Anaesthetic allergy: Overview

Abstract
Rationale: Local anesthesia is a widely used technique for emergency wound closure, with lidocaine among the most commonly employed local anesthetics. Allergic reactions to lidocaine are rare, with anaphylaxis being even more uncommon.

Patient concerns and diagnosis: This report describes a 72-year-old male patient who presented with a right foot injury and underwent wound suturing under lidocaine local anesthesia. Although the procedure went smoothly, the patient developed dizziness, cold sweats, hypotension, and bradycardia 30 minutes later, leading to a diagnosis of anaphylaxis due to lidocaine allergy.

Interventions and outcomes: Immediate treatment for anaphylactic shock was initiated, including intramuscular administration of adrenaline, fluid resuscitation, anti-inflammatory agents, antihistamines, oxygen therapy, and symptomatic supportive care. Within 20 minutes of active treatment, the patient's symptoms were effectively controlled. The patient was safely discharged after 24 hours of observation. Health education was provided to enhance self-management skills.

Lessons: Although rare, anaphylaxis induced by lidocaine can be fatal. Early recognition, prompt intervention, thorough preoperative assessment, and careful postoperative monitoring are critical to improving survival rates.

Abstract
Prescription-event monitoring (PEM) is the current gold standard for determining the risk of rare drug side-effects and comparing the risk between agents; however, spontaneous or prompted reporting schemes have low case-detection rates and exposure may be difficult to estimate. A novel method is described that allows a comparative adverse event rate between two drugs to be estimated-based on patterns of cross-reactivity-requiring only a sample of cases and no direct knowledge of drug exposure rates. Agreement was compared between the novel method and historical estimates of risk using PEM for comparative risk of rocuronium versus vecuronium anaphylaxis. The novel method was applied to a sample of patients investigated by the Western Australian Anaesthetic Drug Reaction Clinic over a 21-year period. Relative population exposure was estimated from the number of patients with either rocuronium or vecuronium anaphylaxis subsequently shown to be reactive on skin testing to both agents. This was used to correct the total number of cases of hypersensitivity triggered by each agent. Measures of spread were by bootstrap sampling. Historical estimates were gathered by literature review. Additional comparisons of agreement between estimates made by the novel method and PEM were made using cross-reactivity data and PEM rates reported in the literature. There was agreement between estimates of comparative anaphylaxis risk between the novel method and PEM. Two-hundred and twenty-eight cases of anaphylaxis were observed, 89% caused by rocuronium. Patients reactive to both agents were more likely to be female, and had a higher acute mast cell tryptase level. Patients with a history of rocuronium anaphylaxis were more likely to be reactive to one agent only (69% vs. 33%, P < 0.01). It was estimated that rocuronium was prescribed 3.9 times more frequently than vecuronium. When the observed proportion of cases was corrected for exposure rate, the risk of rocuronium anaphylaxis was 2.2 times that of vecuronium (95% confidence interval 1.7 to 2.8). The median risk from historical estimates was 4.7 times, while the previous PEM estimate in Western Australian was 3.0 times. Using a subgroup of patients susceptible to the same side-effect of two drugs, the relative exposure rate and corrected comparative risk of an adverse effect can be estimated for a population. Using this technique, which requires assessment only of cases to estimate relative exposure rates, we have estimated that the risk of anaphylaxis from rocuronium to be 2.2 times that of vecuronium in Western Australia.

Abstract
To avoid inhalational anesthetics, total intravenous anesthesia (TIVA) is required in patients with a predisposition to malignant hyperthermia (MH). However, propofol, which is frequently used, may be avoided in patients with egg allergies because of the contraindications in the drug information. Furthermore, some patients may not consent to the use of propofol. We report a case of TIVA using midazolam and dexmedetomidine as substitutes for propofol in a pediatric patient with egg allergy and a predisposition to MH. A 10-year-old boy was scheduled to undergo perforated drainage of an epidural abscess. He had egg allergy, and his uncle had been diagnosed with MH. He also developed a generalized drug eruption caused by antibiotics. Concerned about allergic reactions, he and his parents did not consent to administrating propofol. The patient's perioperative course was uneventful. The combination of midazolam and dexmedetomidine may be a useful option as substitutes for propofol.