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Dr. Ajith Kumar J MD
Dept. of Emergency Medicne
Travancore Medicity, Kollam
India
editor@emmedonline.com

USG GUIDED VOLUME ASSESMENT USING IVC DIAMETER

Inferior vena cava is a large vein that carries deoxygenated blood into the right atrium of the heart. Since the size and shape of the IVC is correlated to CVP and circulating blood volume, sonographic evaluation of the IVC is an instantaneous non invasive measure of volume status.

Pathophysiology

IVC is a thin walled complaint vessel, the vessel contracts and expands with each respiration.
Negative pressure created by the inspiration of the patient increases venous return to the heart, briefly collapsing the IVC. Exhalation decreases venous return and IVC returns to its baseline diameter.

IVC diameter during inspiration varies from 0 – 14 mm at rest and expiratory diameter of 15 – 20 mm at rest.

IVC Collapsible Index (IVCCI)

IVCCI = [(IVC expiratory diameter – IVC inspiratory diameter)/ IVC inspiratory diameter ] * 100
When collapsibility index is closer to 0% , indicates volume overload and towards 100 % indicates volume depletion.

Correlation between IVC size and CVP

IVC Size (cm)	Respiratory Change	Central Venous Pressure(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

How to measure ?

It is measured using a curvilinear (3.5 - 5Mhz) or cardiac probe with abdominal setting at subxiphoid view. The diameter is measured approximately 1cm distal to the IVC hepatic vein junction where the anterior and posterior walls are clearly seen.

Type of Shock	Cardiac Function	IVC	Treatment
Septic	Hyperdynamic left ventricle Hypodynmiac left ventricle	Narrown IVC, collapse with inspiration	IV fluids, pressors
Hypovolemia	Hyperdynamic left ventricle	Narrow IVC collapses	Evaluation of cause, IV fluids and blood replacement
Cardiogenic	Hypodymanic left ventricle	Dilated IVC, Little or no collapse with inspiration	Inotropes
Obstructive (Cardiac Tamponade)	Pericardial effusion Diastolic collapse of right ventricle	Dilated IVC, no collapse with inspiration	Pericardiocentesis
PE	Dilated right ventricle Dilated right atrium	Dilated IVC minimal collapse	Thrombolytics

Reference

USG GUIDEDVOLUME ASSESMENT USING IVC DIAMETER ; By Mathew ; The Open Emergency Medicine Journal 2010

Focus on : Inferior Vena Cava Ultrasound. ACEP .2011. http://www.acep.org/Content.aspx?id=80791

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emmedonline
Dr. Ajith Kumar J MD
Dept. of Emergency Medicne
Travancore Medicity, Kollam
India
editor@emmedonline.com