PurposeProper cannula positioning in single site veno-venous extracorporeal life support (vv-ELS) is cumbersome and necessitates image guidance to obtain a safe and stable position within the heart and the caval veins. Importantly, image-guided cannula positioning alone is not sufficient, as possible recirculation cannot be quantified.Methods and resultsWe present an ultrasound dilution technique allowing quantification of recirculation for optimizing vv-ELS.ConclusionWe suggest quantification of recirculation in addition to image guidance to provide optimal vv-ELS.

A growing body of evidence indicates the superiority of minimized cardiopulmonary bypass (CPB) systems compared to conventional systems in terms of inflammatory reactions and transfusion requirements. Evident benefits of minimized CPB systems, however, do not come without consequences. Kinetic-assisted drainage, as used in these circuits, can result in severe fluctuations of venous line pressures and, consequently, fluctuation of the blood flow delivered to the patient. Furthermore, subatmospheric venous line pressures can cause gaseous microemboli. Another limitation is the absence of cardiotomy suction, which can lead to excessive blood loss via a cell saver. The most serious limitation of minimized circuits is that these circuits are very constrained in the case of complications or changing of the surgery plan. We developed a versatile minimized system (VMS) with a priming volume of about 600 ml. A compliance chamber in the venous line decreases peaks of pressure fluctuations. This chamber also acts as a bubble trap. Additionally, the open venous reservoir is connected parallel to the venous line and excluded from the circulation during an uncomplicated CPB. This reservoir can be included in the circulation via a roller pump and be used as a cardiotomy reservoir. The amount and rate of returned blood in the circulation is regulated by a movable level detector. Further, the circuit can easily be converted to an open system with vacuum-assisted venous drainage in the case of unexpected complications. The VMS combines the benefits of minimized circuits with the versatility and safety of a conventional CPB system. Perfusionists familiar with this system can secure an adequate and timely response at expected and unexpected intraoperative complications.

Introduction Limb ischemia is a severe complication of peripheral veno-arterial extracorporeal life support (V-A ECLS). Several techniques have been developed to prevent this, but it remains a major and frequent adverse event (incidence: 10–30%). In 2019, a new cannula with bidirectional flow (retrograde towards the heart and antegrade towards the distal limb) has been introduced. A single-centre experience with this cannula in patients undergoing peripheral V-A ECLS is herewith reported. Methods This prospective observational study included adults (≥18 years) undergoing V-A ECLS from January 2021 to October 2022 with the use of a bidirectional femoral artery cannula. Primary outcome was limb ischemia requiring intervention during cardio-circulatory support. Secondary outcomes were compartment syndrome, limb amputation, cannulation site bleeding, need for other surgical intervention due to cannula related complications, duplex ultrasound parameters from the femoral vessels, and in-hospital survival. Results Twenty-two consecutive patients were included. During extracorporeal life support (ECLS) support, limb ischemia requiring intervention occurred in one patient (4.5%) and no patients developed a compartment syndrome, or required a fasciotomy or amputation. Significant bleeding was reported in two patients (9%) due to slight cannula dislodgement, easily solved with cannula repositioning. In-hospital survival was 63.6%. Conclusions The bidirectional cannula is associated with a low risk for limb ischemia-related complications compared to current literature, and apparently represents a safe alternative to dedicated distal perfusion cannula. Further studies are warranted to confirm these preliminary findings.

Successes of extracorporeal life support increased the use of centrifugal pumps. However, reports of hemolysis call for caution in using these pumps, especially in neonatology and in pediatric intensive care. Cavitation can be a cause of blood damage. The aim of our study was to obtain information about the cavitation conditions and to provide the safest operating range of centrifugal pumps. A series of tests were undertaken to determine the points at which pump performance decreases 3% and gas bubbles start to appear downstream of the pump. Two pumps were tested; pump R with a closed impeller and pump S with a semiopen impeller. The performance tests demonstrated that pump S has an optimal region narrower than pump R and it is shifted to the higher flows. When the pump performance started to decrease, the inlet pressure varies but close to −150 mmHg in the test with low gas content and higher than −100 mmHg in the tests with increased gas content. The same trend was observed at the points of development of massive gas emboli. Importantly, small packages of bubbles downstream of the pump were registered at relatively high inlet pressures. The gaseous cavitation in centrifugal pumps is a phenomenon that appears with decreasing inlet pump pressures. There are a few ways to increase inlet pump pressures: (1) positioning the pump as low as possible in relation to the patient; (2) selecting appropriate sized venous cannulas and their careful positioning; and (3) controlling patient’s volume status.

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