Question

High spinal anaesthesia is associated with which of the following haemodynamic changes?

• A. Decreased blood pressure and decreased heart rate
• B. Increased blood pressure and decreased heart rate
• C. Decreased blood pressure and increased heart rate
• D. Increased blood pressure and increased heart rate

Hint:

High block knocks out the T1-T4 cardiac accelerators, so both BP and heart rate fall.

Answer 1

The Correct Option is A

Step 1: Spinal anaesthesia blocks the sympathetic fibres that leave the spinal cord. The thoracolumbar sympathetic outflow controls vascular tone and, at the upper thoracic level, supplies the cardiac accelerator fibres (T1 to T4).

Step 2: When the block rises high, into the upper thoracic and cervical levels, widespread sympathetic blockade causes vasodilatation and pooling of blood, which lowers venous return and drops the blood pressure (hypotension).

Step 3: A high block also paralyses the cardiac accelerator fibres (T1 to T4), removing sympathetic drive to the heart and leaving unopposed vagal tone. This produces bradycardia, that is a decreased heart rate.

Step 4: Therefore high spinal anaesthesia gives both decreased blood pressure and decreased heart rate, along with respiratory insufficiency. Options showing increased BP or increased heart rate are incorrect.