxygenation, muscles were exposed to 5 min of sevoflurane 1%, 2%, and 3%, and desflurane 3%, 6%, and 9%. In separate groups, sevoflurane 2% and desflurane 6% were administered in the presence of 100 nM wortmannin, a PI3K inhibitor. Recovery of force after the 60-min reoxygenation period was compared between groups (mean +/- SD).

RESULT

As compared with the Control group (49 +/- 7% of baseline) PostC by sevoflurane 1%, 2%, and 3% (78 +/- 4%, 79 +/- 5%, and 85 +/- 4% of baseline, respectively) and desflurane 3%, 6%, and 9% (74 +/- 5%, 84 +/- 4%, and 86 +/- 11% of baseline, respectively) enhanced the recovery of force. This effect was abolished in the presence of wortmannin (56 +/- 5% of baseline for sevoflurane 2%+wortmannin; 56 +/- 3% of baseline for desflurane 6%+wortmannin). Wortmannin alone had no effect on the recovery of force (57 +/- 7% of baseline).

CONCLUSION

In vitro, sevoflurane and desflurane post-conditioned human myocardium against hypoxia through activation of phosphatidylinositol-3-kinase.

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.

Activation of orexin signal in basal forebrain facilitates the emergence from sevoflurane anesthesia in rat

Orexinergic system may play an important role in the regulation of anesthesia-arousal. However, which region or which pathway mediated the effect of orexins was still unclear. In current study, we investigated whether activation of orexin signals in basal forebrain (BF) may alter electroencephalographic activity, induction and emergence time to sevoflurane anesthesia in rats. Either orexin-A or orexin-B was injected into the BF while measuring electroencephalogram (EEG) under 1.0 minimum alveolar concentration (2.4%) sevoflurane anesthesia. The induction and emergence time of sevoflurane anesthesia were measured respectively after an injection of orexin receptor agonist (orexin-A or orexin-B) or antagonist (SB-334867A) into the BF also. We found that the administration of orexin-A (30, 100 pmol) and orexin-B (100 pmol) changed the burst and suppression patterns to arousal EEG in rat under sevoflurane anesthesia. Comparing with orexin-B, injection of lower dose of orexin-A induced more arousal EEG. Intrabasalis microinjection of orexin-A shorted the emergence time, whereas intrabasalis microinjection of SB-334867A (5 microg, 20 microg) delayed the emergence time to sevoflurane anesthesia, without changing anesthetic induction. These findings indicate that the orexin signals in basal forebrain, a middle region of the cholinergic ventral ascending arousal system, plays a crucial role in the anesthesia-arousal regulation.

Sevoflurane and nitrous oxide exert cardioprotective effects against hypoxia-reoxygenation injury in the isolated rat heart

It is unclear whether nitrous oxide (N(2)O) has a protective effect on cardiac function in vitro. In addition, little is known about the cardioprotective effect of anesthesia administered during hypoxia or ischemia. We therefore studied the cardioprotective effects of N(2)O and sevoflurane administered before or during hypoxia in isolated rat hearts. Rat hearts were excised and perfused using the Langendorff technique. For hypoxia-reoxygenation, hearts were made hypoxic (95% N(2), 5% CO(2)) for 45 min and then reoxygenated (95% O(2), 5% CO(2)) for 40 min (control: CT group). Preconditioning was achieved through three cycles of application of 4% sevoflurane (sevo-pre group) or 50% N(2)O (N(2)O-pre group) for 5 min with 5-min washouts in between. Hypoxic conditions were achieved by administering the 4% sevoflurane (sevo-hypo group) or 50% N(2)O (N(2)O-hypo group) during the 45-min hypoxic period. L-type calcium channel currents (I(Ca,L)) were recorded on rabbit myocytes. (1) Both 4% sevoflurane and 50% N(2)O significantly reduced left ventricular developed pressure (LVDP). Sevoflurane also increased left ventricular end-diastolic pressure, though N(2)O did not. (2) The recoveries of LVDP and pressure-rate product (PRP) after hypoxia-reoxygenation were better in the sevo-pre group than in the CT or N(2)O-pre group. (3) Application of either sevoflurane or N(2)O during hypoxia improved recovery of LVDP and PRP, and GOT release was significantly lower than in the CT group. (4) Sevoflurane and N(2)O reduced I(Ca,L) to similar extents. Although sevoflurane administered before or during hypoxia exerts a cardioprotective effect, while N(2)O shows a cardioprotective effect only when administered during hypoxia.

Hyperglycaemia blocks sevoflurane-induced postconditioning in the rat heart in vivo: cardioprotection can be restored by blocking the mitochondrial permeability transition pore

BACKGROUND

Recent studies showed that hyperglycaemia (HG) blocks anaesthetic-induced preconditioning. The influence of HG on anaesthetic-induced postconditioning (post) has not yet been determined. We investigated whether sevoflurane (Sevo)-induced postconditioning is blocked by HG and whether the blockade could be reversed by inhibiting the mitochondrial permeability transition pore (mPTP) with cyclosporine A (CsA).

