Clinical comparison of two devices for detection of microemboli during cardiopulmonary bypass

Pericardial suction blood (PSB) is known to be contaminated with fat droplets, which may cause embolic brain damage during cardiopulmonary bypass (CPB) This study aimed to investigate the possibility to detect fat emboli by a Doppler technique. An in vitro flow model was designed, with a main pump, a filter, a reservoir, and an injector. A Hatteland Doppler probe was attached to the circulation loop to monitor particle counts and their size distribution. Suspended soya oil or heat-extracted human wound fat was analyzed in the model. The concentrations of these fat emboli were calibrated to simulate clinical conditions with either a continuous return of PSB to the systemic circulation or when PSB was collected for rapid infusion at CPB weaning. For validation purpose, air and solid emboli were also analyzed. Digital image analysis was performed to characterize the nature of the tested emboli. With soya suspension, there was an apparent dose response between Doppler counts and the nominal fat concentration. This pattern was seen for computed Doppler output (p = .037) but not for Doppler raw counts (p = .434). No correlation was seen when human fat suspensions were tested. Conversely, the image analysis showed an obvious relationship between microscopy particle count and the nominal fat concentration (p < .001). However, the scatter plot between image analysis counting and Doppler recordings showed a random distribution (p = .873). It was evident that the Doppler heavily underestimated the true number of injected fat emboli. When the image analysis data were subdivided into diameter intervals, it was discovered that the few large-size droplets accounted for a majority of total fat volume compared with the numerous small-size particles (<10 μm). Our findings strongly suggest that the echogenecity of fat droplets is insufficient for detection by means of the tested Doppler method.

Section: Discussionmentioning

confidence: 99%

Evaluation of the Doppler Technique for Fat Emboli Detection in an Experimental Flow Model

Wikstrand

Linder²,

Engström³

2008

“…The earliest bubble detector for use during CPB was the Technique Laboratories TM-8 detector, which used a continuous wave ultrasound at a frequency of 0.6 MHz, but it is no longer commercially available (43). The Hatteland BD-100 ultra-sonic bubble detector (Hatteland Instrumentering, Royken, Norway) used a pulse wave ultrasound with a transducer frequency of 1.5 MHz, a repetition frequency of 11.3 kHz, and a pulse duration of 5 s and was widely used to detect bubbles in CPB circuits in the 1980s (43). Its updated model, the CMD-10, has proven insufficiently sensitive at detecting gaseous microemboli in the extracorporeal circuit (44).…”

Section: Gaseous Microemboli Detectionmentioning

confidence: 99%

Vacuum-assisted Venous Drainage and Gaseous Microemboli in Cardiopulmonary Bypass

Wang¹,

Ündar²

2008

When conventional gravity siphon venous drainage cannot achieve satisfactory venous drainage during minimally invasive cardiac and neonatal surgeries, assisted venous drainage techniques are needed to ensure adequate flow. One assisted venous drainage technique, vacuum-assisted venous drainage (VAVD), the aid of a vacuum in the venous reservoir, is now widely used to augment venous drainage during cardiopulmonary bypass (CPB) procedures. VAVD permits the use of smaller venous cannulae, shorter circuit tubing, and lower priming and blood transfusion volumes, but increases risk of arterial gaseous microemboli and blood trauma. The vacuum should be set as low as possible to facilitate full venous return, and realtime monitoring of gaseous microemboli in the arterial and venous line should be used to achieve the safest conditions. With current ultrasound technology, it is possible to simultaneously detect and classify gaseous microemboli in the CPB circuit. In this article, we summarize the components, setup, operation, advantages, and disadvantages of VAVD techniques and clinical applications and describe the basic principles of microemboli detectors, such as the Emboli Detection and Classification (EDAC) Quantifier (Luna Innovations, Roanoke, VA) and Bubble Counter Clinical 200 (GAMPT, Zappendorf, Germany). These novel gaseous microemboli detection devices could help perfusionists locate the sources of entrained air, eliminate hidden troubles, and minimize the postoperative neurologic impairments attributed to gaseous microemboli in clinical practice.

“…The present measuring systems allows the detection of larger gaseous microbubbles and classification of the bubble size to roughly 10-15 m. Some instruments has been criticized as causing multiple counting, movement artifacts, and unknown calibration (9). The purpose of our study was to investigate the GME reduction capability of different hollow fiber membrane oxygenators by using a new device that allows a permanent monitoring of the microbubble distribution in the blood flow in a range of 10 to 120 m in diameter.…”

mentioning

confidence: 99%

Gaseous Microemboli and the Influence of Microporous Membrane Oxygenators

Weitkemper

Oppermann²,

Spilker³

et al. 2005

Gaseous microemboli (GME) are still an unsolved problem of extracorporeal circuits. They are associated with organ injury during cardiopulmonary bypass. Microbubbles of different sizes and number are generated in the blood as the result of different components of the extracorporeal circuit as well as surgical maneuvers. The aim of our study was to observe the behavior of microporous membrane oxygenators to GME in the daily use and in an in vitro model. For the detection of microbubbles, we used a two-channel ultrasonic bubble counter based on 2-MHz Doppler-System with special ultrasound probes. The amount and size of GME were monitored before and after membrane. In 28 scheduled cases with 3 different oxygenators and variability of surgical procedures, we observed the bubble activity in the extracorporeal circuit. In addition, we used an in-vitro model to study the ability of six different oxygenators by removing air in various tests. The oxygenators tested were manufactured with different membrane technologies. The results of our investigations showed varying membrane design lead to a partial removal of GME as well as a change in size and numbers of microbubbles.