IVC ultrasound

Background

• Though controversial, IVC measurement by ultrasound can estimate volume status, fluid responsiveness, and fluid tolerance
  • There is evidence to support that IVC diameter is consistently low in hypovolemia versus euvolemia
  • IVC change can estimate fluid responsiveness with a Sn 0.78 and Sp 0.86
• Can use as a dynamic assessment after intervention such as giving fluids or passive leg raise
• Dynamic changes is probably best measured in intubated patients

Indications

• Differentiate causes of shock
• Differentiate causes of shortness of breath

Technique

1. Select probe
   • Curvilinear or phased array probe
2. Location
   • In subxyphoid cardiac view (epigastric), fan probe laterally to view the IVC draining and identify it draining into the right atrium
   • May start with subxyphoid view, place right atrium in center of screen and rotate probe 90 degrees clockwise to find IVC
3. Longitudinal view
   • M-mode to measure IVC collapse during inspiration or estimation can be made in 2D with IVC in longitudinal axis
   • Measure both absolute diameter of IVC and percent collapse during inspiration of spontaneously breathing patients
4. Dynamic measurements
   • Repeat measurements can be made after passive leg raise or IVF bolus

Findings

Classic Ultrasound Findings For Critically Ill Patients

Disease	IVC	Cardiac	Lung (Phased Array)	Lung (Linear)
MI	↑	Focal WMA Mod/Poor squeeze	NL or B-lines	Sliding
Tamponade	↑	RA collapse with filling RV collapse with filling	NL	Sliding
PTX	↑	NL or Hyperdynamic	Lung point Consolidated lung	Absent lung sliding
Sepsis	↓	Hyperdynamic squeeze	NL (see pneumonia)	Sliding
Pneumonia	NL or ↓	Hyperdynamic squeeze	Unilateral B-lines	Sliding
Decompensated HF	↑	Mod/Poor squeeze	Bilateral B-lines	Sliding
PE	↑	RV > LV McConnell's sign	NL or Unilateral B-lines	Sliding

Correlations Between IVC Size and CVP

IVC (cm)	Respiratory Change	CVP (cm H2O)
<1.5	Total collapse	0-5
1.5-2.5	>50% collapse	6-10
1.5-2.5	<50% collapse	11-15
>2.5	<50% collapse	16-20
>2.5	No change	>20

Measure 2cm from IVC/RA junction or 1cm from IVC/hepatic vein junction

Images

Pearls and Pitfalls

• Aorta can be confused for IVC, ensure your visualize the vessel entering the atrium
• Ensure the vessel is viewed in full longitudinal axis as being off center will give falsely narrow measurements

Documentation

Normal Exam

A bedside IVC ultrasound was performed to assess volume status in setting of dehydration. The IVC was identified in longitudinal access. The IVC was neither flat nor plethoric. There was less than 50% collapse with respirophasic measurements. This does not imply that the patient is not volume responsive but rather further testing is needed.

Abnormal Exam

A bedside IVC ultrasound was performed to assess volume status in setting of dehydration. The IVC was identified in longitudinal access. The IVC was flat with over 50% collapse with respirophasic measurements. There was evidence of volume depletion and fluid tolerance.

A bedside IVC ultrasound was performed to assess volume status in setting of fluid overload. The IVC was identified in longitudinal access. The IVC was plethoric with less than 50% collapse with respirophasic measurements. There was evidence of volume overload.

Clips

Normal IVC

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Flat IVC

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Plethoric IVC

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External Links

• Life in the Fastlane - SMACC: The Dark Art of IVC Ultrasound
• ACEP Focus On: Inferior Vena Cava Ultrasound

See Also

• Ultrasound (Main)

References

Authors

Neil Young, Ross Donaldson, Kenn Ghaffarian, Marissa Camilon, Tianjiang Ye, Daniel Eggeman, Daniel Ostermayer