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KEY POINTS

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KEY POINTS

  1. When measuring invasive hemodynamic pressures, attention should be paid to technical aspects, including the zero reference level, dynamic response of the monitoring system, and effects of changes in intrathoracic pressures.

  2. Much diagnostic information can be gleaned from the analog waveform of directly measured pressures, both arterial blood pressure and cardiac filling pressures.

  3. Interpretation of filling pressures, such as central venous pressure (CVP) and pulmonary artery occlusion pressure (PAOP), is confounded by many variables, notably changes in ventricular compliance, cardiac valvular abnormalities, and positive pressure ventilation.

  4. Pulmonary artery catheter monitoring without a structured therapeutic intervention protocol has generally not been found to be beneficial in most perioperative and critical care settings. It might still be justified in very high-risk patients or in critically ill patients who do not respond to empiric therapy, particularly in patients with severe pulmonary hypertension.

  5. There are no accepted “gold standards” for cardiac output measurement. It is more clinically useful to follow trends in cardiac output rather than consider absolute values.

  6. Functional indices based on respiratory variation in hemodynamic parameters are better predictors of fluid responsiveness compared to static filling pressures or volumetric indices.

  7. Metabolic indices, such as lactate, base excess, and venous oxygen saturation, should be included in the evaluation of the hemodynamic status of the critically ill patient.

  8. Preemptive goal-directed therapy, aimed at optimization of volume status and cardiac output in the intraoperative period, has been found to decrease mortality in very high-risk surgical patients and decrease morbidity in high- to moderate-risk patients.

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INTRODUCTION

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British anesthesiologist Joseph T. Clover, MD (1825-1882), could be considered the grandfather of hemodynamic monitoring; he emphasized the need for a “finger on the pulse” while giving chloroform anesthesia (Figure 26-1).1 The word monitor originates in the Latin word monere, meaning “to warn,” but an additional use of the word relates to regulation and control: The anesthetist uses monitoring information to modify therapeutic interventions as well as to gauge the effect of these interventions in a continual feedback-control loop.2 For a monitor to be of benefit, several conditions must be fulfilled. Monitoring data, including technical and physiologic aspects, must be correctly interpreted. Effective clinical interventions should exist to treat the underlying problem. And, risks associated with the monitor itself should be recognized and minimized.3

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FIGURE 26-1.

Joseph T. Clover (1825–1882), a pioneer of monitoring during anesthesia. [Reproduced with permission from the Wellcome Library, London.]

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ARTERIAL BLOOD PRESSURE MONITORING

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BACKGROUND

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Blood pressure describes the driving force for perfusion and is the major determinant of left ventricular (LV) afterload. Accurate, reliable, and timely measurement of arterial blood pressure (ABP) is crucial for the care of critically ill patients and those undergoing surgical procedures. ABP can be measured accurately with invasive and noninvasive methods, ...

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