By Ed Sutton, MD, Alex Johnson, CRNA, Sharon Stroud, CRNA
Case Report: The patient is a 69-year-old male with a history of daily tobacco use, COPD, and essential tremor. Medications included propranolol and Topamax. The patient had no documented food or pharmacologic allergies. No surgical history was noted aside from a colonoscopy with a history of polyps in 2002, with no information on the sedative agent used. The patient was classified as ASA II physical status.
On the day of the colonoscopy, the patient was monitored according to ASA standards and given 250 mg of propofol IV incrementally over 19 minutes. Oxygen supplementation was provided at 2 L/min via nasal cannula. The patient maintained stable vital signs throughout the procedure, with end-of-case vital signs of BP 124/68, HR 98 (NSR), RR 22, SpO₂ 96%, and ETCO₂ 37 mm Hg.
Upon arrival in the PACU, the patient was lethargic but responsive, complaining of severe itching and nausea. Vital signs at that time were BP 71/41, HR 35 (sinus bradycardia), RR 18, and SpO₂ 88%. The patient exhibited a diffuse maculopapular deep red rash across the chest, axilla, and groin. Skin was described as diaphoretic and gray. He was immediately placed on a nonrebreather mask at 10 L/min and treated with ephedrine 10 mg, increased IV fluids, diphenhydramine 25 mg, famotidine 20 mg, and Solu-Medrol 125 mg. Vital signs quickly normalized. The patient was monitored for three hours in the PACU, with moderate improvement of the rash, and was discharged home with instructions to call 911 if symptoms returned or worsened, and to follow up with an allergist within 2–3 weeks.
Anaphylaxis Physiologic Review:
Type I immune-mediated symptoms and anaphylaxis occur with the production of IgE antibodies after exposure to a foreign substance such as food, drugs, pet dander, pollen, or spores. Symptoms may remain localized (e.g., hay fever, asthma, hives, eczema) or become systemic with profound circulatory compromise. After initial exposure, susceptible patients form IgE antibodies that bind to tissue mast cells and circulating basophils. Upon re-exposure, IgE-mediated activation leads to mast cell and basophil degranulation, releasing histamine, proteases, leukotrienes, prostaglandins, and cytokines (including IL-1 through IL-6 and TNF), resulting in inflammation, vasodilation, and tissue injury.
Non–immune-mediated anaphylaxis, also referred to as anaphylactoid reactions, results from direct mast cell or basophil degranulation without IgE involvement. Common perioperative examples include localized itching and flushing with fentanyl, hypotension with vancomycin, and reactions to radiocontrast agents. These reactions may occur with first exposure and can be just as severe as immune-mediated anaphylaxis.
Propofol as an Inducing Agent of Anaphylaxis:
Propofol (2,6-di-isopropylphenol) can cause mild allergic-type symptoms as well as systemic anaphylaxis. Pruritus following deep sedation with propofol is commonly observed. The estimated incidence of hypersensitivity is approximately 1 in 60,000, with true anaphylaxis being rare. The propofol molecule contains two allergenic sites: the isopropyl side chains and the phenolic ring. Patients who develop reactions upon first exposure may have preexisting sensitivities to these components, which are found in various dermatologic products and lipid formulations. Providers should inquire about prior reactions to cosmetics or total parenteral nutrition when evaluating potential propofol allergy.
Propofol is formulated in soybean oil, egg lecithin, and glycerol. After more than 30 years of clinical use and allergy testing, evidence suggests that allergic reactions are not related to soy or egg allergy, but rather to the propofol molecule itself or its lipid formulation. These reactions may also be confounded by exposure to other highly allergenic agents such as antibiotics, neuromuscular blockers, local anesthetics, narcotics, and sugammadex. The American Academy of Allergy, Asthma & Immunology (AAAAI) has stated that patients with soy or egg allergies may safely receive propofol without special precautions. Despite this guidance, FDA-approved labeling continues to list egg and soy allergy as contraindications. Therefore, caution is advised in highly allergy-prone patients, with thorough discussion and documentation during informed consent.
