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Cardiopulmonary bypass (CPB) has been used to assist cardiac surgery for more than 50 yr since its introduction 1953. Technological improvements with CPB and other advances over the last half century have allowed the benefits of cardiac surgery to be extended to older patients with a greater burden of comorbidity. Neurologic complications are of particular concern because of their impact on duration of hospitalization, mortality, health care costs, and quality of life.
Both gross air bubbles and gaseous microemboli have been the subject of several studies, and efforts have been directed at elimination of both types of microemboli. Gross air embolism has been practically eliminated from CPB practice and in our days it is reported only occasionally. However, elimination of gaseous microemboli from conventional CPB has proved more difficult.
Neurologic deficits after coronary artery bypass grafting (CABG) still represent the most devastating complication. The mechanisms contributing to neurologic complications are multifactorial and comprise hemodynamic fluctuations, cerebral embolization (atherosclerotic plaque, air, fat, and platelet aggregates), cerebral hyperthermia, and other inflammatory and neurohumoral derangements associated with surgery. Gaseous microemboli has been implicated as the most common cause of neurologic complications.
The EDAC® QUANTIFIER (Emboli Detection and Classification) blood circuit monitor uses advanced ultrasound technology to non-invasively count and classify gaseous emboli in the extracorporeal bypass circuit. Employing highly sophisticated algorithms, the EDAC® QUANTIFIER device simultaneously monitors up to three locations, detects individual gaseous emboli at rates up to at least 1,000 per second, identifies gaseous emboli from 10 microns in diameter to up to 12.7mm (1/2") in diameter and instantly reports relevant data to the user. Results are displayed on-screen for real-time feedback to immediately adjust tubing and pumps as needed. It has been pointed that the use of EDAC may be considered is one of the most reliable methods destined to verify the efficacy of a given gaseous microemboli protocol and, at the same time, evaluate eventual changes to reduce the amount of gas introduced into the cerebral circulation during CPB.
Note: EDAC Quantifier: http://www.lunamedicalproducts.com/edac.htm
March 25, 2008 10:23 am - Rio de Janeiro / Brazil |
Gary Grist RN CCP, Kansas City, Mo. USA | |
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You don't really need a bubble quantifier to tell you when gaseous microemboli are passing thru. If you are geting a lot of air from the venous line, if the suckers or vent are running high, or if the heart has actually been opened, particularly the left side, the patient is going to get gas emboli. The only choice you have as a perfusionist is to decide if the patient is going to get GME that are mostly nitrogen (which will not dissolve from the capillaries) or mostly oxyen ( which will be quickly absorbed). Turn the oxygenator FiO2 to 100% whenever you suspect the presence of GME. This will change nitrogen bubbles to oxygen bubbles as they pass thru the oxygenator. March 26, 2008 06:15 pm - USA |
Keith Samolyk CCP, LCP | |
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Smaller Circuits and the Proliferation of Micro-Air. Recent discussions on reducing primes to enhance the patient’s hematocrit and oncotic pressure obviously help to improve patient outcomes and avoid allogeneic blood products – but there is a trade-off and a fine line that we walk to decrease ECC volumes and maintain safety economically. Primes less than 1.0 liter for Adults at full flow have faster transit times with no hold up areas to out-gas any venous air (large or small) this also creates far less reaction time for perfusionists who will be on the edge of their seat reluctant to even turn your head to chart. Condensing your already safe and trusted circuit down to primes of 1200-1400 or so and "Rap"ing both sides accomplishes the same goals without the precariousness and the added expense. We do not want to fail to protect our patients (and ourselves) by pushing the line of safety too far to remove an extra 100 -200mls. In our efforts to reduce prime volumes we should not lose sight of the cardinal rules of Perfusion 1. To “Keep it Simple” and 2. “Avoid Systemic Air and Micro-Air Embolisms”. I would say that we already have the CPB procedure honed to a fairly safe and trusted science without going to more expense and further out on a limb to try to reduce priming volumes and jeopardize patient safety, especially when we can auto-prime the circuit economically for free. Improvement and change are important, but where is the risk / benefit limit? Perfusionists have to understand that avoiding hemodilution is not just a "One Discipline" effort; the responsibility cannot be placed only on Perfusion to carry the burden. Blood management should be multidisciplinary with multimodality approaches and that can only be successful with effective team communication. Anesthesia and other members of the team as well as ICU care givers contribute much to the dilution of patients and need to be held accountable as well. The EDAC System is an excellent tool to see what maneuvers are the sources causing air to be generated and how much of it is actually getting through your circuit and systemic causing increased risks for neurological morbidity. The EDAC system really shows the difference between safe practices and dangerous ones. March 29, 2008 06:25 pm - New England USA |
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