METHODS

Chloralose-anaesthetized rats (n=7-11 per group) were subjected to 25 min coronary artery occlusion followed by 120 min reperfusion. Postconditioning was achieved by administration of 1 or 2 MAC sevoflurane for the first 5 min of early reperfusion. HG was induced by infusion of glucose 50% (G 50) for 35 min, starting 5 min before ischaemia up to 5 min of reperfusion. CsA (5 or 10 mg kg(-1)) was administered i.v. 5 min before the onset of reperfusion. At the end of the experiments, hearts were excised for infarct size measurements.

RESULTS

Infarct size (% of area at risk) was reduced from 51.4 (5.0)% [mean (sd)] in controls to 32.7 (12.8)% after sevoflurane postconditioning (Sevo-post) (P<0.05). This infarct size reduction was completely abolished by HG [51.1 (13.2)%, P<0.05 vs Sevo-post], but was restored by administration of sevoflurane with CsA [35.2 (5.2)%, P<0.05 vs HG+Sevo-post]. Increased concentrations of sevoflurane or CsA alone could not restore cardioprotection in a state of HG [Sevo-post2, 54.1 (12.6)%, P>0.05 vs HG+Sevo-post; CsA10, 58.8 (11.3)%, P>0.05 vs HG+CsA].

CONCLUSIONS

Sevoflurane-induced postconditioning is blocked by HG. Inhibition of the mPTP with CsA is able to reverse this loss of cardioprotection.

Preconditioning, but not postconditioning, with Sevoflurane reduces pulmonary neutrophil accumulation after lower body ischaemia/reperfusion injury in rats

BACKGROUND AND OBJECTIVES

Aortic ischaemia and reperfusion may induce pulmonary sequestration of neutrophil granulocytes. Preconditioning and postconditioning with volatile anaesthetics confer protection against reperfusion injury in various organs, such as heart, kidneys or brain. We tested the hypothesis that pre- or postconditioning with Sevoflurane attenuates pulmonary neutrophil accumulation after ischaemia/reperfusion injury of the aorta.

METHODS

Anaesthetized and mechanically ventilated Wistar rats underwent laparotomy and were randomly assigned to one of the following groups: Sham (n = 10), ischaemia/reperfusion (n = 8, lower body ischaemia by clamping of the infrarenal aorta for 2 h followed by 3 h of reperfusion), preconditioning (n = 10, 2.0% Sevoflurane administered over 30 min prior to ischaemia) and postconditioning (n = 9, 2.0% Sevoflurane during reperfusion). Following reperfusion, the lungs were removed for microscopic determination of neutrophil accumulation.

RESULTS

Ischaemia/reperfusion induced a significant increase in pulmonary neutrophil accumulation (mean +/- SD, 29.9 +/- 7.4 vs. 15.8 +/- 6.6 neutrophils per microscopic field in ischaemia/reperfusion vs. Sham, respectively, P < 0.001). Sevoflurane preconditioning resulted in a lower neutrophil count (20.3 +/- 7.1 neutrophils, P < 0.001 vs. ischaemia/reperfusion), while postconditioning showed no effects (25.8 +/- 9.8 neutrophils vs. ischaemia/reperfusion, not significant).

CONCLUSIONS

Preconditioning, but not postconditioning, with Sevoflurane reduces pulmonary neutrophil accumulation after ischaemia/reperfusion injury of the lower body. Since neutrophil accumulation plays a major role in the pathophysiology of acute lung injury, our data suggest a protective effect of Sevoflurane preconditioning on remote pulmonary ischaemia/reperfusion injury.

Caveolin-3 expression and caveolae are required for isoflurane-induced cardiac protection from hypoxia and ischemia/reperfusion injury

Volatile anesthetics protect the heart from ischemia/reperfusion injury but the mechanisms for this protection are poorly understood. Caveolae, sarcolemmal invaginations, and caveolins, scaffolding proteins in caveolae, localize molecules involved in cardiac protection. We tested the hypothesis that caveolae and caveolins are essential for volatile anesthetic-induced cardiac protection using cardiac myocytes (CMs) from adult rats and in vivo studies in caveolin-3 knockout mice (Cav-3(-/-)). We incubated CM with methyl-beta-cyclodextrin (MbetaCD) or colchicine to disrupt caveolae formation, and then exposed the myocytes to the volatile anesthetic isoflurane (30 min, 1.4%), followed by simulated ischemia/reperfusion (SI/R). Isoflurane protected CM from SI/R [23.2+/-1.6% vs. 71.0+/-5.8% cell death (assessed by trypan blue exclusion), P<0.001] but this protection was abolished by MbetaCD or colchicine (84.9+/-5.5% and 64.5+/-6.1% cell death, P<0.001). Membrane fractionation by sucrose density gradient centrifugation of CM treated with MbetaCD or colchicine revealed that buoyant (caveolae-enriched) fractions had decreased phosphocaveolin-1 and caveolin-3 compared to control CM. Cardiac protection in vivo was assessed by measurement of infarct size relative to the area at risk and cardiac troponin levels. Isoflurane-induced a reduction in infarct size and cardiac troponin relative to control (infarct size: 26.5%+/-2.6% vs. 45.3%+/-5.4%, P<0.01; troponin: 27.7+/-4.4 vs. 77.7+/-11.8 ng/ml, P<0.05). Isoflurane-induced cardiac protection was abolished in Cav-3(-/-) mice (infarct size: 53.4%+/-6.1% vs. 53.2%+/-3.5%, P<0.01; troponin: 102.1+/-22.3 vs. 105.9+/-8.2 ng/ml, P<0.01). Isoflurane-induced cardiac protection is thus dependent on the presence of caveolae and the expression of caveolin-3. We conclude that caveolae and caveolin-3 are critical for volatile anesthetic-induced protection of the heart from ischemia/reperfusion injury.

