Noninvasive Hemodynamic Monitoring in the Intensive Care Unit
Section snippets
Shock
Shock is best defined as end-organ dysfunction as a result of hemodynamic compromise [15]. While hypotension is an important marker of shock, it is clear that blood pressure alone cannot be used as the sole determinant of shock [16]. Shock models have demonstrated that the body can develop an “oxygen debt” in the setting of normal blood pressure [16]. This concept underscores the importance of evaluating organ function and microcirculatory perfusion in patients with hemodynamic compromise [17],
Upstream hemodynamic monitoring: Measurement of cardiac output
The cardiac output is the most important upstream hemodynamic parameter. Adolph Fick [22] described the first method of cardiac output estimation in 1870. This method was the reference standard by which all other methods of determining cardiac output were evaluated until the introduction of the PAC in the 1970s [8]. Despite its limitations, cardiac output measurement with a PAC using the bolus thermodilution method has become the de facto gold standard for measurement of cardiac output and is
Lactate
The concept that hypoxic tissues can generate a lactic acidosis has been understood since the 1970s [98]. To generate energy, the body must convert glucose into CO2 via the Krebs cycle. In anaerobic environments, the Krebs cycle cannot completely metabolize glucose, so instead a partial metabolic pathway is followed, which generates lactate. The greater the oxygen deficit and with increased metabolic demands, the more lactate is produced. Lactic acidosis is, however, not limited to shock.
Summary
The quest for the holy grail of noninvasive cardiac output assessment methods continues. Although no tool is perfect, a number of noninvasive methods to determine the cardiac output of critically ill patients are now available. It is, however, important to stress that the cardiac output should be interpreted in conjunction with dynamic indices of volume responsiveness and downstream markers of tissue oxygenation. Furthermore, patients cannot be managed by simplistic algorithms or bundles but
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Pulmonary Embolism in Intensive Care Unit
2020, Critical Care ClinicsCitation Excerpt :Supportive therapies of the RV failure include afterload reduction, inotropic augmentation supported by vasopressors, and fluid management.16,22 It is essential for intensivists to understand the complex interplay of cardiovascular support and oxygenation support by positive pressure.42,43 Supportive interventions may be as simple as oxygen supplementation to the extreme of extracorporeal membranous oxygenation (ECMO).25,44–46
Fluid management in adults and children: Core curriculum 2014
2014, American Journal of Kidney DiseasesCardiogenic Shock
2013, Cardiology ClinicsCitation Excerpt :No clinical trial has yet established a clinical benefit with the use of this modality in this clinical setting. Less invasive or noninvasive alternatives, such as transpulmonary thermodilution, pulse contour analysis, thoracic electrical bioimpedance, and bedside Doppler echocardiography are being used with increasing frequency.16 Nevertheless, monitoring with a PAC may serve multiple important functions in the setting of CS (Box 3), and most authorities continue to recommend the insertion of a PAC in patients with CS.17
Assessment of intravascular volume status and volume responsiveness in critically ill patients
2013, Kidney InternationalCitation Excerpt :CVP is dependent on venous return (VR) to the heart, right ventricular compliance, peripheral venous tone, and posture, and the CVP is particularly unreliable in pulmonary vascular disease, right ventricular disease, patients with tense ascites, isolated left ventricular failure, and valvular heart disease.24,29 In patients with an intact sympathetic response to hypovolemia, the CVP may actually fall in response to fluid, as compensatory venoconstriction is reduced.29 Thus, it is possible to have a low CVP and not be volume responsive, as well as have a high CVP and be volume responsive.
Monitoring fluid responsiveness
2011, Acta Anaesthesiologica TaiwanicaCitation Excerpt :The prediction of fluid responsiveness is, obviously, crucial for an adequate management of fluid administration and goal-oriented hemodynamic optimization. It will help to determine the ideal strategy of increasing CO and oxygen delivery.11 Therefore, reliable sensitive and specific variables are required.
NON-INVASIVE METHODS for MATERNAL CARDIAC OUTPUT MONITORING
2014, Fetal and Maternal Medicine Review