Bailliere's clinical anaesthesiology最新文献

Minimally invasive heart surgery, for either coronary artery or valve surgery, has been evaluated for a few years. Surgeons and anaesthesiologists have encountered new challenges with these new techniques. There is no doubt that ‘minimally invasive’ surgery increases the technical difficulty for the surgeon and limits the exposure of the heart. Transoesophageal echocardiography (TOE), by giving complete and on-line anatomical and haemodynamic information, will obviously take a major place in this setting. It gives an instantaneous view of the filling of cavities and the contractility of both ventricles, in a situation where the heart is not exposed. It allows a more complete de-airing to be performed at the end of surgery. Mitral valve repair can be evaluated at the end of surgery, which is mandatory in a situation where surgical difficulties are increased. Other indications of TOE are also presented; some development might arise in the future since minimally invasive surgery is still evolving.

Transoesophageal echocardiography has gained the role of a standard monitoring technique for both cardiac surgical patients and patients with increased cardiac risk under-going non-cardiac surgery. It offers unique information about left ventricular global and regional performance on a ‘beat-to-beat’ basis without subjecting the patient to a major degree of invasiveness. In addition to the fact that considerable experience is required to obtain reliably (and to maintain) the standard monitoring view of the left ventricle and to identify correctly the cardiac structures of interest, there are some other limitations inherent to the method that have to be recognized in order to obtain reliable results. In particular, the fact that with recent technological advances, such as acoustic quantification, on-line display of various left ventricular function parameters is provided which could blind us to possible sources of error. This and future technological developments should be used to their full potential but any pseudoaccuracy must not be overlooked.

Transoesophageal echocardiography (TOE) offers real-time diagnosis and monitoring of a variety of structural and functional abnormalities of the heart in critically ill patients. It provides, in particular, useful information on cardiac contractivity, filling status and output, valvular morphology and function and the structure of the ascending and descending aorta. The anaesthetist disposes of the full range of echocardiographic modalities, including M-mode, two-dimensional and colour Doppler echocardiography. This chapter describes how different two-dimensional images can be obtained, presents a summary of the anatomical and functional information available in those images and relates this information to the clinical questions which form the indications to perform TOE.

Transoesophageal echocardiography (TOE) is an outstanding tool for the clinical management of trauma patients. It provides valuable information on haemodynamic instability, diagnosis of myocardial contusion, traumatic valve dysfunction, traumatic aortic injuries, intrathoracic bleeding and systemic gas embolism related to pulmonary contusion. The accuracy of TOE in the diagnosis of traumatic aortic injuries is not perfectly determined: the main limitation is the operator dependency. Experience of trauma patients and specific signs of cardiovascular injuries are the keys to the extensive use of TOE in trauma centres. The main interest in TOE is the capability to perform TOE promptly upon admission, in the intensive care unit and in the operative room. In the case of delayed surgery of aortic injuries, TOE examination can participate in the decision-making process.

Transoesophageal echocardiography (TOE) is an important tool used to investigate closely all cardiac valves. With respect to cardiac valvular surgery, TOE has gained a most important place as an intraoperative diagnostic and monitoring technique. In this chapter, both mitral and aortic valvular disease with respect to intraoperative management will be discussed. Repair of the mitral valve is another important issue in modern cardiac surgery. Accurate and meticulous assessment of the mitral valve morphology and function by means of multiplane TOE provides a crucial asset for the cardiac surgeon during and after repair of the valve, improving outcome and reducing costs.

Transoesophageal echocardiography has rapidly become an important diagnostic modality for patients with aortic atherosclerosis or aortic dissection. Use of this modality can help direct patients to proper therapeutic modalities. This paper will review the role of transoesophageal echocardiography in these disease processes.

Advances in transoesophageal echocardiography (TOE) have made this modality a powerful diagnostic tool in the critical care unit. TOE in combination with stress (atrial pacing, pharmacological stress) provides important information about myocardial ischaemia and myocardial viability. Recent progress in transducer technology and computerized image processing brings three-dimensional and contrast-enhanced TOE closer to the critical care unit. Finally, miniaturization of probes and automated contour detection techniques make TOE a sensitive and continuous monitor of global and segmental left ventricular function.

While assessment of ventricular loading conditions is readily accessible at the patient's bedside, evaluation of contractile function is remarkably more complicated. The difficulty in obtaining contractility measurements in patients is directly related to the intimate interrelation between inotropic state and ventricular loads at the level of the intact organism. Despite the inherent problems in measuring contractility, it is of crucial importance in experimental research as well as in clinical medicine to separate the effects of a primary change in load from a primary change in contractility, whenever a clinical situation with severe left ventricular dysfunction presents itself. The most useful approaches for assessing contractility in clinical medicine involve transoesophageal echocardiography. By providing estimations of clinically important but previously inaccessible physiological parameters, this technology paved the way for a more quantitative assessment of cardiac function. Three different non-invasive techniques to measure left ventricular contractility by means of echocardiography have been applied in humans: (1) the reconstruction of the end-systolic pressure-volume relation; (2) the end-systolic meridional wall stress-rate-corrected mean velocity of fibre shortening relation; and (3) the pre-concept of preload-adjusted maximal power.

Over the last 15 years diastolic dysfunction has been recognized as a separate pathophysiological and clinical entity. At the same time two-dimensional echocardiography and Doppler echocardiography have evolved to become the method of choice to evaluate diastolic function in daily clinical practice. For correct interpretation and assessment of diastolic function parameters from Doppler velocity profiles, their relationship to the underlying pathophysiological mechanisms should be understood. This chapter will focus on the complex interaction between the different determinants of left ventricular diastolic function and the intracardiac Doppler velocity profiles. Ambiguities in interpretation and limitations of the technique as well as the latest technological advances and future directions will be discussed.