Ichiro Toyota MD, PhD, Presenter: Nothing to Disclose

Hisao Tonami MD, Abstract Co-Author: Nothing to Disclose

Toshishige Shibamoto MD, Abstract Co-Author: Nothing to Disclose

Anaphylactic shock is sometimes accompanied by local interstitial edema due to increased permeability. We performed examination of magnetic resonance (MR) imaging to detect edema in the larynx and brain during anaphylactic hypotension in anesthetized rats, with comparison of that during vasodilator-induced hypotension.

Male Sprague Dawley rats were subjected to hypotension induced by the ovalbumin antigen (n=8) and a vasodilator sodium nitroprusside (n=8). Apparent diffusion coefficient and T2-relaxation time were quantified on MR imaging performed repeatedly for up to 68 min after an injection of either agent. The presence of laryngeal edema was also examined by histological examination. Separately, the occurrence of brain edema was assessed by measuring brain water content using the wet/dry method in the rats with anaphylaxis (n=5) or sodium nitroprusside (n=5), and the non-hypotensive control rats (n=5). Mast cells in the hypothalamus were morphologically examined. 

Mean arterial blood pressure similarly decreased to 35 mmHg after an injection of the antigen or sodium nitroprusside. Hyperintensity on T2-weighted images, as reflected by elevated T2-relaxation time, was found in the larynx as early as 13 min after an injection of the antigen but not sodium nitroprusside. Postmortem histological examination revealed epiglottic edema in the rats with anaphylaxis, but not sodium nitroprusside. In contrast, no significant changes in T2-relaxation time or apparent diffusion coefficient were detectable in the brain of any rats studied. In separate experiments, brain water content quantified was not increased in either anaphylaxis or sodium nitroprusside rats, as compared with the non-hypotensive control rats. The number of mast cells was similar in the hypothalamus of rats with anaphylaxis and sodium nitroprusside, suggesting absence of anaphylactic reaction in the brain. 

MR imaging elucidates presence of edema in larynx, but not brain, during anaphylactic hypotension in experimental study.

MR evaluation by T2-relaxation time as well as apparent diffusion coefficient elucidates presence of edema in larynx, but not brain, during anaphylactic hypotension.

Toyota, I, Tonami, H, Shibamoto, T, MR Evaluation of Brain and Laryngeal Edema during Anaphylactic Hypotension: An Experimental Study.  Radiological Society of North America 2013 Scientific Assembly and Annual Meeting, December 1 - December 6, 2013 ,Chicago IL. http://archive.rsna.org/2013/13016403.html