A patient develops severe anaphylaxis during anesthesia and remains hypotensive despite repeated doses of intravenous adrenaline and fluid resuscitation. Which of the following agents might be considered as an adjunctive therapy in this refractory situation, especially if the patient is on beta-blockers?

Explanation

In cases of refractory anaphylaxis, where hypotension persists despite adequate adrenaline and fluid administration, several adjunctive therapies can be considered. Glucagon is particularly useful in patients on beta-blockers, as it bypasses beta-adrenergic receptors to increase intracellular cAMP and myocardial contractility, thereby improving cardiac output and blood pressure. Vasopressin can be used for its potent vasoconstrictive effects, especially in distributive shock, by acting on V1 receptors. Methylene blue is an emerging therapy that inhibits nitric oxide synthase and guanylate cyclase, thereby reducing nitric oxide-mediated vasodilation and improving vascular tone in severe, refractory vasodilatory shock, including anaphylaxis. Therefore, all these agents may be considered in refractory cases.