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Medline ® Abstracts for References 90,91

of 'Anaphylaxis: Emergency treatment'

Time of Onset and Predictors of Biphasic Anaphylactic Reactions: A Systematic Review and Meta-analysis.
Lee S, Bellolio MF, Hess EP, Erwin P, Murad MH, Campbell RL
J Allergy Clin Immunol Pract. 2015 May-Jun;3(3):408-16.e1-2. Epub 2015 Feb 11.
BACKGROUND: A biphasic reaction is a potentially life-threatening recurrence of symptoms after initial resolution of anaphylaxis without re-exposure to the trigger. The infrequent nature of these reactions has made them difficult to study and predict.
OBJECTIVE: The aim of this study was to evaluate the time of onset and predictors of biphasic anaphylactic reactions.
METHOD: Original research studies that described biphasic reactions in case series or cohort studies were included. Studies that did not describe biphasic reactions and case series with less than 2 biphasic reactions were excluded. Data sources included MEDLINE, EMBASE, Web of Science, and Scopus from inception to January 2014 and bibliographies of included articles. Pooled odds ratios (ORs) with 95% confidence intervals (CIs) were calculated for dichotomous variables. Inconsistency among studies was assessed with the I(2) statistic.
RESULTS: Twenty-seven observational studies that enrolled 4114 patients with anaphylaxis and 192 patients with biphasic reactions were included. The median time of symptom onset was 11 (range 0.2 to 72.0) hours. Food as the inciting trigger was associated with decreased risk (pooled OR 0.62, 95% CI: 0.4 to 0.94, I(2) = 0%) and an unknown inciting trigger with increased risk (pooled OR 1.72, 95% CI: 1.0 to 2.95, I(2) = 61%). Initial presentation with hypotension (pooled OR 2.18, 95% CI: 1.14 to 4.15, I(2) = 79%) was also associated with the development of a biphasic reaction.
CONCLUSION: Biphasic anaphylatic reactions were less likely among patients with food as an inciting trigger. Patients who present with hypotension or have an unknown inciting trigger may be at increased risk of a biphasic reaction. Clinicians should tailor observation periods for patients individually based on clinical characteristics.
Department of Emergency Medicine, Mayo Clinic Health System, Mankato, Minn. Electronic address: Lee.Sangil@mayo.edu.
Biphasic anaphylactic reactions: occurrence and mortality.
Rohacek M, Edenhofer H, Bircher A, Bingisser R
Allergy. 2014;69(6):791.
BACKGROUND: Monitoring after complete resolution of anaphylactic reactions is recommended. The aim of this study was to define the occurrence of biphasic - and clinically important biphasic - anaphylactic reactions, the number of transfers to intensive care units (ICU) because of anaphylaxis, and the number of deaths within 10 days of presentation to the emergency department (ED).
METHODS: Clinical records of patients visiting the ED of a tertiary care hospital were analysed retrospectively. Hospital databases, direct contact with patients and caregivers, and the Internet were used to obtain mortality rates.
RESULTS: Of 259 557 ED presentations from February 2001 through to August 2013, 1334 (0.51%) episodes of allergic reactions were detected, and 532 (0.20%) episodes in 495 patients fulfilled the definition of anaphylaxis. In 227 (44.8%) episodes, the length of hospital stay was≥8 h (median 22 h, IQR 16-24). There were 507 uniphasic and 25 (4.5%) biphasic anaphylactic reactions. Twelve (2.3%) were clinically important, including 2 (0.36%) that occurred during hospital stay, one of whom (0.19%) was transferred to ICU for shock. No risk factors for biphasic reactions could be found. Eight patients were lost to follow-up. There were no deaths during the 10-day follow-up.
CONCLUSION: Biphasic anaphylactic reactions, especially clinically important ones, occurred rarely, and no mortality was found, whether the monitoring was for≥8 h or for<8 h. Our study could motivate physicians to consider discharging patients after complete resolution of an anaphylactic reaction and to dispense with prolonged monitoring.
Department of Emergency Medicine, University Hospital Basel, Basel, Switzerland.