Anesthetic Preconditioning Combined with Postconditioning Offers No Additional Benefit Over Preconditioning or Postconditioning Alone

BACKGROUND

Recent investigations demonstrate that anesthetic preconditioning and postconditioning reduce myocardial infarct size to a degree comparable to that achieved with ischemic preconditioning. We hypothesized that the combination of sevoflurane preconditioning and postconditioning would result in greater preservation of myocardium.

METHODS

Langendorff perfused rat hearts were divided into four groups: control, preconditioning, postconditioning, and preconditioning plus postconditioning. During reperfusion, left ventricular function (left ventricular developed pressure, left ventricular end diastolic pressure, and dp/dt) were measured. At the end of reperfusion, the infarct sizes were measured with 2,3,5 triphenyltetrazolium chloride staining. Nuclear magnetic resonance was used to measure intracellular pH, Na(+), and Ca(2+).

RESULTS

Left ventricular developed pressure, left ventricular end diastolic pressure, left ventricular dp/dt(max) and dp/dt(min) were significantly improved in the treatment groups when compared with those in the controls. Myocardial infarct size (24% +/- 7%, 16% +/- 8%, and 22% +/- 7% in preconditioning, postconditioning, and pre-plus postconditioning groups versus 44% +/- 8% in the control group, P < 0.05) and intracellular Na(+) and Ca(2+) were significantly decreased in all experimental groups at the end of reperfusion when compared with those in control. However, there were no differences between these variables in each treatment group.

CONCLUSION

Sevoflurane postconditioning is as effective as preconditioning in protecting myocardial function after global ischemia. The combination of sevoflurane preconditioning and postconditioning offered no additional benefit over either intervention alone.

Cardioprotection with volatile anesthetics: clinical relevance

PURPOSE OF REVIEW

Increasing experimental evidence is indicating that volatile anesthetic agents may exert direct cardioprotective effects. They have been shown to directly precondition or indirectly enhance ischemic preconditioning. This results in protection against reversible and irreversible ischemic myocardial damage. In addition, volatile anesthetics also decrease the extent of the reperfusion injury when administered only during the reperfusion period. The implementation of these properties during clinical anesthesia might provide an additional tool in the treatment and prevention of ischemic cardiac dysfunction in the perioperative period.

RECENT FINDINGS

In clinical practice, these effects should be associated with improved cardiac function, ultimately resulting in a better outcome in patients with coronary artery disease. This potential application of anesthetic agents has only recently been explored and its applicability in clinical practice is the subject of ongoing research.

SUMMARY

This review will summarize the current knowledge in this field and also discuss the potential mechanisms involved in cardioprotection by anesthetic agents.

Pre-occlusion ischaemia, not sevoflurane, successfully preconditions the myocardium against further damage in porcine in vivo hearts

BACKGROUND

Sevoflurane is proposed to possess important tissue protective effects based on experimental ischaemia-reperfusion studies from models with collateral coronary flow, unlike that of the normal human or the porcine heart. The objective was to evaluate the infarct-reducing capability of pre-ischaemic sevoflurane inhalation on myocardial infarct size in a porcine model.

METHODS AND MATERIALS

The study comprised 33 pigs under pentobarbital anaesthesia. Animals were divided into three groups: control (CON), sevoflurane intervention (SEVO) and ischaemic preconditioning (IP). The distal left anterior descending coronary artery was occluded for 40 min with a percutaneous coronary intervention catheter. Before occlusion, group IP underwent two 5-min ischaemia cycles, whereas SEVO received two 5-min sevoflurane 4%v/v inhalation cycles. Animals were reperfused for 150 min. We then measured risk area (AAR) and infarct size (IS) after tetrazolium staining. The [IS/AAR-ratio] was calculated. Haemodynamics and transthoracic tissue-Doppler echocardiography were monitored.

RESULTS

Control animals developed a myocardial infarction in 46.4 (+/- 6.2)% (mean +/- SEM) of the AAR. Both SEVO and IP groups had infarction mitigated, to 34.4 (5.7)% and 23.1 (5.3)%, respectively; however, only in the IP group was this significant. No significant differences between groups with respect to AAR, haemodynamics or echocardiographic variables were found.

CONCLUSION

Pre-ischaemic sevoflurane was found to reduce the extent of myocardial necrosis, but the change was not significant, whereas IP reduced IS by 50% (P= 0.038). Cardioprotection is species related and no previous results from porcine models have found sevoflurane to reduce IS. Anaesthetic washout, insufficient exposure or collateral coronary blood supply, dissimilar to human, may account for positive results in rodent models.

Effects of Sevoflurane on Biomechanical Markers of Hepatic and Renal Dysfunction After Coronary Artery Surgery

OBJECTIVE

The purpose of this study was to compare the effects of a total intravenous and a volatile anesthetic regimen on biochemical markers of hepatic and renal dysfunction after coronary artery surgery.

DESIGN

Prospective, double-blind, randomized clinical study.

SETTING

University hospital, single institutional.

