Question 13.1

List the techniques / measurements that are available to assess the circulation status of a patient in the intensive care unit.

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College Answer

Physical examination [warm hands, urine output, mentation]
Vital signs – heart rate, blood pressure, oxygenation Lactate
Urine output

Blood pressure response to passive leg raise or fluid challenge

Invasive arterial monitoring [Vigileo/LiDCO (cardiac output, stroke volume variation, stroke volume)]

Central venous pressure measurement, central venous oxygen saturation

Invasive cardiac monitoring
- PiCCO measurements [Intra thoracic blood volume, global end diastolic volume, cardiac output, stroke volume variation]
- Pulmonary Artery Flotation Catheter [pulmonary artery occlusion pressure, cardiac output, mixed venous oxygenation]
Echocardiogram [cardiac output, left ventricular ejection fraction, IVC collapsibility]

Transcutaneous Doppler [cardiac output/stroke volume variation]

Research tools
- Techniques for measuring microvascular perfusion eg contrast US, SDF Techniques for measuring tissue oxygenation eg, gastric tonometry [D pCO2], sublingual tonometry, microdialysis
- Impedance cardiography [cardiac output, stroke volume variation, stroke volume]

Discussion

This question is a "list" question, and thus one should resist the temptation to critically evaluate, or to compare and contrast. A list of techniques is reasonably easy to generate. Specifically, techniques to assess volume-responsiveness are extensively discussed in the section concerned with Fluid Resuscitation, Vasopressors and Inotropes. If one needed to generate a dumb noncomparative list for whatever reason, one should do so in a manner which follows a system of some sort.

Techniques for the Assessment of Circulation
Clinical techniques Capillary refill Heart rate Temperature of the extremities Urine output Mental state Pressure-based techniques Non-invasive blood pressure Invasive blood pressure (arterial line) Central venous pressure Flow-based techniques Thermodilution cardiac output measurements Right heart (PA catheter) Trans-pulmonary (PiCCO) Trans-thoracic Echocardiography (TTE) Transoesophageal echo (TOE) Continuous oesophageal PW Doppler Transcutaneous Doppler	Static indices of fluid responsiveness LVEDVI, RVEDVI GEDVI ITBV Dynamic indices of fluid responsiveness Response to fluid challenge Passive leg raise Pulse pressure variation Stroke volume variation Assessment of circulatory efficacy Lactate measurements Central or mixed venous saturation Oxygen extraction ratio a-A CO₂ difference Assessment of microcirculation Gastric tonometry Sublingual tonometry Microdialysis Experimental techniques Impedance cardiography

References

Marik, Paul E. "Hemodynamic parameters to guide fluid therapy." Transfusion Alternatives in Transfusion Medicine 11.3 (2010): 102-112.

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