Departments of 1 Anaesthesiology and 2 Cardiovascular Surgery, University Hospital Lausanne (CHUV), CH-1011 Lausanne, Switzerland. 3 Department of Cardiac Anaesthesiology, CHU Brugmann, B1020 Brussels, Belgium. 4 Institute of Anaesthesiology, University Hospital Zürich (USZ), CH-8091 Zürich, Switzerland 5 Present address: Centre Hospitalier Universitaire de Sherbrooke, Sherbrooke, Québec J1H 5N4, Canada
*Corresponding author. E-mail: donat.spahn@chuv.hospvd.ch
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Abstract |
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Br J Anaesth 2004; 92: 40013
Keywords: anaesthesia, cardiovascular; complications, intraoperative myocardial ischaemia; heart, manipulation technique; monitoring; outcome studies; surgery, off-pump coronary artery bypass
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Introduction |
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Off-pump coronary revascularization is an old technique, performed first in St Petersburg in 1964,62 but was soon outshone by the rapid development of CPB and cardioplegia. A revival of the technique occurred during the 1980s in isolated series, and in centres where limited resources favoured off-pump techniques. Accordingly, large series have been undertaken in Buenos Aires (700 patients),12 São Paulo (1274 patients),20 Ankara (2052 patients),114 and New Dehli (2800 patients).116
Off pump coronary artery surgery has been developed following two different approaches. Minimally invasive direct-access coronary artery bypass (MIDCAB) consists of anastomozing the left internal mammary artery to the left anterior descending coronary artery through a small anterior left thoracotomy. Nowadays, this technique has largely been abandoned, because it allows only single vessel surgery, is technically demanding, and may lead to suboptimal results. Moreover, postoperative pain is usually more severe after thoracotomy than after sternotomy.39 The second approach is multivessel grafting without CPB performed through a standard median sternotomy, which gives access to all coronary vessels, and allows standard techniques of mammary artery harvesting. The recent introduction of sophisticated stabilizing devices and exposure techniques13 has resulted in an increased graft patency rate,25 and in the widespread use of this technique for all coronary territories and for as many anastomoses as needed to treat the patients coronary artery disease.4 106 This review will focus exclusively on the latter procedure, called off-pump coronary artery bypass (OPCAB).
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Rationale for avoiding CPB |
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The results are not clear-cut concerning neurological outcome. Cross-clamping and cannulation of the ascending aorta, as well as the flow jet from the arterial cannula of CPB, are eliminated in OPCAB surgery; this should reduce the incidence of embolic events from the atheromatous aorta.94 Although the total number of embolic events on transcranial Doppler is effectively decreased,16 38 122 the occurrence of strokes was only found to be significantly lower in isolated studies,93 94 116 or in octogenarians.36 99 The incidence of postoperative strokes may depend on the manipulation of the ascending aorta for proximal anastomoses, and reduced stroke rates may be achieved by surgical techniques avoiding aortic clamping completely, such as branching bypass grafts on peripheral arteries emerging from the aortic arch.23 24 The effect on cognition is also debatable, because the few published studies show conflicting results.38 63 85 113 117
There is increasing evidence that off-pump procedures are associated with reduced postoperative rise in markers of systemic inflammatory response (SIRS), such as C3a, C5a, TNF-, or interleukin (IL)-6 and IL-8.8 33 37 77 However, the clinical significance of these data is still uncertain, because IL-8 and C3a are linked to the amount of surgical tissue injury, IL-10 has anti-inflammatory properties, and heparin inhibits complement activation.79 The effects of CPB on SIRS depend largely on the balance between pro-inflammatory and anti-inflammatory mediator release. As some population subgoups might show a greater pro-inflammatory cytokine response, such as elderly patients or patients with left ventricular (LV) dysfunction, they should benefit particularly from off-pump procedures.8 115
In a low-risk population, surgical coronary revascularization, with or without CPB, has low morbidity and mortality rates.89 Possible advantages of OPCAB surgery are therefore more likely to be found in high-risk patients with significant comorbidities and an expected mortality of 610%.106 Mortality appears to be lower in some series,1 4 106 but not all89 100 (Table 1). In elderly patients, results are improved with OPCAB surgery: mortality and postoperative complication rates are significantly lower;17 63 99 111 the incidence of a low postoperative cardiac output is reduced from 32% to 10%; and strokes are reduced from 9% to 1%.2 17 36 99 Similarly, emergency coronary surgery or surgery performed on patients with impaired ventricular function (ejection fraction <0.35) have shown encouraging results.83 112 126 Available reports show only some trend toward possible renal protection, but there is probably no difference for patients on dialysis.1 6 48 70 The results concerning insulin-dependent diabetics show no improvement in comparison with conventional surgery.4 83
