Photons Plus Ultrasound: Imaging and Sensing 2014, 2014
ABSTRACT Circulatory shock may be fatal unless promptly recognized and treated. The most commonly... more ABSTRACT Circulatory shock may be fatal unless promptly recognized and treated. The most commonly used indicators of shock (hypotension and tachycardia) lack sensitivity and specificity. In the initial stages of shock, the body compensates by reducing blood flow to the peripheral (skin, muscle, etc.) circulation in order to preserve vital organ (brain, heart, liver) perfusion. Characteristically, this can be observed by a greater reduction in peripheral venous oxygenation (for instance, the axillary vein) compared to central venous oxygenation (the internal jugular vein). While invasive measurements of oxygenation are accurate, they lack practicality and are not without complications. We have developed a novel optoacoustic system that noninvasively determines oxygenation in specific veins. In order to test this application, we used lower body negative pressure (LBNP) system, which simulates hemorrhage by exerting a variable amount of suction on the lower body, thereby reducing the volume of blood available for central circulation. Restoration of normal blood flow occurs promptly upon cessation of LBNP. Using two optoacoustic probes, guided by ultrasound imaging, we simultaneously monitored oxygenation in the axillary and internal jugular veins (IJV). LBNP began at -20 mmHg, thereafter was reduced in a step-wise fashion (up to 30 min). The optoacoustically measured axillary oxygenation decreased with LBNP, whereas IJV oxygenation remained relatively constant. These results indicate that our optoacoustic system may provide safe and rapid measurement of peripheral and central venous oxygenation and diagnosis of shock with high specificity and sensitivity.
Obtaining IV access for fluid administration is a critical step in treating hemorrhage. However, ... more Obtaining IV access for fluid administration is a critical step in treating hemorrhage. However, expertise, supplies and personnel to accomplish this task can be delayed or even absent in austere environments. An alternative approach that can 'buy time' and improve circulation when iv fluids are absent is needed. Preclinical studies show that intrathoracic pressure regulation [ITPR] can increase perfusion in hypovolemia in the absence of iv fluid. We compared ITPR to placebo in humans undergoing a 15% hemorrhage under general anesthesia. Paired healthy volunteers (n=7, age 21 - 35 yrs) received either ITPR or placebo on different study days. IRB informed consent was obtained. Subjects were anesthetized using propofol, intubated and mechanically ventilated and hemorrhaged (10 mL/kg). Twenty minutes after hemorrhage, ITPR (-12 cmH2O vacuum) or placebo (device but no vacuum) was administered for another 60 min. IV fluid was administered when systolic BP < 85 mmHg. Hemodynamics, cardiac function by echocardiography, and volumetric data were compared. Data expressed in Δ Mean ± SEM before and after ITPR/placebo intervention. There were no differences in MAP [ITPR (2.1 ± 3 mmHg); placebo (-0.7 ± 3 mmHg)] or fluid in [ITPR (17.4 ±4 mL/kg); placebo (18.6±5 mL/kg)]. Urinary output and plasma volume also were not significantly different. ITPR augmented stroke volume [ITPR (22 ± 5 mL; placebo (6 ± 4 mL), p <0.05], Ejection fraction% [ITPR (4±1%); placebo (0±1%) and diastolic function (ΔE/e') [ITPR (-0.8 ± 0.4) vs. placebo = +0.81 ± 0.6; p <0.05). ITPR did not improve mean arterial pressure in healthy volunteers age 21-35 years. However, ITPR augmented stroke volume, which could due to improved ventricular function.
Photons Plus Ultrasound: Imaging and Sensing 2014, 2014
ABSTRACT Circulatory shock may be fatal unless promptly recognized and treated. The most commonly... more ABSTRACT Circulatory shock may be fatal unless promptly recognized and treated. The most commonly used indicators of shock (hypotension and tachycardia) lack sensitivity and specificity. In the initial stages of shock, the body compensates by reducing blood flow to the peripheral (skin, muscle, etc.) circulation in order to preserve vital organ (brain, heart, liver) perfusion. Characteristically, this can be observed by a greater reduction in peripheral venous oxygenation (for instance, the axillary vein) compared to central venous oxygenation (the internal jugular vein). While invasive measurements of oxygenation are accurate, they lack practicality and are not without complications. We have developed a novel optoacoustic system that noninvasively determines oxygenation in specific veins. In order to test this application, we used lower body negative pressure (LBNP) system, which simulates hemorrhage by exerting a variable amount of suction on the lower body, thereby reducing the volume of blood available for central circulation. Restoration of normal blood flow occurs promptly upon cessation of LBNP. Using two optoacoustic probes, guided by ultrasound imaging, we simultaneously monitored oxygenation in the axillary and internal jugular veins (IJV). LBNP began at -20 mmHg, thereafter was reduced in a step-wise fashion (up to 30 min). The optoacoustically measured axillary oxygenation decreased with LBNP, whereas IJV oxygenation remained relatively constant. These results indicate that our optoacoustic system may provide safe and rapid measurement of peripheral and central venous oxygenation and diagnosis of shock with high specificity and sensitivity.
Obtaining IV access for fluid administration is a critical step in treating hemorrhage. However, ... more Obtaining IV access for fluid administration is a critical step in treating hemorrhage. However, expertise, supplies and personnel to accomplish this task can be delayed or even absent in austere environments. An alternative approach that can 'buy time' and improve circulation when iv fluids are absent is needed. Preclinical studies show that intrathoracic pressure regulation [ITPR] can increase perfusion in hypovolemia in the absence of iv fluid. We compared ITPR to placebo in humans undergoing a 15% hemorrhage under general anesthesia. Paired healthy volunteers (n=7, age 21 - 35 yrs) received either ITPR or placebo on different study days. IRB informed consent was obtained. Subjects were anesthetized using propofol, intubated and mechanically ventilated and hemorrhaged (10 mL/kg). Twenty minutes after hemorrhage, ITPR (-12 cmH2O vacuum) or placebo (device but no vacuum) was administered for another 60 min. IV fluid was administered when systolic BP < 85 mmHg. Hemodynamics, cardiac function by echocardiography, and volumetric data were compared. Data expressed in Δ Mean ± SEM before and after ITPR/placebo intervention. There were no differences in MAP [ITPR (2.1 ± 3 mmHg); placebo (-0.7 ± 3 mmHg)] or fluid in [ITPR (17.4 ±4 mL/kg); placebo (18.6±5 mL/kg)]. Urinary output and plasma volume also were not significantly different. ITPR augmented stroke volume [ITPR (22 ± 5 mL; placebo (6 ± 4 mL), p <0.05], Ejection fraction% [ITPR (4±1%); placebo (0±1%) and diastolic function (ΔE/e') [ITPR (-0.8 ± 0.4) vs. placebo = +0.81 ± 0.6; p <0.05). ITPR did not improve mean arterial pressure in healthy volunteers age 21-35 years. However, ITPR augmented stroke volume, which could due to improved ventricular function.
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