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Dr. Ajith Kumar J MD
Dept. of Emergency Medicne
Travancore Medicity, Kollam
India
editor
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.
VIDEO : Click this external link to view measuring of IVC diameter by sonosite.
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