Alkalization of local anesthetics solutions by the addition of sodium bicarbonate has following benefit except-

Addition of sodium bicarbonate prevents causation of drug and spreads the onset -, improves the quality, increases duration and decreased pain at site of injection. Explanation The addition of sodium bicarbonate to local anesthetics improves the speed of onset, reduces the minimum concentration of the local anesthetic required and improves the quality of block. Adding sodium bicarbonate increases the pH of the local anesthetic solution, and thus more amount of free uncharged drug is available which can increase the rate of diffusion across the nerve sheath and improve the onset of anesthesia. Subcutaneous injections of local anesthetics are painful. Alkalinization of the solution by adding sodium bicarbonate before injecting can decrease the pain. Addition of adrenaline or any vasoconstriction causes decrease in systemic toxicity.