ULTRASOUNDOF

INFERIOR VENA CAVA

OBJECTIVES

Describe indications for using ultrasound at the bedside to image the inferior vena cava.

Describe how to performing bedside ultrasound of the inferior vena cava.

Use the findings on ultrasound to guide assessment of intravascular volume status.

Generate group discussion regarding the potential value of learning this procedure for patient management

CASE46 M was admitted with alcoholic hepatitis and newly diagnosed cirrhosis with ascites. On exam he had flat JVD in supine position, tense abdominal distension, and moderate leg edema to the knees. He was started on a 28 day Trental protocol Hospital Course

Day 1-9 - 3 paracenteses; - removal of 11 liters of ascitic fluid. Day 10 - JVD flat in supine position - Abdomen still distended but not tense - moderate leg edema - Na = 136, Cr = 1.0, BUN = 11 - furosemide started at 20 mg QD - spironolactone started at 50mg QD.

CASE

Day 12 - JVD flat in supine position - persistent leg edema - apparent increase in abdominal girth on exam - Na = 134, Cr = 0.7, BUN = 12 - furosemide increased to 40mg QD

Day 19 - JVD flat in supine position - persistent leg edema - abdominal girth same to slightly decreased - Na = 136, Cr = 0.8, BUN = 12 - furosemide increased to 80mg QD - spironolactone increased to 200mg QD

CASE Day 21 - JVD flat in supine position - leg edema the same - Abdominal girth the same - Na = 130, Cr = 0.9, BUN = 10

Day 24 - JVD flat in the supine position - leg edema the same - Abdominal girth the same to slightly increased - Na = 127, Cr = 0.7, BUN = 13, Urine Na < 10

Daily weights and Input/Output measures were collected sporadically and could not be assessed for any trends.

CLASSIC HYPONATREMIA

Hypovolemic Euvolemic Hypervolemic

UNa UNaUOsm > SOsm

UNa > 40

< 10 < 10> 20 > 20YES NO

Volume Depletion

Mineralcorticoid Deficiency

SIADH OTHER

Volume Replacement

Fluid Restriction

Fluid Restriction

plus Diuretics

CirrhosisNephrosisCHF

CKD

QUESTION

What type of hyponatremia does this patient have and how should it be managed?

A. Hypovolemic hyponatremia stop diuretics; begin normal saline infusion; liberalize po fluid intake;

monitor Na over the course of the next several days; if Na does not improve or worsens, entertain hypervolemic hyponatremia as the cause

B. Hypervolemic hyponatremia increase the diuretics and tighten the fluid restriction; monitor Na over

the course of the next several days; if Na does not improve or worsens, entertain hypovolemic hyponatremia as the cause.

C. Not sure consult nephrology for an opinion about the hyponatremia

INDICATIONS

IVC Ultrasound

Spontaneously Breathing

Mechanical Ventilation

Volume Status / CVP Fluid Responsiveness

INDICATIONS

Assessing Intravascular Volume Status / CVP

VOLUME DEPLETED STATES- Hyponatremia- Acute Kidney Injury (? Prerenal)- Diuretic therapy- Sepsis

VOLUME OVERLOAD STATES-Hyponatremia- Heart Failure-Cirrhosis with ascites- Anasarca

INDICATIONS

Assessing Fluid Responsiveness in Shock

- IVC diameter does not correlate with right atrial pressure in patients who are intubated with shock

- Measuring the variation in IVC diameter in these situations can help determine whether the patient’s blood pressure will respond to fluids or whether inotropic support (i.e. dobutamine) will be needed

AnatomyThe inferior vena cava returns

blood from the body to the right atrium

Formed by the convergence of the illiac veins

RetroperitonealRight of the aorta Normal size <2.5 cmVaries w respiration

Respiratory variation

Expands w/ expiration

Contracts w/ inspiration Due to changing intrathoracic pressures.

Respiratory Variation

Figure 2: Physiological respiratory variations in IVC diameter in a healthy volunteer breathing quietly.: From: http://www.pifo.uvsq.fr/hebergement/webrea/index.php?option=com_content&task=view&id=36&Itemid=93IVC diameter decreases on each inspiration.

http://www.criticalecho.com/content/tutorial-4-volume-status-and-preload-responsiveness-assessment

Measuring the IVC Diameter

Measure IVC 2cm distal to right atrium

Inspiratory (Minimal) IVC Diameter

Maximum (Expiratory) IVC Diameter

M-Mode IVC Diameters

CAVAL INDEX (CI)

CI =

minimal (inspiratory) diameter

maximum (expiratory) diameter

maximum (expiratory) diameter

CAVAL INDEX (CI)

Volume Depletion

Volume Overload

0% 100%

IVC v CVP

Correlation Between IVC Diameter Plus CI and CVP

IVC Max Diameter (cm)

CI CVP (mmHg)

< 1.5 100% (total collapse) 0-5

1.5-2.5 > 50% 6-10

1.5-2.5 < 50% 11-15

> 2.5 < 50% 16-20

> 2.5 0% (no collapse) >20

M-Mode Volume Depletion

M-Mode Volume Overload

IVC v CVP

Correlation Between IVC Diameter Plus CI and CVP

IVC Max Diameter (cm)

CI CVP (mmHg)

