Final answer:
The statement that adrenaline causes tissue acidosis at the site of epidural injection with a local anaesthetic is NOT true. Adrenaline prolongs the action of local anesthetics like bupivacaine through vasoconstriction but does not cause acidosis.
Step-by-step explanation:
Regarding the addition of adrenaline to a local anaesthetic administered epidurally, the statement that is NOT true is that it causes tissue acidosis at the site of injection. When adrenaline is added to a local anesthetic like bupivacaine, it causes vasoconstriction, which limits blood flow to the area, thereby prolonging the duration of action of the local anaesthetic. However, adrenaline does not cause tissue acidosis; instead, by reducing blood flow, it may reduce the clearance of local anesthetic, leading to a prolonged effect. The ability of adrenaline to induce vasoconstriction helps to maintain a higher concentration of the anesthetic at the nerve blockade site, enhancing and prolonging the action of the anesthetic.
Local anesthetics such as lidocaine work by blocking voltage-gated sodium channels, preventing the initiation and transmission of nerve impulses that convey sensation, including pain. As these drugs are reversible, normal nerve function returns once the medication is metabolized or dispersed.