A vasopressor agent[1] is any medication that tends to raise reduced blood pressure.[2] Some antihypotensive drugs act as vasoconstrictors to increase total peripheral resistance, other sensitize adrenoreceptors to catecholamines - glucocorticoids, and the third class increase cardiac output - dopamine, dobutamine.
If hypotension is due to loss of blood then preparations increasing volume of blood circulation -- particularly blood products (PRBC) but also plasma-substituting solutions, colloid solutions, crystalloid solutions (salt solutions).[3] will raise the blood pressure without any direct vasopressor activity. Other causes of either absolute (dehydration, loss of plasma via wound/burns) or relative (3rd space losses) vascular volume depletion also respond, although blood products are only indicated if significantly anemic.
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