A patient's blood pressure rises sharply immediately after local anaesthetic administration under intravenous sedation. What is the most likely cause?

Correct answer: C. Epinephrine in the local anaesthetic

• A. Fentanyl also lowers blood pressure and heart rate. It is a common cause of hypotension and bradycardia under sedation, not hypertension.
• B. Midazolam LOWERS blood pressure through venodilation and mild myocardial depression. It cannot explain a rise.
• C. CORRECT. Epinephrine produces a transient rise in systolic pressure and heart rate, and the effect is pronounced with inadvertent intravascular injection or in a patient taking a non-selective beta blocker, where unopposed alpha stimulation can produce marked hypertension with reflex bradycardia. The timing — immediately after injection — points directly to it.
• D. Lidocaine at clinical doses is a myocardial depressant and would tend to lower rather than raise blood pressure.

Note: The friend was right. Both sedatives listed are hypotensive agents. Anything producing an acute pressure SPIKE immediately after injection is epinephrine — or, less commonly, inadequate anaesthesia causing an endogenous catecholamine surge from pain.