Vasomotor reversal phenomenon after administration of an a adrenergic blocker is seen with
**Core Concept**
The vasomotor reversal phenomenon is a clinical observation where the administration of a vasodilator or an a-adrenergic blocker leads to an increase in blood pressure due to the unopposed action of sympathetic vasoconstrictor tone on the blood vessels. This phenomenon is closely related to the concept of a-adrenergic blockade and its effects on the autonomic nervous system's regulation of blood pressure.
**Why the Correct Answer is Right**
The vasomotor reversal phenomenon occurs due to the blockade of a-adrenergic receptors, which are responsible for mediating the vasoconstrictive effects of sympathetic nerve stimulation. When a-adrenergic blockers are administered, the vasoconstrictive tone is reduced, leading to vasodilation. However, this vasodilation is not uniform and can be countered by the unopposed action of sympathetic vasoconstrictor tone, leading to an increase in blood pressure. This phenomenon is particularly relevant in clinical settings where a-adrenergic blockers are used to manage hypertension.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not accurately describe the vasomotor reversal phenomenon. The phenomenon is not related to the blockade of b-adrenergic receptors, which are primarily involved in mediating the effects of catecholamines on the heart.
**Option B:** This option is incorrect because it does not accurately describe the vasomotor reversal phenomenon. The phenomenon is not related to the administration of vasopressors, which are used to increase blood pressure.
**Option C:** This option is incorrect because it does not accurately describe the vasomotor reversal phenomenon. The phenomenon is not related to the blockade of alpha-2 adrenergic receptors, which are primarily involved in mediating the feedback inhibition of sympathetic nerve activity.
**Option D:** This option is incorrect because it does not accurately describe the vasomotor reversal phenomenon. The phenomenon is not related to the administration of a-adrenergic agonists, which would be expected to increase blood pressure.
**Clinical Pearl / High-Yield Fact**
The vasomotor reversal phenomenon is a critical concept in understanding the clinical effects of a-adrenergic blockers and is relevant to the management of hypertension and other cardiovascular disorders. It highlights the importance of carefully titrating a-adrenergic blockers to avoid hypotension and ensure optimal blood pressure control.
**Correct Answer:** C. Alpha-2 adrenergic agonists.