Seminars in Cardiothoracic and Vascular Anesthesia

The influence of anesthetic choices and techniques upon outcomes in cardiac surgery is difficult to ascertain because of the low incidence of morbid and fatal outcomes that are attributable to anesthetic management. This discussion summarizes several areas that have been addressed in clinical trials, including temperature management, intraoperative hemodynamics, and glucose control.

Diabetes and impaired glucose tolerance are largely under-diagnosed in patients with acute atherosclerotic events. This glucose-unawareness is an obstacle for aggressive treatment in these patients. It is suggested to check fasting glucose levels in patients scheduled for cardiovascular surgery and to give intensive insulin therapy perioperatively if fasting glucose levels are greater than 7.0 mmol/L (126 mg/dL). If fasting glucose levels are not elevated an oral glucose tolerance test should be considered so that unknown diabetes can be detected and treated.

The anesthetic approach to the patient with a thoracic aortic aneurysm depends on the urgency of repair. Symptomatic patients with leaking aneurysms require urgent intervention, and there is generally little time to perform more than the most basic preoperative assessment. For elective repair, however, one must consider nearly every organ system. Many of the specific issues are inherent to the underlying pathophysiology that has resulted in aneurysm formation, and some stem from the requirements of the surgical procedure itself. A thorough knowledge of the extent and location of the aneurysm, the functional status of the heart, and the coronary artery anatomy are critical. Most patients aged older than 40 years undergo coronary angiography preoperatively, as do younger patients with specific risk factors for myocardial ischemia. Respiratory failure is one of the most common sequelae of these procedures, and a thorough preoperative pulmonary work-up is mandatory. Neurologic deficits are not uncommon postoperatively, and pre-existing deficits in the central nervous system must be sought. Coagulopathy is common in the immediate postoperative period, and preoperative assurance of hemo-static competence is important. Computed tomography scans and magnetic resonance imaging are the mainstay of diagnosis, although the adjunctive use of echocardiography provides important information. Routine preoperative laboratory studies include complete blood count, chemistries, coagulation profile, and indices of renal function; an electrocardiogram, and chest radiograph. Close communication with the surgeon regarding the operative procedure, cannulation strategy (where applicable), and planned evoked potential monitoring is necessary to ensure appropriate perioperative management. Prophylactic antibiotics and antifibrinolytics are routine.

Perioperative myocardial infarction following noncardiac surgery is a complex process with a variety of proposed etiologic factors. Perioperativeb-blockade has been reported to reduce perioperative myocardial infarction and cardiac death, with possible direct effects on longer-term outcome, particularly after vascular surgery. Despite two high-profile studies that have pushed this topic into the mainstream of medicine, the number of patients studied and outcomes observed remains limited, especially for a therapy recommended for widespread adoption in millions of patients globally. Observational analyses, small meta-analyses, and newer randomized trial data (primarily in abstract format) suggest the therapy is of benefit in high-risk patients, whereas in patients at intermediate or low risk, it is either mildly efficacious or neutral in effect. Adverse effects appear to be limited to the expected primary hemodynamic side effects of bradycardia and hypotension, although a suggestion of increased mortality has been reported in one observational analysis in the lowest-risk group.b-Blockade may be associated with reduction in length of stay and reduced analgesic requirements, although these effects remain controversial. A single mega-trial being conducted outside of the United States with a target goal of 10,000 patients is ongoing and promises to provide definitive data within the next few years. Ongoing research into various etiologies of perioperative myocardial infarction and other medications with potential efficacy in this setting, including the important antiplatelet agents, must also be considered in developing recommendations for widespread adoption of perioperativeb-blockade.

Patients with left ventricular dysfunction who are undergoing major noncardiac vascular surgery are at increased risk of adverse postoperative events. We sought to evaluate whether perioperative medication use, including angiotensin-converting enzyme (ACE) inhibitors,b-blockers, statins, and aspirin, was associated with a reduced incidence of postoperative in-hospital mortality in these high-risk patients. The study enrolled 511 patients with left ventricular dysfunction (left ventricular ejection fraction <30%) who were undergoing major noncardiac vascular surgery. Cardiac risk factors and medication use were noted before surgery. Preoperative dobutamine stress echocardiography (DSE) was performed to identify patients with stress-induced myocardial ischemia. The end point was postoperative in-hospital mortality. Univariate and multivariate logistic regression analyses were performed to evaluate the relation between perioperative medication use and mortality. The mean age of the study population was 64 ± 11 years, and 75% were men. Perioperative use of ACE inhibitors, b-blockers, statins, and aspirin was recorded in 215 (48%), 139 (27%), 107 (21%), and 125 patients (24%), respectively. Stress-induced myocardial ischemia occurred in 82 patients (16%). Sixty-four patients (13%) died. Perioperative use of ACE inhibitors (odds ratio [OR], 0.33; 95% confidence interval [CI], 0.12-0.91), b-blockers (OR, 0.03; 95% CI, 0.01-0.26), statins (OR, 0.06; 95% CI, 0.01-0.53), and aspirin (OR, 0.13; 95% CI, 0.03-0.55), was significantly associated with a reduced incidence of mortality, after adjusting for cardiac risk factors and DSE results. In conclusion, the present study showed that the perioperative use of ACE inhibitors,b-blockers, statins, and aspirin is independently associated with a reduced incidence of in-hospital mortality in patients with left ventricular dysfunction who are undergoing major noncardiac vascular surgery.