PARTICIPANTS

Three hundred twenty patients undergoing elective coronary artery surgery were divided into 2 different anesthetic protocols: propofol group (n = 160) and sevoflurane group (n = 160).

INTERVENTIONS

Hemodynamic data were registered before the start of surgery, before the start of CPB, 15 minutes after the end of CPB, at arrival in the intensive care unit, and 6 and 12 hours after arrival in the intensive care unit. Serum glutamic oxaloacetic transaminase (SGOT), serum glutamate pyruvate transaminase (SGPT), serum lactate dehydrogenase (LDH), and serum creatinine concentrations were measured before surgery, at arrival in the intensive care unit, and after 6, 12, 24, and 48 hours.

MEASUREMENTS AND MAIN RESULTS

Postoperative levels of serum SGOT, SGPT, and LDH increased transiently in both anesthetic groups, but the increase was significantly lower in the sevoflurane group compared with the propofol group. Creatinine levels remained largely unchanged in both groups.

CONCLUSION

Postoperative biochemical markers of hepatic dysfunction were lower with a sevoflurane-based anesthetic regimen in patients undergoing coronary artery surgery with cardiopulmonary bypass.

Post-conditioning by a short administration of desflurane reduced renal reperfusion injury after differing of ischaemia times in rats

BACKGROUND

'Anaesthetic post-conditioning', that is administration of anaesthetics during early reperfusion, is known to have positive effects on several organs. For the kidney, however, the effects of post-conditioning by volatile anaesthetics are not well researched. We examined renal function and morphology after post-conditioning by desflurane.

METHODS

Anaesthetized rats were subjected to 30 or 45 min of renal ischaemia 14 days after contralateral nephrectomy. Post-conditioning was achieved by administration of 1 MAC desflurane (6.7 vol%) for 15 min during early reperfusion (all groups n=8). Cystatin C (CyC), creatinine clearance (Cl(Cr)) and fractional sodium excretion (FE(Na)) were measured in the awake rats over 3 days. Cell damage was graded from 1 to 4 in histological sections. Functional variables [mean (SD)] were compared statistically by a one-way anova followed by Bonferroni's multiple comparison test and histological scores (median and range) by Kruskal-Wallis test followed by Dunn's multiple comparison test.

RESULTS

Pre-ischaemia function did not differ between the groups, but was markedly reduced after ischaemia. After 30 min ischaemia, the area under the curve (AUC) for Cl(Cr) was smaller in the desflurane than in the control group [21.5 (5.0) vs 31.6 (5.1) ml min(-1) h, P<0.05]. After 45 min desflurane reduced the AUC compared with the control group for both CyC [15 (4) vs 21 (3) mg litre(-1) h] and FE(Na) [1054 (221) vs 1570 (572)% h, both P<0.05). Morphological differences were greater between the 30 min groups [control: 2.75 (2.0-3.5) vs desflurane: 1.5 (1.0-2.5); P<0.05] than between the 45 min groups [control: 3.5 (3.0-4.0) vs desflurane: 3.0 (1.5-4.0)].

CONCLUSION

Desflurane post-conditioning protects renal function and tissue. This protection was greater after the short episode than after the long episode of ischaemia.

Cardioprotective Properties of Sevoflurane in Patients Undergoing Aortic Valve Replacement with Cardiopulmonary Bypass

In coronary surgery patients the use of a volatile anesthetic regimen with sevoflurane was associated with a better recovery of myocardial function and less postoperative release of troponin I. In the present study we investigated whether these cardioprotective properties were also apparent in the cardiac surgical setting of aortic valve replacement (AVR) surgery for the correction of aortic stenosis. Thirty AVR surgery patients were randomly assigned to receive either target-controlled infusion of propofol or inhaled anesthesia with sevoflurane. Cardiac function was assessed perioperatively using a pulmonary artery catheter. Perioperatively, a high-fidelity pressure catheter was positioned in the left ventricle. Postoperative concentrations of cardiac troponin I were followed for 48 h. After cardiopulmonary bypass (CPB), stroke volume and dP/dt(max) were significantly higher in the patients with sevoflurane. Post-CPB, the effects of an increase in cardiac load on dP/dt(max) were similar to pre-CPB in the sevoflurane group (1.0 % +/- 5.4% post-CPB versus 1.3% +/- 8.6% pre-CPB) but more depressed in the propofol group (-8.2% +/- 4.4% post-CPB versus 0.1% +/- 4.9% pre-CPB). The rate of relaxation was significantly slower post-CPB in the propofol group. Postoperative levels of troponin I were significantly lower in the sevoflurane group. Our data indicate that the use of a volatile anesthetic regimen in AVR surgery was associated with better preservation of myocardial function and a reduced postoperative release of troponin I.

