Safe to Use Topical Lidocaine Before KTP Laser?

Topical anesthetics strong enough to work through the normal skin barrier often contain several agents, and frequently cause visible blanching (vasoconstriction). If small vessels are to be treated, this is obviously not recommended. If brown spots (only) are the targets, then by all means, go ahead and use a topical anesthetic agent. Your esthetician is obviously well-informed, and likely works at a clinic or med-spa whose supervising physician is doing good teaching. That being said, I do recommend that laser treatments be performed by a physician experienced in that wavelength.

Your esthetician is partially correct.  Some of the compounded numbing creams have a vasoconstrictor in them.  The lidocaine itself has an initial vasoconstriction then a vasodilating property.  That being said, using a topical numbing cream before a laser to treat blood vessels may not be advised, and is not part of my practice.

In New York an aesthetician can not run a vascular laser such as the KTP. As long as the local does not contain epinephrine, which causes vessel constriction, it is ok to use it.

Topical lidocaine should not cause constriction of blood vessels although there are topical anesthetics that may cause blanching, like EMLA for example.

I would recommend having the procedure done by a board-certified, experienced dermatologist and not an aesthetician.  KTP laser is a very powerful machine that may have potential side effects.  You would want to know that the person performing the procedure has both training and experience in this.