Question

During surgery for aortic arch aneurysm under deep hypothermic circulatory arrest, which of the following anaesthetic agents, when administered prior to circulatory arrest, also provides cerebral protection?

• A. Etomidate
• B. Thiopental sodium
• C. Propofol
• D. Ketamine

Hint:

Barbiturates cut brain oxygen use and cause burst suppression, the classic protective step before circulatory arrest.

Answer 1

The Correct Option is B

Step 1: Understanding the Question:
Deep hypothermic circulatory arrest lets a surgeon stop all blood flow for a short window while repairing the aortic arch. Along with cooling the body, certain intravenous anaesthetic agents are given just before the arrest to add a further layer of brain protection, and we need to name that drug.

Step 2: Key Formula or Approach:
Barbiturates such as thiopental sodium cut the brain's oxygen demand and can push the EEG into burst suppression, meaning the brain runs on far less energy and tolerates the no flow period better. This is the classic drug based add on to hypothermia used before circulatory arrest in aortic arch surgery.

Step 3: Detailed Explanation:
Etomidate does lower cerebral oxygen use, but it also suppresses the adrenal glands even after a single dose, which is a real risk in a long, high stress cardiac operation. It is not the standard drug chosen for this specific protective role.
Thiopental sodium lowers cerebral oxygen consumption and produces burst suppression, and it has long been the reference drug given before circulatory arrest in aortic arch surgery, often paired with cooling and sometimes mannitol. This matches what the question is asking for.
Propofol can also lower cerebral metabolism, but it drops blood pressure more than thiopental does, which is unwelcome right before a period with no circulation in patients who are already haemodynamically fragile from cardiac surgery.
Ketamine raises cerebral blood flow and metabolic rate in ordinary use, the opposite of what is wanted here, so it is not a protective choice.

Step 4: Final Answer:
The agent classically given before circulatory arrest for cerebral protection is thiopental sodium, option 2.
Note on the answer key: the original paper marks etomidate with a question mark, showing doubt in its own key. Anaesthesia literature on aortic arch surgery consistently names thiopental sodium, not etomidate, as the drug given for cerebral protection before circulatory arrest, so this answer follows thiopental sodium.