Allergic-like contrast reactions in the ED: Incidence, management, and impact on patient disposition

Impact of iodinated contrast allergies on emergency department operations

OBJECTIVES

Adverse reactions to intravenous (IV) iodinated contrast media are classified by the American College of Radiology (ACR) Manual on Contrast Media as either allergic-like (ALR) or physiologic (PR). Premedication may be beneficial for patients who have prior documented mild or moderate ALR. We sought to perform a retrospective analysis of patients who received computed tomography (CT) imaging in our emergency department (ED) to establish whether listing of an iodinated contrast media allergy results in a delay in care, increases the use of non-contrast studies, and to quantify the incidence of listing iodinated contrast allergies which do not necessitate premedication.

METHODS

We performed a retrospective analysis of CT scans performed in our academic medical center ED during a 6-month period. There were 12,737 unique patients of whom 454 patients had a listed iodinated contrast allergy. Of these, 106 received IV contrast and were categorized as to whether premedication was necessary. Descriptive statistics were used to evaluate patient demographics, clinical characteristics, and operational outcomes. A multivariate linear regression model was used to predict time from order to start (OTS time) of CT imaging while controlling for co-variates.

RESULTS

Non-allergic patients underwent contrast-enhanced CT imaging at a significantly higher rate than allergic patients (45.9% vs. 23.3%, p < 0.01). The OTS time for allergic patients who underwent contrast-enhanced CT imaging was 360 min and significantly longer than the OTS time for non-allergic patients who underwent contrast-enhanced CT imaging (118 min, p < 0.001). Of the 106 allergic patients who underwent contrast-enhanced CT imaging, 27 (25.5%) did not meet ACR criteria for necessitating premedication. The average OTS time for these 27 patients was 296 min, significantly longer than the OTS for non-allergic patients (118 min, p < 0.01) and did not differ from the OTS time for the 79 patients who did meet premedication criteria (382 min, p = 0.23). A multivariate linear regression showed that OTS time was significantly longer if a contrast allergy was present (p < 0.001).

CONCLUSION

A chart-documented iodinated contrast allergy resulted in a significant increase in time to obtain a contrast-enhanced CT study. This delay persisted among patients who did not meet ACR criteria for premedication. Appropriately deferring premedication could potentially reduce the ED length-of-stay by over 4 h for these patients.

Combining Failure Modes and Effects Analysis and Cause-Effect Analysis: A Novel Method of Risk Analysis to Reduce Anaphylaxis Due to Contrast Media

BACKGROUND

Contrast media agents are essential for computed tomography-based diagnoses. However, they can cause fatal adverse effects such as anaphylaxis in patients. Although it is rare, the chances of anaphylaxis increase with the number of examinations. Thus, we aimed to design a quality-improvement initiative to reduce patient risk to these agents.

METHODS

We analysed computed tomography processes using contrast iodine in a tertiary-care academic hospital that performs approximately 14,000 computed tomography scans per year in Japan. We applied a combination of failure modes and effects analysis and cause-effect analysis to reduce the risk of patients developing allergic reactions to iodine-based contrast agents during computed tomography imaging.

RESULTS

Our multidisciplinary team comprising seven professionals analysed the data and designed a 56-process flowchart of computed tomography imaging with iodine. We obtained 177 failure modes, of which 15 had a risk-probability number higher than 100. We identified the two riskiest processes and developed cause-and-effect diagrams for both: one was related to exchange of information between the radiation and hospital information system regarding the patient's allergy, the other was due to education and structural deficiencies in observation following the exam.

CONCLUSION

The combined method of failure mode effect analysis and cause-and-effect analysis reveals high-risk processes and suggests measures to reduce these risks. Failure modes and effects analysis is not well-known in healthcare but has significant potential for improving patient safety. Our findings emphasise the importance of adopting new techniques to reduce patient risk and carry out best practices in radiology.

Risk of Hypersensitivity Reactions to Iopromide After Intra-Arterial Versus Intravenous Administration: A Nested Case-Control Analysis of 133,331 Patients

Objective

The aim of this study was to compare the risk of hypersensitivity reactions to iopromide after intra-arterial (IA) administration and intravenous (IV) administration.

Materials and Methods

Four observational studies were pooled. Almost half of the study population (48.1%) was from Europe, and one quarter each from China (27.6%) and other Asia countries (24.1%). All patients received iopromide either intra-arterially or intravenously for angiographic procedures (mostly cardio-angiography) or contrast-enhanced computed tomography. A nested case-control analysis, including a multivariable logistic regression model, was performed. Cases were defined by patients with a typical and unequivocal hypersensitivity (assumed non–IgE-mediated) reaction; controls were patients without any recorded reaction. The primary target variable is the odds ratio of having a hypersensitivity reaction after IA versus IV administration.

Results

A total of 133,331 patients met the inclusion criteria, 105,460 and 27,871 patients received iopromide IV or IA, respectively. Hypersensitivity reactions were recorded for 822 patients, and 132,509 patients served as controls.

Major risk factors for hypersensitivity reactions were method of injection (IV vs IA), age (18 to <50 years vs ≥65 years), history of allergy or previous contrast media reaction (all P < 0.001), and asthma (P = 0.005).

A total of 766 patients (0.7%) and 56 patients (0.2%) were recorded with hypersensitivity reactions after IV or IA administration, respectively (P < 0.0001).

Adjusted odds ratio (IA vs IV) was 0.23 (95% confidence interval, 0.16–0.32) for all countries together: for China only, 0.22 (0.11–0.44); for all countries without China, 0.36 (0.25–0.53).

Most frequent reactions were erythema/urticaria/rash, pruritus, and cough/sneezing.

Conclusions

Hypersensitivity reactions to iopromide were significantly less frequently recorded after IA administrations. This could be related to the delayed and diluted arrival of iopromide to the lungs.

Diagnosis of pulmonary embolism: Following the evidence from suspicion to certainty

Accurate, timely and cost-effective identification of pulmonary embolism remains a diagnostic challenge. This article reviews the pulmonary embolism diagnostic process with a focus on the best practice advice from the American College of Physicians. Benefits and risks of each diagnostic step are discussed. Emerging diagnostic tools, not included in the algorithm, are briefly reviewed.