Use of dilutional ultrasound monitoring to detect changes in recirculation during venovenous extracorporeal membrane oxygenation in swine.

Since recirculation during venovenous extracorporeal membrane oxygenation (VV ECMO) reduces oxygen delivery to the patient, monitoring recirculation is necessary to guide clinicians in interventions that may reduce recirculation and thereby optimize patient care. The use of dilutional ultrasound may be a clinically practical way to quantify recirculation during VV ECMO. This study evaluates in a swine model of VV ECMO a dilutional ultrasound techniques ability to provide accurate recirculation data under changing conditions. One 16-kg swine was cannulated with a dual-lumen cannula and placed on VV ECMO. Recirculation measured by using blood oxygen saturations (r = S(preox) - SVO2/S(postox) - SVO2) was compared with recirculation measured by a saline dilution ultrasound technique. Dilutional ultrasound was then used to measure changes in baseline recirculation in the face of (a) cannula repositioning and (b) a drug-induced cardiac output change. The comparison of recirculation calculations between the saturation method and dilutional ultrasound were similar at all flow rates measured. The time for results was much faster with the use of dilutional ultrasound. Induction of recirculation changes by repositioning the cannula or changing cardiac output was rapidly detected using dilutional ultrasound and showed significant differences from baseline recirculation. Dilutional ultrasound provides a clinically practical method to quantify and monitor recirculation in VV ECMO applications and may aid in assessing interventions to improve oxygen delivery.