Ever finally step away from a busy resuscitation and someone stops you for peripheral IV access? You set up everything, have the patient positioned, and then notice there is no sterile ultrasound gel. No gel? No problem. The trick is to eliminate anything of poor acoustic impedance between the ultrasound probe and the patient’s skin.
Trick of the Trade
1. Apply a transparent adhesive dressing with a thin alcohol layer on the probe
2. Use sterile saline instead of gel on the patient’s skin
Squirt normal saline flush on the patient’s skin to create a coupling medium between the probe and the patient.
Why it works:
Ultrasound procedures use a range of frequencies (1.5-20 MHz) to visualize internal structures and require a medium to replace air, which has a poor acoustic impedance for the ultrasound waves . Acoustic impedance is defined as the resistance of the propagation of ultrasound waves through tissues and is the product of the density and speed of sound in the tissue . Ultrasound gel has an acoustic impedance that is similar to soft tissue and is therefore considered the ideal medium . Because most soft tissue is comprised of water, the acoustic impedance of water, and therefore 0.9% saline, is actually pretty similar , as demonstrated by water bath techniques for ultrasounding distal extremity injuries .
We find great visual clarity for performing ultrasound-guided peripheral IVs using this trick, as shown in Figure 1.
Figure 1: Peripheral IV ultrasound using alcohol under transparent film dressing and topical saline flush – all without ultrasound gel
Afzal S, Zahid M, Rehan ZA, et al. Preparation and Evaluation of Polymer-Based Ultrasound Gel and Its Application in Ultrasonography. Gels. 2022 Jan 6;8(1):42. doi: 10.3390/gels8010042. PMID: 35049577; PMCID: PMC8774352
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