On some machines M-mode can be applied off-line on a 2D image (anatomical M-mode)

Respiratory triggering can be obtained from the ECG leads on some machines

50% collapse during spontaneous inspiration is normal

In severe hypovolemia, e.g. during blood loss, the IVC will often be constantly and extensively collapsed

During the following conditions the IVC will often be distended without respiratory changes:
– Severe volume overload
– Pulmonary embolus
– Right heart failure
– Pulmonary hypertension

Increased diameter and reduced dynamics is normal in long distance runners

Be careful not to make incorrect assumptions about a patient’s fluid status as volume loading in fluid replete individuals will decrease IVC dynamics but it is not an indicator of underfilling

IVC dynamics during positive pressure ventilation is extremely difficult to interpret

Using IVC dynamic changes for volume responsiveness should be done with caution and only in conjunction with all other available clinical information

Reference values given by Feissel and Moreno

Image obtained from the short axis view of the abdominal vessels

– Place the transducer subcostally in the midline
– OM should be directed towards the patient’s left side
– Identify the the short axis view of the IVC (left side of the screen) and the abdominal aorta (right side of the screen)
– Place the the IVC in the center of the screen by moving the tail of the transducer towards the patient’s left side
– Counterclockwise rotate the transducer until a long axis view is displayed on the screen
– Depth: 10-18 cm

Notice the OI is on the left side of the screen of the top image as an abdominal probe and machine setting is used

Video showing the IVC target view

Starting from the sub-costal short axis view of the IVC and abdominal aorta followed by counterclockwise rotation of the transducer until a long axis view of the IVC is present on the screen

The diameter of the IVC should be measured at end-expiration 1-3 cm before it merges with the RA just proximal to the hepatic vein

Measurement is done on a 2D image or on an M-mode scan

– The reference diameter is the largest diameter

– Measure as perpendicular to the vessel walls as possible

– Measure at end-expiration

In radiology and emergency medicine it is general practice to display the IVC as a mirror image

Notice the orientation marker (yellow “V”) is now on the left side of the screen

Familiarize yourself with both ways of presentation

The probe is placed on the skin subcostally

The OM is orientated cranially

The OI is on the right side of the screen

The right atrium will be displayed to the right and the IVC to the left and the liver on top of the screen

By convention, in cardiac ultrasound the orientation indicator is placed on the right side of the screen

The target view is the IVC long axis image corresponding to the scanning plane indicated on the torso in the picture

As the IVC transects the liver, liver tissue will appear both in the near and far fields

By convention, the orientation marker in cardiac ultrasound is directed cranially

The structures identified in FATE position 1, IVC view

Identify:
– Liver
– RA: Right atrium
– IVC: Inferior vena cava
– Lung tissue

To avoid mistaking the abdominal aorta for the IVC:
1) Identify the entry point of the IVC into the RA
2) Pulsation of the vessel will more likely suggest aortic imaging