Question:medium
High spinal anaesthesia is associated with which of the following haemodynamic changes?
High spinal anaesthesia is associated with which of the following haemodynamic changes?
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High block knocks out the T1-T4 cardiac accelerators, so both BP and heart rate fall.
Updated On: Jun 24, 2026
- Decreased blood pressure and decreased heart rate
- Increased blood pressure and decreased heart rate
- Decreased blood pressure and increased heart rate
- Increased blood pressure and increased heart rate
Show Solution
The Correct Option is A
Solution and Explanation
Step 1: The central mechanism is loss of sympathetic tone. A spinal block is essentially a chemical sympathectomy, and the height of the block decides how much of the sympathetic chain is silenced.
Step 2: Loss of vasomotor tone in the splanchnic and lower-body vessels causes pooling and a fall in systemic vascular resistance and preload, so arterial pressure drops. Hypotension is in fact the commonest intraoperative complication of spinal anaesthesia.
Step 3: When the level climbs above T4 it knocks out the cardioaccelerator fibres. With sympathetic input gone and vagal tone now unopposed, the heart slows, giving bradycardia rather than a compensatory tachycardia.
Step 4: Combining the two effects, the picture is hypotension plus bradycardia (and impaired respiration if it ascends to cervical roots). Hence both pressure and rate go down.
\[\boxed{\text{Decreased blood pressure and decreased heart rate}}\]
Step 2: Loss of vasomotor tone in the splanchnic and lower-body vessels causes pooling and a fall in systemic vascular resistance and preload, so arterial pressure drops. Hypotension is in fact the commonest intraoperative complication of spinal anaesthesia.
Step 3: When the level climbs above T4 it knocks out the cardioaccelerator fibres. With sympathetic input gone and vagal tone now unopposed, the heart slows, giving bradycardia rather than a compensatory tachycardia.
Step 4: Combining the two effects, the picture is hypotension plus bradycardia (and impaired respiration if it ascends to cervical roots). Hence both pressure and rate go down.
\[\boxed{\text{Decreased blood pressure and decreased heart rate}}\]
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