Abstract
Recent interest in functional hemodynamic monitoring for the bedside assessment of cardiovascular insufficiency has heightened. Functional hemodynamic monitoring is the assessment of the dynamic interactions of hemodynamic variables in response to a defined perturbation. Accordingly, fluid responsiveness can be predicted in a quantities fashion by measuring as arterial pulse pressure variation and left ventricular stroke volume variation during positive pressure breathing or the change in cardiac output response to a passive leg raising maneuver. However, volume responsiveness, though important, reflects only part of the overall spectrum of functional physiological variables that can be measured to define physiologic state and monitor response to therapy. Dynamic tissue O2 saturation (StO2) responses to complete stop flow conditions, which can be created by measuring hand StO2 and occluding flow with a blood pressure cuff, assesses cardiovascular sufficiency and microcirculatory blood flow distribution. Furthermore, these measures can be made increasingly more sensitive and specific if coupled to other "traditional" measures of organ perfusion, such as blood lactate levels.
Highlights
Increased interest in a more proactive use of monitoring technologies has emerged, using the response to the measured variables to a defined stress to unveil the physiological state of the subject
The primary types of functional hemodynamic monitoring for which clinical trials have shown clinical usefulness are related to predicting volume responsiveness and identifying occult cardiovascular insufficiency
A fundamental concept often ignored by proponents of functional hemodynamic monitoring approaches is the integration of other clinical variables, such as the clinical condition, serum lactate levels, etc., a priori into the decision analysis of cardiovascular instability and its response to therapy
Summary
Increased interest in a more proactive use of monitoring technologies has emerged, using the response to the measured variables to a defined stress to unveil the physiological state of the subject. In the early stages, compensated by autonomic mechanisms, such regional vasoconstriction, in an attempt to maintain central blood pressure and vital organ perfusion above an anaerobic threshold In this stage of compensated shock, microcirculatory measures, such as arterial pressure or cardiac output often are inside the range of values defined as normal and, insensitive as early predictors of subsequent decompensation due to the increased risk of tissue ischemia and subsequent development of multiorgan failure and death. This study shows the usefulness of the microcirculation dynamic assessment in the early stages of the trauma injury, when cardiovascular insufficiency is not suspected with the macrocirculatory indexes, providing the possibility to start early the appropriate treatment and decide the inhospital disposition These studies show that microcirculation status, measured by a dynamic test, such the StO2 VOT, can be more accurate than the microcirculatory and static classic values assessing the cardiovascular insufficiency in patients with shock. It has not been reflected in superiority against standard base excess predicting mortality, nor tested as goal of directed therapy in shock patients [21,22]
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