Methods: A retrospective review of immediate hypersensitivity reactions to ICM that occurred between 2006-2008 in King Chulalongkorn Memorial Hospital was performed. Severity of the reactions was graded by Ring and Messmer's classification.
Results: A total of 34,365 ICM were administered for radiologic procedures during the study period. There were 193 immediate hypersensitivity reactions, representing the frequency of 0.56%. Mild (grade I and II) and severe (grade III and IV) reactions developed in 181 (0.53%) and 12 (0.03%) patients, respectively. The most common reactions were skin manifestations (rash, urticaria and angioedema) which occurred in 179 patients (92.7%). Respiratory, gastrointestinal and cardiovascular symptoms developed in 12 (6.2%), 2 (1%) and 10 (5.2%) patients, respectively. The patients who have allergic diseases more frequently developed grade III reactions (particularly asthmatic attack) than other reactions. Anaphylaxis, defined as multi-organ involvement, occurred in 8 patients (4.1%). Two patients (1%) had cardiopulmonary arrest. No fatality was reported. Seventy-nine patients (40.9%) had previous exposure to ICM, while 23 patients (11.9%) experienced previous reactions to ICM and of that 14 patients (60.9%) developed the reactions despite premedications. A history of previous reactions to ICM and premedications use were not found to be associated with severity of the reactions. Mean time to onset of reactions was 13 minutes after ICM administration and almost all patients (188, 97.4%) developed the reactions within 30 minutes. One hundred seventy-five patients (90.7%) received active treatments. Antihistamines, corticosteroids and epinephrine were administered in 172 (89.1%), 33 (17.1%) and 9 (4.7%) patients, respectively. Five patients (6.2%) required cardiopulmonary resuscitation. Median time of symptoms resolution was 30 minutes after receiving treatments and almost all patients (187, 96.9%) recovered within 60 minutes.
Conclusions: Immediate hypersensitivity reactions to ICM are uncommon. Most patients develop mild reactions and respond well to treatments. The patients with allergic diseases may have a greater risk of asthmatic attack after receiving ICM. Although severe reactions are rare, all patients should be observed under medical supervision for at least 30 minutes after ICM administration