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  • No hemodynamic monitoring device will improve patient outcome unless coupled to a treatment which itself improves outcome.

  • Circulatory shock is the expression of inadequate organ perfusion, it is not a disease; thus, the treatment must also focus on mitigating the etiology of shock as well as restoring organ perfusion.

  • Targeting macrocirculatory parameters of normalcy, like arterial pressure and cardiac output, does not ensure adequate resuscitation, but it is a good start.

  • Low venous oxygen saturations need not mean circulatory shock, but do imply circulatory stress, as they may occur in hypoxemia, anemia, exercise, chronic heart failure, as well as circulatory shock.

  • Resuscitating to specific cardiovascular pressure and flow levels is the initial step in shock resuscitation but supporting a sufficient cardiovascular reserve to handle increased metabolic stress is essential to promote recovery and to tolerate such metabolic stressors like weaning from mechanical support systems (eg, artificial ventilation, dialysis).

  • There is no “normal” cardiac output, only one that is adequate or inadequate to meet the metabolic demands of the body. Thus, targeting a specific cardiac output value without reference to metabolic need, or oxygen-carrying capacity of the blood, is dangerous.

  • Cardiac output is estimated, not measured, by all devices routinely used in bedside monitoring (though we shall call it measured in this text).

  • Using dynamic parameters of volume responsiveness to guide fluid resuscitation in circulatory shock will limit giving fluids to a nonvolume response patient, minimizing fluid overload while still increasing intravascular volume to those who will respond.

  • Since metabolic demands can vary rapidly, continuous or frequent measures of cardiac output and the adequacy of that flow are preferred to single or widely spaced individual measures.

  • Tissue metabolism assessment has four components: O2 consumption, CO2 production, intermediary metabolism (lactate levels and acid-base status), and organ-specific function.

  • Assessing organ function is central to defining the adequacy of resuscitation efforts, and the measures used to assess their adequacy vary widely depending on the organ (eg, brain, heart, gut, kidney, and liver).

  • Integrating several physiologic variables as listed above in the assessment of the adequacy of the circulation usually gives a clearer picture than just looking at one variable.

  • Integrating cardiac output with other measures, like venous oxygen saturation and CO2 flux, can be very helpful in defining the adequacy of blood flow.


The goal of the cardiorespiratory system is to sustain adequate delivery of oxygen (O2) to the tissues and removal of carbon dioxide (CO2) to meet metabolic demands. Under normal conditions, this system has significant flow and O2 carrying capacity reserve to handle all but the most demanding metabolic stresses or primary organ dysfunction. Indeed, once overt cardiorespiratory failure is present, the degree of cardiorespiratory impairment is often advanced with secondary end-organ ischemic dysfunction. Hemodynamic monitoring plays an important role in the management of these critically ill patients with cardiovascular dysfunction. It is ...

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