This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Anaesthesia
The most effective method to prevent hypotension during spinal anaesthesia is 
Select and explain. 
A. Preloading with crystalloids, B. Metanephrine, C. Dopamine, D. Tredelenberg's position
A: Preloading with crystalloids
Answer: A: Preloading with crystalloids 
Explanation: Here hypotension is due to block of sympathetic vasoconstrictor out flow to blood vessels resulting in venous pooling and a decreased return to hea.