Question

Anaesthetic agents with vasoconstrictor properties are contraindicated in?

• A. Finger block
• B. Spinal block
• C. Epidural block
• D. Surface anaesthesia for bronchoscopy

Hint:

Think of regions supplied by end arteries with no collateral flow.

Answer 1

The Correct Option is A

Step 1: Recall why vasoconstrictors are added.
Adrenaline (epinephrine) is added to local anaesthetics to cause local vasoconstriction. This slows systemic absorption, prolongs the block, reduces local anaesthetic peak plasma levels and limits bleeding.

Step 2: Identify the danger.
Vasoconstriction is hazardous where the tissue is supplied by end arteries without collateral flow. Profound vasoconstriction there can cause ischaemia and gangrene.

Step 3: Apply to a finger block.
The digits (fingers and toes) are supplied by end arteries. Adding a vasoconstrictor to a digital (ring) block risks ischaemic necrosis of the digit, so adrenaline-containing solutions are classically contraindicated in finger blocks. The same caution applies to the toes, penis, ear lobe and nose tip.

Step 4: Exclude the others.
Spinal and epidural blocks and surface anaesthesia of the airway are not supplied by isolated end arteries in the same vulnerable way, so a vasoconstrictor is not contraindicated there on the grounds of end-artery ischaemia.

Step 5: Conclusion.
Correct answer: Finger block.