Anesthesia Knowledge Test 1 (AKT-1) Practice

The addition of NaHCO3 (sodium bicarbonate) to a local anesthetic improves the non-ionized fraction of the anesthetic. Local anesthetics are weak bases and exist in equilibrium between their ionized (charged) and non-ionized (uncharged) forms. The non-ionized form is more lipid-soluble and can more easily penetrate the neural membranes to exert its anesthetic effect. When NaHCO3 is added to a local anesthetic solution, it increases the pH of the solution, which shifts the equilibrium towards the non-ionized form. This results in a larger proportion of the anesthetic being available in its active form, enhancing the onset and effectiveness of anesthesia. This phenomenon is particularly beneficial when the local anesthetic is used in inflamed or acidic tissues, where the local pH is lower, thus the barrier to diffusion into nerves is much higher. Improving the non-ionized fraction in this manner does not necessarily affect the potency of the anesthetic directly but allows for a more rapid onset of action and can improve the efficacy of the administered anesthetic due to better tissue penetration.