Maximum dose of lignocaine given with adrenaline for infiltration anaesthesia is :
**Core Concept**
The question is testing the knowledge of the maximum safe dose of lignocaine (lidocaine) when used with adrenaline (epinephrine) for infiltration anesthesia. This is a critical concept in local anesthesia, as exceeding the maximum dose can lead to systemic toxicity.
**Why the Correct Answer is Right**
Lignocaine with adrenaline is a commonly used combination for infiltration anesthesia. The maximum dose of lignocaine when used with adrenaline is 7 mg/kg without any upper limit on the adrenaline concentration. This is because the vasoconstrictive effect of adrenaline reduces the absorption of lignocaine into the systemic circulation, thereby reducing the risk of systemic toxicity. The maximum dose is based on the lignocaine concentration, and the adrenaline concentration does not affect the maximum dose.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because the maximum dose of lignocaine with adrenaline is not 5 mg/kg. This is a common mistake, as the maximum dose of lignocaine without adrenaline is 4.5 mg/kg.
* **Option B:** This option is incorrect because the maximum dose of lignocaine with adrenaline is not 10 mg/kg. Exceeding this dose can lead to systemic toxicity, including central nervous system and cardiovascular effects.
* **Option C:** This option is incorrect because the maximum dose of lignocaine with adrenaline is not 5 mg/kg with a maximum adrenaline concentration of 1:100,000. The adrenaline concentration does not affect the maximum dose of lignocaine.
**Clinical Pearl / High-Yield Fact**
When using lignocaine with adrenaline for infiltration anesthesia, it is essential to remember that the maximum dose is based on the lignocaine concentration, and the adrenaline concentration does not affect the maximum dose. Always calculate the maximum dose of lignocaine using the patient's weight and the lignocaine concentration.
**Correct Answer: B. 7 mg/kg**