Myocardial protection with volatile anaesthetic agents during coronary artery bypass surgery: a meta-analysis

Previous studies have investigated the role of volatile anaesthetic agents in myocardial protection during coronary artery bypass graft (CABG) surgery, and some have identified beneficial effects. However, these studies have been too small to identify a significant effect on myocardial infarction (MI) or mortality. We undertook a systematic overview and meta-analysis of all randomized trials comparing volatile with non-volatile anaesthesia in CABG surgery. We identified 27 trials that included 2979 patients. There was no significant difference in myocardial ischaemia, MI, intensive care unit length of stay or hospital mortality between the groups (all P>0.05). Post-bypass, patients randomized to receive volatile anaesthetics had 20% higher cardiac indices (P=0.006), significantly lower troponin I serum concentrations (P=0.002) and lesser requirement for inotropic support (P=0.004) compared with those randomized to receive i.v. anaesthetics. Duration of mechanical ventilation was reduced by 2.7 h (P=0.04), and there was a 1 day decrease in hospital length of stay (P<0.001). Some of these outcomes were based on a smaller number of trials because of incomplete data, largely because the individual trials focused on one or more surrogate endpoints. We found some evidence that volatile anaesthetic agents provide myocardial protection in CABG surgery, but larger adequately powered trials with agreed, defined outcomes need to be done to fully assess a possible beneficial effect of volatile anaesthetic agents on the risk of MI and mortality.

Effect of sevoflurane preconditioning on ischaemia/reperfusion injury in the rat kidney in vivo

BACKGROUND AND OBJECTIVE

Whereas the protective effect of anaesthetic and ischaemic preconditioning has been described for several organs, it is uncertain whether this mechanism is also effective in the kidney. We compared the effect of preconditioning with sevoflurane and preconditioning with short episodes of ischaemia on renal ischaemia/reperfusion injury in the rat in vivo.

METHODS

Fourteen days after right-sided nephrectomy, anaesthetized male Wistar rats were randomly assigned to a sham-operated group (no arterial occlusion, n = 5) or underwent 45 min of left renal artery occlusion (control group, n = 9) followed by 3 days of reperfusion. Two further experimental groups of animals were preconditioned prior to ischaemia either by administering 1 MAC sevoflurane for 15 min followed by 10 min of washout (sevoflurane group, n = 10) or by subjecting the animals to three short episodes of renal ischaemia (ischaemia-preconditioned group, n = 8). Blood creatinine was measured during reperfusion and morphological damage was assessed by histological examination.

RESULTS

Baseline creatinine values were similar in all four groups (0.7 +/- 0.2 mg dL-1; mean +/- SD) and remained unchanged in the sham-operated animals after 3 days (0.8 +/- 0.2 mg dL-1). Creatinine levels increased in the ischaemic preconditioning group (3.3 +/- 1.2 mg dL-1) and sevoflurane preconditioning group (4.0 +/- 1.1 mg dL-1) compared to the control group (1.6 +/- 0.6 mg dL-1). Morphological damage was less severe in the control group, i.e. in animals without preconditioning, than in both preconditioning groups.

CONCLUSION

Neither sevoflurane nor ischaemic preconditioning preserves renal function or attenuates cell damage in the rat in vivo.

Sevoflurane-remifentanil versus propofol-remifentanil anesthesia at a similar bispectral level for off-pump coronary artery surgery: no evidence of reduced myocardial ischemia

OBJECTIVE

Sevoflurane could decrease myocardial ischemic injury in patients undergoing off-pump coronary artery bypass surgery. This study was designed to compare postoperative troponin I (cTnI) concentrations after sevoflurane-remifentanil versus propofol-remifentanil anesthesia.

DESIGN

Prospective, randomized single-blind clinical study.

SETTING

University hospital.

PARTICIPANTS

Eighteen patients.

INTERVENTIONS

General anesthesia was conducted with sevoflurane-remifentanil (n = 9) or propofol-remifentanil (n = 9). Administration of sevoflurane and propofol was adjusted to maintain the bispectral index (BIS) between 40 and 60.

MEASUREMENTS AND MAIN RESULTS

Groups were comparable regarding the patients' characteristics. The objective of BIS was maintained in both groups except during the period of coronary artery grafts (p < 0.001) when the BIS number in the propofol group fell below 40 and was significantly lower than in the sevoflurane group. Intraoperative hemodynamic variables were similar between groups. No patient required cardiopulmonary bypass. Need for inotropic and vasoactive support during the first graft was not necessary in the propofol group and occurred in 4 patients in the sevoflurane group (not significant). During the second graft, 2 patients in the propofol group and 3 in the sevoflurane group needed hemodynamic support. Postoperative hemodynamic variables were comparable between groups. Areas under the curve of postoperative increases in cTnI were 27.0 +/- 38.6 and 17.4 +/- 14.6 ng/mL/hour in the sevoflurane and propofol groups, respectively (not significant).

CONCLUSION

This study does not support cardioprotective effects of sevoflurane. The particularly short total cumulative duration of ischemia and the relatively low administered end-tidal sevoflurane concentrations may explain this result.

The influence of mitochondrial KATP-channels in the cardioprotection of preconditioning and postconditioning by sevoflurane in the rat in vivo

