23. Point-of-Care Ultrasound in the ICU

Point-of-care ultrasound: the application of ultrasound by the bedside clinician for the purpose of answering diagnostic questions or guiding procedures

Of great value in the ICU, where the patient’s status changes rapidly and diagnostic and therapeutic applications of ultrasound are necessary without delay

Main Variables that Determine Ultrasound Image Quality

Frequency

Largely determined by transducer selection

High-frequency transducers provide excellent resolution but limit the depth at which structures can be viewed.

For structures close to the body surface → high-frequency transducer

For deep structures → low-frequency transducer

Depth

Increasing depth allows the user to view more structures.

Increased depth causes reduction in resolution.

Gain

Increasing gain increases the intensity, or brightness, of the image

Under-gained images are too dark to interpret

Over-gained images are too bright to interpret

Ways to Manipulate the Ultrasound Transducer

Move

The transducer can be moved to a different location on the body

Tilt

Pitch: tilt up and down, cephalad/caudad, or in the sagittal plane

Yaw: tilt side to side, right/left, or in the transverse plane

Rotate about an axis

To achieve optimal imaging, the user must alter only the location or the tilt or the rotation at one time.

Focused Echocardiography

Bone effectively blocks the transmission of ultrasound waves; so the user must employ a small-headed transducer and anatomic “windows” to view the heart:

1. Parasternal

2. Apical

3. Subcostal

Reprinted with permission from authors, Ferrada P, Murthi S, Anand RJ, et al. Transthoracic focused rapid echocardiographic examination: real-time evaluation of fluid status in critically ill trauma patients. J Trauma. 2011;70(1):56-62.

Goals of Focused Transthoracic Echocardiography

Answer specific clinical questions:

Left ventricle