U Ulceroglandular Tularemia Refers to disease caused by Francisella tularensis involving the skin or mucous membranes and associated lymphade- nopathy. Most patients also have systemic symptoms, including fever, chills, and mylagias, in addition to a typical ulcerative lesion. This group includes the clinical syndromes of ulceroglandular, glandular, and oculoglandular tularemia. Ultrafiltration Ultrafiltration is the process by which a fluid passes through a semipermeable membrane by the effect of a hydrostatic, osmotic, or oncotic gradient. The ultrafil- trate is composed of the fluid that passed through the semipermeable membranes and the solutes that followed, according to their sieving coefficient. ▶ Convective Clearance Ultrasonography ▶ Imaging for Acute Abdominal Pain Ultrasound: Uses in ICU NEKTARIA XIROUCHAKI,DIMITRIOS GEORGOPOULOS Department of Intensive Care Medicine, University Hospital of Heraklion, University of Crete, Heraklion, Crete, Greece Synonyms Bedside ultrasonography; Echography; FAST; ICU ultra- sound; TCD Definition In 1790, the Italian biologist and physiologist Spalanzani demonstrated that bats, although blind, could navigate using the echo-reflection of inaudible sound. Sound waves are mechanical vibrations that induce alternate refractions and compressions of any physical medium through which they pass. The interaction between ultrasound (US) and tissues has been studied since the 1920s. From 1960 onward an ever-increasing number of physicians began to accept and employ ultrasound in clinical practice. Ultrasound technology was introduced into intensive care units (ICU) in the 1980s, and became an established bedside technique in 1990. Over the past decade (2000– 2010), its use in ICUs has further increased, to the point where it now plays a fundamental role in the management of critically ill patients. Characteristics Echocardiography and Critically Ill Patients Echocardiography is a vital diagnostic and monitoring imaging modality for intensivists. For over 50 years, ultra- sound has provided noninvasive information about the structure and function of the heart. First introduced by Frazin et al. in 1976, esophageal echocardiography has since improved in terms of image quality and diagnostic status, and is now an important informative tool for the intensivist. Both transthoracic (TTE) and transesophageal (TEE) echocardiography provide real-time bedside infor- mation in ICUs about a variety of structural and func- tional abnormalities of the heart. Indications for transthoracic echo examination of the heart in an ICU environment include: (1) hemodynamic instability, (2) exclusion of pericardial tamponade, (3) acute RV overload (e.g., pulmonary embolism, PE), and (4) thoracic trauma (e.g., myocardial contusion) [1, 2]. In addition to common TEE indications (such as endocarditis, source of embolus, and suspected aorta dis- section), indications for transesophageal echocardiogra- phy in critically ill patients are: (1) inadequate depiction by TTE, (2) hemodynamic instability, (3) unexplained hypoxemia, (4) prone position, (5) post-cardiac surgery, Jean-Louis Vincent & Jesse B. Hall (eds.), Encyclopedia of Intensive Care Medicine, DOI 10.1007/978-3-642-00418-6, # Springer-Verlag Berlin Heidelberg 2012