Abstract
Occurrence of microbubbles (MB) is a major problem during venoarterial extracorporeal life support (ECLS) with partially severe clinical complications. The aim of this study was to establish an in vitro ECLS setup for the generation and detection of MB. Furthermore, we assessed different MB elimination strategies. Patient and ECLS circuit were simulated using reservoirs, a centrifugal pump, a membrane oxygenator, and an occluder (modified roller pump). The system was primed with a glycerin solution of 44%. Three different revolution speeds (2500, 3000, and 3400rpm) were applied. For MB generation, the inflow line of the pump was either statically or dynamically (15rpm) occluded. A bubble counter was used for MB detection. The effectiveness of the oxygenator and dynamic bubble traps (DBTs) was evaluated in regard to MB elimination capacities. MB generation was highly dependent on negative pressure at the inflow line. Increasing revolution speeds and restriction of the inflow led to increased MB activity. The significant difference between inflow and outflow MB volume identified the centrifugal pump as a main source. We could show that the oxygenator's ability to withhold larger MB is limited. The application of one or multiple DBTs leads to a significant reduction in MB count and overall gas volume. The application of DBT can significantly reduce the overall gas volume, especially at high flow rates. Moreover, large MB can effectively be broken down for faster absorption. In general, the incidence of MBs is significantly dependent on pump speed and restriction of the inflow. The centrifugal pump was identified as a major source of MB generation.
Highlights
Venoarterial extracorporeal life support (ECLS) is a promising, yet a highly invasive therapeutic option in cardiovascular intensive care medicine.[1,2,3] It is associated with a high incidence of complications and recently attention has been directed to the emergence of microbubbles (MB) within the circulatory system.[4,5] MB can lead to neurological morbidity or mortality due to a cascade of pathophysiological reactions, including diffuse cerebral microischemia as well as inflammatory reactions and activation of the complement system.[6]
There are two common ways of MB formation within the ECLS circuit: they can form via bubbling due to hypobaric conditions[7] or suction can lead to MB by centrifugal pumphead‐ or oxygenator‐induced microsplitting.[8]
We provide a structured assessment on the development of MB in a standard ECLS circuit
Summary
Venoarterial extracorporeal life support (ECLS) is a promising, yet a highly invasive therapeutic option in cardiovascular intensive care medicine.[1,2,3] It is associated with a high incidence of complications and recently attention has been directed to the emergence of microbubbles (MB) within the circulatory system.[4,5] MB can lead to neurological morbidity or mortality due to a cascade of pathophysiological reactions, including diffuse cerebral microischemia as well as inflammatory reactions and activation of the complement system.[6] There are two common ways of MB formation within the ECLS circuit: they can form via bubbling due to hypobaric conditions (according to the Henry's law)[7] or suction can lead to MB by centrifugal pumphead‐ or oxygenator‐induced microsplitting.[8] As ECLS is based on a closed system, the induced MB cannot dissolve into the atmosphere as it is the case in an open HLM circuit. The implementation of a venous compliance reservoir (eg, Better‐Bladder, etc.) or a pressure controlled pump management has been proposed.[9,10] But to our knowledge, no strategy has been described so far to achieve a sufficient reduction of already existing MB. The aim of this study was to mimic the MB formation in an experimental in vitro ECLS circuit and to evaluate different strategies for MB removal including dynamic bubble traps (DBTs) and the oxygenator (OXY) without the bubble trap
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