Ultrasound is a high frequency sound which penetrates tissue in a very specific way related to the ability of the ability to absorb or reflect it. Tissues with much water such as blood tend to absorb the sound wave whereas bone will reflect the sound. This will show up in a specific way and will allow a clinician to identify blood vessels, nerves, lung and bone.
This tool will allow a needle to be advanced near a large nerve bundle or directly into a blood vessel with great accuracy. Using these instruments anesthesiologists have been very effective in performing nerve blocks that are effective and with much less risk to the nerve with the needle they use to inject medications. In addition they are now using ultrasound on almost all procedures to insert large catheters into large blood vessels in the neck area and in the upper chest.