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Focused Cardiac Ultrasound

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  1. Welcome

    Introduction to FoCUS
    2 Topics
  2. Section 1
    Video: Cardiac Anatomy
  3. Cardiac Anatomy
    3 Topics
  4. Section 2
    Key Video: Obtaining the 5 Views
  5. Acquisition & the 4Ps
    4 Topics
    |
    1 Quiz
  6. Acquiring The 5 Views
    5 Topics
    |
    1 Quiz
  7. Clinical Case Scenario
  8. Section 3
    Interpretation
    11 Topics
    |
    2 Quizzes
  9. Interpretation: The RUSH Protocol
    1 Quiz
  10. Section 4
    Medical Management
  11. Foundations of Echocardiography
  12. References
    References & Further Reading

Quizzes

Focused Cardiac Ultrasound Interpretation Hypovolaemic Shock
Lesson 8, Topic 10
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Hypovolaemic Shock

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Hypovolaemic Shock

Focused Cardiac Ultrasound Findings in Hypovolaemic Shock:

  • Small LV Cavity in End Systole
  • Small LV Cavity in End Diastole
  • Hyperdynamic Heart
  • Kissing Ventricle in End Systole – PSAX View – Obliteration of LV Cavity
  • *IVC Size – Not very useful on its own.
  • **IVC Respiratory Variability

*Static measure of IVC size < 1.0 cm is a predictor of fluid responsiveness.

**IVC Respiratory Variability of > 50% in spontaneously breathing patients.

**In mechanically ventilated patients, a change in IVC size of 16-18% indicates likely fluid responsiveness.

** A negative IVC respiratory variability test cannot be used to rule out fluid responsiveness. The test is also better at predicting fluid responsiveness in mechanically ventilated patients.

**The IVC can be measured with 2D or M-mode. The measurement is prone to error due to movement of the IVC with the diaphragm during respiration. The angle of the ultrasound beam may not be perpendicular to the IVC resulting in underestimation of the size.

Look for evidence of haemmorhage: The ascending, descending thoracic and abdominal aorta should be evaluated for evidence of aneurysm, dissection or rupture. Free fluid in the abdominal RUQ or LUQ may be present, indicative of haemmorrhage in the trauma setting.

Parasternal Short Axis View
What is seen above ? Click to open.

Parasternal Short Axis View: Hypovolemia, The LV walls appear to almost completely obliterate the LV cavity in end systole. This is termed a ‘kissing ventricle’.

Imaging the IVC

Image shows the IVC & aorta and relationship to the liver. Seen from posteriorly. It can be easy to mistake the aorta for the IVC during imaging.
Subcostal IVC view showing respiratory variability in size. Compare this with the aorta below.
This is the abdominal aorta in long axis. It can be differentiated from the IVC by (1) not having liver posterior to it, (2) pulsatile, (3) thicker walls, (4) does not drain into the RA and (5) has the spinal vertebrae directly posterior to it.

Fluid Responsiveness

Patient’s in circulatory failure often receive fluid resuscitation. It is however estimated that only 50% of these patients actually demonstrate an increase in stroke volume after a fluid challenge. Often the administration of fluids does not impact haemodynamics positively, and can lead to increases in right atrial pressure, fluid overload and venous congestion.

The importance of predicting fluid responsiveness lies in minimizing the risks of over-resuscitation with intravenous fluids in patients with acute circulatory failure. 

Fluid responsiveness can be defined as an increase in stroke volume of >10% following a fluid challenge. A fluid challenge may be an intravenous bolus of 500 mL (10 mL/kg) of fluid, or a passive leg raise (PLR) test.

Several echocardiographic parameters can be used to evaluate fluid responsiveness. Limitations include the intermittent nature of measurements, requirement to look at trends as opposed to single measurements and issues with obtaining adequate windows. The latter is common in mechanically ventilated patients.

Parameters used include:

  • SVC diameter
  • IVC diameter
  • LVOT or AV VTI respirtatory variations (Doppler)
  • Visual assessment of the LV
  • LV end diastolic area
  • Venous Doppler (VExUS)

Some of these parameters are beyond the scope of point of care focused cardiac ultrasound. They are increasingly performed as part of a critical care echo study and will not be covered further here. The reader should however be aware of these measurements. The topic is covered in more detail in the quantification in focused cardiac ultrasound course.

Echo parameters used to determine fluid responsiveness
Image shows a selection of echo parameters that can be used to evaluate volume status & fluid responsiveness. Reference: How can assessing hemodynamics help to assess volume status? De Backer et al. Intensive Care Medicine 2022
POCUS for Evaluation of Volume Status and Hemodynamics. Talk by A/Prof Abhilash Koratala from Wisconsin (USA)
ESICM. How to assess fluid responsiveness. Echo and more.

Selection of Further Reading:

  1. Comprehensive Assessment of Fluid Status by Point-of-Care Ultrasonography. Argaiz, Koratala & Reisinger. Kidney360. 2021
  2. Does Respiratory Variation in Inferior Vena Cava Diameter Predict Fluid Responsiveness. Elliot et al. Shock 2017.
  3. Predicting and measuring fluid responsiveness with echocardiography. Miller & Mandeville. Echo Research & Practice. 2016
  4. Assessing dynamic fluid-responsiveness using transthoracic echocardiography in intensive care. Desai & Gary. Brittish Journal of Anaesthesia. 2018.
  5. Echocardiography as a guide for fluid management. Boyd et al. Critical Care. 2016.
  6. How can assessing hemodynamics help to assess volume status? De Backer et al. Intensive Care Medicine 2022
  7. POCUS in dyspnoea, non-traumatic hypotension & shock. A systematic review of existing evidence. Kok et al. European Journal of Internal Medicine. 2022