This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Surgery
The role of sodium bisulphate in a L.A solution is: 
Select and explain. 
A. Reducing agent, B. Aesthetic agent, C. Vasoconstrictor, D. Preservative
A: Reducing agent
Answer: A: Reducing agent 
Explanation: Reducing agent (Ref: Malamed-4th Ed/Pg 274) Contents of LA caridge: Ingredient Function Local anesthetic agent (Lignocaine) Conduction blockade Vasoconstrictor (adrenalin) |es absorption of LA anesthesia & toxicity Sodium sulphide Antioxidant for vasoconstriction Methyl paraben Preservative Sodium chloride Isotonicity of solution Sterile water Diluent