In perioperative anaphylaxis, what is the first-line treatment?

• A. Administer intramuscular epinephrine
• B. Administer intravenous antibiotics
• C. Increase inhaled anesthetic
• D. Provide warm blankets

Answer: (A)

The immediate action in perioperative anaphylaxis is administering epinephrine intramuscularly. This medicine tackles the three life-threatening features of anaphylaxis: airway edema and bronchospasm, and shock from widespread vasodilation. Epinephrine’s alpha-adrenergic effects constrict dilated blood vessels to raise blood pressure and reduce mucosal swelling; its beta-adrenergic effects improve heart rate and contractility to maintain perfusion; its beta-2 effects relax bronchial smooth muscle and help limit further mediator release from mast cells. Giving it by intramuscular injection into the mid–outer thigh provides rapid, reliable absorption and is safer and quicker in an emergency than starting with an IV dose, especially before IV access is secure. A typical approach is a dose of about 0.01 mg/kg (up to 0.5 mg), with repetition as needed every several minutes based on response. If the situation worsens or IV access is already established, IV epinephrine can be used with careful monitoring, but intramuscular epinephrine remains the first-line treatment. Supportive measures like securing the airway, providing oxygen, and establishing IV fluids are important adjuncts, while antibiotics, increasing inhaled anesthetic, or warming blankets do not address the immediate life-threatening mechanisms of the reaction.