OPCAB has been shown to be feasible in almost all patients requiring coronary bypass. The only contraindications are the presence of intracavitary thrombi, malignant ventricular arrhythmias, deep intramyocardial vessels, and procedures combined with valve replacement or ventricular aneurysmectomy. Despite difficulties because of pericardial adhesions, beating-heart reoperations for single- and multiple-vessel disease have been performed through thoracotomy or sternotomy incisions.80
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Problems associated with OPCAB |
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Haemodynamic alterations with cardiac manipulation
Surgical access to the left anterior descending coronary artery is relatively easy through a median sternotomy but, in order to work on the posterior or lateral walls, the heart must be lifted and tilted out of the pericardial cradle. This displacement of the heart has important haemodynamic consequences, resulting in a significant increase in atrial pressures, and a marked decrease in cardiac output (cardiac index <2 litre min1 m2), leading to a reduced mixed-venous saturation (SvO2), often <70%. Different parts of the procedure produce different haemodynamic disturbances.
First, the heart is tilted in a vertical position with the apex at its zenith; the atria are then situated below the corresponding ventricles, and the blood must flow up into the ventricular cavities. Therefore, the filling pressures, as measured in the right and left atria, are increased much more than the corresponding ventricular end-diastolic pressures,78 and must be maintained at a higher than normal level to maintain ventricular filling.90 The atrial size can increase by 50% and become larger than the ventricle (Fig. 1).49 78 Mitral and pulmonary venous flows show patterns of impaired diastolic filling and moderate diastolic dysfunction.49
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Third, a vertical position of the heart induces distortions of the mitral and tricuspid annuli, as the intracardiac structures are folded primarily at the atrioventricular groove. The annular plane of the valves is modified, and significant regurgitation may occur. The mitral annulus, reconstructed in three dimensions with transoesophageal echocardiographic (TOE) monitoring, is bent over, folded and twisted.49 This may result in significant mitral and tricuspid regurgitation (Figs 2 and 3). The sudden appearance of large v waves (>30 mm Hg) on the pulmonary artery catheter readings, without signs of LV failure, illustrates the same mechanism. The distortion of the atrioventricular annulus can also result in a functional stenosis. The most profound effect seems to occur on abnormal valves, which become more distorted. The same phenomenon may be observed on the aortic valve; a trivial aortic regurgitation may become severe when the heart is enucleated from the pericardium.
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The first technique consists of displacing the heart with gauze pads and/or rocking it with suction stabilizer devices. In these conditions, the thin right ventricle (RV) is squeezed between the pericardium and the bulky left ventricle, and compressed under the right hemi-sternum, resulting in severe haemodynamic compromise (Fig. 4).90 Transoeso phageal echocardiography reveals a bulging of the interatrial septum to the left, no dilatation of the LV, and part of the cramped small RV with right outflow tract obstruction.90 In an animal model, Gründeman51 reported a 165% increase in RV end-diastolic pressure and a 62% decrease in RV end-diastolic area; LV pressures did not change although LV diastolic cross-sectional area decreased by 20%. Opening of the right pleura may reduce haemodynamic compromise.90 The Trendelenburg manoeuvre re-establishes the circulatory status and the coronary blood flow at the expense of a further rise in RV preload, an increased LV preload, and an increased heart rate.50
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Intraoperative myocardial ischaemia
During OPCAB surgery, coronary artery cross-clamping to ensure bloodless anastomotic conditions results in brief periods of myocardial ischaemia, usually manifested by ST-segment elevation and new regional wall motion abnormalities (RWMA) on echocardiographic imaging.81 A 16 min mean occlusion time of the left anterior descending artery necessary to perform an anastomosis is associated with a decrease in peak systolic shortening from 5.8% to 1.8%,18 and results in myocardial lactate production. The significance of the ischaemia depends on the percentage stenosis of the target vessel and of the degree of collateralization; occlusion of highly collateralized vessels produces less ischaemia than occlusion of terminal vessels.61 The most intense ischaemic events occur when flow is interrupted in a discretely stenotic vessel, usually between 50 and 80% stenosis, with poor collateralization.26 Severe ischaemia during clamping of a non-occlusive right coronary artery (RCA) can result in dangerous arrhythmias such as complete atrioventricular (AV) block attributable to interruption of the blood flow in the AV node artery. Some surgeons therefore favour revascularization of the RCA through distal anastomoses placed beyond its bifurcation.41 84 Usually, it is recommended to start the sequential anastomoses with the most severely stenotic or occluded vessel.26 84
Different techniques are available in order to reduce the consequences of coronary blood flow interruption during OPCAB surgery: improvement in myocardial oxygen balance, ischaemic and pharmacological preconditioning, pharmacological prophylaxis, and surgical shunting.
