Vasopressor of choice in hypotension produced during sub-arachnoidblock
**Core Concept**
The management of hypotension during subarachnoid block involves the use of vasopressors to increase peripheral vascular resistance and maintain cerebral perfusion pressure. The ideal vasopressor should have a rapid onset of action, be easily titratable, and have minimal systemic effects.
**Why the Correct Answer is Right**
During subarachnoid block, the sympathetic blockade can lead to vasodilation and hypotension. **Ephedrine** is a vasopressor of choice in this scenario because it works through a unique mechanism that involves the release of norepinephrine from the nerve terminals, as well as direct vasoconstriction. Ephedrine also has a rapid onset of action, making it ideal for acute hypotension management. Additionally, ephedrine has a more favorable effect on cardiac output compared to other vasopressors, which is beneficial during subarachnoid block.
**Why Each Wrong Option is Incorrect**
**Option A:** **Noradrenaline** is a potent vasopressor but is not the first-line choice for hypotension during subarachnoid block due to its potential to cause tachycardia and increased systemic vascular resistance.
**Option B:** **Adrenaline** is a strong vasopressor but is not typically used for hypotension during subarachnoid block due to its potential to cause arrhythmias and increased myocardial oxygen demand.
**Option C:** **Phentolamine** is an alpha-adrenergic antagonist that would actually worsen hypotension during subarachnoid block, making it an incorrect choice.
**Clinical Pearl / High-Yield Fact**
Ephedrine is a unique vasopressor that works through both direct and indirect mechanisms, making it an effective choice for managing hypotension during subarachnoid block.
**Correct Answer: C. Phentolamine**