All volatile anesthetics have been shown to induce a dose-dependent decrease in myocardial contractility and cardiac loading conditions. These depressant effects decrease myocardial oxygen demand and may, therefore, have a beneficial role on the myocardial oxygen balance during myocardial ischemia. Recently, experimental evidence has clearly demonstrated that in addition to theseindirect protective effects, volatile anesthetic agents also havedirect protective properties against reversible and irreversible ischemic myocardial damage. These properties have not only been related to a direct preconditioning effect but also to an effect on the extent of reperfusion injury. The implementation of these properties during clinical anesthesia can provide an additional tool in the treatment or prevention, or both, of ischemic cardiac dysfunction in the perioperative period. In the clinical practice, these effects should be associated with improved cardiac function, finally resulting in a better outcome in patients with coronary artery disease. The potential application of these protective properties of volatile anesthetic agents in clinical practice is the subject of ongoing research. This review summarizes the current knowledge on this subject.

Patients with heart failure have a diminished cardiac reserve capacity that may be further compromised by anesthesia. In addition to depression of sympathetic activity, most anaesthetics interfere with cardiovascular performance, either by a direct myocardial depression or by modifying cardiovascular control mechanisms. Etomidate causes the least cardiovascular depression. It is popular for induction of anesthesia in cardiac-compromised patients; however, it is not suitable for maintenance of anesthesia because it depresses adrenocortical function. Ketamine has a favorable cardiovascular profile related to central sympathetic stimulation and inhibition of neuronal catecholamine uptake. These counteract its direct negative inotropic effect. In patients with a failing myocardium, however, the negative inotropic effects may be unmasked, resulting in deterioration in cardiac performance and cardiovascular instability. Propofol is the most popular intravenous anesthetic for maintenance of anesthesia. It does have a negative inotropic effect, but the net effect on myocardial contractility is insignificant at clinical concentrations, probably because of a simultaneous increase in the sensitivity of the myofilaments to Ca²⁺. Propofol protects the myocardium against ischemiareperfusion injury, an action derived from its antioxidant and free-radical-scavenging properties as well as the related inhibition of the mitochondrial permeability transition pore. For intravenous anesthesia, propofol is always combined with an opioid. Opioids have relatively few cardiovascular side effects and, in particular, do not cause myocardial depression. Indeed, they are cardioprotective, with antiarrhythmic activity, and induce pharmacologic preconditioning of the myocardium by a mechanism similar to the inhalational anesthetics.

Multiplane transesophageal echocardiography (TEE) is a semiinvasive, very low-risk imaging procedure utilizing the upper gastric and esophageal echo windows to image the heart with the use of high-frequency transducers. It allows for high spatial resolution and access to structures that are routinely not well seen by transthoracic echocardiography, such as the left atrial appendage, the thoracic aorta, and the pulmonary veins, or where transthoracic imaging may be insufficient to answer a specific question, such as the presence of small vegetations, endocarditic abscesses, abnormalities of the interatrial septum, and others. Another important indication is the ventilated patient or the patient in the operating room, where transthoracic echocardiography is unrewarding or impossible. A particular role has emerged for TEE for identifying candidates for mitral valve repair by providing detailed functional and morphologic information on the diseased valve and by checking intraoperatively the results of surgery. A set of cross-sections, defined by anatomic landmarks, has been compiled, which can be systematically sought, evaluated, and modified according to the clinical question in order to extract the maximal information from TEE.

Until recently, more than 2200 Swan Ganz catheters were used annually in the operating rooms (OR) and intensive care unit (ICU) of the Catharina Hospital in Eindhoven, The Netherlands. After cardiologists who were specialists in echocardiography (ECHO) trained anesthesiologists in ECHO, the need for these catheters in cardiac and noncardiac surgery was reduced. Initially intended as a local teaching project, an ECHO teaching compact disk (CD) was produced during the training and distributed later worldwide, thanks to a positive review in a major anesthesiology publication. By reducing the number of Swan Ganz catheters, the hospital could finance and acquire two echocardiography machines for the OR and ICU. The availability of these machines resulted in a further reduction of the number of Swan Ganz catheters. However, the need for quantification (eg, measurements of cardiac output) remained. During the creation of the ECHO teaching CD, the idea was born to apply indicator-dilution principles on injected echo contrast. This study was performed in cooperation with the Signal Processing Department of the Eindhoven University of Technology. Advanced signal processing and modelling were used to develop algorithms to enable quantification of intrapulmonary blood volume, ejection-fraction, and flow from the transesophageal echocardiography approach. These quantitative measurements, which can be performed on an outpatient basis, may become a real asset in cardiology, anesthesiology, and intensive care.