Volatile anesthetics induce myocardial preconditioning and can also protect the heart when given at the onset of reperfusion-a practice recently termed "postconditioning." We investigated the role of mitochondrial KATP (mKATP)-channels in sevoflurane-induced cardioprotection for both preconditioning and postconditioning alone and whether there is a synergistic effect of both. Rats were subjected to 25 min of coronary artery occlusion followed by 120 min of reperfusion. Infarct size was determined by triphenyltetrazolium staining. The following protocols were used: 1) preconditioning (S-Pre, n = 10, achieved by 2 periods of 5 min sevoflurane administration (1 MAC) followed by 10 min of washout); 2) sevoflurane postconditioning (1 MAC of sevoflurane given for 2 min at the beginning of reperfusion; S-Post, n = 10); 3) administration before and after ischemia (S-Pre + S-Post, n = 10). Protocols 1-3 were repeated in the presence of 5-hydroxydecanoate (5HD), a specific mKATP-channel-blocker (S-Pre + S-Post + 5HD, S-Pre + 5HD: n = 10; S-Post + 5HD: n = 9). Nine rats served as untreated controls (CON) or received 5HD alone (5HD, n = 10). Both S-Pre (23% +/- 13% of the area at risk, mean +/- sd) and S-Post (18% +/- 5%) reduced infarct size compared with CON (49% +/- 11%, both P < 0.05). S-Pre + S-Post resulted in a larger reduction of infarct size (12% +/- 5%, P = 0.054 versus S-Pre) compared with administration before or after ischemia alone. 5HD diminished the protection in all three sevoflurane treated groups (S-Pre + 5HD, 35% +/- 12%; S-Post + 5HD, 44% +/- 12%; S-Pre + S-Post + 5HD, 46% +/- 14%;) but given alone had no effect on infarct size (41% +/- 13%). Sevoflurane preconditioning and postconditioning protects against myocardial ischemia-reperfusion injury. The combination of preconditioning and postconditioning provides additive cardioprotection and is mediated, at least in part, by mKATP-channels.

Cardioprotection by volatile anesthetics

Preconditioning describes a very powerful endogenous mechanism by which the heart may be protected against ischemia and reperfusion injury. Transient administration of a volatile anesthetic before a prolonged ischemic episode reduces myocardial infarct size to a degree comparable to that observed during ischemic preconditioning. Many components of the signal transduction pathways responsible for cardioprotection are shared by anesthetic and ischemic preconditioning. Exposure to volatile anesthetics generates small "triggering" quantities of reactive oxygen species (ROS) by directly interacting with the mitochondrial electron transport chain or indirectly through a signaling cascade in which G-protein-coupled receptors, protein kinases, and mitochondrial ATP-sensitive potassium (K(ATP)) channels play important roles. Several clinical studies also suggest that preconditioning by volatile anesthetics exerts beneficial effects in patients undergoing cardiac surgery. This review summarizes some of the recent major developments in the understanding of cardioprotection by volatile anesthetics.

Isoflurane preconditioning protects against ischemia-reperfusion injury partly by attenuating cytochrome c release from subsarcolemmal mitochondria in isolated rat hearts

AIM

To examine if isoflurane preconditioning can attenuate ischemia/reperfusion injury by reducing cytochrome c release from inner mitochondrial membrane.

METHODS

Isolated hearts of Sprague-Dawley rats were perfused on Langendorff apparatus. Hearts were randomly assigned to a non-treated group (CON group, n=12) or three isoflurane preconditioning groups (0.5% ISC group, 1.0% ISC group, and 2.0% ISC group; n=12). In the latter three groups, isoflurane was given at concentrations of 0.5%, 1.0%, and 2.0% for 15 min with 15-min washout before 30-min ischemia. Subsarcolemmal mitochondria of the myocardium were isolated after 60-min reperfusion. Hemodynamics of the each heart was recorded, infarct size of the hearts and contents of cytosolic cytochrome or mitochondrial cytochrome c were measured at the end of reperfusion. Morphology of isolated mitochondria in the four groups was evaluated, respectively.

RESULTS

Compared with the CON group, cytosolic cytochrome c in 0.5% ISC group, 1.0% ISC group, and 2.0% ISC group were significantly decreased along with a significant increase of mitochondrial cytochrome c. Infarct size of the hearts in the four groups were 56%+/-12%, 41%+/-12%, 32%+/-7% and 33%+/-11%, respectively. The values of the three isoflurane preconditioning groups were significantly lower than that of the CON group (P<0.05). Isoflurane exposure before ischemia can attenuate the change of morphology of mitochondria after reperfusion. The effects of 2.0% isoflurane on reducing cytochrome c release were more remarkable than 0.5% and 1.0% concentrations of isoflurane.

CONCLUSION

Myocardioprotective effects of isoflurane preconditioning were associated with attenuation of cytochrome c loss from the inner membrane of subsarcolemmal mitochondria.

The noble gas xenon induces pharmacological preconditioning in the rat heart in vivo via induction of PKC-epsilon and p38 MAPK

Xenon is an anesthetic with minimal hemodynamic side effects, making it an ideal agent for cardiocompromised patients. We investigated if xenon induces pharmacological preconditioning (PC) of the rat heart and elucidated the underlying molecular mechanisms. For infarct size measurements, anesthetized rats were subjected to 25 min of coronary artery occlusion followed by 120 min of reperfusion. Rats received either the anesthetic gas xenon, the volatile anesthetic isoflurane or as positive control ischemic preconditioning (IPC) during three 5-min periods before 25-min ischemia. Control animals remained untreated for 45 min. To investigate the involvement of protein kinase C (PKC) and p38 mitogen-activated protein kinase (MAPK), rats were pretreated with the PKC inhibitor calphostin C (0.1 mg kg(-1)) or the p38 MAPK inhibitor SB203580 (1 mg kg(-1)). Additional hearts were excised for Western blot and immunohistochemistry. Infarct size was reduced from 50.9+/-16.7% in controls to 28.1+/-10.3% in xenon, 28.6+/-9.9% in isoflurane and to 28.5+/-5.4% in IPC hearts. Both, calphostin C and SB203580, abolished the observed cardioprotection after xenon and isoflurane administration but not after IPC. Immunofluorescence staining and Western blot assay revealed an increased phosphorylation and translocation of PKC-epsilon in xenon treated hearts. This effect could be blocked by calphostin C but not by SB203580. Moreover, the phosphorylation of p38 MAPK was induced by xenon and this effect was blocked by calphostin C. In summary, we demonstrate that xenon induces cardioprotection by PC and that activation of PKC-epsilon and its downstream target p38 MAPK are central molecular mechanisms involved. Thus, the results of the present study may contribute to elucidate the beneficial cardioprotective effects of this anesthetic gas.

