LPS-induced endotoxic shock does not cause early brain edema formation - an MRI study in rats.

OBJECTIVE AND DESIGN: Early microcirculatory failure is assumed as a key factor in the development of a septic encephalopathy. However, brain edema is also a common finding in sepsis syndromes possibly interfering with the vasoregulative mechanisms of the brain. We assessed the occurrence of brain edema in a rat model of endotoxic shock.

MATERIAL AND SUBJECTS: Eleven mechanically ventilated male CD-rats.

TREATMENT: Intravenous application of 5 mg/kg LPS (n = 8) or vehicle (n = 3).

METHODS: Apparent diffusion coefficient (ADC) and T2-relaxation time (T2RT) were quantified on cerebral MRI at baseline and repeatedly for up to 3.5 h after LPS-injection. Change in blood pressure was compensated with norepinephrine. Brain water content was quantified using the wet/dry method.

RESULTS: All LPS-treated rats developed endotoxic shock. No significant difference in T2RT or ADC was detectable before and after LPS-injection (T2RT: baseline 60.33 +/- 1.21; after 3.5 h 60.15 +/- 0.59; ADC: baseline 6.86 +/- 0.51; after 3.5 h 6.75 +/- 0.33). Post-mortem analysis did not indicate a difference in brain water content between septic and non-septic animals.

CONCLUSIONS: Reports of early microcirculatory failure seem not to be related to the occurrence of early (< or =3.5 h) brain edema.