Final answer:
The statement is false as cold packs cause vasoconstriction, not vasodilation. This constricts blood vessels and leads to numbness due to reduced nerve signal conduction. Lidocaine also causes numbness by inhibiting nerve signals.
Step-by-step explanation:
The statement "Application of cold packs causes vasodilation and numbness of the area." is false. Applying cold packs typically induces vasoconstriction, which is the narrowing of blood vessels, thereby reducing blood flow to the area. This can lead to numbness as the temperature decreases. Numbness occurs due to the slowdown of nerve conduction as a result of the cold temperature. When you stick your hand in a bucket of ice, and it grows numb, it is because the cold temperature blocks the sensation of touch from signaling to the brain due to slowed nerve signaling.
The use of cold packs, such as those containing ammonium nitrate (NH4NO3), can produce temperatures less than 0°C, providing localized cold therapy that is beneficial for injury treatment. On the contrary, vasodilation increases blood flow and is typically associated with applying heat to the body. Vasodilation can help to warm the body and improve circulation.
Additionally, lidocaine, a local anesthetic that blocks voltage-gated sodium channels, causes numbness in a similar fashion; by blocking these channels, nerve signal transmission for pain and touch is inhibited, leading to numbness.