Which IV bolus amount is commonly recommended prior to spinal anesthesia to reduce hypotension risk?

• A. IV fluid bolus (500-1000 mL)
• B. 100-200 mL
• C. 2000-2500 mL
• D. 0 mL

Answer: (A)

Spinal anesthesia can cause sudden vasodilation and pooling of blood in the peripheral vessels, which lowers venous return to the heart and can lead to hypotension. Giving an IV fluid bolus beforehand increases intravascular volume, boosts preload, and helps maintain cardiac output when the sympathetic block occurs. In adults, a common preload is about 500–1000 mL of crystalloid solution. This amount is enough to improve venous return without risking fluid overload. Very small volumes (like 100–200 mL) are often insufficient to prevent hypotension, while very large volumes (2000–2500 mL) increase the risk of fluid overload and related complications. Zero volume would not counteract the expected drop in blood pressure.