IVC ultrasound

Background

• Though contriversal, IVC measurement by ultrasound can estimate volume status and fluid responsiveness
  • There is moderate evidence to support that IVC diameter is consistently low in hypovolemia vs euvolemia
  • It is suggested that IVC change can estimate fluid responsiveness with a Sn 0.78 and Sp 0.86
• Measure both absolute diameter of IVC and percent collapse during inspiration of spontaneously breathing patients
• Can use as a dynamic assessment after intervention (giving fluids)
• Unclear if applicable to intubated patients

Technique

• Use curvilinear (abdominal) probe or phased array (cardiac) probe
• In subxyphoid cardiac view (epigastric), fan probe laterally to view the IVC 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
  • Use M-mode to measure IVC collapse during inspiration or estimation can be made in 2D with IVC in longitudinal axis

Measurements

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

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

See Also

• Ultrasound (Main)