Improvement of myocardial oxygen balance
Improvement of myocardial oxygen balance can be achieved by decreasing myocardial oxygen consumption and/or increasing myocardial oxygen supply. A reduction in oxygen consumption can be achieved through a decrease in heart rate and contractility. This is usually realized by ß-blockers and calcium antagonists. With the verticalization of the heart, LV wall tension remains low despite increasing atrial filling pressures, as these pressures do not reflect the actual end-diastolic pressure of the ventricle. Therefore, it should not contribute to an increase in oxygen demand.
An adequate coronary perfusion pressure is crucial for myocardial oxygen supply. Physiologically, aortic diastolic pressure is the driving force for coronary perfusion. Clinically, its closest measurement is the mean arterial pressure (MAP) measured in the radial or femoral artery.92 101 During anaesthesia with halogenated agents, a MAP <65 mm Hg, or a coronary perfusion pressure <50 mm Hg, are associated with intraoperative ischaemia,69 which is in agreement with OPCAB literature, where the accepted minimal MAP ranges from 60 mm Hg5 70 90 113 to 80 mm Hg.41 It seems advisable to keep a MAP 70 mm Hg allowing a safety margin above the critical coronary perfusion pressure. This may be achieved by administration of a vasopressor like phenylephrine or norepinephrine. A lower value is acceptable as long as signs of ischaemia are absent.
The aim is an overall equilibrium, where a low cardiac output is tolerated in so far as it meets the demands of the organism, as shown by an SvO2 >60%; the MAP is maintained at or above 70 mm Hg without LV dilatation as monitored by TOE. In order to prevent increased myocardial oxygen demand when ischaemia is threatening, ß-stimulants are best avoided until complete revascularization.
Preconditioning
Ischaemic preconditioning, or improvement of tolerance to ischaemia by brief ischaemic bouts followed by reperfusion, is an attractive technique for protecting the myocardium during the obligatory period of myocardial ischaemia required by OPCAB surgery.66 67 Preconditioning may also be induced pharmacologically, which appears more desirable in high-risk patients in whom an ischaemic type of preconditioning may further jeopardize diseased myocardium. Experimental studies have shown that volatile anaesthetics such as isoflurane or sevoflurane protect the myocardium against ischaemia by activation of a preconditioning-like mechanism when administered at 2 minimum alveolar concentration (MAC) at least 30 min before the ischaemic insult.27 57 127 128 So far, preconditioning by halogenated anaesthetics has been favourably evaluated only in patients undergoing on-pump CABG surgery.11 35 52 55 Propofol and etomidate, if used at clinically relevant concentrations, should not affect the preconditioning mechanism.35 Collectively, these observations tend to indicate that administration of halogenated anaesthetics may limit the adverse effects of ischaemic myocardial damage.
Pharmacological prophylaxis
In patients suffering from coronary artery disease (CAD), perioperative use of ß-blocking agents has been shown to be the most effective preventive measure.45 Possible benefit has been obtained with 2-agonists such as clonidine.86 Preoperative treatment of patients scheduled for coronary revascularization is maintained and included in the premedication. During the operation, a short-acting selective ß1-blocker like esmolol, given as repeated bolus or continuous infusion, is very efficient in lowering excessive heart rate.5 28 However, it might seriously reduce LV function, as measured by a 42% decrease in mean arterial pressure and a 35% drop in cardiac output, resulting in a decrease in SvO2 from 81 to 65%.28 This LV depression leads to an increase in the pulmonary arterial pressure (PAP), whereas right intraventricular pressure might already be elevated because of right outflow tract compression or sudden mitral regurgitation.
