## **Core Concept**
The combination of adrenaline (epinephrine) with local anesthetics like lignocaine (lidocaine) is a common practice to prolong the duration of anesthesia and reduce systemic toxicity. Adrenaline acts as a vasoconstrictor, which helps in reducing the blood flow at the site of injection, thereby prolonging the action of the local anesthetic.

## **Why the Correct Answer is Right**
The correct percentage of adrenaline added to lignocaine for local infiltration is typically 1:200,000 to 1:500,000. This dilution helps in achieving the desired vasoconstriction without causing tissue ischemia. A 1:200,000 dilution of adrenaline is equivalent to 5 micrograms per milliliter (mcg/mL) of adrenaline. This combination is widely used for procedures requiring local anesthesia, as it provides a good balance between efficacy and safety.

## **Why Each Wrong Option is Incorrect**
- **Option A:** 1:1000 is a very high concentration of adrenaline, typically used for intravenous administration in cardiac arrest scenarios, not for local infiltration with lignocaine.
- **Option B:** 1:10000 is less commonly referenced for local anesthesia and is not the standard concentration when combining with lignocaine for infiltration.
- **Option D:** 1:50000 is higher than the commonly used concentrations for local infiltration and could potentially lead to tissue ischemia or systemic effects due to excessive vasoconstriction.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that the addition of adrenaline to local anesthetics like lignocaine helps in reducing systemic absorption and prolonging the duration of action, but it should be used cautiously in areas with end-arterial blood supply (like fingers, toes, or penis) due to the risk of ischemia.

## **Correct Answer:** .