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Chapter 32: Hemodynamic Monitoring

H. Bryant Nguyen; David T. Huang; Michael R. Pinsky

INTRODUCTION

Hemodynamic monitoring can identify cardiovascular insufficiency and ensure optimal treatment of the critically ill. Advanced techniques help identify and prioritize various causes of hemodynamic instability and can enable tailored interventions.

Hemodynamic monitoring changes therapeutic decisions in more than 50% of patients and can detect cryptic cardiovascular compromise. We will focus on techniques applicable to the ED: blood pressure monitoring, central venous pressure (CVP) monitoring, cardiac output (CO) monitoring, and blood oxygenation and organ perfusion monitoring (Table 32-1). Use of any technology must be associated with a therapy and a response to therapy—functional hemodynamic monitoring. Applying a technology without a therapeutic strategy limits any potential benefit. In practice, it is best to use more than one approach and monitor therapeutic responses (Table 32-2).1

TABLE 32-1Hemodynamic Variables Obtainable in the ED
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TABLE 32-1 Hemodynamic Variables Obtainable in the ED
Hemodynamic Variable Method of Measurement
Hemoglobin oxygen saturation, % Pulse oximetry, arterial blood gas analysis
Heart rate, beats/min Physical examination, pulse oximetry, electrocardiography
Blood pressure, mm Hg Sphygmomanometry, oscillometry, intra-arterial catheterization
Central venous pressure, mm Hg Jugular venous pulsation, US, central venous catheterization
Cardiac output, L/min Thoracic bioimpedance or bioreactance, esophageal Doppler US, transcutaneous Doppler US, pulse contour analysis, lithium dilution, transpulmonary (arterial) thermodilution, pulmonary artery thermodilution
Central venous oxygen saturation, % Central venous catheterization for intermittent venous blood sampling or continuous measurement
Lactate, mmol/L Arterial, venous, or capillary sampling
Tissue oxygen saturation, % Near-infrared spectroscopy
TABLE 32-2Hemodynamic Monitoring Principles1
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TABLE 32-2 Hemodynamic Monitoring Principles1

No hemodynamic monitoring technique can improve outcome by itself.

Monitoring requirements may vary over time and can depend on local equipment availability and training.

There are no optimal hemodynamic values that are applicable to all patients.

We need to combine and integrate hemodynamic variables.

Measurements of SvO2 can be helpful.

A high cardiac output and a high SvO2 are not always best.

Cardiac output is estimated, not measured.

Monitoring hemodynamic changes over short periods of time is important.

Continuous measurement of all hemodynamic variables is preferable.

Noninvasiveness is not the only issue.

Abbreviation: SvO2 = venous oxygen saturation.

ARTERIAL BLOOD PRESSURE

Blood pressure is the force exerted by the circulating blood through a blood vessel. Assessing arterial pressure is very important, as hypotension implies tissue hypoperfusion; shock is a state of organ hypoperfusion but is not always associated with hypotension. Hypotension is always pathologic and reflects a failure of normal circulatory homeostatic mechanisms, whereas normotension does not necessarily indicate cardiovascular stability. Normal blood pressure can occur in the setting of profound circulatory shock in the face of significant vasoconstriction or in a patient with antecedent high arterial pressure. For example, a patient in cardiogenic or hypovolemic shock may remain normotensive ...

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