A calcium antagonist such as diltiazem may has some theoretical advantages over ß-blockers in the intraoperative period. It has been shown that, for the same decrease in heart rate, diltiazem lowers PAP, whereas esmolol tends to increase it.28 In addition to reducing AV conduction and heart rate as ß-blockers do, calcium antagonists offer the advantage of inducing vasodilation in arterial conduits.105 Moreover, as an increase in intracellular free calcium is one of the primary causes of reperfusion injury and post-ischaemic myocardial dysfunction, calcium antagonists might prevent some post-ischaemic lesions.105 Some centres administer a continuous infusion of diltiazem (0.1 mg kg1 h1) from incision to chest closure.28 84 91 However, there is no objective evidence that calcium antagonists may improve outcome in OPCAB surgery.
Magnesium ions, up to 20 mmol in the form of chloride or sulphate, act similarly on myocardial cells; the only side-effect is a slight arterial vasodilatation.44 Moreover, its use during cardiac surgery tends to decrease the incidence of atrial tachycardia.43 76 123 Some centres recommend the use of MgCl2 or MgSO4 before pericardial opening.76 84 106
Even if nitroglycerin prevents arterial spasm on isolated human radial artery segments better than diltiazem, nitrates have never been proven to be efficient in preventing myocardial ischaemia during non-cardiac or conventional cardiac procedures.47 107 In OPCAB studies, nitroglycerin has been used to reduce pulmonary arterial pressure,15 to treat active ischaemia,26 41 or as a hypothetical prophylactic measure. However, the nitroglycerin-induced decrease in preload is detrimental during heart verticalization when the filling pressures need to be increased to ensure optimal ventricular filling. Metabolic support with an intravenous glucose-insulin-potassium (GIK) solution does not offer significant clinical benefit for myocardial protection during OPCAB surgery.108
Surgical technique
In order to decrease the ischaemic time during anastomoses, the surgeon can insert a small shunt (13 mm size) into the coronary artery, which allows some blood flow, sufficient to prevent segmental wall motion abnormalities and to normalize or stabilize ST-segment elevation.73 When coronary blood flow is maintained during the grafting procedure, only transient impairment of LV function is observed during the anastomoses.125
Monitoring technique
Conventional 5-lead surface ECG with automated ST-segment analysis is routine. However, heart manipulation modifies the positional relationships of the heart to the surface electrodes, and restricts its contact with surrounding tissues.90 The shape of the tracing is altered, and the amplitude of the signal is reduced. For adequate monitoring of myocardial ischaemia, a new baseline must be established after each change in heart position in order to correctly interpret the observed ECG changes. Nevertheless, when the heart is completely enucleated, the diagnostic accuracy of ECG monitoring is reduced.
Invasive arterial blood pressure monitoring is mandatory to ensure adequate blood pressure. Of the studies reviewed, 74% consider a floated pulmonary arterial catheter (PAC) to be necessary. Right atrial and pulmonary wedge pressures must be interpreted within the framework of heart verticalization, as they should be significantly increased in order to push the blood up into the ventricle. SvO2 is a useful tool to evaluate global tissue oxygenation: an SvO2 decrease below 50% has been associated with the development of bowel ischaemia.10 It is essential to maintain the tip of the PAC in the mainstream of a large pulmonary artery, as the handling of the heart might advance the tip of the catheter into the periphery, towards smaller pulmonary vessels that can be disrupted with balloon inflation.
During heart manipulation, RV and LV outflow might be momentarily asymmetrical. The continuous pulse contour cardiac output (PCCO), which provides a beat-to-beat measurement of cardiac output from the arterial pulse curve, might complete the data on cardiac pressures with information on LV output. However, both PAC and PCCO measurements have been found to be in close agreement.
The presence of air surrounding the heart, and the use of a posterior pericardial stitch and swab close to the oesophagus, restrict considerably the performance of TOE, particularly when the heart is in the vertical position. The images are usually of poor quality, although still interpretable. TOE is a useful device for evaluating ventricular function and effective ventricular end-diastolic volume, and for diagnosing new RWMA. During coronary flow interruption, new RWMA are found in 64% of patients, of which 50% recover completely and 33% only partially after anastomosis.81 Mitral and pulmonary flow changes, typical of moderate diastolic impairment, can be observed during heart verticalization along with a reduced size of the LV and quantitative variation in mitral regurgitation.49 TOE can also identify a patent foramen ovale, should an unexplained refractory hypoxaemia supervene. It is also useful for excluding intracavitary thrombus, which is a contraindication to beating heart surgery. As mortality and morbidity from TOE are extremely low (0 and 0.2%, respectively),56 its riskbenefit ratio makes it a valuable tool for monitoring during OPCAB surgery.81 It is used routinely in 52% of the reviewed series.
