Forum Πρωτοβάθμιας Φροντίδας Υγείας
ΠΦΥ -Εκπαίδευση => Αποσπάσματα από τον έντυπο & ηλεκτρονικό τύπο => Μήνυμα ξεκίνησε από: Argirios Argiriou στις 22 Ιουλίου 2015, 22:05:15
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July 21, 2015
Pretreatment to Prevent Radiocontrast Reactions During CT Procedures
David J. Amrol, MD reviewing Mervak BM et al. AJR Am J Roentgenol 2015 Jul.
Among patients with previous reactions during computed tomography, more than 500 would require pretreatment to prevent 1 severe reaction.
Low-osmolality contrast material (LOCM) can cause non–IgE-mediated allergic-type reactions in patients undergoing computed tomography (CT) procedures. Risk for these reactions is 0.6% in all patients and rises to 3.5% in those who have reacted previously. Patients with previous reactions typically receive prednisone (50 mg) at 13 hours, 7 hours, and 1 hour before intravenous LOCM administration and diphenhydramine (50 mg) at the 1-hour mark. In this retrospective study, researchers determined the rate of breakthrough reactions among 1051 inpatients (age range, 5–97) who were pretreated before undergoing LOCM-enhanced CT. Sixty percent of patients had experienced previous allergic-type reactions to LOCM; 40% had other reasons for pretreatment, including asthma and allergic reactions to other substances.
For patients with previous LOCM reactions, the breakthrough reaction rate was 2.1%; no breakthrough reactions occurred among patients without previous reactions who were pretreated for other reasons. The number needed to treat (NNT) to prevent 1 reaction of any severity was 69, and the NNT to prevent 1 severe reaction was 569. Among patients with previous reactions to LOCM, younger patients and those with multiple risk factors (especially severe allergies to ≥2 substances, such as drugs and foods) had higher breakthrough-reaction rates.
Comment
This study is limited by its retrospective design and its use of previous studies to determine predicted reaction rates. The high NNT to prevent severe reactions makes me wonder if pretreatment is worth using at all. However, until we have further prospective studies, I'll continue to pretreat patients who've had previous allergic-type reactions to radiocontrast, paying special attention to atopic patients with asthma, food allergies, and drug allergies.
Editor Disclosures at Time of Publication
Disclosures for David J. Amrol, MD at time of publication Equity Abbott; AbbieVie; Express Scripts; Johnson and Johnson; Novartis; Pfizer; United Health Leadership positions in professional societies Allergy Society of South Carolina (Past President)
Citation(s):
Mervak BM et al. Rates of breakthrough reactions in inpatients at high risk receiving premedication before contrast-enhanced CT. AJR Am J Roentgenol 2015 Jul; 205:77. (http://dx.doi.org/10.2214/AJR.14.13810)
PubMed abstract (Free):
http://www.ncbi.nlm.nih.gov/pubmed/26102383?access_num=26102383&link_type=MED&dopt=Abstract
http://www.jwatch.org/na38503/2015/07/21/pretreatment-prevent-radiocontrast-reactions-during-ct?query=etoc_jwgenmed#sthash.X1DHvqel.dpuf