pprroocceeeeddiinnggss Cardiovascinu Ilnatre Annseivset hCeasriea REVIEW ARTICLE Endorsed by 105 Volatile anaesthetic myocardial protection: a review of the current literature E. Lin, J.A. Symons Department of Anaesthesia and Perioperative Medicine, Alfred Hospital, Monash University; Melbourne, Australia HSR Proceedings in Intensive Care and Cardiovascular Anesthesia 2010; 2: 105-109 ABSTRACT Ischaemic preconditioning is a powerful innate adaptive phenomenon whereby brief periods of sublethal isch- aemia result in marked tolerance to subsequent lethal ischaemia. Halogenated anaesthetics have been shown to mimic ischaemic preconditioning, modifying and attenuating ischaemia reperfusion injury. This review aims to present the current animal and human data, discuss the possible mechanisms of action and review the clinical evidence for volatile anaesthetic-induced myocardial protection. There is class Ia evidence for the myocardial protective properties of sevoflurane and desflurane in low risk patients undergoing coronary artery bypass grafting surgery. These volatile anaesthetics have been shown to improve clinical outcomes and health economics following cardiac surgery, reducing intensive care and hospital stay. The evidence for the benefit of volatile anaesthetics in non-cardiac surgery is less robust and further large randomized controlled trials are required to elucidate this question. Keywords: volatile anaesthetics, myocardial protection, ischaemic preconditioning, mechanisms, cardiac anaes- thesia, outcomes. InTRoduCTIon Mechanism of myocardial protection Ischaemic preconditioning is a powerful in- There is strong evidence for volatile anaes- nate adaptive phenomenon discovered by thetic induced myocardial protection in ex- Murry and colleagues (1), whereby brief perimental studies. periods of sublethal ischaemia results in Despite this weight of evidence in animal marked tolerance to subsequent lethal isch- studies, the translational into human trials aemia. Halogenated anaesthetics have been has borne less consistent results. shown to mimic ischaemic precondition- This review aims to present the current an- ing, modifying and attenuating ischaemia imal and human data, discuss the possible reperfusion injury (2). mechanisms of action and review the clini- Two periods of ischaemic preconditioning cal evidence. have been described; early or classical pre- conditioning that occurs immediately, and induces potent protection that lasts one to Corresponding author: two hours. Joel A Symons, MD Late preconditioning or the second win- Department of Anaesthesia and Perioperative Medicine, Alfred Hospital, Monash University dow of preconditioning occurs 24 hours Victoria, 3800 - Melbourne, Australia after the initial stimulus, induces a less pro- e.mail: [email protected] HSR Proceedings in Intensive Care and Cardiovascular Anesthesia 2010, Vol. 2 E. Lin, J.A. Symons 106 nounced cardio-protection, but lasts for up ly separate these two protective effects of to 72 hours (3). volatile anaesthetics on the myocardium. Early and late preconditioning probably This is best demonstrated by the fact that involves different signalling pathways that studies have also suggested the maximum have yet to be fully elucidated. Early pre- protection is yielded by the administration conditioning is thought to involve opening of volatile anaesthetics throughout the op- mitochondrial ATP dependent potassium erative procedure (18). channels (4-9), increasing mitochondrial reactive oxygen species (4, 10, 11), decreas- Clinical evidence in cardiac surgery ing cytosolic and mitochondrial calcium Since 1985, when Freedman and colleagues loading (12), protection of endothelial (19) reported that enflurane could im- coronary cells by mediating nitric oxide prove post-ischemic myocardial recovery, release (13) and by suppressing neutrophil there has been extensive research into the activation and the neutrophil-endothelium potential benefits of anaesthetic myocar- interactions that cause myocardial dysfunc- dial protection in both animal and human tion (14, 15). models. The majority have been performed Pathways of late preconditioning involve on patients undergoing CABG (coronary attenuation of nuclear factor kB (NFkB), artery bypass grafting). Unfortunately, to activation and reduced expression of tu- date, these studies have been observational mour necrosis factor k (TNFk), interleu- in nature or if randomized have been too kin 1 (IL1), intracellular adhesion mol- small and underpowered to identify effects ecules, eNOS, a reduction of the hyper- on significant outcomes such as myocardial contraction that follows reperfusion and infarction and mortality. Studies have gen- activation of anti-apoptotic kinases (Akt, erally used surrogate markers for myocardi- ERK 1-2) (2). al protection such as the cardiac troponins Volatile anaesthetics have been shown in a as a measure of myocardial injury. number of animal ex vivo and in vivo ex- To date there have been 3 meta-analyses periments to be able to precondition the performed including only randomized con- myocardium in a similar way to classical trolled trials (RCTs) to try and answer the ischaemic preconditioning. Similarly, vol- question does volatile anaesthesia improve atile anaesthetics have the ability to post- outcomes in coronary surgery? condition the myocardium whereby ex- Yu and Beattie performed the first meta- posure to volatiles during the reperfusion analysis in 2006 (20). The authors identi- period also protects the myocardium (16). fied 32 randomized studies involving 2841 There is now increasing evidence that vola- patients. Volatile anaesthetics included hal- tile anaesthetics can induce late precondi- othane, enflurane, isoflurane, sevoflurane tioning, raising the potential of myocardial and desflurane and were administered in protection that persists after the exposure any combination of the pre-bypass, during in the operating theatre (16, 17). bypass and post-bypass periods. When com- In addition to the ability to precondition pared with intravenous anaesthetics, those the