Cardioprotection with volatile anesthetics: mechanisms and clinical implications

Cardiac surgery and some noncardiac procedures are associated with a significant risk of perioperative cardiac morbid events. Experimental data indicate that clinical concentrations of volatile general anesthetics protect the myocardium from ischemia and reperfusion injury, as shown by decreased infarct size and a more rapid recovery of contractile function on reperfusion. These anesthetics may also mediate protective effects in other organs, such as the brain and kidney. Recently, a number of reports have indicated that these experimentally observed protective effects may also have clinical implications in cardiac surgery. However, the impact of the use of volatile anesthetics on outcome measures, such as postoperative mortality and recovery in cardiac and noncardiac surgery, is yet to be determined.

Préconditionnement myocardique induit par les agents anesthésiques halogénés : bases fondamentales et implications cliniques

OBJECTIVE

Volatile halogenated anaesthetics offer a myocardial protection when they are administrated before a myocardial ischaemia. Cellular mechanisms involved in anaesthetic preconditioning are now better understood. The objectives of this review are to understand the anaesthetic-induced preconditioning underlying mechanisms and to know the clinical implications.

DATA SOURCES

References were obtained from PubMed data bank (http://www.ncbi.nlm.nih.gov/entrez/query.fcgi) using the following keywords: volatile anaesthetic, isoflurane, halothane, sevoflurane, desflurane, preconditioning, protection, myocardium.

DATA SYNTHESIS

Ischaemic preconditioning (PC) is a myocardial endogenous protection against ischaemia. It has been described as one or several short ischaemia before a sustained ischemia. These short ischaemia trigger a protective signal against this longer ischaemia. An ischemic organ is able to precondition a remote organ. It is possible to replace the short ischaemia by a preadministration of halogenated volatile anaesthetic with the same protective effect, this is called anaesthetic PC (APC). APC and ischaemic PC share similar underlying biochemical mechanisms including protein kinase C, tyrosine kinase activation and mitochondrial and sarcolemnal K(ATP) channels opening. All halogenated anaesthetics can produce an anaesthetic PC effect. Myocardial protection during reperfusion, after the long ischaemia, has been shown by successive short ischaemia or volatile anaesthetic administration, this is called postconditioning. Ischaemic PC has been described in humans in 1993. Clinical studies in human cardiac surgery have shown the possibility of anaesthetic PC with volatile anaesthetics. These studies have shown a decrease of postoperative troponin in patient receiving halogenated anaesthetics.

Sevoflurane but Not Propofol Preserves Myocardial Function During Minimally Invasive Direct Coronary Artery Bypass Surgery

Volatile anesthetics exert cardioprotective properties in experimental and clinical studies. We designed this study to investigate the effects of sevoflurane on left ventricular (LV) performance during minimally invasive direct coronary artery bypass grafting (MIDCAB) without cardiopulmonary bypass. Fifty-two patients scheduled for MIDCAB surgery were randomly assigned to a propofol or a sevoflurane group. Apart from the anesthetics used, there was no difference in surgical and anesthetic management. After determination of cardiac troponin T, creatine kinase, and creatine kinase MB, electrocardiographic (ECG) data and echocardiography variables (myocardial performance index and early to atrial filling velocity ratio) the left anterior descending coronary artery (LAD) was clamped until anastomosis with the left internal mammary artery was completed. During LAD occlusion and during reperfusion, echocardiography measurements were repeated. Blood samples were obtained repeatedly for up to 72 h. After LAD occlusion, myocardial performance index and early to atrial filling velocity ratio in the propofol group deteriorated significantly from 0.40 +/- 0.12 and 1.29 +/- 0.35 to 0.49 +/- 0.10 and 1.13 +/- 0.22, respectively, whereas there was no change in the sevoflurane group. In the propofol group myocardial performance index remained increased (0.47 +/- 0.11) compared with baseline during reperfusion. There were no significant differences in ECG and laboratory values between groups. In conclusion, during a brief period of ischemia in patients undergoing MIDCAB surgery, sevoflurane preserved myocardial function better than propofol.

Role of protein kinase C-ε (PKCε) in isoflurane-induced cardioprotection

BACKGROUND

Volatile anaesthetics precondition the heart against infarction, an effect partly mediated by activation of the epsilon isoform of protein kinase C (PKCepsilon). We investigated whether cardioprotection by activation of PKCepsilon depends on the isoflurane concentration.

