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.