myocardium, all volatile anaesthet- who were exposed to volatile anaesthetics ics induce a dose dependent decrease in had an observed reduction in mortality that myocardial contractility, decrease myocar- did not reach statistical significance (OR, dial oxygen demand and therefore improve 0.65; 95% CI 0.36-1.18). Furthermore, re- myocardial oxygen balance during isch- moving studies that used halothane or en- aemia. It is often difficult to experimental- flurane in their study protocols also failed HSR Proceedings in Intensive Care and Cardiovascular Anesthesia 2010, Vol. 2 Volatile anaesthetic myocardial protection to show a statistically significant reduction ics throughout the entire procedure. Only 107 in mortality. Similarly, no statistical differ- a few of the RCTs were of high quality and ence was seen in the incidence of AMI be- all the studies included numbers that were tween groups. However, post hoc analysis too small to allow for assessment of impor- of patients that received sevoflurane or des- tant clinical outcome variables such as AMI flurane showed that these patients experi- and death. enced significantly less Troponin I leakage Data pooling and analysis showed that than patients receiving intravenous anaes- when compared with intravenous anaes- thesia. thesia, sevoflurane and desflurane were Symons and Myles performed a similar associated with significant reductions in meta-analysis in 2006 (21). They identified the rates of all major clinical outcome vari- 27 randomized studies including 2979 pa- ables. Volatile anaesthesia significantly re- tients comparing volatile with non-volatile duced the degree of troponin I leakage (OR anaesthesia for CABG. Volatile anaesthetics 0.47; 0.29, 0.76). Importantly, the risk of again included halothane, enflurane, isoflu- all-cause mortality and AMI was also sig- rane, sevoflurane and desflurane and were nificantly reduced by volatile anaesthesia administered during pre-bypass, bypass and (OR 0.31; 0.12,0.80 and OR 0.51; 0.32,0.84 post-bypass periods. There was no signifi- respectively). Furthermore, the use of sevo- cant difference between volatile and non- flurane and desflurane was associated with volatile anaesthetic groups with respect to a significant reduction in the duration of death, myocardial infarction, myocardial mechanical ventilation, length of ICU stay ischaemia or ICU length of stay. However, and time to hospital discharge. patients randomized to receive volatile an- Though this represents strong class Ia evi- aesthetics had significantly higher cardiac dence for myocardial protection with mod- indices, lower troponin I concentrations, ern volatile anaesthetic agents in patients reduced requirement for inotropic support, undergoing CABG, results from a large ob- shorter duration of mechanical ventilation servational study published in 2007 are not and shorter length of hospital stays than quite so conclusive. Data from a retrospec- those randomized to receive intravenous tive Danish database of 10,535 patients un- anaesthetics. The results indicated that dergoing cardiac surgery with sevoflurane volatile anaesthetics may indeed be able to or propofol anaesthesia showed no differ- change outcomes in cardiac surgery. ence in overall post-operative mortality or More recent animal evidence suggests that myocardial infarction (28). The group sur- sevoflurane and desflurane display more mise that both propofol and sevoflurane prominent cardioprotection than the older have different cardioprotective properties. halogenated anaesthetics (22-26). This lead Sub-group analysis revealed that in patients to the most recent meta-analysis performed undergoing non-coronary cardiac surgery, by Landoni and colleagues in 2007 (27). sevoflurane was superior to propofol whilst Their group identified 22 randomised stud- propofol was superior to sevoflurane in ies involving 1922 patients where compari- patients with severe ischaemia, cardiovas- sons of the modern volatile anaesthetics cular instability or those requiring urgent sevoflurane and desflurane were made with surgery. This finding may reflect the anti- intravenous anaesthesia in CABG surgery. oxidant properties of propofol and the isch- Most studies were performed on patients aemic preconditioning effect of unstable undergoing on-pump CABG and most au- angina negating the myocardial protection thors administered the volatile anaesthet- offered by volatile anaesthesia. HSR Proceedings in Intensive Care and Cardiovascular Anesthesia 2010, Vol. 2 E. Lin, J.A. Symons 108 Clinical evidence in non-cardiac surgery 2. Landoni G, Bignami E, Oliviero F, Zangrillo A. Landoni and colleagues performed a meta- Halogenated anaesthetics and cardiac protection in cardiac and non-cardiac anaesthesia. Ann Card analysis of RCTs comparing sevoflurane or Anaesth 2009; 12: 4-9. desflurane anaesthesia with intravenous 3. Yellon DM, Downey JM. Preconditioning the myo- anaesthesia in adult patients undergoing cardium: from cellular physiology to clinical cardi- non-cardiac surgery in 2007 (29). Seventy- ology. Physiol Rev 2003; 83: 1113-1151. 4. de Ruijter W, Musters RJ, Boer C, et al. The car- nine studies and over 6000 patients were dioprotective effect of sevoflurane depends on pro- included in the analysis but firm conclu- tein kinase C activation, opening of mitochondrial sions could not be made due to the low K+ATP channels, and the production of reactive incidence of cardiovascular events in both oxygen species. Anesth Analg 2003; 97: 1370- groups. 1376. 5. Hanouz J-L, Yvon A, Massetti M, et al. Mechanisms Nevertheless, the most recent American of desflurane-induced preconditioning in isolated College of Cardiology/American Heart As- human right atria in vitro. Anesthesiology 2002; sociation Guidelines recommend the use 97: 33-41. of volatile anaesthetic agents during non- 6. Hara T, Tomiyasu S, Sungsam C, et al. Sevoflurane cardiac surgery in patients at risk for AMI protects stunned myocardium through activation of mitochondrial ATP-sensitive potassium channels. 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