Assessment and management of circulatory shock in critically ill patients requires rapid measurement of two critical variables: mixed venous oxyhemoglobin saturation (venous SO2) and total blood hemoglobin concentration [Hgb] to identify insufficient oxygen delivery and anemia and to determine the need for therapy with fluids, inotropic or vasodilator drugs or blood transfusion. Current invasive techniques for measurement of venous SO2 and [Hgb] require central venous or pulmonary arterial catheterization and blood sampling. In emergency department patients with septic shock, management based on maintaining venous SO2 at e 70%, as measured invasively in the superior vena cava, reduced mortality from 46.5% to 30.5%. At present, no available noninvasive technique measures venous SO2 and [Hgb] to guide treatment. Our research team has pioneered optoacoustic imaging techniques for accurate, non-invasive, real-time measurement of SO2 and [Hgb]. We designed, built, and performed in vitro and in vivo testing of a novel, compact, high-resolution optoacoustic imaging system that measures SO2 and [Hgb] directly from blood vessels. The optoacoustic imaging is based on generation of ultrasonic (optoacoustic) waves by near infra-red laser light pulses and detection of optoacoustic waves by a sensitive wide-band acoustic transducer. Optoacoustic waves are linearly dependent on SO2 and [Hgb]. Our in vitro and in vivo tests of the system with optoacoustic probes demonstrated that the system is capable of measuring oxygenation and [Hgb] measurement with high accuracy approaching that of the CO-Oximeter, the conventional gold standard method for measuring oxygen saturation in blood. In this application, our multidisciplinary team of bioengineers and intensivists proposes to develop and test novel, highly-portable clinical, prototype with unique capabilities for rapid, noninvasive assessment and management of circulatory shock in surgical and critically ill patients.
The proposed project will have a substantial impact on care of patients undergoing surgery, critically ill patients, and patients in shock. The proposed optoacoustic system will replace invasive, intermittent diagnostic testing of central venous blood oxygenation hemoglobin with noninvasive, rapid, and continuous monitoring.
