The Journal of critical illness最新文献

Dobutamine stress echocardiography (DSE) can be performed safely at the bedside and offers more immediate results and lower cost than other pharmacologic imaging methods. Applications in the intensive care unit include detection of coronary artery disease and assessment of myocardial viability. DSE is also a useful adjunctive study for examining valvular function or revealing obstructive cardiomyopathy. Dobutamine infusion is started at 5 mug/kg/min and peaks at 40 or 50 mug/kg/min. Four standard echocardiographic views are used to show left ventricular wall segment responses; both the extent of thickening and type of motion are assessed.

Changes in left ventricular systolic wall motion and thickness (systolic function) may develop in response to dobutamine infusions; such changes can be detected echocardiographically--a technique called dobutamine stress echocardiography (DSE). By mapping the changes to graded doses of dobutamine, DSE permits us to detect myocardial ischemia and to assess whether myocardial damage is reversible. As a result, this test can help predict which patients are likely to benefit from revascularization. DSE also allows us to determine a specific point at which evidence of ischemia begins. The test is highly accurate, safe, and comparatively inexpensive.

Efficient calculation, storage, and retrieval of hemodynamic and oxygen transport data can be a problem in the clinical setting. A free computer program is now available to calculate commonly used hemodynamic and oxygen transport variables and to provide results in a chart-ready format or in a side-by-side comparison when serial measurements are performed. The program was developed to be easy to use, menu-driven, and usable at various institutions. The program automatically conducts error checking during the simple data entry process as well as during data calculation and retrieval.

Potential kidney transplant recipients must be thoroughly evaluated to ensure that scarce donor organs are used appropriately. Begin by determining the cause of renal failure (some diseases can recur in transplanted organs; others are associated with increased post-transplant morbidity and mortality). Cancer, active infection, some forms of thrombosis and atherosclerosis, and patient noncompliance usually contraindicate kidney transplantation. A careful patient assessment can identify other factors that may increase the risks of significant postoperative complications; however, most of these factors can be modified before proceeding with transplantation.

Single-lung transplantation, long successful in resolving interstitial lung disease, can now be used in COPD patients and shows promise in managing pulmonary hypertension. The bilateral procedure, which often avoids cardiopulmonary bypass, is preferred when chronic airway infection is present. Heart-lung transplants, now rare, are used when pulmonary hypertension is complicated by congestive cardiomyopathy or irreparable cardiac defects. Mechanical ventilation, prior cardiothoracic surgery, and corticosteroid use no longer constitute absolute contraindications to lung transplantation. The growing scarcity of donor organs is increasing waiting times; thus, earlier recognition of potential recipients is necessary.

Before hemodynamic monitoring, carefully select and test the appropriate equipment and calibrate all monitors. To insert the catheter, use strict aseptic technique and, whenever possible, fluoroscopic guidance. The internal jugular vein is generally preferred for cannulation, but cutdown of an antecubital vein may be better for patients receiving anticoagulants or thrombolytics. The balloon remains deflated until the catheter tip is in the right atrium. Characteristic pressure wave forms signal the catheter's passage through each heart chamber. In most patients, advancement from the right atrium to wedge position is completed within 20 to 30 seconds.

Hemodynamic monitoring is an important adjunct to clinical evaluation. Nevertheless, it should not be performed unless the derived data are needed to establish a diagnosis or guide treatment. Successful use of the flotation catheter requires technical skill in insertion and maintenance, knowledge of cardiopulmonary physiology, an understanding of potential complications (and their avoidance), and the ability to correctly interpret and apply results. To maintain competence, physicians should perform at least 50 procedures a year. It is unlikely that a large clinical trial of the general efficacy of hemodynamic monitoring could ever be conducted; however, more limited studies could help define the role of this procedure in certain settings.

Hemodynamic data can be used to differentiate a variety of cardiopulmonary disorders, including right ventricular dysfunction, massive pulmonary embolism, and precapillary pulmonary hypertension. In patients with acute pulmonary edema, low-output states, or shock, hemodynamic measurements can help guide therapy; they also provide a precise estimate of a patient's response to vasoactive or inotropic drugs. Consider a flotation catheter for patients with complicated MIs, critically ill patients with multiorgan or major organ dysfunction, and high-risk cardiac patients undergoing surgery.

Small-catheter aspiration may be preferable to chest tube drainage in many patients with primary spontaneous or iatrogenic pneumothoraces, as well as in some patients with pneumothoraces resulting from minor trauma. It is also less invasive than chest tube drainage, allows greater control over the rate of air removal, and produces less patient discomfort. Following administration of a local anesthetic, the catheter can be inserted into the pleural space using either a trocar or modified Seldinger technique. Addition of a Heimlich valve (with or without a suction device) permits continued air removal. Complications are infrequent and generally minor.