The Role of Lignocaine with Adrenaline in Anesthesia

The combination of lignocaine (also known as lidocaine) with adrenaline (epinephrine) is a widely used practice in medical and dental settings. This article explores the reasons behind this common practice and highlights the key benefits of using both agents together.

How Lignocaine and Adrenaline Work Together

Lignocaine is a local anesthetic that works by blocking sodium channels in neurons, preventing the conduction of electrical impulses. Adrenaline, on the other hand, is a vasoconstrictor that causes the blood vessels to narrow. When lignocaine is administered with adrenaline, the following physiological effects occur:

Prolonged Anesthesia

One of the primary reasons for using lignocaine with adrenaline is to prolong the duration of anesthesia. Adrenaline causes vasoconstriction, which reduces blood flow to the injection site. This significantly delays the absorption of lignocaine into the bloodstream, thus enhancing the local anesthetic effect. This is particularly beneficial for longer surgical procedures where maintaining anesthesia is crucial.

Reduced Systemic Toxicity

Another significant advantage of using adrenaline with lignocaine is the reduction of systemic toxicity. By limiting the amount of lignocaine that enters the systemic circulation, adrenaline minimizes the risk of adverse systemic reactions. This is especially important in cases where high doses of lignocaine are administered, as the risk of toxicity increases with the amount of the drug that enters the bloodstream.

Decreased Bleeding

The vasoconstrictive properties of adrenaline also contribute to reduced bleeding at the surgical site. This is particularly advantageous during surgical procedures where minimal bleeding is required for optimal visibility. Additionally, the pro-coagulant effect of adrenaline assists the clotting process, further reducing bleeding and aiding in surgical precision.

Enhanced Pain Relief

Combining lignocaine and adrenaline can significantly enhance pain relief, making it more effective for painful procedures. The prolonged anesthetic effect and reduction in bleeding contribute to a more comfortable and tolerable experience for the patient.

Practical Considerations and Risks

The use of adrenaline with lignocaine is a common practice in various medical and dental procedures. However, there are certain situations where this combination should be avoided or used with caution:

Blind Infiltration and Hemostasis Identification

While the primary use of adrenaline in local anesthetics is to prolong the duration of effects and reduce bleeding, there is a secondary, rarer use to identify accidental intravenous injection. However, the author personally does not use this practice and has not encountered it in over 33 years of practice. Surgeons they work with do use it, though with varying success and occasional adverse side effects.

Special Cases: Fingers and External Ears

Lignocaine without adrenaline is often preferred for nerve blocks in areas with end arteries, such as the fingers and external ears. In these areas, the risk of ischemia and necrosis due to vasoconstriction is higher, making the addition of adrenaline contraindicated.

In summary, the use of lignocaine with adrenaline is highly beneficial in many surgical and dental procedures due to its ability to prolong anesthesia, reduce systemic toxicity, decrease bleeding, and enhance pain relief. However, its use must be meticulously considered to avoid potential risks and adverse effects. Understanding the underlying mechanisms and practical considerations is essential for safe and effective administration.