Lignocaine and adrenaline not used for repair of injury to digitalis because:

AIIMS Delhi NO- 2019

Pharmacology

Medium

Appeared in: AIIMS Delhi NO- 2019

Explanation

Adrenaline (epinephrine) is a powerful vasoconstrictor, meaning it narrows blood vessels.
Digits (fingers and toes) have an 'end-arterial' blood supply, meaning there is limited collateral circulation.
Injecting adrenaline in these areas can severely restrict blood flow, leading to ischemia (lack of oxygen) and potentially irreversible tissue death (necrosis or gangrene).
This makes the combination of lignocaine with adrenaline contraindicated for procedures on digits.

Option B: This statement is factually opposite to the intended effect. Adrenaline is added to lignocaine specifically to prolong its anesthetic effect by slowing its systemic absorption.
Option C: While systemic absorption of adrenaline can cause systemic effects (like tachycardia or hypertension), the primary and most dangerous reason for avoiding it in digits is its local vasoconstrictive effect leading to tissue ischemia.
Option D: This is factually incorrect. Adrenaline's primary action on these blood vessels is potent vasoconstriction (narrowing), not vasodilation (widening).

Clinical Relevance

Nursing practice connection: Knowing Contraindications of vasoconstrictors with local anesthetics helps nurses interpret findings accurately and avoid errors in routine assessment, medication administration, and patient teaching.
Patient Safety: A nurse assisting with or performing a procedure must be vigilant about the medications being used. Questioning the use of lignocaine with adrenaline for a finger or toe laceration is a critical patient safety intervention that can prevent devastating outcomes like amputation.
Medication Knowledge: This highlights the importance of not just knowing what a drug does, but also where and when it is unsafe to use. The 'where' (body part) is as important as the 'what' (drug).
What if? Scenario: If the laceration were on the forearm instead of a finger, the combination of lignocaine and adrenaline would be appropriate and beneficial. It would provide longer-lasting anesthesia and a less bloody field for suturing, as the forearm has a rich collateral blood supply that is not compromised by local vasoconstriction.

How to Approach the Question

First, identify the key terms in the question: 'Lignocaine', 'adrenaline', and 'digitalis'. Recognize that 'digitalis' is likely a typo for 'digits' (fingers/toes).
Recall the primary pharmacological action of adrenaline (epinephrine) when used with a local anesthetic: it's a vasoconstrictor.
Consider the unique anatomy of digits: they have an end-arterial blood supply.
Connect the pharmacology to the anatomy: What happens when you use a potent vasoconstrictor in an area with a limited blood supply?
Evaluate the options based on this reasoning. Option A directly describes the risk of vasoconstriction leading to ischemia and necrosis.
Eliminate the other options: Option B is the opposite of the truth, Option D is the opposite of adrenaline's action, and Option C describes a secondary concern, not the primary contraindication.

Concept Tested & Keywords

Concept Tested: Contraindications of vasoconstrictors with local anesthetics
Stem keywords: Lignocaine, adrenaline, injury, digitalis, repair
Lead-in keywords: because
Clinical cues: The question contains a common typo, 'digitalis' for 'digits', which is crucial to recognize for correct interpretation.
Negative lead-in flag: false

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E6 Pharmacology Nurses Shanbhag 3e p. 146-148

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