Immediate Perioperative Hypersensitivity and Anaphylaxis in Neuroanesthesia Practice: A Focused Review

Perioperative hypersensitivity reactions are uncommon but potentially catastrophic. Neurosurgical and spine patients are especially vulnerable, as the injured brain and spinal cord tolerate anaphylaxis-induced hypotension poorly, cerebral and spinal perfusion may fall precipitously, and draping of the head and torso may obscure cutaneous signs. These procedures also rely heavily on topical hemostatic agents. National audits estimate the incidence of perioperative anaphylaxis at roughly 1 in 5000 to 10,000 anesthetics, but estimates vary geographically. No study has reported a denominator-based incidence confined to neurosurgery, leaving the true burden uncharacterized for this surgical specialty. This focused review summarizes the agents, mechanisms, and perioperative implications of immediate hypersensitivity and anaphylaxis relevant to neuroanesthesia. Immediate reactions are immunologic (IgE-mediated, or IgG- and complement-mediated) or nonimmunologic (direct mast-cell activation) but converge on mast-cell and basophil mediator release, which renders their presentations largely indistinguishable. We examine agents of relevance to neurosurgery, including neuromuscular blocking agents, cefazolin and other β-lactams, chlorhexidine, sugammadex, gelatin-based and other hemostatic agents, protamine, tranexamic acid, fluorescent and dye agents, and iodinated contrast media-alongside their mechanisms and safer alternatives. Management follows international consensus recommendations centered on prompt epinephrine administration and fluid resuscitation titrated to severity. Antihistamines and corticosteroids are useful adjuncts but should not delay resuscitation. Improved outcomes depend on greater awareness, careful allergy assessment and appropriate de-labeling, surgical-anesthesia communication, and wider access to testing and dedicated surveillance.