During the first 30 min after revascularization, the surface ECG frequently demonstrates significant T-wave inversion which might be linked to reperfusion injury.31 120 Quantitative bypass blood flow measurement using an ultrasound transit time flowmeter is therefore convenient after the grafting procedure. The measured flow should be pulsatile and biphasic, with two forward components of short protosystolic and large diastolic flow, and one small component of retrograde telesystolic flow. The diastolic flow velocity should be >15 cm s1, and the mean graft flow at least 20 ml min1.34 If the anastomosis is stenotic, the flow curve becomes spiky and mainly systolic. Absolute flow values are less significant than the pulsatility index (PI), which is obtained by dividing the difference between the maximal and the minimal flow by the mean flow; the optimal PI is between 1 and 5.34 A low flow rate and an augmented PI have a high prognostic value for mid-term graft occlusion, and should lead to immediate graft reconstruction.72 TOE is helpful in evaluating post-anastomosis regional contractility. Persistent RWMA have an accurate prognostic value for postoperative cardiac complications.81
Haemodynamic management
Knowing the haemodynamic patterns of the OPCAB procedure, it becomes possible to adopt a strategy that aims at maintaining an optimal myocardial oxygen balance. This is usually achieved by keeping myocardial oxygen consumption as low as possible, and by preserving a relatively high coronary artery perfusion pressure (MAP 70 mm Hg) with an infusion of vasopressor and an increased preload.41 A reduced cardiac output is accepted as long as the SvO2 remains >60% and metabolic acidosis does not develop. The Buffington ratio is a useful index. It stipulates that patients suffering from coronary stenoses are at particular risk of myocardial ischaemia when their mean arterial pressure is less than the heart rate (MAP/heart rate <1).19
The patient frequently becomes hypotensive when the heart is tilted into a new position. Myocardial preload can be increased by leg elevation,88 and by administration of fluids. Total fluid input is surprisingly similar to that during CABG performed on CPB. In our series, the mean amount of fluids infused during OPCAB surgery was 850 ± 230 ml of colloid and 2800 ± 800 ml of crystalloid.84 Alternatively, -adrenergic agents such as phenylephrine or norepinephrine are indicated when MAP remains low despite optimization of circulating blood volume, in order to prevent excessive fluid administration and a detrimental increase in lung water content. Many different regimens are used. Possible LV dilatation is monitored by TOE. Excessive heart rate is usually treated with a ß-blocker, most frequently esmolol, after exclusion of hypovolaemia or inadequate anaesthesia. An
2-adrenoreceptor agonist like dexmedetomidine might be useful in unresponsive cases.102 If excessive bradycardia (heart rate <50 min1) develops, pacemaker wires connected to the right atrium can be used to increase the heart rate to 5065 beats min1.119 For main RCA anastomoses, a ventricular wire must be in place to avoid complete AV block. It seems advisable to avoid ß-stimulation before revascularization as myocardial ischaemia might increase because of excessive oxygen demand. Although theoretically sound, this concept has not yet been proven clinically in OPCAB surgery.90
Anticoagulation is mandatory during OPCAB surgery. As there is no contact with foreign surfaces unlike CPB, the targeted activated coagulation time (ACT) is usually kept at 250300 s as in major vascular surgery.75 84 This is reached by the i.v. administration of heparin 12 mg kg1 (100200 IU kg1) before section of the internal mammary artery. The ACT is repeated every 30 min, and heparin added as required. This lesser degree of anticoagulation and the lower platelet activation in comparison with CPB significantly decreases the haemorrhagic risk and the transfusion rate.9 114 Heparin reversal with protamine is optional. Mariani reported a hypercoagulable state after off-pump procedures,75 which might put patients at risk of bypass thrombosis or thromboembolism. Some centres start aspirin and/or clopidogrel at the end of the procedure,1 as aspirin reduces mortality and ischaemic complications after coronary bypass surgery.74
Indications for conversion to CPB remain difficult to define (Table 2). The limits are usually set at the following values, if they persist for >15 min despite aggressive therapy: cardiac index <1.5 litre min1 m2, SvO2 <60%, MAP <50 mm Hg, malignant arrhythmias, ST modifications >2 mm, and/or complete cardiovascular collapse.91 The rate of conversion to CPB varies between <1 and 4.9%.22 67 119 Good communication with the surgeon is essential, and the repositioning of the heart is probably the first step to take before conversion.41 The presence of a perfusionist with a dry ready CPB machine in the operating suite is therefore current practice. The main factors associated with major haemodynamic instability leading to CPB assistance are cardiomegaly, lateral wall compression during anastomoses on the obtuse marginal or ramus intermedius, and ischaemia during main RCA grafting.119 In cases of severe LV dysfunction (ejection fraction 20%), OPCAB can be performed under the assistance of intra-aortic balloon pumping in order to avoid CPB conversion.59 Flow-controlled centrifugal or axial mini-pumps can offer a right-side as well as a left-side support of 13 litre min1.71 With experience, however, OPCAB has become a procedure that can be performed without support, and these devices are mainly used for short-term circulatory support in cases of acute heart failure.
