title: Tissue hyperosmolality and brain edema in cerebral contusion.
abstract: Severe cerebral contusion is often associated with nonhemorrhagic mass effect that progresses rapidly within 12 to 48 hours posttrauma. The mechanisms underlying such a rapid progression of mass effect cannot be fully explained by classic concepts of vasogenic and cytotoxic brain edema. Data from previous clinical trials, including diffusion-weighted magnetic resonance imaging studies, have indicated that cells in the central (core) area of the contusion undergo shrinkage, disintegration, and homogenization, whereas cellular swelling is located predominately in the peripheral (rim) area during this period. The authors hypothesized that high osmolality within the contused brain tissue generates an osmotic potential across the central and peripheral areas or causes blood to accumulate a large amount of water. To elucidate the role of tissue osmolality in contusion edema, they investigated changes in tissue osmolality, specific gravity, and ion concentration in contused brain in both experimental and clinical settings. Their results demonstrated that cerebral contusion induced a rapid increase in tissue osmolality from a baseline level of 311.4 +/- 11.3 to 402.8 +/- 15.1 mOsm at 12 hours posttrauma (p < 0.0001). Specific gravity in tissue significantly decreased from 1.0425 +/- 0.0026 to 1.0308 +/- 0.0028 (p < 0.01), reflecting water accumulation in contused tissue. The total ionic concentration [Na+] + [K+] + [Cl-] did not change significantly at any time point. Inorganic ions do not primarily contribute to this elevation in osmolality, suggesting that the increase in colloid osmotic pressure through the metabolic production of osmoles or the release of idiogenic osmoles can be a main cause of contusion edema.
authors.affiliation: Department of Neurological Surgery, Nihon University School of Medicine, Tokyo, Japan. kawamata@med.nihon-u.ac.jp <kawamata@med.nihon-u.ac.jp>
authors.forename: Tatsuro
authors.initials: T
authors.lastname: Kawamata
authors.forename: Tatsuro
authors.initials: T
authors.lastname: Mori
authors.forename: Shoshi
authors.initials: S
authors.lastname: Sato
authors.forename: Yoichi
authors.initials: Y
authors.lastname: Katayama
mesh_terms: D000818:Animals; D001924:Brain Concussion / Q000150:complications*; D001929:Brain Edema / Q000209:etiology* / Q000473:pathology*; D004195:Disease Models, Animal; D006801:Humans; D009417:Nerve Tissue / Q000503:physiopathology*; D009994:Osmolar Concentration; D051381:Rats; D017208:Rats, Wistar; D013997:Time Factors; D014882:Water-Electrolyte Balance / Q000502:physiology*