Identifying patients at risk for augmented renal clearance in the ICU : limitations and challenges

Augmented renal clearance (ARC) is an important determinant of antibiotic exposure in critically ill patients, and identifying patients at risk is therefore an important goal. There is a growing body of evidence that a younger patient with a low to moderate degree of organ dysfunction typically is at risk of ARC and therefore decreased exposure to renally eliminated antibiotics. Mechanisms potentially involved, such as increased cardiac output, have, however, not been identified as appropriate surrogate markers, and the search for suitable alternatives to readily identify patients with ARC continues

Review and classification of fretting fatigue test rigs

There is no standard or generally accepted test rig for fretting fatigue experiments. Therefore, researchers adopt an existing concept, or build a new test rig that meets their specific requirements. However, too many different test rigs may be disadvantageous because the results of two different test rigs are hard to compare. The increasing amount of diversity is mainly caused by the lack of a recent literature survey on fretting fatigue test rigs. In 1994, Hills and Nowell described a few test rigs in Mechanics Of Fretting Fatigue. In this study, the authors made a classification of test rigs based on the contact geometry, which is determined by the test specimens, not by the test rig itself. The authors of this article present a review of the available literature, and present a classification based on the properties of test rigs. Fretting fatigue test rigs are first divided in two categories based on the geometry of the test specimen: full scale and coupon scale test rigs. The latter are mostly used to perform research and are subdivided in categories based on increasing functionalities. This is the ability to apply a fatigue load, a constant normal force, and an alternating slip in the range of some micrometers. In time, from the fifties until now, progress has been seen in the design of fretting fatigue test rigs. More parameters can be controlled during experiments and more measuring techniques are incorporated. State of the art test rigs are classified in the last category with mostffunctionalities, but still have imperfections. Future designers can use this article to classify their needs, or help to design a better test rig knowing the imperfections of the state of the art test rigs

What every ICU clinician needs to know about the cardiovascular effects caused by abdominal hypertension

The effects of increased intra-abdominal pressure (IAP) on cardiovascular function are well recognized and include a combined negative effect on preload, afterload and contractility. The aim of this review is to summarize the current knowledge on this topic. The presence of intra-abdominal hypertension (IAH) erroneously increases barometric filling pressures like central venous (CVP) and pulmonary artery occlusion pressure (PAOP) (since these are zeroed against atmospheric pressure). Transmural filling pressures (calculated by subtracting the pleural pressure from the end-expiratory CVP value) may better reflect the true preload status but are difficult to obtain at the bedside. Alternatively, since pleural pressures are seldom measured, transmural CVP can also be estimated by subtracting half of the IAP from the end-expiratory CVP value, since abdominothoracic transmission is on average 50%. Volumetric preload indicators, such as global and right ventricular end-diastolic volumes or the left ventricular end-diastolic area, also correlate better with true preload. When using functional hemodynamic monitoring parameters like stroke volume variation (SVV) or pulse pressure variation (PPV) one must bear in mind that increased IAP will increase these values (via a concomitant increase in intrathoracic pressure). The passive leg raising test may be a false negative in IAH. Calculation of the abdominal perfusion pressure (as mean arterial pressure minus IAP) has been shown to be a better resuscitation endpoint than IAP alone. Finally, it is re-assuring that transpulmonary thermodilution techniques have been validated in the setting of IAH and abdominal compartment syndrome. In conclusion, the clinician must be aware of the different effects of IAH on cardiovascular function in order to assess the volume status accurately and to optimize hemodynamic performance

A role for prophylactic antibiotics in necrotizing pancreatitis? Why we may never know the answer ...

The use of prophylactic antibiotics in patients with severe acute pancreatitis remains an intensely debated topic. Although animal studies consistently demonstrated an advantage of antibiotic prophylaxis, the only two blinded randomized controlled trials could not confirm these findings. Translation of the experimental models in human clinical practice is hampered by a number of fundamental differences between experimental pancreatitis and human disease, and therefore it is highly unlikely that the pronounced benefit found in experimental pancreatitis will ever be demonstrated in human disease. Early and accurate risk stratification to identify the patient at risk for infection early in the course of the disease seems to be the greatest challenge. Until we are able to demonstrate an advantage of antibiotic prophylaxis in a high-risk human population, the absence of proven benefit and potential side effects of this strategy should be acknowledged and the use of antibiotics should be limited to the treatment of documented infection