< 1.5 100% (total collapse) 0-5

1.5-2.5 > 50% 6-10

1.5-2.5 < 50% 11-15

> 2.5 < 50% 16-20

> 2.5 0% (no collapse) >20

PROCEDURE

Positioning 1 Supine2 Degree of head elevation has not been

shown to make a significant difference in measurements

PROCEDURE

Probe Selection

1 Low frequency 2-5 MHz2 Curvalinear probe

PROCEDURE

Approach #1 – Xiphoid View

PROCEDURE

Landmarks Aproach #1 – Xiphoid View1 Most common approach2 Place probe longitudinally just below the

xiphoid process with the probe marker to the patient’s head

3 Look for IVC going into right atrium – may need to move probe 1-2cm to patient’s right and then tilt it slightly towards the heart

IVC Longitudinal

PROCEDURE

Approach #2 – Anterior Mid-Axillary View

PROCEDURELandmarks

Aproach #2 – Anterior Mid-Axillary View1 Place probe longitudinally in right anterior

mid-axillary line with marker towards the head

2 Look for IVC running longitudinally adjacent to liver crossing the diaphragm.

3 Track superiorly until it enters right atrium confirming that it is the IVC and not the aorta.

IVC Anterior Mid-Axillary View

PEARLS

Bowel Gas 1 May impede visualization in the xiphoid view2 Gentle graded pressure may help move

bowel out of way3 Don’t press too hard or will collapse IVC

causing false measurements4 Consider anterior mid-axillary view

PEARLS

Plethoric (dilated/sluggish) IVC 1 Volume overload2 Cardiac tamponade3 Mitral regurgitation4 Aortic stenosis

PEARLS

Mechanical Ventilation 1 Causes reversal of IVC changes with

respiration2 Maximum diameter with inspiration,

minimum diameter with expiration

PEARLS

AortaThick, echogenic wallsPulsatileHigh flow velocityNot compressableNo respiratory variationAbove vertebral bodies

IVCThin wallsUsually not pulsatileLow flow velocityCompressableRespiratory variationRight of vertebral bodies

IVC v Aorta

Aorta – Longitudinal View

SonoSite 180 Plus

SonoSite 180 Plus

SonoSite 180 Plus

Changing and Inserting the Transducer

SonoSite 180 Plus

Insert the transducerTwist lock counterclockwise

SonoSite 180 Plus

Fold lock down

SonoSite 180 Plus

Ready to power-up machine

SonoSite 180 Plus

Power Button

SonoSite 180 Plus

SonoSite 180 Plus

SonoSite 180 Plus

SonoSite 180 Plus

Wrong Transducer is Connected

Correct Transducer Menu-GYN-OB-Abdominal

SonoSite 180 Plus

M-Mode

2D View (default)

SonoSite 180 Plus

GAINChanges the contrast on the screen

SonoSite 180 Plus

SonoSite 180 Plus

CASE An IVC Ultrasound was performed at the bedside.

Maximum IVC diameter during expiration = 1.10 cm. The

Minimum IVC diameter during inspiration = 0 cm.

Caval Index = 100% (total collapse)

CASECorrelation Between IVC Diameter Plus CI and CVP

IVC Max Diameter (cm)

CI CVP (mmHg)

< 1.5 100% (total collapse) 0-5

1.5-2.5 > 50% 6-10

1.5-2.5 < 50% 11-15

> 2.5 < 50% 16-20

> 2.5 0% (no collapse) >20

Interpretation: Mixed hyponatremia

(intravascular volume depletion plus free water excess from cirrhosis)

CASE

Treatment: - one liter of normal saline IV to expand intravascular volume

- reduced free water oral intake from 1500cc to 1000cc/d - Continued current diuretic dosing to remove free water

Result: In 3 days, the patient’s Na progressively increased to 136

REFERENCES-De Lorenzo RA, Morris MJ, William JB, et al. Does a simple bedside sonographic measurement of the inferior vena cava correlate to central venous pressure? J. Emer. Med. 2011; 42(4); 429-436.

-Kosiak W, Swieton D, Piskunowicz M. Sonographic inferior vena cava/aorta diameter index, a new approach to the body fluid status assessment in children and young adults in emergency ultrasound preliminary study. Acad. J. Emerg. Med. 2008;26:320-5

-Blehar DJ, Dickman E, Gaspari R. Identification of congestive heart failure via respiratory variation of inferior vena cava diameter. Am. J. Emerg. Med. 2009;27:71-5. -Chen L, Santucci KA, Kim Y. Use of ultrasound measurement of the inferior vena cava diameter as an objective tool in the assessment of children with clinical dehydration. Acad. Emerg. Med. 2007:14:841-5. -Feissel M, Michard F, Faller JP, et al. The respiratory variation in inferior vena cava diameter as a guide to fluid therapy. Intensive Care Med. 2004;30:1834-7.

-Fields JM, Lee PA, Jenq KY, et al. The interrater reliability of inferior vena cava ultrasound by bedside clinician sonographers in emergency department patients. Acad. Emerg. Med. 2011;18:98-101. -Kircher BJ, Himelman RB, Schiller NB. Noninvasive estimation of right atrial pressure from the inspiratory collapse of the inferior vena cava. Am J. Cardiol. 1990;66:493-6. -Randazzo MR, Snoey ER, Levitt MA, et al. Accuracy of emergency physician assessment of left ventricular ejection fraction and central venous pressure using echocardiography. Acad. Emerg. Med.2003;10:973-7.

-ACEP Policy Statement on Emergency Ultrasound Guidelines. Ann. Emerg. Med. 2009;53:550-70

-Nagdev AD, Merchant RC, Tirado-Gonzalez A, et al. Emergency department bedside ultrasonographic measurement of the caval index for noninvasive determination of low central venous pressure. Ann. Emerg. Med. 2010;55:290-5.

DISCUSSION