Association Between Intravenous Thrombolysis and Anaphylaxis Among Medicare Beneficiaries With Acute Ischemic Stroke.

Background and Purpose- Allergic reactions, including anaphylaxis, can sometimes occur after intravenous thrombolysis in patients with acute ischemic stroke. However, it remains unclear whether patients with stroke who receive thrombolytic agents face a higher risk of anaphylaxis than those who do not receive thrombolytics. Methods- We performed a retrospective cohort study using inpatient and outpatient claims between 2008 and 2015 from a nationally representative 5% sample of Medicare beneficiaries. We included patients who were ≥65 years old and hospitalized with acute ischemic stroke, defined by validated diagnosis codes. Our exposure was treated with an intravenous thrombolytic agent during the index hospitalization ( code 99.10). Our primary outcome was anaphylaxis, defined using an accepted code algorithm (989.5, 995.0-4, 995.6x, E905, E905.3, E905.5, or E905.8-9). A secondary outcome was anaphylactic shock (995.0 or 995.6x). Multiple logistic regression was used to evaluate the association between intravenous thrombolysis and anaphylaxis after adjustment for demographics, vascular risk factors, the Charlson comorbidity index, exposure to intravenous contrast dye, treatment with mechanical thrombectomy, and history of allergic reactions. Results- Among 66 989 patients with stroke, the 3176 (4.7%) who underwent intravenous thrombolysis more often had atrial fibrillation (47.7% versus 37.4%) and more often received intravenous contrast dye (44.3% versus 21.9%) but were otherwise similar in terms of demographics and comorbidities. Anaphylaxis developed in 17 (0.54%; 95% CI, 0.31%-0.86%) patients who received intravenous thrombolysis versus 45 (0.07%; 95% CI, 0.05%-0.09%) who did not. After adjustment for demographics, comorbidities, contrast dye, mechanical thrombectomy, and history of allergies, there was a significant association between receipt of intravenous thrombolysis and anaphylaxis (odds ratio, 7.8; 95% CI, 4.3-13.9). We found a similar association for anaphylactic shock. Conclusions- Although a rare occurrence, the risk of anaphylaxis among patients with acute ischemic stroke was significantly higher among those who received intravenous thrombolysis.