METHODS

Anaesthetized rats underwent 25 min of coronary artery occlusion followed by 120 min of reperfusion and were randomly assigned to the following groups (n=10 in each group): isoflurane preconditioning induced by 15 min administration of 0.4 minimal alveolar concentration (MAC) (0.4MAC), 1 MAC (1MAC) or 1.75 MAC (1.75MAC) followed by 10 min washout before ischaemia. Each protocol was repeated in the presence of the PKC inhibitor staurosporine (10 microg kg(-1)): 0.4MAC+S, 1MAC+S and 1.75MAC+S. Controls were untreated (CON) and additional hearts received staurosporine without isoflurane (S). In a second set of experiments (n=6 in each group) hearts were excised before the infarct inducing ischaemia, and phosphorylation and translocation of PKCepsilon were determined by western blot analysis.

RESULTS

Isoflurane reduced infarct size from a mean of 61(SEM 2)% of the area at risk in controls to 20(1)% (0.4MAC), 26(3)% (1MAC) and 30(1)% (1.75MAC) (all P<0.01 vs CON or S). This protection was partially reversed by administration of staurosporine in the 0.4MAC+S group (30[2]%; P<0.05 vs 0.4MAC) group, but not after administration of 1 MAC or 1.75 MAC isoflurane (26[2]% and 31[2]%, respectively). Thus 0.4MAC increased PKCepsilon phosphorylation, and this effect was blocked by staurosporine. Higher concentrations of isoflurane did not change PKCepsilon phosphorylation. PKCepsilon was translocated to the membrane fraction after administration of 0.4 MAC isoflurane, but not after 1.0 or 1.75 MAC.

CONCLUSIONS

Although isoflurane preconditioning resulted in a reduction in infarct size at all concentrations used, the protection was mediated by phosphorylation and translocation of PKCepsilon only at 0.4 MAC.

Cardioprotective effects of desflurane: effect of timing and duration of administration in rat myocardium

BACKGROUND

We compared the cardioprotective effects of 1 minimum alveolar concentration (MAC) desflurane administered before, during or after ischaemia, or throughout the experiment (before, during and after ischaemia) on myocardial infarct size following 30 min occlusion of the left anterior descending coronary artery and 3 h reperfusion in adult rats.

METHODS

Fifty male Sprague-Dawley rats were anaesthetized with pentobarbital, intubated and mechanically ventilated. Blood gases, pH and body temperature (37.5-38 degrees C) were controlled. Heart rate and arterial pressure were measured continuously. Animals were randomly assigned to the following groups (n=10 in each group): pentobarbital only ("Pento"); 15 min desflurane administration followed by 10 min of washout before 30 min ischaemia and 3 h reperfusion ("Precond"); 30 min desflurane administration during ischaemia period ('Isch'); desflurane administration during the 15 first min of reperfusion ("Reperf") and desflurane administration throughout the experiment (before, during and after ischaemia; "Long"). Volumes at risk and infarct sizes were assessed by Indian ink and with 2,3,5-triphenyltetrazolium chloride staining, respectively.

RESULTS

Physiological parameters and volumes at risk were not significantly different between groups. In the Pento group, mean myocardial infarct size was 65 (sd 15)% of the volume at risk; myocardial infarct size was reduced to a significant and comparable extent in the desflurane-treated groups (Precond 42 (14)%; Isch 34 (11)%; Reperf 41 (15)%; Long 33 (10)%; P<0.0002 vs Pento group).

CONCLUSIONS

In rats, desflurane 1 MAC significantly decreased myocardial infarct size whatever the period and duration of administration.

Cardioprotection against reperfusion injury is maximal with only two minutes of sevoflurane administration in rats

PURPOSE

Volatile anesthetics can protect the heart against reperfusion injury. When sevoflurane is given for the first 15 min of reperfusion, a concentration corresponding to one minimum alveolar concentration (MAC) provides a maximum protective effect. The present study addresses the question of how long sevoflurane has to be administered to achieve the best cardioprotection.

METHODS

Chloralose anesthetized rats were subjected to a 25-min occlusion of a major coronary artery, followed by 90 min of reperfusion. During the initial phase of reperfusion, an end-tidal concentration of 2.4 vol.% of sevoflurane (1 MAC) was given for two (n = 8), five (n = 8) or ten minutes (n = 7). Seven rats served as untreated controls. We measured left ventricular (LV) pressure, mean aortic pressure and infarct size (triphenyltetrazolium staining).

RESULTS

Administration of sevoflurane for two minutes resulted in the greatest reduction of infarct size to 15% (8-22 [mean (95% confidence interval)] of the area at risk compared with controls [51 (47-55) %, P < 0.001]. Five or ten minutes of sevoflurane administration reduced infarct size to 26 (18-34) and 26 (18-35) % [P < 0.05], respectively. The cardiodepressant effect of sevoflurane varied with the duration of its administration: LV dP/dt was reduced from 6332 mmHg x sec(-1) (5771-6894) during baseline to 4211 mmHg x sec(-1) (3031-5391), 3811 mmHg x sec(-1) (2081-5540) and 3612 mmHg x sec(-1) (2864-4359) after two, five and ten minutes of reperfusion, respectively.

CONCLUSION

Administration of 1 MAC sevoflurane for the first two minutes of reperfusion effectively protects the heart against reperfusion injury in rats in vivo. A longer administration time had lesser cardioprotective effects in this experimental model.