Allergic reactions to anesthesia

Life-threatening hypersensitivity reactions occurring during surgery and anesthesia is around 1 in 10,000 procedures.^[1] More recent studies have reported a broader range, that is, 1 in 386 to 1 in 13,000 procedures result in a hypersensitivity reaction.^[2] Severe allergic reactions to anesthetic medications are rare and are usually attributable to factors other than the anesthetic. Neuromuscular blocking agents, natural rubber latex, and antibiotics are the most common triggers of a serious allergic reaction during surgery.^[3] The reported mortality rate from these reactions ranges between 3-9%.^[4]

Anesthesia hypersensitivity
Topical hypersensitivity reaction from topical anesthesia
Specialty	Anesthesiology
Symptoms	Low blood pressure, hives, wheezing, swelling
Diagnostic method	Clinical diagnosis
Treatment	Epinephrine, withdrawal of offending agent, airway management
Frequency	1 in 10,000 procedures

Successful immediate treatment requires prompt recognition by the attending anesthetist, or in the United States, the attending anesthesiologist or nurse anesthetist. Anesthetists are trained to identify signs if an allergic reaction is occurring. The identification of a reaction is made by the recognition of issues including low blood pressure, hives, wheezing, rash, swelling around the eyes or in the mouth and throat, and other breathing difficulties.^[5] Adrenaline (epinephrine) remains the mainstay of treatment, with corticosteroids and antihistamines providing limited benefit in the acute situation.

Risk Factors and Mechanisms

Certain factors can increase a patient's sensitivity and incline them to a reaction. Patients with a history of drug allergies are at a higher risk of resulting in hypersensitivity reactions under anesthesia. ^[6]

Most anesthetic related allergic reactions are IgE-mediated. These antibodies activate mast cells and basophils, which lead to the release of histamine along with other inflammatory mediators. This immune response results in tissues to swell, a difficulty in breathing, and bronchospasm. ^[6]

Other risk factors include past exposure to other anesthetic agents, genetics, and underlying medical conditions such as asthma or eczema. Reactions may also occur on the first exposure if the patient has been affected with similarly structured substances.

Recognition and Management

Early recognition of an allergic reaction during anesthesia is crucial as hypersensitivity reactions can progress rapidly. The attending anesthesiologist or nurse anesthetist monitors for clinical signs the whole time anesthesia is being administered. A sudden drop in blood pressure, widespread rash, and airway or facial swelling are examples to what they are looking for. The most common feature is cardiovascular collapse and is often the first indication of a severe reaction. ^[7]

Future Avoidance

Subsequent investigation aims to determine the responsible agent to allow its future avoidance. Skin testing is often useful to identify potentially cross-reactive compounds and appropriate therapeutic alternatives. This is done weeks after the initial reaction to allow the immune system to reset itself. However, skin testing can be misleading in giving false positive and false negative results.

Anaphylaxis during anesthesia

Although complications during anesthesia are rare, potentially life-threatening consequences may occur if an anaphylactic reaction develops. The severity of the reaction whilst under anesthesia is because the anesthetist is only made aware of the allergy when it is severe enough to compromise the cardiovascular system and the respiratory system. At this stage, there is little time to manage the situation and recognize the severity of the condition.^[8]

The immediate management of the issue consists of three processes:

• The withdrawal of the substances

• Interrupting the effects of the preformed substances released in response to toxin presentation
• Prevention of further substance release

Since the full withdrawal of the offending substance is near impossible, the administration of adrenaline is the main treatment to counteract the effects. Once the patient is stable they will need close observation for 24 hours.^[8]