Lightweight noninvasive trauma monitor for early indication of central hypovolemia and tissue acidosis: A review

Reflectance Medical, Inc, Westboro, Massachusetts, USA.
The journal of trauma and acute care surgery 08/2012; 73(2 Suppl 1):S106-11. DOI: 10.1097/TA.0b013e318260a928
Source: PubMed


Hemorrhage is a major cause of soldier death; it must be quickly identified and appropriately treated. We developed a prototype patient monitor that noninvasively and continuously determines muscle oxygen saturation (SmO₂), muscle pH (pHm), and a regional assessment of blood volume (HbT) using near-infrared spectroscopy. Previous demonstration in a model of progressive, central hypovolemia induced by lower body negative pressure (LBNP) showed that SmO₂ provided an early indication of impending hemodynamic instability in humans. In this review, we expand the number of subjects and provide an overview of the relationship between the muscle and sublingual microcirculation in this model of compensated shock.
Healthy human volunteers (n = 30) underwent progressive LBNP in 5-minute intervals. Standard vital signs, along with stroke volume (SV), total peripheral resistance, functional capillary density, SmO₂, HbT, and pHm were measured continuously throughout the study.
SmO₂ and SV significantly decreased during the first level of central hypovolemia (-15 mm Hg LBNP), whereas vital signs were later indicators of impending cardiovascular collapse. SmO₂ declined with SV and inversely with total peripheral resistance throughout LBNP. HbT was correlated with declining functional capillary density, suggesting vasoconstriction as a cause for decreased SmO₂ and subsequently decreased pHm. CLINICAL TRANSLATION: The monitor has been miniaturized to a 58-g solid-state sensor that is currently being evaluated on patients with dengue hemorrhagic fever. Early results demonstrate significant decreases in SmO₂ similar to those observed with progressive reductions in central blood volume. As such, this technology has the potential to (1) provide a monitoring capability for both nontraumatic and traumatic hemorrhage and (2) help combat medics triage casualties and monitor patients during lengthy transport from combat areas.

1 Follower
13 Reads
  • [Show abstract] [Hide abstract]
    ABSTRACT: Survival after severe traumatic shock can be complicated by a number of pathophysiologic processes that ensue after the initial trauma. One of these is trauma-induced coagulopathy (TIC) whose onset may occur before initial fluid resuscitation. The pathogenesis of TIC has not yet been fully elaborated, but evolving evidence appears to link severe tissue hypoxia and damage to the endothelium as key factors, which evolve into measurable structural and biochemical changes of the endothelium resulting in a coagulopathic state. This paper will provide a general review of these linkages and identify knowledge gaps as well as suggest new approaches and areas of investigation, which may both limit the development of TIC as well as produce insights into its pathophysiology. A better understanding of these issues will be necessary in order to advance the practice of remote damage control resuscitation.
    Transfusion 02/2013; 53(S1). DOI:10.1111/trf.12034 · 3.23 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: New patient monitoring technologies can noninvasively and directly provide an assessment of the adequacy of tissue perfusion through the simultaneous determination of muscle oxygen saturation (SmO2) and muscle pH (pHm). Non-pulsatile near infrared spectroscopy is used to determine these microvascular parameters. Two separate studies were conducted using an isolated perfused swine limb preparation to widely vary venous blood oxygen saturation (SviO2) and pH (pHvi) to assess the accuracy of a noninvasive sensor with the capability to simultaneously measure both parameters. The isolated limb model is necessary to establish equilibrium between the venous output of the perfusion circuit and the venule measurement of the spectroscopic sensor. The average absolute difference between SmO2 and SviO2 determined over 50 conditions of SviO2 between 13% and 83% on 3 pig limbs was 3.8% and the coefficient of determination (R(2)) was 0.95. The average absolute difference between pHm and pHvi determined over 69 conditions of pHvi between pHvi 6.9 and pHvi 7.5 on 3 pig limbs was 0.045 pH units with an R(2) of 0.92. Measured accuracy was acceptable to support clinically relevant decision making for the assessment of impaired tissue perfusion and acidosis. Sensors were also evaluated on human subjects. There was no statistical difference in SmO2 by gender or location when multiple sensors were evaluated on the right and left calf, deltoid, and thigh of resting men and women (N = 33). SmO2 precision for subjects at rest was 5.6% over the six locations with four different sensors.
    Physiological Measurement 07/2013; 34(8):859-871. DOI:10.1088/0967-3334/34/8/859 · 1.81 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: To stress the local, regional and global impact of degloving injuries of abdominal wall based on which the surgeon can design the management protocol. A retrospective series of seven cases who met with high velocity run-over accidents between the year 2002 to 2007. All patients were clinically examined and the findings confirmed radiologically, which guided the management. Out of the seven patients treated, six survived. All patients had open degloving injury of abdominal wall and in different areas of the lower limbs, while three had an additional closed degloving in the back, thighs and gluteal regions. All of them had pelvic fractures of various types. Three patients had peritoneal injury, of whom one had additional diaphragmatic injury. None of them had hollow viscus perforation or injury to solid viscera despite the varied severity of injuries to the abdominal wall, pelvic bone and diaphragm. Degloving injuries of the abdominal wall are rarely encountered in our practice. The associated morbidity and mortality are very high. However, the prognosis can be improved by successful revival and rehabilitation of these patients, which is possible by early resuscitation, recognition of all bony and soft tissue injuries, early debridement and coverage.
    Journal of Wound Care 10/2013; 22(10):562-8. DOI:10.12968/jowc.2013.22.10.562 · 1.07 Impact Factor
Show more