Question

A 5 year old child is scheduled for strabismus (squint) correction. Induction of anesthesia is uneventful. After conjunctival incision, as the surgeon grasps the medial rectus, the anesthesiologist looks at the cardiac monitor. Why do you think he did that?

• A. He wanted to check the depth of anaesthesia.
• B. He wanted to be sure that the blood pressure did not fall.
• C. He wanted to see if there was an oculocardiac reflex.
• D. He wanted to make sure there were no ventricular dysrhythmias which normally accompany incision.

Hint:

Traction on the medial rectus can trigger the oculocardiac (Aschner) reflex, causing sudden bradycardia.

Answer 1

The Correct Option is C

Step 1: Understanding the Question:
The surgeon is pulling on the medial rectus muscle during a squint (strabismus) surgery in a child, and the anesthesiologist immediately checks the cardiac monitor. We need to know what specific event this traction can trigger.

Step 2: Key Concept:
Traction on any extraocular muscle, especially the medial rectus, can trigger the oculocardiac reflex, also called the Aschner reflex or trigeminovagal reflex. Pulling on the eyeball or its muscles sends a signal through the ophthalmic branch of the trigeminal nerve, and the brainstem replies through the vagus nerve to slow the heart.

Step 3: Detailed Explanation:
The afferent, sensing, limb of this reflex is the trigeminal nerve, carrying the signal from the eye to the brainstem.
The efferent, response, limb is the vagus nerve, which slows the heart rate and can cause bradycardia, junctional rhythm, or even asystole in severe cases.
This reflex is common in children undergoing strabismus surgery because the medial rectus is pulled directly, and children have higher vagal tone than adults.
The anesthesiologist watches the monitor right when traction starts because the reflex can appear within seconds of the muscle being pulled, so early recognition lets the team ask the surgeon to release traction and give atropine if needed.
Checking depth of anaesthesia, watching for a blood pressure drop, or expecting ventricular dysrhythmias from the skin incision are not the specific, well known response to extraocular muscle traction, the oculocardiac reflex is.

Step 4: Final Answer:
The anesthesiologist looked at the monitor because pulling on the medial rectus can set off the oculocardiac reflex, producing sudden bradycardia or other arrhythmias.