Sometimes, it is the technique of making the emulsion and/or the step you are adding Lidocaine Hcl. Also, The pH of emulsion (Cream). Usually for Cream: 5.5 - 6.0 unless you are using Salicylic Acid for Acne Cream or making Hair Conditioner.
You ca dissolve Lidocaine HCL in D.I water at room temp (try to dissolve it in the least amount of water). Sometimes, You may warm the water to 35C - 40C (for faster dissolution), and dissolve Lidocaine HCL in it, then, add it (post-emulsification) to the emulsion at 40 C and Mixing Speed 500 - 600 RPM. You need to look at the emulsion at this point, if you see it “grainy”, you may homogenize it using Silverson Homogenizer at 5000 rpm for 3 min. at the same temp. (40C)
Also, the thickener you are using and its concentration can be a reason for the “grainy” appearance. You may try Xanthan Gum at 0.1% if you still have the same grainy effect at the end of the emulsion. you may try Sodium Hyaluronate at 0.1% which can give a significantly smoother result. It is recommended to make a slurry of either Xanthan Gum or Sodium Hyaluronate with Glycerin, then, add it to the water phase with moderate mixing till complete hydration. You should make sure that you attained the complete hydration step and no more fisheyes. If it still has fisheyes you don’t notice, it may turn into small grains by the end of the emulsion or luckily the heat may dissolve these small fisheyes as long as you are using Natural Thickeners. The case is different if you are using Synthetic thickener like carbopol (Acrylates/C10-30 Alkyl Acrylate Crosspolymer), you may not be able to get ride of these fisheyes by the end of the emulsion