The rationale and clinical use of Doppler echocardiography for the assessment of left ventricular diastolic dysfunction is described with focus on recent developments. Noninvasive measurement of elevated left atrial pressure can be performed with transthoracic and transesophageal echocardiography in daily practice and thus, can be used for clinical management in patients with heart failure.

Transesophageal echocardiography (TEE) provides high-resolution images of the mitral valve apparatus, permitting detailed evaluation of its structure and function. Mitral valve evaluation is invaluable during mitral valve repair surgery, providing insight into the mechanism of valve dysfunction and formulation of a plan for repair. TEE provides immediate detection of inadequate repair after bypass and allows correction during the same operative setting. Intraoperative TEE is a valuable tool for improving patient outcome and offers the cardiovascular anesthesiologist a role in perioperative surgical decisions.

Ischemic mitral regurgitation is the regurgitation seen with structurally normal valve leaflets that occurs in approximately 20% of patients after myocardial infarction and 56% of patients with congestive heart failure caused by ischemic or nonischemic cardiomyopathy. The initiating event is an ischemic insult that results in remodeling of the left ventricle toward a more spherical shape and new wall motion abnormalities. These changes lead to annular dilation and subvalvular distortion that prevent the mitral leaflets from coapting and closing completely during the contraction phase. Treatment options include coronary revascularization, ring annuloplasty, valve repair and replacement, or left ventricle reconstruction by way of localized reshaping or resection. Pharmacotherapy, aimed at raising left ventricular pressure without increasing tethering or left ventricular volume, is included in the treatment options for improving ischemic mitral regurgitation.

In the busy emergency department, time-effective and accurate diagnostic and prognostic evaluation is essential Although clinical examination remains the mainstay of appropriate evaluation, remaining diagnostic uncertainty may need to be resolved by use of additional techniques. Echocardiography appears very well suited to the unique environment in the emergency department. It is portable to the patient's bedside, can be performed in minimal time, and results are immediately available. This facilitates correct triage and disposition of complicated cases. Small, hand-carried echocardiography systems have been developed with full imaging and Doppler capabilities. Thus, availability of echocardiography is increasing. Because both image acquisition and interpretation are operator-dependent, realization of full diagnostic potential requires extensive training and post-training experience to maintain proficiency.

Aortic dissection and aortic intramural hematoma are highly lethal diseases occurring mostly in patients with arterial hypertension or Marfan syndrome. Transesophageal echocardiography (TEE) is the diagnostic imaging procedure of choice in the unstable patient. Hallmarks of dissection are the presence of an intimal membrane, or flap, dividing a true and a false lumen, entry and reentry tears, periaortic hematoma, pericardial effusion or tamponade, and aortic regurgitation in dissection of the ascending aorta. TEE allows detection of involvement of the ascending aorta, which places the patient in an extremely high-risk group and necessitates urgent operation. The accuracy of TEE is similar to computed tomography and magnetic resonance imaging, with the added benefit of being feasible at the bedside or in the operating room. Precautions have to be taken during TEE to avoid an abrupt rise in blood pressure. Aortic intramural hematoma is often a precursor of classic dissection or accompanies it and can also be diagnosed by TEE, although the diagnosis is frequently difficult.

Transesophageal echocardiography (TEE) is especially suitable for examination of prosthetic valves because of the proximity of the esophagus to the heart and absence of interference with lungs and ribs. This article reviews normal and abnormal morphologic characteristics of prosthetic valves such as spontaneous echocontrast, microbubbles, strands, sutures, vegetations or thrombus. Doppler echocardiographic characteristics of normal and pathologic prosthetic valve function and the management of prosthetic valve pathology is discussed. Physicians taking care of patients with prosthetic valves should be familiar with the characteristics of normal and abnormally functioning prosthetic valves.

Detection of myocardial ischemia in the perioperative period is important because it allows for intervention that may prevent progression of ischemia to myocardial infarction. Perioperative ischemia is also an important predictor of adverse cardiovascular outcomes. Patients should first be stratified according to their risk of having cardiovascular disease by identifying major, intermediate, and minor predictors of adverse cardiovascular outcome. Electrocardiographic (ECG) monitoring for ischemia is inexpensive and noninvasive, but may not be applicable to all patients and is not perfectly sensitive or specific. Modern operating room monitors can automate ST segment monitoring and be set to alarm if changes occur. Increases in central venous pressure and pulmonary artery pressure can be caused by myocardial ischemia, but have been shown to be very insensitive compared to ECG. Also, detection of these hemodynamic changes requires insertion of invasive monitoring devices. Transesophageal echocardiography can be used to detect myocardial ischemia by identifying changes in regional wall motion. These transesophageal echocardiography changes occur sooner and more frequently than ECG changes, but require greater knowledge and skill to properly interpret.

Echocardiography has been evolving to play a pivotal role in hemodynamic management, both intraoperatively and at the bedside. A full assessment of hemodynamics necessitates the use of all of the options available on modern echocardiographs. This introductory review provides insight into three important issues of hemodynamic monitoring by echocardiography: evaluation of preloading conditions, assessment of systolic function, and contractility and estimation of afterload. Mastering these three features will help in a minimally invasive approach of hemodynamic instability.