Question

Which of the following intravenous anaesthetic agents is safe even if accidentally injected intra-arterially?

• A. Thiopentone
• B. Propofol
• C. Midazolam
• D. Methohexitone

Hint:

Barbiturates and benzodiazepines damage arteries; the lipid-emulsion induction agent does not.

Answer 1

The Correct Option is B

Step 1: The question tests which induction agent will not harm the artery if the cannula is mistakenly placed intra-arterially instead of intravenously.

Step 2: Agents that cause damage share a common feature - they either are strongly alkaline and crystallise (the barbiturates thiopentone and methohexitone) or belong to the high-risk list (benzodiazepines like midazolam). Other notorious offenders include phenothiazines, narcotics and tubocurarine.

Step 3: Propofol is formulated as a lipid emulsion at near-physiological pH and has been documented in standard anaesthesia texts to cause no vascular injury after intra-arterial or extravascular injection. Etomidate behaves similarly.

Step 4: Comparing the four choices, three carry a real risk of arterial damage and ischaemia, leaving propofol as the agent that is safe.

\[\boxed{\text{Propofol}}\]