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From a survey of 46 recent studies where the technique is clearly described, the anaesthetic technique appears conventional (Table 3): fentanyl, propofol or isoflurane have been used in about two-thirds of the institutions. In some cases, general anaesthesia combined with intrathecal (sufentanil-morphine or bupivacaine),14 or thoracic epidural (bupivacaine) analgesia is favoured.2 40 68 91 Thoracic epidural anaesthesia has been shown to increase the diameter of epicardial arteries, increase collateral blood flow, decrease myocardial oxygen demand, decrease the incidence of arrhythmias and the rate of chest infection, and provide adequate postoperative analgesia.60 104 Despite the advantages of cardiac sympatholysis for OPCAB surgery, randomized studies comparing general vs combined anaesthesia, did not show significant difference in patient outcome, except for a trend towards earlier extubation.14 91 104 An ultra-fast technique with extubation in the operating room does not seem to be of any additional benefit to the patient or to be cost-effective.40 82 As beating-heart surgery requires less heparinization than CABG on CPB, the risk of epidural haematoma is reduced compared with conventional cardiac surgery, and should be the same as in major vascular surgery. There is a trend to keep patients on aspirin and antiplatelet drugs until surgery. Therefore, the place of regional analgesia, although very attractive in OPCAB surgery, needs to be further defined. Table 2 suggests an anaesthetic protocol; many other options may be suitable or even better adapted to local practices.
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Whatever the anaesthetic technique used, the primary goals of the anaesthetist are to manage the haemodynamic disturbances associated with heart manipulation and to treat the ischaemic events caused by coronary occlusion. As the difference in outcome of OPCAB vs CABG on CPB appears mainly in high-risk cases, it is of the utmost importance for the anaesthetist to master the pathophysiological processes involved, because proper handling of compromised patients could make a significant difference to morbidity and mortality.
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Conclusions |
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Longer version of this review |
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To help clarifying the comparison between different publications with dissimilar methodologies, the references are annotated into levels of evidence according to the guidelines of evidence-based medicine. Level I of evidence contains studies with prospective, randomized selection of patients, blinding and clear-cut results. Level II contains controlled non-randomized prospective studies. Level III comprises non-controlled non-randomized studies with contemporaneous controls. Level IV corresponds to retrospective studies with historical controls. Level V includes uncontrolled case series, observational studies and expert opinions. Technical descriptions, review articles and meta-analyses are not coded.
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Addendum |
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The reduction in transfusion requirements, in myocardial injury as evidenced by troponin-I release, in length of ICU and hospital stay, and in global costs, have all been confirmed by three randomized prospective studies.131133 Morbidity and mortality are decreased in patients having OPCAB compared to conventional CABG surgery in two large comparative analyses of 7808 patients, the difference being greater in high-risk patients.129134 Neurological dysfunction and stroke were also reduced in OPCAB surgery compared with conventional CABG surgery in a prospective randomized study on 60 patients.131
The benefit of pharmacological preconditioning by volatile anaesthetics55 128 has been confirmed in a prospective randomized controlled clinical trial in patients undergoing OPCAB surgery.130 Patients receiving sevoflurane anaesthesia had less myocardial injury as evidenced by less postoperative troponin-I release compared with patients anaesthetized with propofol.130
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References |
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