A 45-year-old male undergoing laparoscopic cholecystectomy under general anesthesia suddenly develops severe hypotension (BP 60/30 mmHg), tachycardia (HR 130 bpm), and bronchospasm. The most appropriate immediate first-line drug to administer is:

Explanation

This clinical scenario describes acute anaphylaxis, a life-threatening systemic hypersensitivity reaction. Intravenous adrenaline (epinephrine) is the first-line and most critical drug for managing anaphylaxis due to its rapid onset and broad pharmacological effects. It acts on alpha-1 receptors to cause vasoconstriction (increasing blood pressure), beta-1 receptors to improve myocardial contractility and heart rate, and beta-2 receptors to cause bronchodilation. Hydrocortisone (corticosteroid) and chlorpheniramine (antihistamine) are adjunctive therapies that help prevent further mediator release and reduce inflammation, but they are not first-line for acute cardiovascular collapse or bronchospasm. Nebulized salbutamol might help bronchospasm but will not address the severe cardiovascular instability.