What effect does adding bicarbonate to a local anesthetic solution have?

Adding bicarbonate to a local anesthetic solution primarily increases the concentration of the nonionic form of the anesthetic. Local anesthetics are typically weak bases, and when they are dissolved in solution, they exist in equilibrium between their ionized (charged) and nonionic (uncharged) forms. The nonionic form is more lipid-soluble and is better able to pass through nerve cell membranes to exert its anesthetic effect.

When bicarbonate is added, it increases the pH of the solution, which causes a larger proportion of the anesthetic to exist in its nonionic form. This can lead to a quicker onset of action because the nonionic form can diffuse more effectively through biological membranes. Therefore, the presence of bicarbonate enhances the effectiveness and quickens the action of the local anesthetic.

Other options do not capture the primary effect of bicarbonate accurately. The delay in onset would not be correct; instead, the onset is usually faster due to a higher concentration of the nonionic form. A fall in pH is contrary to what actually happens when bicarbonate is added, as it raises the pH of the solution. While there may be specific recommendations regarding the use of bicarbonate with certain anesthetics, the assertion that it should